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Jeremy White

Forget supersonic, the future of super-fast flight is sub-orbital

When Elon Musk’s SpaceX team returned their Falcon Heavy side booster rockets back to Cape Canaveral in February, after placing one of his Tesla Roadster cars in space, it marked a turning point.

With SpaceX, Blue Origin and Virgin Galactic rapidly raising the profile of the commercial space race (Jeff Bezos is liquidating $1 billion a year of Amazon stock to fund Blue Origin), you could be forgiven for thinking that as orbital space flight is more technically difficult and costly, we may soon be experiencing the holy grail of long-haul travel: sub-orbital flight.

Previously the stuff of science fiction, sub-orbital flight would let you travel from one side of the planet to the other in less than an hour. On a London to Sydney trip, it would be difficult to squeeze in an in-flight meal, let alone a Hollywood action film. What makes sub-orbital flight different to orbital space travel? Velocity. In sub-orbital flight, orbital velocity is not achieved, so a vehicle cannot follow a path consistent with the curvature of the Earth - this means it is constantly pulled back down to the surface of our planet. And that makes sub-orbital a real engineering headache.

Despite not quite getting into orbit, sub-orbital passengers would still technically enter space. Such flights would likely climb to altitudes of up to 100 kilometres. That's well beyond the Kármán line, the point above sea level that marks the start of space. Indeed, the US Department of Transport awards commercial astronaut wings to pilots and crew on board a licensed launch vehicle that exceeds 80.45km.

And it won't be cheap, either. According to the UK's Department for Transport, when it does become a reality a seat aboard a sub-orbital flight will likely cost upwards of £200,000 per person.

According to Phillip Atcliffe, senior lecturer in aeronautical engineering at University of Salford, Manchester, Robert Heinlein’s 1982 sci-fi novel Friday accurately describes the passenger experience of sub-orbital flight, as the protagonist boards the SB Abel Tasman ballistic shuttle.

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Angela Watercutter

Madeline Ashby

“The high-G blast off always feels as if the cradles would rupture and spurt fluid all over the cabin. The breathless minutes in free-fall that feel as if your guts were falling out. And then re-entry, and that long, long glide that beats any sky ride ever built. Presently free fall went away and we entered the incredibly thrilling sensations of hypersonic glide. The computer was doing a good job of smoothing out the violence, but you still feel the vibration in your teeth.

We dropped through trans-sonic rather abruptly, then spent a long time sub-sonic, with the scream building up. Then we touched and the retros cut in, and shortly we stopped. We had lifted at North Island at noon Thursday, so we arrived 40 minutes later at Winnipeg the day before, in the early evening on Wednesday, 1940 hours.”

While the sub-orbital in-flight experience may not lend itself to drinks trolleys and hot towels, the allure of intercontinental travel times becoming less than the duration of an episode of Bake Off is strong. But where are we right now with this technology? How safe will it be and how long before we are regularly skimming the limits of the Earth’s atmosphere to make an appointment in Shenzhen and returning the same afternoon? Atcliffe brings us up to speed on the sub-orbital space race.

WIRED: Where are we with sub-orbital flight now?

Atcliffe: In terms of manned flight, as opposed to military missiles, we’re right at the start. Crawling rather than walking, and don’t even think about running for a while. A problem with sub-orbital flight is that, by its very nature, it’s tangled up with spaceflight, space tourism, hypersonic flight and so on, and it can be difficult to separate one from the other – if, indeed, they can be separated.

The major effort at the moment is for space tourism, such as that offered by Virgin Galactic, SpaceX and Blue Origin – short hops into space above the Kármán line that take place basically for the thrill of it. No-one will be taking a scheduled flight like that to and from specific destinations for some time.

The other significant object of work is the single-stage-to-orbit (SSTO) satellite launcher, which would not be a commercial aircraft for passengers, but might be the basis of such a design. Reaction Engines’ Skylon spaceplane has been proposed in two variants: an SSTO vehicle and a hypersonic airliner. The latter may or may not be a sub-orbital vehicle, but it’s close enough.

How long will it be until this technology might be used for, say, passengers flying to Australia in just an hour?

Your guess is as good as mine. It will require new technology, the will to proceed with what won’t be a simple challenge, and the money to do it. It could happen in a relatively short time – don’t ask me how long, we’re probably talking at least a decade. Otherwise, supersonic flight is a likely example of what might happen: only now, more than 40 years after Concorde went into service, is there a possible successor that has got as far as producing hardware. There have been regular streams of paper projects, but none of them have resulted in an actual aircraft until now.

What will be the cost of sub-orbital flights?

Certainly to begin with, a commercial sub-orbital flight – that is, the equivalent of an airline flight – will cost big money. Space tourism flights are six figures or more, so it’s likely that a sub-orbital service won’t be cheap.

Of course, neither were the first commercial flights, the first intercontinental flights, the first jet flights, the first supersonic flights. People are so used to cheap commercial flights today that they tend to forget that once upon a time, any sort of flight was an adventure and a luxury – and correspondingly expensive. It’s only with the advent of the Boeing 747 in 1969, and the subsequent large airliners designed to carry hundreds of passengers at a time (as opposed to, say, the Comet 1 ’s maximum complement of 44) that mass air travel became a reality. It started small, and hence expensive, and so will sub-orbital flight if and when it eventuates.

What are the technical obstacles that need to be overcome to make commercial sub-orbital flight a reality?

Much the same as with any new aircraft, only more so. Producing and then combining the engines and airframe in order to produce the required performance is what it’s all about, made more difficult in this case by the extreme conditions under which the vehicle will operate.

The biggest challenges are heat, propulsion and fuel capacity. Heat may require new materials and methods of construction; propulsion is key to anything in these sort of conditions, to the point that engine/airframe integration can make or break a design; and fuel capacity because cryogenic fuels (liquid hydrogen and oxygen, most commonly) are not very dense and so require large volumes for storage, which leads to a big airframe – which may require a bigger engine and more fuel, which makes the airframe bigger and heavier. And then there’s the infrastructure to support the thing – “spaceports”, access to them, fuel and supplies, navigational methods and regulations, airspace controls, training, diversion fields, regulatory authorities, and so on, and so on. It all needs to be set up and built.

What will be the impact on the commercial aviation industry?

Unpredictable. It may fragment it, leading to extremes of sub-orbital services for the rich and ultra-large high-density low-cost subsonic services for the rest of us, possibly with something in the middle, maybe supersonic services, for the well-off but not rich, and maybe business travellers.

We’ve seen this sort of thing before: in 1969, two very different aircraft made their maiden flights – Concorde and the Boeing 747. One was intended to lead to supersonic travel all over the world, while the other did lead to mass travel at a much lower cost all over the world. Concorde did not sell well for a variety of reasons, and no-one managed to produce a similar aircraft, so the potential split didn’t happen in quite the way airlines expected, but I wouldn’t be surprised if hypersonic/sub-orbital flight produced such a divide. Airlines will have to decide which kind of service they want to specialise in, always remembering that the low-volume, high-cost ultra-fast service will be very vulnerable to any sort of shift in the market. This is what happened after the attacks on September 11, 2001, for instance.

Commercial aviation is currently the safest way to travel. Will sub-orbital flight be safer or carry greater risks?

Eventually, I expect sub-orbital travel to be just as safe as modern commercial aviation. But it must be remembered that it is not a mature technology. We’ve been flying in civil jet aircraft, carrying more than 600 people at a time, for nearly 70 years now. We have yet to fly a single paying passenger sub-orbitally. We hope we know what the risks are, and engineers will do their best to cope with them, but what about the risks we don’t know about?

We didn’t know about explosive decompression due to metal fatigue from repeated pressurisation cycles until it happened to the Comet 1 back in the 1950s, so there may be failure modes lurking out there waiting to cause disaster that we haven’t thought of, and have had no reason to... yet. Expecting perfect safety, or even modern standards of air safety for subsonic aircraft right from the start is dangerously naive. We are effectively back in the equivalent of the pre- or just post-WWI era for civil aviation as far as sub-orbital flight goes. There will be accidents, and lives will be lost, but we’ll learn from them, and, with time and effort, those problems will be overcome.

Read more: What can sci-fi teach us about Donald Trump's Space Force?

What can be done, if anything, in the event of engine failure or loss of cabin pressure in sub-orbital flight?

Two separate problems here, though they may well occur together. Engine failure is not such a biggie, especially if it happens once the aircraft is well off the ground. The Space Shuttle had procedures for this, most notably a series of airfields scattered all over the world to which it could abort a launch if it had to. If the aircraft is sufficiently high and/or sufficiently fast when something goes wrong, then it has the flexibility to make use of these alternate landing sites. Of course, you may end up a long way from where you wanted to be.

Close to the ground, there may not be a lot anyone can do – but that’s much the same as a commercial airliner today. The Miracle on the Hudson shows that when an aircraft loses power at low altitude, it’s going down, and the question becomes how to survive the eventual impact. Hopefully, in such an incident, the flight crew will be up to the standards of airmanship of Chesley Sullenberger and his crew, but we also have to face the possibility that even a crew like that may not be able to cope with the situation, whatever it may be. It becomes a question of what is considered an acceptable risk.

The nature of the engine failure could be a problem, and will depend on the type of engine. A functioning sub-orbital vehicle may need systems to jettison either or both the engines and the fuel and oxidiser. In particular, something like liquid oxygen is very dangerous if there’s any sort of fire, or even just a leak. But so is aviation fuel, so experience will hopefully lead to acceptably safe designs. Once again, engineers will do everything they can to get this right the first time, but only the School of Hard Knocks can tell us if they managed that.

Loss of cabin pressure could be anything from a minor inconvenience to an utter disaster, depending on when and where it happens – and therefore, what damage to the airframe caused it and might be caused by it. At one end of the spectrum of possible outcomes, it won’t be much different to a decompression in an airliner. There may be a more-or-less violent suction towards the hole that caused it, oxygen masks drop down from the cabin ceiling and the aircraft aborts to the nearest landing field.

At the other, there is major structural damage and the possibility of the aircraft breaking up. Both have happened in civil aviation in the past, and this would be no different. In the middle, between the two extremes, there might be the need for additional measures like, say, sealed flight suits that could become what amounts to spacesuits if there’s a problem. Or if people don’t like that idea, perhaps the cabin could be divided into multiple separate sealed units so that as few passengers as possible are affected by a leak. You wouldn’t be able to go for a stroll along the length of the aircraft, but is that such a loss given the alternative?

This article is part of our WIRED on Space series. From the global fight over how we handle first contact with aliens to the endless search for dark matter and the inside story of China's top-secret space ambitions, we're taking an in-depth look at humanity's future amongst the stars.

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This article was originally published by WIRED UK

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Sub-Orbital Travel Is Going to Make the World Feel Really, Really Small

Our small world is about to get even smaller—for those who can afford to fly sub-orbitally

Mary Beth Griggs

The real-estate consulting company Knight-Frank  is envisioning a future where our small world gets even smaller. In the company's latest Wealth Report, its analysts say that, essentially, because 70 super-rich people (combined wealth of $220 billion) are interested in investing sub-orbital travel, it's a very real possibility that travel times could be decimated in the future. 

A flight from Moscow to New York in just one hour instead of nine sounds great, doesn't it? And it might just be possible. Scott Smith over at Quartz reports : 

According to the report, having suborbital escape options means not only looking at the possibilities of getting from London to Sydney in around 2 1/2 hours, but possibly reaching less expensive markets for luxury property such as Sao Paolo or Cape Town in a similar amount of time. Richard Branson’s Virgin Galactic, which says it will fly this year, or Jeff Bezos-backed Blue Origin are poised to not only satisfy thrill seekers, but perhaps take a bite out of private jets and opulent first-class cabins over the long term. These services employ reusable aircraft-like vehicles to enter low Earth orbit briefly and return to a ground station via traditional landing— eliminating the time suck of long-haul flights. That is, if you don’t mind donning a pressure suit over your power suit and have $250,000 to drop on a one-way ride.

In other words, the titans of industry on Wall Street might just start weekending at their second home in New Zealand instead of the Hamptons.

That's great for them, but what about everybody else? Right now, the sub-orbital technology in development is focused on taking wealthy tourists into space , research or a combination of the two—not on establishing an alternative to air travel.

Once more spaceports start to open up (let's just stop for a second, and notice that we're now talking about  multiple commerical spaceports , which is pretty cool), it's possible that sub-orbital travel could expand beyond a quick sojurn to space and become an actual means of transportation between two locations. It will still likely only be accessible to people with money to burn…at first. But with the infrastructure in place and the initial R&D of sub-orbital travel finished, there is the possibility that prices could drop, opening up those shorter travel times to more people. 

Knight-Frank is interested in how these quick continent-hopping jaunts will affect property prices, too.  On the company's blog :

Ticket price will be critical. If this is a technology for billionaires only, then property market disruption might be limited to a wider choice of global lunch options. But if the price drops to allow the merely very wealthy to access sub-orbital flights, then every assumption about current property prices will have to be reconsidered. Liam Bailey states: “Take second homes in Europe. Right now, demand is mainly restricted to European investors, who try to limit their travel to less than two hours. In future, that same time limit could allow Chinese or Indian investors to pop over for the weekend to visit their Tuscan farmhouse.”

Ok, so maybe it’ll take a little more time for people who aren’t “merely very wealthy” to travel into space. But as Bailey told Quartz , cars, planes and cruise liners used to be the province of the wealthy, too.

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Mary Beth Griggs is a freelance science journalist based in New York City.

Low Earth orbit: Definition, theory and facts

Most satellites travel in low Earth orbit. Here's how and why

• Theory of orbits
• Satellite orbits

Additional resources

Bibliography.

In very simple terms, low Earth orbit (LEO) is exactly what it sounds like: An orbit around the Earth with an altitude that lies towards the lower end of the range of possible orbits. This is around 1,200 miles (2,000 kilometers) or less. The majority of satellites are to be found in LEO, as is the International Space Station (ISS).

In order to remain in this orbit, a satellite has to travel at around 17,500 miles per hour (7.8 kilometers per second), at which speed it takes around 90 minutes to complete an orbit of the planet. 

Low Earth orbit theory

Orbits are possible due to the force of gravity — the same force that holds us to the surface of the planet. Just as we would float off into space if gravity didn’t exist, so a satellite would fly off at a tangent if that force wasn’t there to keep it travelling round the Earth. 

This really does happen in the case of a spacecraft that’s travelling extremely fast — faster than the Earth’s escape velocity, which is 25,000 mph (11.2 km/s). On the other hand, if an object is travelling much more slowly, such as Blue Origin’s suborbital rocket New Shepard , it will fall back to Earth just as surely as you do when you jump up into the air. 

Related: Laika the space dog: First living creature in orbit

The speed of 17,500 mph (7.8 km/s) is the speed at which  the force of gravity  prevents an object from flying off at a tangent. The result is that an object moving at this speed will simply go round and round the Earth . This is a horizontal speed, parallel to the surface of the planet. 

This may seem confusing if you’ve ever watched a space launch, because rockets generally go straight up vertically when they blast off. But that’s because they need to get up above the atmosphere — or the greatest part of it — as quickly as possible to avoid drag forces. But once they are above the atmosphere they switch to horizontal motion. When a satellite reaches orbital speed, it is officially in orbit.

Satellites in low Earth orbit

The orbital speed of 7.8 km/s (17,500 mph), refers to the LEO regime just above the Earth’s atmosphere . At higher altitudes, the speed required to keep a satellite in orbit changes. In fact, this actually decreases with the increase in altitude. 

However, this does not mean that a rocket needs to expend less energy in order to put a satellite into a higher orbit. This is because it takes a huge amount of energy just to reach that higher altitude. This extra effort in getting to higher altitudes is one of the reasons most satellites are placed in LEO, together with other considerations such as the higher resolution views that Earth-observing satellites can get from closer range.

— What's the difference between orbital and suborbital spaceflight?

— Artificial gravity: Definition, future tech and research

— Orion spacecraft: NASA's next-gen capsule to take astronauts beyond Earth orbit

There is, however, one particular high-altitude orbit that’s worth the extra effort to get to — and that’s Geosynchronous orbit (GEO). 

A satellite in LEO completes around 16 orbits every day, or for every complete rotation of the Earth itself. However GEO is at an altitude of around 22,000 miles (36,000 km), at which point the orbital speed has slowed, so a single orbit corresponds to precisely one rotation of the Earth. 

This means that a satellite at that altitude effectively hovers over a single spot on the Earth’s surface, which makes it especially useful for satellite TV and other communications systems.

Satellite orbits usually follow an oval-type path called an ellipse, the length and width of which are known as the major and minor axes. 

When these two axes are equal in size, the orbit is a perfect circle, which is just a special case of an ellipse. Most satellites have near-circular orbits, but in a few cases the ellipse can be much more elongated, with a major axis much longer than the minor axis. 

The Molniya orbit, for example, used for communications in northerly latitudes, has a low point of around 308 miles (495 km) but a high point around 25,000 miles (40,000 km).

LEO is the most common type of orbit, but not the only one; here's some others. 

For more information about low Earth orbit and satellite design check out " Low Earth Orbit Satellite Design (Space Technology Library Book 36) " by George Sebestyen, et al, and NASA's webpage on " Low-Earth Orbit Economy ".

• ESA, " Low Earth orbit ", March 2020. 
• ESA, " Types of orbits ", March 2020. 
• Australian Space Academy, " Specifying Satellite Orbits ", accessed May 2022. 
• Rhett Allain, " What's So Special About Low Earth Orbit? ", Wired, September 2015. 
• Hight Point University, " Orbits ", accessed May 2022. 

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Andrew May holds a Ph.D. in astrophysics from Manchester University, U.K. For 30 years, he worked in the academic, government and private sectors, before becoming a science writer where he has written for Fortean Times, How It Works, All About Space, BBC Science Focus, among others. He has also written a selection of books including Cosmic Impact and Astrobiology: The Search for Life Elsewhere in the Universe, published by Icon Books.

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Preparing for “Earth to Earth” space travel and a competition with supersonic airliners

Commercial spaceflight companies are preparing to enter a new market: suborbital flights from one place to another on Earth. Aiming for fast transportation for passengers and cargo, these systems are being developed by a combination of established companies, such as SpaceX and Virgin Galactic, and new ones like Astra.

Technical and business challenges lie ahead for this new frontier, and an important piece is the coming wave of supersonic aircraft which could offer safer but slower alternatives to spaceflight. These two different approaches could face off in the 2020s to be the future of transportation on Earth.

(Lead image via Mack Crawford for NSF/L2)

Suborbital space travel

The most prevalent concept for suborbital Earth to Earth transportation comes from none other than Elon Musk and SpaceX . Primarily designed for transporting large payloads to Mars for the purpose of colonization, the next generation Starship launch system offers a bonus capability for transporting large amounts of cargo around Earth.

Musk first presented this idea in 2017, envisioning suborbital spaceflights between spaceports offshore from major cities. These launch and landing facilities would be far enough to reduce the disruption of rocket launch noise levels and sonic booms produced by landing vehicles, connected to land by a high speed form of transportation such as speedboats or a hyperloop.

Originally, these Earth to Earth flights were expected to use both stages of the Big Falcon Rocket (BFR) rocket, since evolved and renamed to the Starship spacecraft and Super Heavy booster. In 2019, Musk revealed that these suborbital flights could instead utilize only the Starship vehicle with no booster, achievable for distances of approximately 10,000 kilometers or less. In order to meet thrust requirements, a single stage suborbital Starship would include an additional two to four Raptor engines .

Given the inherent danger of rocket powered space travel, the Starship system will complete many, possibly hundreds of flights before flying passengers, with the first Earth to Earth test flights beginning as early as 2022 .

Another side effect of the Starship Mars architecture, which requires that methane be captured from Martian resources to refuel spacecraft and return to Earth, is that the same propellant production processes can be used on Earth to make Starship operations carbon neutral.

The idea of carbon neutrality, removing as much carbon from the atmosphere as is emitted by the system, is a crucial part of ensuring that future transportation systems do not contribute to the harmful effects of climate change. Musk has confirmed that carbon neutrality is an important goal of the Starship program.

SpaceX is not the only major commercial spaceflight company with a suborbital transportation concept. Richard Branson’s Virgin Galactic also has a vision of space travel around Earth. SpaceX’s Crew Dragon flying astronauts to Low Earth Orbit, and Virgin Galactic’s SpaceShipTwo flying crew on suborbital trajectories above the official American boundary of space at 80 kilometers altitude, are the only two commercial companies actively flying humans to space today. A successor to SpaceShipTwo is planned that could provide trans-continental spaceflights for passengers.

A bit of an Easter Egg from Richard Branson. Talking about a global network of spaceports, trans-continental supersonic space flights, delivering passengers anywhere on the world within a couple of hours. pic.twitter.com/WBZ6xvsfPO — Chris Bergin – NSF (@NASASpaceflight) May 10, 2019

While no technical details of a “SpaceShipThree” have been announced by Virgin Galactic, it is fairly likely that the vehicle would be air launched, similar to the SpaceShipOne and SpaceShipTwo suborbital spaceplanes. SpaceShipThree was originally intended to be a orbital vehicle, developed jointly by Virgin Galactic and Scaled Composites.

Scaled Composites was the manufacturer of SpaceShipOne, the first private crewed spacecraft which won the Ansari X Prize by completing two crewed spaceflights using a reusable spacecraft in 2004. Scaled Composites also built the first SpaceShipTwo, the VSS Enterprise, as well as the WhiteKnightTwo carrier aircrat VMS Eve, before jointly founding The Spaceship Company with Virgin Group. Scaled Composites is now a wholly owned subsidiary of Northrop Grumman , and The Spaceship Company currently manufactures SpaceShipTwo vehicles for Virgin Galactic.

While the name SpaceShipThree has not been mentioned recently, plans for a suborbital point-to-point transportation system are still planned by Virgin Galactic. Branson has mentioned a successor to SpaceShipTwo that can provide trans-continental spaceflights as recently as 2019. No timeline for test flights or commercial operations with this system have been announced yet.

For both of these systems, it is possible that suborbital cargo transportation could precede passenger flights as a way of proving the reliability of the vehicles. One company has no intention of flying people, but is pursuing suborbital spaceflight as a cargo transportation market: the smallsat launch company Astra .

Astra Rocket 3.2 launches from Kodiak, Alaska, in December 2020 – via Astra/John Kraus

Astra recently launched their second orbital launch attempt , Rocket 3.2, which came up just short of achieving orbit for the first time in Astra’s history. The company is expected to achieve orbit with a paying customer payload on board Rocket 3.3 in 2021.

For suborbital transportation, Astra has proposed an upgrade to the Rocket 3 family, named Rocket 5. The first stage of Rocket 5 would be identical to that on Rocket 3. The second stage would be similar to the first stage, except with a single engine instead of five. The final stage of Rocket 5 would be the same as Rocket 3’s upper stage. This vehicle could be available for suborbital cargo deliveries no earlier than 2022.

The Competition: Supersonic Airliners

While multiple suborbital transportation concepts proceed through development, several supersonic aircraft designs are also expected to debut, creating competition for the market of high speed transportation around the planet.

One such entrant is Boom Supersonic, which rolled out the XB-1 prototype aircraft in November 2020. The XB-1 will reach supersonic speeds during test flights which will inform the design of a supersonic airliner named Overture. Flight tests are expected to begin in 2021 in Mojave, California. The XB-1 has three General Electric J85-15 engines, from the same family of engines which power NASA’s T-38 Talon training aircraft and powered the WhiteKnightOne carrier aircraft which air-launched SpaceShipOne.

Boom Supersonic’s XB-1 Demonstrator Aircraft – via Boom Supersonic

The Overture airliner is planned to roll out by 2025, and be operational by 2029, carrying up to 88 passengers at ranges up to approximately 7,870 kilometers. The aircraft will be powered by a to-be-determined engine provided by Rolls-Royce. Both the XB-1 test program and the Overture airliner are planned to be carbon neutral.

Orders for the Overture from both Japan Airlines and the Virgin Group have been announced. It is unclear whether the Virgin Group orders are from Virgin Galactic, who did enter a partnership with Boom on Overture in 2016, or possibly the Virgin Atlantic airline.

Despite having their own suborbital design concept, Virgin Galactic is involved in the supersonic airline effort. While their partnership with Boom has not been promoted by either company recently, Virgin Galactic unveiled a partnership with Rolls-Royce for a Mach 3 capable aircraft in August 2020. The aircraft would have a passenger capacity of up to 19 people.

Concept render of Virgin Galactic’s Mach 3 airliner – via Virgin Galactic

Another offeror in the market is Aerion Supersonic, developing their AS2 Supersonic Business Jet. Aerion recently broke ground on a new headquarters at Melbourne International Airport, just south of the Cape Canaveral Space Force Station and Patrick Space Force Base on Florida’s space coast.

The AS2 jet is a partnership with Boeing and General Electric, and is designed to carry up to 10 passengers at speeds up to Mach 1.4 over open water. The AS2 would be flown closer to Mach 1.2 near land to mitigate the intensity of sonic booms, or subsonic if required. Historically, disturbances on the ground from sonic booms have contributed to the retirement of Aérospatiale and British Aircraft Corporation’s Concorde and the hesitation from other companies to pursue supersonic air travel.

Technical and Financial Challenges

The ideas of hypersonic suborbital space travel and subsonic atmospheric flight vary in their approaches to a similar problem, but also face some common challenges. Both methods do produce sonic booms, which can disrupt people living on the ground and, in extreme cases, cause damage or injuries. Supersonic aircraft produce sonic booms along the entire flight path, with varying intensities depending on speed, altitude, and the geometry of the aircraft. Rockets, on the other hand, only cause sonic booms to be heard during landing, as the shockwaves created during launch move upwards, away from any observers that could hear them.

In order to better understand the effects of sonic booms from aircraft, Lockheed Martin’s Skunk Works division is developing the X-59 QueSST (Quiet Supersonic Technology) for NASA’s Low-Boom Flight Demonstration Program. The X-59 is uniquely shaped to decrease the intensity of the supersonic shockwave so as not to disturb populated areas while flying overhead.

Render of the X-59 QueSST aircraft – via NASA

Powered by a General Electric F414 engine, the same as is used in the Boeing F/A-18 Super Hornet fighter jet, Lockheed Martin test flights are scheduled to begin in 2021, followed by delivery to NASA in 2022. The goal of the Low-Boom program is to collect data on the volume of sonic booms in order to inform legislation on approving supersonic air travel over populated areas. X-59 flights to contribute towards this mission begin in 2023, in addition to flights already underway using NASA’s F/A-18 fleet.

Sonic booms are not the only noise concern with these new methods of travel. Rockets produce potentially dangerous noise levels during launch, especially those on the scale of Starship. SpaceX plans to solve this by launching and landing far offshore from population centers, which means using a slower form of transportation to travel between the spaceport and the destination city.

Large rockets like Starship, especially if the Super Heavy booster is used, also have large blast danger areas in the event of a catastrophic anomaly while fully fueled. However, before flying commercial passengers, the Starship system will need to prove reliability comparable to that of present day airliners. This will surely include demonstrating a negligible risk of such an anomaly occurring. The Starship launch system also has no in-flight abort capability in the event that the Super Heavy booster or Starship’s Raptor propulsion system fails during flight, a risk that will need to be retired by flying many missions with only cargo on board, including both space missions and Earth to Earth test flights.

Another safety advantage winged aircraft have over propulsively landed rockets is the ability to glide in the event of an engine failure. Both these new supersonic airliners and spaceplane concepts like SpaceShipThree would be able to glide towards a controlled emergency landing during an emergency. This was recently demonstrated during Virgin Galactic’s most recent SpaceShipTwo flights, when VSS Unity glided back to the runway at Spaceport America after aborting during engine ignition . Vehicles which rely on their engines to land safely, such as Starship, do not have this contingency.

Looking past the important but solvable technical issues, the business case for faster Earth travel also remains to be proven. The costs of space launches and the limited capacity on upcoming supersonic airliners will likely mean higher ticket prices than today’s subsonic aircraft. The appeal of shorter travel times will need to outweigh the increased price.

An aspect of tourism may also come into play, as some travelers book travel not as commuters, but just to experience high speed air travel or suborbital spaceflight. However, this brings in even more competition from systems designed for suborbital space tourism, such as Blue Origin ‘s New Shepard rocket or Virgin Galactic’s own SpaceShipTwo. Orbital space tourism on board SpaceX’s Crew Dragon and Starship vehicles may also draw customers away from the suborbital options.

Suborbital spaceflight offers faster travel times than supersonic airliners, arriving anywhere on Earth in under an hour versus a couple hours on an aircraft. But space travel also offers additional challenges for safety and for noise levels on the ground. The key to systems like Starship being successful for Earth to Earth transportation will be proving the same level of safety as an airliner. If this can be done, than a combination of spaceflight and high speed airliners may be the future of travel around humanity’s home planet.

SLS Core Stage Green Run WDR countdown ends early – Next steps considered

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Look down on planet earth from new, awe-inspiring heights.

The Karmen Line is widely considered as the border between the earth’s atmosphere and outer space and sits at roughly 100km above sea level. Beyond this, entering into a low earth orbit means reaching an altitude of between 160km to 1000km.   

With launch providers Virgin Galactic, SpaceX and Blue Origin all offering opportunities to enter a sub orbital and low earth orbit or to fly beyond the Karmen Line, change how you view the world and allow Stellar Frontiers to plan, customise and execute this life-altering experience, pairing you with the right launch provider and the right spacecraft.

Enter low earth orbit aboard the SpaceX Dragon spacecraft. This fully autonomous, 4-passenger craft orbits the earth every 90 minutes and features Draco thrusters allowing for orbital manoeuvring, thus permitting a customised flight route. Fly over the Amazon River, the Great Barrier Reef, or the Pyramids of Giza, the choice is yours.    

This is the first space tourism experience provided using completely America technology as the Dragon will be launched by the companies Falcon 9 rocket, the same launch vehicle SpaceX uses to transport NASA astronauts to the International Space Station .   

Stellar Frontiers can negotiate a customised flight experience with SpaceX or can match you with one of their scheduled commercial spaceflight missions. 

Virgin Galactic

Virgin Galactic offers private citizens as well as the research community the opportunity to train as an astronaut and to reach the edge of space in the Virgin Galactic-commissioned VSS Unity spaceship.  

This passenger carrying spacecraft will run a regular spaceflight schedule from Spaceport America in New Mexico, the first commercial spaceport of its kind.  

Private astronauts that fly with Virgin Galactic will also have to opportunity to contribute to their Science, Technology, Engineering and Mathematics (STEM) initiatives operated through their outreach program, Galactic Unite.  

“It’s only when you’re flying above it that you realise how incredible the Earth really is.” – Philippe Perrin, CNES and European Space Agency Astronaut

Blue Origin

Blue Origin’s reusable New Shepard rocket system offers an astronaut crew of six the opportunity to fly beyond the Karmen Line. From take-off to landing, this 11-minute experience will see you ascend into space from Blue Origin’s launch site located in the Guadeloupe Mountains of West Texas. The New Shepard passenger capsule will separate from its booster at T+3 minutes as you enter a state of weightlessness. Pass an altitude of 100km above sea level before descending softly, guided by parachutes, to touch down in the Texan desert.   

Named after Alan Shepard, the first American astronaut to go to space, the fully autonomous, 6-seater New Shepard capsule has been designed with passenger comfort in mind and boasts the largest windows of any vehicle to have flown in space. It has completed 15 missions since 2012 with successful testing of its redundant safety systems.   

Through the Blue Origin Foundation, Club for the Future, there is scope for private astronauts to contribute to inspiring and supporting a future generation of space scientists, engineers and mathematicians.  

Images courtesy of Blue Origin

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Privacy Overview

Until 10 years ago, relatively few things were in Earth’s orbit.

Now it’s a traffic jam.

So What’s in Space Right Now?

AN EVEN MORE INTERNATIONAL SPACE STATION When China launched the last stage of its space station in October 2022, it opened up low orbit for scientists far beyond its borders. Tiangong has so far agreed to host projects from 12 countries. In May, the first experimental equipment reached the 54-foot-long station.

A NEW MOON BUGGY In August, with the success of the Chandrayaan-3 mission, India became the fourth country to safely land on the moon (following the Soviet Union, the United States and China). The six-wheeled rover, Pragyan, explored near the lunar south pole, where scientists think deep craters may hold ice.

COOPERATIVE COMMUNICATIONS SATELLITES More than 80 countries have sent satellites into orbit, including many smaller nations, which often share costs and expertise. TurkmenAlem52°E/MonacoSAT, a communications satellite built in France and launched from Cape Canaveral, Fla., is shared by Monaco and Turkmenistan.

EYES IN THE SKY Imagery from satellite constellations from the space-intelligence company Maxar has contributed to several Pulitzer Prizes for reporting. Photos taken by its satellites are used for geospatial intelligence by the U.S. government.

ELON MUSK’S EVER-MULTIPLYING SATELLITES Over 50 percent of all active satellites — currently about 5,000 — are from the Elon Musk-owned company Starlink. Musk plans to eventually have as many as 42,000 of the communications satellites in orbit, as The Times reported this July.

LOTS AND LOTS OF JUNK In 2009, a dead Russian satellite, Cosmos 2251, crashed into an operational telecommunications satellite, creating . . .

CLOUDS OF DEBRIS According to NASA, there are 28,000 pieces of debris in low Earth orbit that are larger than a softball, half a million pieces roughly the size of a marble and 100 million about the size of a pea. Even paint flecks can damage satellites, space stations or spacecraft when traveling at 17,500 miles per hour.

AUTONOMOUS MINERS In April 2021, the China-based company Origin Space launched NEO-01, its first robot designed to test asteroid-mining capabilities. In April 2023, the start-up AstroForge launched a satellite and is now assessing its ability to vaporize and sort an asteroidlike material in orbit.

SCIENTISTS AND THEIR EXPERIMENTS The International Space Station houses astronauts, yes, but we’re not the only living things sent into orbit. Scientists on the station completed around 500 experiments from September 2022 to September 2023.

They have recently worked with 120 Hawaiian bobtail squid to understand how bacteria interact with their hosts during spaceflight.

And they have grown Red Robin dwarf tomatoes to help develop agricultural methods for long space flights.

There’s also a nonhuman member of the current space-station crew: Sasha, a stuffed-animal three-toed sloth, brought as a zero-g indicator; when Sasha started to float in the cabin, the astronauts knew they were entering orbit.

LOGOS, LOGOS, LOGOS If you looked closely at the Ispace lander as it headed for the moon on April 25, you might have recognized some shapes emblazoned on its side: the Suzuki “S”; the crane of Japan Airlines; the rhombuses of SMBC, a Japanese bank. The age of space advertising is here.

WORKS OF ART, BOTH HUGE AND EXTREMELY TINY Art in space ranges from the minuscule to the size of spacecraft. In 2018, the aerospace manufacturer Rocket Lab sent a reflective geodesic sphere called “ Humanity Star ” into orbit; viewers could see the shining disco ball from Earth. W orks from a second grader and a fourth grader in Florida will soon head into orbit as winners of the state’s Space Art Contest.

In December, the Lunar Codex, a collection featuring works from over 30,000 artists, will launch its first set of more than 5,000 prints, songs, stories, poems and films to the Sinus Viscositatis region of the moon via an Astrobotic mission lander. The artwork is digitized and miniaturized into tiny images, which are imprinted onto a piece of nickel-based nanofiche the size of a dime.

DRUG LABS Commercial drug manufacturing is often easier in microgravity, because protein crystals grown in space tend to form more uniform structures than those grown on Earth. This year, Bristol Myers Squibb led an experiment on the I.S.S. to crystallize medications. The start-up Varda Space Industries launched its first spacecraft in June to test crystal production of ritonavir, an antiviral H.I.V. drug.

ROBOTIC SPACE PLANES The United States and China currently have reusable robotic spacecraft regularly in orbit: two X-37Bs, built by Boeing and operated by the U.S. Space Force; and a vehicle believed to be operated by the Chinese Ministry of National Defense. Combined, the two X-37B craft have flown six times in space since 2010, most recently landing after 908 days in November 2022.

TELESCOPES NOT CALLED WEBB OR HUBBLE There are several telescopes in Earth orbit answering urgent questions about the universe. The IXPE , or Imaging X-ray Polarimetry Explorer, observes some of the most extreme objects in our universe (like supernova explosions and jet streams shot from black holes) to learn how they work.

Charley Locke is a writer who often covers youth and elders. She last wrote for the magazine about pandemic funding and public education. Sean Dong is a motion and 3-D designer in Baltimore. His work often condenses stories of intricate subjects into brief, looping animations.

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Never miss an eclipse, a meteor shower, a rocket launch or any other 2024 event  that’s out of this world with  our space and astronomy calendar .

A celestial image, an Impressionistic swirl of color in the center of the Milky Way, represents a first step toward understanding the role of magnetic fields  in the cycle of stellar death and rebirth.

Scientists may have discovered a major flaw in their understanding of dark energy, a mysterious cosmic force . That could be good news for the fate of the universe.

A new set of computer simulations, which take into account the effects of stars moving past our solar system, has effectively made it harder to predict Earth’s future and reconstruct its past.

Dante Lauretta, the planetary scientist who led the OSIRIS-REx mission to retrieve a handful of space dust , discusses his next final frontier.

Is Pluto a planet? And what is a planet, anyway? Test your knowledge here .

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Axiom launch: why commercial space travel could be another giant leap for air pollution

Associate Professor in Physical Geography, UCL

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Eloise Marais receives funding from the European Commission and the UK Natural Environment Research Council.

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The Axiom-1 mission to send four private astronauts to the International Space Station is the first of many missions planned by NASA to expand the ISS for commercial use as part of what’s being called the low-Earth orbit economy .

The commander of the Axiom-1 mission has emphatically stated that this is not an example of space tourism , as the crew have undergone training and the mission includes plans to conduct biomedical research.

Crew members – all men aged 52 to 71 – reportedly paid a whopping US$55 million (£42.3 million) per ticket, an amount that would no doubt fund a formidable biomedical research programme here on Earth. But beyond the ludicrous ticket price, I’m concerned about the potential environmental impacts of such space jaunts.

The mission is using a SpaceX Falcon 9 Block 5 rocket, with the crew located in the Crew Dragon spacecraft at its apex. The rocket has two stages: the reusable booster that holds most (about four-fifths) of the fuel and that returns to Earth for reuse, and a discarded second stage.

The booster reaches an altitude of about 140km before returning to Earth. The energy required to propel the spacecraft to the ISS is achieved from the combustion reaction between rocket-grade kerosene and liquid oxygen, releasing byproducts hazardous to the environment.

Rocket launches and returning reusable components release air pollutants and greenhouse gases into multiple atmospheric layers. In the middle and upper atmosphere, these can persist for years compared with equivalent pollutants released at or near the Earth’s surface, which linger for weeks at most. This is because there are fewer chemical reactions or weather events to flush pollutants out of middle and upper layers.

Potent pollutants

The kerosene fuel used by SpaceX Falcon rockets is a mix of hydrocarbons, composed of carbon and hydrogen atoms. These react with liquid oxygen to form carbon dioxide (CO₂), water vapour (H₂O) and black carbon or soot particles that are released from the rocket exhaust .

CO₂ and H₂O are potent greenhouse gases, and black soot particles are very efficient at absorbing the sun’s rays. That means all these chemicals contribute to warming the Earth’s atmosphere.

Read more: Ax-1: why the private mission to the International Space Station is a gamechanger

Nitrogen oxides (NOx), reactive air pollutants, also form during launch due to very high temperatures causing a bonding reaction between usually stable nitrogen and oxygen molecules. NOx is also produced when the rocket’s reusable components return to Earth , due to extreme temperatures produced by friction on its heat shields as they whizz through the mesosphere at 40km-70km.

When these particles make contact with the ozone layer (in the stratosphere), they convert ozone to oxygen , depleting the fragile sheath that protects the planet from the sun’s harmful UV radiation.

Although total CO₂ emissions from this launch will be small in comparison to those from the global aircraft industry, emissions per passenger will be around 100 times those from a long-haul flight.

Soot emissions are also much less than those from the aircraft industry, but when released into the middle and upper atmosphere, soot has a warming effect 500 times greater than at levels closer to Earth. This is in part because there are typically no clouds and few to no aerosols competing with soot to absorb the sun’s rays.

Read more: Ukraine war: how it could play out in space – with potentially dangerous consequences

The potential opportunities of creating industry and trade networks within low-Earth orbit have been likened by an Axiom co-founder to the early days of developing the internet , now an almost universally accessible technology. If we extend that analogy to imagine similarly high levels of access to the low-Earth orbit economy, rocket launches are likely to become far more common than just the 146 launches achieved in 2021.

Such a scenario would substantially alter Earth’s climate and undermine our significant progress in repairing the ozone layer. At the very least, research is urgently needed to assess the consequences of a flourishing low-Earth orbit economy for our planet down below.

Don’t have time to read about climate change as much as you’d like? Get a weekly roundup in your inbox instead. Every Wednesday, The Conversation’s environment editor writes Imagine, a short email that goes a little deeper into just one climate issue. Join the 10,000+ readers who’ve subscribed so far.

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Nasa lays out how spacex will refuel starships in low-earth orbit, "the fundamental flow mechanism is the pressure delta across the umbilical.".

Stephen Clark - Apr 30, 2024 12:19 am UTC

Some time next year, NASA believes SpaceX will be ready to link two Starships in orbit for an ambitious refueling demonstration, a technical feat that will put the Moon within reach.

SpaceX is under contract with NASA to supply two human-rated Starships for the first two astronaut landings on the Moon through the agency's Artemis program, which aims to return people to the lunar surface for the first time since 1972. The first of these landings, on NASA's Artemis III mission, is currently targeted for 2026, although this is widely viewed as an ambitious schedule.

Last year, NASA awarded a contract to Blue Origin to develop its own human-rated Blue Moon lunar lander, giving Artemis managers two options for follow-on missions.

Designers of both landers were future-minded. They designed Starship and Blue Moon for refueling in space. This means they can eventually be reused for multiple missions, and ultimately, could take advantage of propellants produced from resources on the Moon or Mars.

Amit Kshatriya, who leads the "Moon to Mars" program within NASA's exploration division, outlined SpaceX's plan to do this in a meeting with a committee of the NASA Advisory Council on Friday. He said the Starship test program is gaining momentum, with the next test flight from SpaceX's Starbase launch site in South Texas expected by the end of May.

"Production is not the issue," Kshatriya said. "They're rolling cores out. The engines are flowing into the factory. That is not the issue. The issue is it is a significant development challenge to do what they’re trying to do ... We have to get on top of this propellant transfer problem. It is the right problem to try and solve. We're trying to build a blueprint for deep space exploration."

Road map to refueling

Before getting to the Moon, SpaceX and Blue Origin must master the technologies and techniques required for in-space refueling. Right now, SpaceX is scheduled to attempt the first demonstration of a large-scale propellant transfer between two Starships in orbit next year.

There will be at least several more Starship test flights before then. During the most recent Starship test flight in March , SpaceX conducted a cryogenic propellant transfer test between two tanks inside the vehicle. This tank-to-tank transfer of liquid oxygen was part of a demonstration supported with NASA funding. Agency officials said this demonstration would allow engineers to learn more about how the fluid behaves in a low-gravity environment.

Kshatriya said that while engineers are still analyzing the results of the cryogenic transfer demonstration, the test on the March Starship flight "was successful by all accounts."

"That milestone is behind them," he said Friday. Now, SpaceX will move out with more Starship test flights. The next launch will try to check off a few more capabilities SpaceX didn't demonstrate on the March test flight.

These will include a precise landing of Starship's Super Heavy booster in the Gulf of Mexico, which is necessary before SpaceX tries to land the booster back at its launch pad in Texas. Another objective will likely be the restart of a single Raptor engine on Starship in flight, which SpaceX didn't accomplish on the March flight due to unexpected roll rates on the vehicle as it coasted through space. Achieving an in-orbit engine restart—necessary to guide Starship toward a controlled reentry—is a prerequisite for future launches into a stable higher orbit, where the ship could loiter for hours, days, or weeks to deploy satellites and attempt refueling.

In the long run, SpaceX wants to ramp up the Starship launch cadence to many daily flights from multiple launch sites. To achieve that goal, SpaceX plans to recover and rapidly reuse Starships and Super Heavy boosters, building on expertise from the partially reusable Falcon 9 rocket. Elon Musk, SpaceX's founder and CEO, is keen on reusing ships and boosters as soon as possible . Earlier this month, Musk said he is optimistic SpaceX can recover a Super Heavy booster in Texas later this year and land a Starship back in Texas sometime next year.

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A Remarkable New Thruster Could Achieve Escape Velocity—and Interplanetary Travel

Scientists are on the brink of a propulsion breakthrough.

• Ion thrusters are the most common primary engine powering satellites through orbital maneuvers today.
• But to travel from low-Earth orbit (LEO) to farther orbits—or even the Moon—requires a different kind of ion thruster capable of achieving escape velocity and orbital capture maneuvers.
• Using technology originally developed for NASA’s upcoming lunar space station, the space agency has miniaturized its high-power solar electric tech into an engine that could make more complex satellites and planetary missions possible.

These engines are as old as rocketry itself— Soviet and German rocket leaders first dreamed up their future uses more than a century ago. And today, these electric propulsion systems power the swarms of satellites around Earth that make modern life possible. Unlike chemical rockets that throw out gasses for propulsion, ion engines are powered by individual atoms , which makes them much more fuel efficient and allows satellites to operate for longer.

However, they’re not perfect. In the future, spacecraft will need to perform high-velocity propulsive maneuvers—such as achieving escape velocity and orbital capture—that current ion engines can’t deliver. That’s why NASA developed the H71M sub-kilowatt Hall-effect thruster , a next-generation ion engine that can supply a velocity change.

The propulsion system must operate using low power (sub-kilowatt) and have high-propellant throughput (i.e., the capability to use a high total mass of propellant over its lifetime) to enable the impulse required to execute these maneuvers. While commercial ion thrusters are good enough for most LEO satellites , these engines only use “10% or less of a small spacecraft’s initial mass in propellant,” according to NASA. The H71M thruster uses 30 percent, and could operate for 15,000 hours.

“Small spacecraft using the NASA-H71M electric propulsion technology will be able to independently maneuver from low-Earth orbit (LEO) to the Moon or even from a geosynchronous transfer orbit (GTO) to Mars,” NASA wrote on its website regarding the new ion thruster. “The ability to conduct missions that originate from these near-Earth orbits can greatly increase the cadence and lower the cost of lunar and Mars science missions.”

The creation of this thruster grew from NASA’s work on the Power and Propulsion Element for Gateway , NASA’s planned lunar orbital space station. The team essentially miniaturized the high-power solar electric technologies that will make that lunar mission possible into a package that could provide thrust for smaller space missions.

One of the first spacecraft companies that will use this next-gen technology is SpaceLogistics, a space subsidiary of Northrop Grumman. The company’s NGHT-1X Hall-effect thrusters are based on NASA’s technology, and will allow its Mission Extension Pod (MEP)—which, as its name suggests, is essentially a satellite repair vehicle—to reach geosynchronous Earth orbit, where it’ll attach itself to a larger satellite. Acting as a “propulsion jet pack,” the MEP will act as an ion-powered symbiote that extends the larger satellite’s mission by at least six years.

If all goes well, this small-yet-mighty thruster could enable planetary missions once considered impossible to pull off.

Darren lives in Portland, has a cat, and writes/edits about sci-fi and how our world works. You can find his previous stuff at Gizmodo and Paste if you look hard enough. 

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To the Moon, and Beyond: The Realities of Commercial Space Travel

In 2020, the billionaire space race was in full swing. Richard Branson, Jeff Bezos, and Elon Musk were vying to send everyday astronauts into low orbit for the first time. Each of the billionaires successfully launched at least once, and Bezos and Branson were even passengers aboard their own businesses’ rocket ships. Comercial space travel was reaching new heights, and the momentum appeared unstoppable, at least for a time.

Since then, the aftereffects of the global coronavirus pandemic have had noticeably dampened our outlook on space travel: many are less interested in hearing about Blue Origin’s latest design features, and instead are more concerned with domestic events unfolding here on earth. Among these, the war in Ukraine and, as a byproduct, the recent news that Russia has pulled out of the international space station, would seem to further distance us from the final frontier.

However, in recent days, NASA’s ambitions to land on the moon once again with its Artemis mission have recaptured the public imagination for space travel. Although NASA’s initial SLS rocket test recently failed to launch, a second attempt has now been announced for September 27.

If commercial space travel into Earth’s orbit–or even to the moon and beyond–does eventually become a possibility there will still be significant challenges for individuals looking to buy their ticket to the final frontier. Here are just a few of the kinds of issues we will be looking at in the decades ahead.

Costs and Resources

It’s easy to get swept up in the fervor for space travel and believe that we’ll all be living the Jetson lifestyle by the end of the decade. But space travel still requires massive amounts of money, planning, and resources. Even the ever-optimistic Elon Musk puts the minimum cost of space travel at $10 million per flight.

In an interview, Musk stated that the “cost efficiency of SpaceX is the best in history,” and it is “designed to be fully reusable.” This means that, according to Musk’s quick math, the cost of SpaceX is around 5-10% of the Saturn V project (the last rocket to send humans to the moon).

Musk also revealed that significant planning and administrative approval are needed to send rocket ships into and beyond low orbit. The Federal Aviation Administration will need to review SpaceX’s request for space travel and will account for environmental factors and human interests.

The organization has already caught some flack for causing damage to local ecosystems and displacing residents when SpaceX obtained Boca Chica beach in Texas. As resident Mary McConnaughey explained, “They’re here to stay and they want us to leave.” Dealing with disgruntled locals may seem like a trivial matter compared to the boundless cosmos above our heads. But, failing to work collaboratively with the folks here on earth is a genuine hurdle with which all space travelers must contend.

Global Collaboration on Space Travel

A few years ago, space travel seemed to be a beacon of hope for everyone who wanted to see nations work more on collaborative efforts than divisive ones. However, recent news that Russia has pulled out of the space station project has dampened optimism and thrown a wrench in collaborative plans.

Of course, global collaboration for space travel isn’t completely necessary. Independent governmental organizations and billionaires may thrust us into the future. However, a lack of international collaboration will likely slow the space race down rather than speed it up — as scientists will have to guard space-related secrets rather than work in open transparency.

The International Space Station does look set to wind down post-2024. In the meantime, it continues to prove that collaboration is necessary for the kinds of tests and experiments needed to solve the realities of space travel. Even Russia, which positions itself as a global powerhouse, doesn’t have the means to create a space station of its own.

Former ISS commander, Dr. Leroy Chaio, explains, “They [Russia] don’t have the money to build their own station” and will be left with no access to a space station without the ISS. This will further compound collaborative space travel issues, as the European Space Agency has already ended collaboration with the Russian Roskosmos project.

Things could, theoretically, get worse if collaboration turned into a competition. Space travel could be susceptible to cyber war as Nation State Actors exploit vulnerabilities. Governmental agencies and corporations will have to use AI to detect hackers and malicious activities in real-time. AI-led behavior detection may have to prevent bad actors from gaining access to rocketships and ensure that passengers have a safe living and working environment in space.

Life in Space

When we think of space travel, most people imagine floating through hallways, eating dehydrated dinners, and staring into the void for hours on end. All of these activities underline a less-thought-of reality: life in space would be lonely.

‘Strategic Location’ For Future Base at the Lunar South Pole is Being Rocked by Mysterious Moonquakes, NASA Images Reveal

Almost all astronauts describe their first journey into space as a life-altering experience. However, that doesn’t mean that the folks who live and work beyond the earth’s surface won’t fall foul of burnout. The myth that, in 1972, astronauts at SkyLab went on strike due to ignored requests to lighten their workload has now been proven false. But, the story is an important reminder that burnout is real and can affect us all.

Offering professional social support can prevent loneliness and burnout in space. Social care specialists will be able to help passengers and staff avoid excessive stress and illness by listening to the human issues that folks in space experience. A little pre-planned compassion may go a long way for folks who encounter the enigmatic cosmos for the first time.

Of course, while mental stressors like isolation and confinement might necessitate solutions such as prescribed social time , there are also physical effects that come with living in space — and some of them are downright harmful. Space radiation means suits and structures need sufficient shielding to mitigate cancer risks, while prolonged exposure to low-gravity and weightlessness can lead to muscle and bone density deterioration as well as kidney stones. Fortunately, modern technology helps astronauts monitor and solve these issues with relative ease.

The Path Forward

Significant hurdles still stand in the way of frequent, accessible space travel. As recent world events have shown, costs associated with spaceflight can quickly become an issue, and international politics may stifle progress. If the general public ever reaches space, they’ll need professional social support, and sophisticated software to ensure their travels into the final frontier are managed as safely as possible.

All this taken into consideration, space travel “for the rest of us” is nonetheless slowly becoming a reality — even if that reality is reserved, for now, for billionaire producers of 21st century space technologies, and the similarly wealthy passengers willing to pay the steep prices to tag along. In any case, SpaceX, Blue Origin, and Virgin Galactic have given us hope that many more of us could one day be given an opportunity to take a flight into low orbit, or perhaps even to further distant locales beyond our planet.

Adrian Johansen is a freelance writer whose work focuses on business, tech and marketing. She is especially passionate about issues related to accessibility and sustainability. You can read more of her work at her website .

Types of orbits

Our understanding of orbits dates back to Johannes Kepler in the 17th century. Europe now operates a family of rockets at Europe’s Spaceport to launch satellites to many types of orbit .

What is an orbit?

An orbit is the curved path that an object in space (such as a star, planet, moon, asteroid or spacecraft) takes around another object due to gravity. 

Gravity causes objects in space that have mass to be attracted to other nearby objects. If this attraction brings them together with enough momentum, they can sometimes begin to orbit each other. 

Objects of similar mass orbit each other with neither object at the centre, whilst small objects orbit around larger objects. In our Solar System, the Moon orbits Earth, and Earth orbits the Sun, but that does not mean the larger object remains completely still. Because of gravity, Earth is pulled slightly from its centre by the Moon (which is why tides form in our oceans) and our Sun is pulled slightly from its centre by Earth and other planets. 

During the early creation of our Solar System, dust, gas, and ice travelled through space with speed and momentum, surrounding the Sun in a cloud. With the Sun being so much larger than these small bits of dust and gas, its gravity attracted these bits into orbit around it, shaping the cloud into a kind of ring around the Sun. 

Eventually, these particles started to settle and clump together (or ‘coalesce’), growing ever larger like rolling snowballs until they formed what we now see as planets, moons, and asteroids. The fact that the planets were all formed together this way is why all the planets have orbits around the Sun in the same direction, in roughly the same plane.

When rockets launch our satellites, they put them into orbit in space. There, gravity keeps the satellite on its required orbit – in the same way that gravity keeps the Moon in orbit around Earth.

This happens in a way that is similar to throwing a ball out of the window of a tall tower – to get the ball going, you need to first give it a ‘push’ by throwing it, making the ball fall towards the ground on a curved path. Whilst it is your throw that gives the ball its initial speed, it is gravity alone that keeps the ball moving towards the ground once you let go. 

In a similar fashion, a satellite is put into orbit by being placed hundreds or thousands of kilometres above Earth’s surface (as if in a very tall tower) and then being given a ‘push’ by the rocket’s engines to make it start on its orbit.

As shown in the figure, the difference is that throwing something will make it fall on a curved path towards the ground – but a really powerful throw will mean that the ground starts to curve away before your object reaches the ground. Your object will fall ‘towards’ Earth indefinitely, causing it to circle the planet repeatedly. Congratulations! You have reached orbit.

In space, there is no air and therefore no air friction, so gravity lets the satellite orbit around Earth with almost no further assistance. Putting satellites into orbit enables us to use technologies for telecommunication, navigation, weather forecast, and astronomy observations.

Launch to orbit 

Europe’s family of rockets operate from Europe’s Spaceport in Kourou, French Guiana. On each mission, a rocket places one or more satellites onto their individual orbits.

The choice of which launch vehicle is used depends primarily on the mass of the payload, but also on how far from Earth it needs to go. A heavy payload or a high altitude orbit requires more power to fight Earth’s gravity than a lighter payload at a lower altitude.

Ariane 5 is Europe’s most powerful launch vehicle, capable of lifting one, two, or multiple satellites into their required orbits. Depending on which orbit Ariane 5 is going to, it is able to launch between approximately 10 to 20 tonnes into space – that is 10 000—20 000 kg, which is about the weight of a city bus.

Vega is smaller than Ariane 5, capable of launching roughly 1.5 tonnes at a time, making it an ideal launch vehicle for many scientific and Earth observation missions. Both Ariane 5 and Vega can deploy multiple satellites at a time.

ESA’s next generation of rockets includes Ariane 6  and Vega-C . These rockets will be more flexible and will extend what Europe is capable of getting into orbit, and will be able to deliver payloads to several different orbits in a single flight – like a bus with multiple stops. 

Types of orbit

Upon launch, a satellite or spacecraft is most often placed in one of several particular orbits around Earth – or it might be sent on an interplanetary journey, meaning that it does not orbit Earth anymore, but instead orbits the Sun until its arrival at its final destination, like Mars or Jupiter. 

There are many factors that decide which orbit would be best for a satellite to use, depending on what the satellite is designed to achieve.

• Geostationary orbit (GEO) 
• Low Earth orbit (LEO) 
• Medium Earth orbit (MEO) 

Polar orbit and Sun-synchronous orbit (SSO)

Transfer orbits and geostationary transfer orbit (gto).

• Lagrange points (L-points)

Geostationary orbit (GEO)

Satellites in geostationary orbit (GEO) circle Earth above the equator from west to east following Earth’s rotation – taking 23 hours 56 minutes and 4 seconds – by travelling at exactly the same rate as Earth. This makes satellites in GEO appear to be ‘stationary’ over a fixed position. In order to perfectly match Earth’s rotation, the speed of GEO satellites should be about 3 km per second at an altitude of 35 786 km. This is much farther from Earth’s surface compared to many satellites.

GEO is used by satellites that need to stay constantly above one particular place over Earth, such as telecommunication satellites. This way, an antenna on Earth can be fixed to always stay pointed towards that satellite without moving. It can also be used by weather monitoring satellites, because they can continually observe specific areas to see how weather trends emerge there.

Satellites in GEO cover a large range of Earth so as few as three equally-spaced satellites can provide near global coverage. This is because when a satellite is this far from Earth, it can cover large sections at once. This is akin to being able to see more of a map from a metre away compared with if you were a centimetre from it. So to see all of Earth at once from GEO far fewer satellites are needed than at a lower altitude.

ESA’s European Data Relay System (EDRS) programme has placed satellites in GEO, where they relay information to and from non-GEO satellites and other stations that are otherwise unable to permanently transmit or receive data. This means Europe can always stay connected and online.

Low Earth orbit (LEO)

A low Earth orbit (LEO) is, as the name suggests, an orbit that is relatively close to Earth’s surface. It is normally at an altitude of less than 1000 km but could be as low as 160 km above Earth – which is low compared to other orbits, but still very far above Earth’s surface.

By comparison, most commercial aeroplanes do not fly at altitudes much greater than approximately 14 km, so even the lowest LEO is more than ten times higher than that.

Unlike satellites in GEO that must always orbit along Earth’s equator, LEO satellites do not always have to follow a particular path around Earth in the same way – their plane can be tilted. This means there are more available routes for satellites in LEO, which is one of the reasons why LEO is a very commonly used orbit.

LEO’s close proximity to Earth makes it useful for several reasons. It is the orbit most commonly used for satellite imaging, as being near the surface allows it to take images of higher resolution. It is also the orbit used for the International Space Station (ISS), as it is easier for astronauts to travel to and from it at a shorter distance. Satellites in this orbit travel at a speed of around 7.8 km per second; at this speed, a satellite takes approximately 90 minutes to circle Earth, meaning the ISS travels around Earth about 16 times a day.

However, individual LEO satellites are less useful for tasks such as telecommunication, because they move so fast across the sky and therefore require a lot of effort to track from ground stations.

Instead, communications satellites in LEO often work as part of a large combination or constellation, of multiple satellites to give constant coverage. In order to increase coverage, sometimes constellations like this, consisting of several of the same or similar satellites, are launched together to create a ‘net’ around Earth. This lets them cover large areas of Earth simultaneously by working together.

Ariane 5 carried its heaviest 20-tonne payload, the Automated Transfer Vehicle (ATV) , to the International Space Station located in low Earth orbit.

Medium Earth orbit (MEO)

Medium Earth orbit comprises a wide range of orbits anywhere between LEO and GEO. It is similar to LEO in that it also does not need to take specific paths around Earth, and it is used by a variety of satellites with many different applications.

It is very commonly used by navigation satellites, like the European Galileo system (pictured). Galileo powers navigation communications across Europe, and is used for many types of navigation, from tracking large jumbo jets to getting directions to your smartphone. Galileo uses a constellation of multiple satellites to provide coverage across large parts of the world all at once.

Satellites in polar orbits usually travel past Earth from north to south rather than from west to east, passing roughly over Earth's poles.

Satellites in a polar orbit do not have to pass the North and South Pole precisely; even a deviation within 20 to 30 degrees is still classed as a polar orbit. Polar orbits are a type of low Earth orbit, as they are at low altitudes between 200 to 1000 km.

Sun-synchronous orbit (SSO) is a particular kind of polar orbit. Satellites in SSO, travelling over the polar regions, are synchronous with the Sun. This means they are synchronised to always be in the same ‘fixed’ position relative to the Sun. This means that the satellite always visits the same spot at the same local time – for example, passing the city of Paris every day at noon exactly.

This means that the satellite will always observe a point on the Earth as if constantly at the same time of the day, which serves a number of applications; for example, it means that scientists and those who use the satellite images can compare how somewhere changes over time.

This is because, if you want to monitor an area by taking a series of images of a certain place across many days, weeks, months, or even years, then it would not be very helpful to compare somewhere at midnight and then at midday – you need to take each picture as similarly as the previous picture as possible. Therefore, scientists use image series like these to investigate how weather patterns emerge, to help predict weather or storms; when monitoring emergencies like forest fires or flooding; or to accumulate data on long-term problems like deforestation or rising sea levels.

Often, satellites in SSO are synchronised so that they are in constant dawn or dusk – this is because by constantly riding a sunset or sunrise, they will never have the Sun at an angle where the Earth shadows them. A satellite in a Sun-synchronous orbit would usually be at an altitude of between 600 to 800 km. At 800 km, it will be travelling at a speed of approximately 7.5 km per second.

Transfer orbits are a special kind of orbit used to get from one orbit to another. When satellites are launched from Earth and carried to space with launch vehicles such as Ariane 5, the satellites are not always placed directly on their final orbit. Often, the satellites are instead placed on a transfer orbit: an orbit where, by using relatively little energy from built-in motors, the satellite or spacecraft can move from one orbit to another.

This allows a satellite to reach, for example, a high-altitude orbit like GEO without actually needing the launch vehicle to go all the way to this altitude, which would require more effort – this is like taking a shortcut. Reaching GEO in this way is an example of one of the most common transfer orbits, called the geostationary transfer orbit (GTO).

Orbits have different eccentricities – a measure of how circular (round) or elliptical (squashed) an orbit is. In a perfectly round orbit, the satellite is always at the same distance from the Earth’s surface – but on a highly eccentric orbit, the path looks like an ellipse.

On a highly eccentric orbit like this, the satellite can quickly go from being very far to very near Earth’s surface depending on where the satellite is on the orbit. In transfer orbits, the payload uses engines to go from an orbit of one eccentricity to another, which puts it on track to higher or lower orbits.

After liftoff, a launch vehicle makes its way to space following a path shown by the yellow line, in the figure. At the target destination, the rocket releases the payload which sets it off on an elliptical orbit, following the blue line which sends the payload farther away from Earth. The point farthest away from the Earth on the blue elliptical orbit is called the apogee and the point closest is called the perigee. 

When the payload reaches the apogee at the GEO altitude of 35 786 km, it fires its engines in such a way that it enters onto the circular GEO orbit and stays there, shown by the red line in the diagram. So, specifically, the GTO is the blue path from the yellow orbit to the red orbit.

Lagrange points

For many spacecraft being put in orbit, being too close to Earth can be disruptive to their mission – even at more distant orbits such as GEO.

For example, for space-based observatories and telescopes whose mission is to photograph deep, dark space, being next to Earth is hugely detrimental because Earth naturally emits visible light and infrared radiation that will prevent the telescope from detecting any faint lights like distant galaxies. Photographing dark space with a telescope next to our glowing Earth would be as hopeless as trying to take pictures of stars from Earth in broad daylight.

Lagrange points, or L-points, allow for orbits that are much, much farther away (over a million kilometres) and do not orbit Earth directly. These are specific points far out in space where the gravitational fields of Earth and the Sun combine in such a way that spacecraft that orbit them remain stable and can thus be ‘anchored’ relative to Earth. If a spacecraft was launched to other points in space very distant from Earth, they would naturally fall into an orbit around the Sun, and those spacecraft would soon end up far from Earth, making communication difficult. Instead, spacecraft launched to these special L-points stay fixed, and remain close to Earth with minimal effort without going into a different orbit.

The most used L-points are L1 and L2. These are both four times farther away from Earth than the Moon – 1.5 million km, compared to GEO’s 36 000 km – but that is still only approximately 1% of the distance of Earth from the Sun.

Many ESA observational and science missions were, are, or will enter an orbit about the L-points. For example, the solar telescope SOHO and LISA Pathfinder at the Sun-Earth L1 point; Herschel, Planck, Gaia, Euclid, Plato, Ariel, JWST, and the Athena telescope are or will be at the Sun-Earth L2 point. 

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NASA's groundbreaking new thruster could unlock interplanetary travel

A next-generation thruster developed by NASA may have brought the long awaited advent of interplanetary travel a step closer, harnessing the power of ion engine technology.

The technology is already used to power the satellites circling Earth that enable internet access, GPS, television, and much more.

Ion engines differ from chemical rockets in that they are powered by individual atoms, making them far more fuel efficient and and greatly extending how long satellites can be in operation, according to science and tech outlet Popular Mechanics .

But the spacecraft will need to be capable of feats current ion engines can't achieve, such as reaching escape velocity (to resist the gravitation attraction of planets and other objects).

To address these constraints, NASA has developed a new propulsion system, the NASA-H71M sub-kilowatt Hall-effect thruster, an ion engine designed to allow small spacecraft to achieve the velocity needed for interplanetary trips, and capture orbits.

READ MORE: China launches new lunar mission amid escalating space race with US

Do you want up-to-the-minute news, tantalizing celebrity insights, sports updates, and lifestyle stores delivered straight to your phone? All it takes is a simple click on this link , entering your US phone number, and clicking "continue".

Today's satellites already use hall-effect thrusters, which have proved efficient for collision avoidance manoeuvres as more and more satellites are deployed.

But according to the space agency, the new thruster will extend operational lifetimes allowing more than 15,000 hours of operation.

Most of today's commercial spacecraft lack the capacity move from low Earth orbit to other planets like the moon or Mars, requiring a boost from the launch vehicle.

For many, the implications the new booster will have for humanity's future as a space-faring species will be the most tantalizing.

"Small spacecraft using the NASA-H71M electric propulsion technology will be able to independently maneuver from low- Earth orbit (LEO) to the Moon or even from a geosynchronous transfer orbit (GTO) to Mars," NASA wrote on its website discussing the new thruster.

"The ability to conduct missions that originate from these near- Earth orbits can greatly increase the cadence and lower the cost of lunar and Mars science missions."

China sends 3 new astronauts into orbit as NASA chief declares new space race [REPORT]

Distant planet twice Earth's size may be emitting gas 'only produced by life' [INSIGHT]

Hitchhiking aliens are already traveling between planets, new research suggests [LATEST]

The space agency essentially created a miniature version of the high-power solar electric tech that will enable a lunar mission that could bring the thrust needed to carry out smaller space missions.

SpaceLogistics, a space subsidiary of Northrop Grumman, will be one of the first firms to use this game-changing innovation.

The company aims to use the tech in its Mission Extension Pod, increasing the lifespans of satellites by adjusting their trajectory while in geosynchronous Earth orbit.

The firm's NGHT-1X Hall-effect thruster is based on the NASA-H71M.

It's hoped that if the booster performs well it could represent a giant leap toward planetary missions once thought impossible.

Follow our social media accounts here on http://facebook.com/ExpressUSNews Link and ExpressUSNews Link

April 22, 2024

Low-Earth Orbit Faces a Spiraling Debris Threat

Millions of human-made objects travel at high speeds in low-Earth orbit, polluting space and increasing the chance of collision with satellites and other spacecraft

By Aneli Bongers & José L. Torres

Mark Garlick/Science Photo Library/Getty Images

Space is getting crowded, with junk. Essential satellites delivering navigation, weather forecasts, the Internet and other services face this threat daily. Old rockets, decaying spacecraft and human operations in space leave behind orbital debris that increasingly threatens collisions, menacing a growing space economy. A decade ago the film Gravity dramatized the consequences of space pollution, with an avalanche of space junk sweeping across the sky to batter everything in orbit, including its astronaut hero. We haven’t done anything serious about it since then.

NASA defines space junk, or orbital debris , as “any human-made object in orbit that no longer serves a useful purpose, including spacecraft fragments and retired satellites.” A 2009 incident, when the U.S. communications satellite Iridium 33 collided with the defunct Russian military satellite Kosmos 2251, serves as a good reminder of its growing threat. That single collision created more than 2,200 pieces of new debris measuring over five centimeters in diameters, according to NASA .

More of these collisions are coming. In February an abandoned Russian satellite passed within about 20 meters of a NASA satellite. SpaceX’s Starlink satellite constellation alone carried out more than 25,000 collision-avoidance maneuvers from December 2022 to May 2023. And even on Earth, space junk is a problem, with a Florida home struck in March by a battery that fell from an International Space Station cargo mission.

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In space, debris comes from the frequent breakup of expended rocket bodies , explosion of satellites, dead satellites , collisions , paint flakes and even tools lost by astronauts. Around 85 percent of this debris resides within low-Earth orbit, which is below 2,000 kilometers in altitude. NASA estimates this orbit contains around 34,000 pieces of debris larger than 10 cm in diameter, 900,000 objects between 1 cm and 10 cm, and more than 128 million fragments between 1 mm and 1 cm. But let’s not be fooled by the size. Even small debris traveling at high velocities can trigger catastrophic collisions, with the added problem that fragments smaller than 10 cm are impossible to track with existing surveillance technology . An even more dangerous threat is self-propagation. Called the “ Kessler syndrome ,” this phenomenon occurs when collisions produce so much debris that Earth’s orbit becomes unusable for any human activity.

We must stop the growth of space debris, while realizing it is a demanding task. Neither national governments nor international organizations control property rights on orbit, apart from spacecraft ownership. Therefore, space activities are not subject to any centralized regulation or property rights scheme. In outer space “first come, first serve” instead applies. Like other global economic failures on Earth (such as fisheries in international waters, high seas sailing and climate change ) that international cooperation has failed to solve or left only partly solved, overuse and depletion are direct consequences of such a “ tragedy of the commons .”

In all these cases, including orbital debris, pollution exerts a cost on society where market prices do not capture the impact. Such “ externalities ” are market failures that, in most cases, require intervention from a government or other central authority. Simply put, rocket launch prices don’t reflect their real costs, which include clean-up expenses. We must reverse this situation before the cost becomes too high. Although human exploration and economic exploitation of outer space are relatively recent (the first human-made spacecraft, Sputnik, successfully launched in 1957 ), evident market failures and other economic, legal and political issues are arising at rocket speed as commercial, military and scientific activities in outer space expand. SpaceX is now developing a massive rocket that will launch 1.25-ton satellites like a Pez dispenser , adding to a fleet of 5,500 Starlink satellites already in space, part of a planned constellation of 42,000. That’s particularly alarming, because, according to a study of ours published last year in Ecological Economics , low-Earth orbit can only hold about 72,000 satellites without a real risk of a Kessler syndrome event, under current debris conditions.

LEO stands for low Earth orbit and is the region of space within 2,000 km of the Earth's surface. It is the most concentrated area for orbital debris, represented with white dots and scaled to optimize visibility.

No surprise, spacefaring nations that are most dependent on satellites face the biggest risks of space debris. Instead of cooperating to mitigate space debris, however, they have failed to take decisive action. That’s despite the increasing probability of losing satellites, resulting in more resources that must be dedicated to debris surveillance tracking and collision-avoidance maneuvers that interrupt services and burn fuel. That, in turn, reduces the operational life of satellites, adding to their costs as the threat burgeons. Nonetheless, spacefaring companies have no incentive to minimize debris generation except for protecting their own spacecraft, which they do with shields .

We need to take both passive and active measures before space junk gets out of control. Space agencies and the United Nations have elaborated guidelines for debris mitigation. Some include changing the design of satellites with shields and reinforcing fuel systems to avoid breakups. Another recommends that all spacefarers provide spacecraft with maneuverability and add reserve fuel to de-orbit derelict spacecraft.

On the active measures side , developing debris-free recovery launch vehicles will greatly help to eliminate the primary source of debris. But there are still other sources, and given current orbiting derelict stock, active depolluting actions are also necessary. That’s because the life spans of orbital debris vary depending on altitude. Below 200 kilometers, it may only last a few days, whereas those at 1,000 km can last up to a thousand years. At 2,000 km, the debris can remain in orbit for up to 50,000 years without human intervention.

Cleaning space requires designing and implementing active debris removal (ADR) projects . ADR vehicles can be equipped with robotic arms, nets, collecting balloons and other tools. Earth-based lasers might also increase the atmospheric drag of debris, as another option. Policy makers must explore financing the cost of removal policies with instruments already in place for mitigating pollution on Earth. They should also develop guidelines and regulations to share the space junk removal cost among all spacefaring agents.

Finally, there is also a more alarming problem to pay attention to: the military’s use of space. Space pollution results not only from commercial and scientific activities, but also because of outer space’s growing strategic value for defense, security and warfare. Hard as it is to understand, Earth's orbit has been polluted not only accidentally but also intentionally, as some countries have conducted antisatellite tests using missiles that destroyed their own satellites. The last one, performed by Russia in 2021, created a vast cloud of hundreds of thousands of fragments , dramatically increasing orbital debris at the most congested and polluted altitudes.

The militarization and weaponization of outer space contribute to orbital debris while acting as a roadblock to the de-pollution of space. Development of debris removal vehicles and devices is hindered by their dual-use status as antisatellite weapons, a significant obstacle to implementing international policies for eliminating orbital pollution. Any ADR technology could also be viewed as an offensive weapon, as it could remove enemy satellites from orbit. For the same reason, the militarization of outer space could threaten the development of new in-space industries for the servicing, refueling, upgrading, maintenance and repair of satellites. Humanity instead needs a clean, safe and regulated space environment to build a better world on Earth.

This is an opinion and analysis article, and the views expressed by the author or authors are not necessarily those of Scientific American.

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NASA's groundbreaking new thruster could unlock interplanetary travel

Most of today's commercial spacecraft lack the capacity move from low Earth orbit to other planets like the moon or Mars, requiring a boost from the launch vehicle.

A next-generation thruster developed by NASA may have brought the long awaited advent of interplanetary travel a step closer, harnessing the power of ion engine technology.

The technology is already used to power the satellites circling Earth that enable internet access, GPS, television, and much more.

Ion engines differ from chemical rockets in that they are powered by individual atoms, making them far more fuel efficient and and greatly extending how long satellites can be in operation, according to science and tech outlet Popular Mechanics .

But the spacecraft will need to be capable of feats current ion engines can't achieve, such as reaching escape velocity (to resist the gravitation attraction of planets and other objects).

To address these constraints, NASA has developed a new propulsion system, the NASA-H71M sub-kilowatt Hall-effect thruster, an ion engine designed to allow small spacecraft to achieve the velocity needed for interplanetary trips, and capture orbits.

READ MORE: China launches new lunar mission amid escalating space race with US

Sign up to Daily Express US's SMS updates

Do you want up-to-the-minute news, tantalizing celebrity insights, sports updates, and lifestyle stores delivered straight to your phone? All it takes is a simple click on this link , entering your US phone number, and clicking "continue".

Today's satellites already use hall-effect thrusters, which have proved efficient for collision avoidance manoeuvres as more and more satellites are deployed.

But according to the space agency, the new thruster will extend operational lifetimes allowing more than 15,000 hours of operation.

For many, the implications the new booster will have for humanity's future as a space-faring species will be the most tantalizing.

“Small spacecraft using the NASA-H71M electric propulsion technology will be able to independently maneuver from low- Earth orbit (LEO) to the Moon or even from a geosynchronous transfer orbit (GTO) to Mars,” NASA wrote on its website discussing the new thruster.

“The ability to conduct missions that originate from these near- Earth orbits can greatly increase the cadence and lower the cost of lunar and Mars science missions.”

China sends 3 new astronauts into orbit as NASA chief declares new space race [REPORT]

Distant planet twice Earth's size may be emitting gas 'only produced by life' [INSIGHT]

Hitchhiking aliens are already traveling between planets, new research suggests [LATEST]

The space agency essentially created a miniature version of the high-power solar electric tech that will enable a lunar mission that could bring the thrust needed to carry out smaller space missions.

SpaceLogistics, a space subsidiary of Northrop Grumman, will be one of the first firms to use this game-changing innovation.

The company aims to use the tech in its Mission Extension Pod, increasing the lifespans of satellites by adjusting their trajectory while in geosynchronous Earth orbit.

The firm's NGHT-1X Hall-effect thruster is based on the NASA-H71M.

It's hoped that if the booster performs well it could represent a giant leap toward planetary missions once thought impossible.

Follow our social media accounts here on   http://facebook.com/ExpressUSNews   and   ExpressUSNews

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The Docking Hub (Inner Ring)

Photo by: Gateway Foundation

Gateway Foundation

Comfort will be paramount for both visitors and crew, so artificial gravity is a crucial factor according to Tim Alatorre, one of the space station’s architects. “Microgravity is just brutal on our bodies,” he said. “We need artificial gravity – a mechanism to give us a dosage of gravity to give us the ability to live long-term in space.”

Larger projects will follow Voyager Station, with a spaceport simply called ‘The Gateway’ in planning – not to be confused with NASA’s Lunar Gateway that will orbit the moon as a staging post for landings and space exploration. More than twice the size of the 200m wide Voyager, guest capacity will be 1,250 alongside 150 crew.

Despite the financial risks – a competitor space station called Aurora shut down its operations and refunded all deposits – Alatorre is confident that Voyager is the true genesis for off-world exploration. It will “create a starship culture where people are going to space, and living in space, and working in space," he told CNN. "And we believe that there's a demand for that."

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• EO Explorer

• Global Maps
• Catalog of Earth Satellite Orbits

Just as different seats in a theater provide different perspectives on a performance, different Earth orbits give satellites varying perspectives, each valuable for different reasons. Some seem to hover over a single spot, providing a constant view of one face of the Earth, while others circle the planet, zipping over many different places in a day.

There are essentially three types of Earth orbits: high Earth orbit, medium Earth orbit, and low Earth orbit. Many weather and some communications satellites tend to have a high Earth orbit, farthest away from the surface. Satellites that orbit in a medium (mid) Earth orbit include navigation and specialty satellites, designed to monitor a particular region. Most scientific satellites, including NASA’s Earth Observing System fleet, have a low Earth orbit.

The height of the orbit, or distance between the satellite and Earth’s surface, determines how quickly the satellite moves around the Earth. An Earth-orbiting satellite’s motion is mostly controlled by Earth’s gravity. As satellites get closer to Earth, the pull of gravity gets stronger, and the satellite moves more quickly. NASA’s Aqua satellite, for example, requires about 99 minutes to orbit the Earth at about 705 kilometers up, while a weather satellite about 36,000 kilometers from Earth’s surface takes 23 hours, 56 minutes, and 4 seconds to complete an orbit. At 384,403 kilometers from the center of the Earth, the Moon completes a single orbit in 28 days.

Changing a satellite’s height will also change its orbital speed. This introduces a strange paradox. If a satellite operator wants to increase the satellite’s orbital speed, he can’t simply fire the thrusters to accelerate the satellite. Doing so would boost the orbit (increase the altitude), which would slow the orbital speed. Instead, he must fire the thrusters in a direction opposite to the satellite’s forward motion, an action that on the ground would slow a moving vehicle. This change will push the satellite into a lower orbit, which will increase its forward velocity.

In addition to height, eccentricity and inclination also shape a satellite’s orbit. Eccentricity refers to the shape of the orbit. A satellite with a low eccentricity orbit moves in a near circle around the Earth. An eccentric orbit is elliptical, with the satellite’s distance from Earth changing depending on where it is in its orbit.

Inclination is the angle of the orbit in relation to Earth’s equator. A satellite that orbits directly above the equator has zero inclination. If a satellite orbits from the north pole (geographic, not magnetic) to the south pole, its inclination is 90 degrees.

Together, the satellite’s height, eccentricity, and inclination determine the satellite’s path and what view it will have of Earth.

Three Classes of Orbit

High earth orbit.

When a satellite reaches exactly 42,164 kilometers from the center of the Earth (about 36,000 kilometers from Earth’s surface), it enters a sort of “sweet spot” in which its orbit matches Earth’s rotation. Because the satellite orbits at the same speed that the Earth is turning, the satellite seems to stay in place over a single longitude, though it may drift north to south. This special, high Earth orbit is called geosynchronous.

A satellite in a circular geosynchronous orbit directly over the equator (eccentricity and inclination at zero) will have a geostationary orbit that does not move at all relative to the ground. It is always directly over the same place on the Earth’s surface.

A geostationary orbit is extremely valuable for weather monitoring because satellites in this orbit provide a constant view of the same surface area. When you log into your favorite weather web site and look at the satellite view of your hometown, the image you are seeing comes from a satellite in geostationary orbit. Every few minutes, geostationary satellites like the Geostationary Operational Environmental Satellite (GOES) satellites send information about clouds, water vapor, and wind, and this near-constant stream of information serves as the basis for most weather monitoring and forecasting.

Because geostationary satellites are always over a single location, they can also be useful for communication (phones, television, radio). Built and launched by NASA and operated by the National Oceanic and Atmospheric Administration (NOAA), the GOES satellites provide a search and rescue beacon used to help locate ships and airplanes in distress.

Finally, many high Earth orbiting satellites monitor solar activity. The GOES satellites carry a large contingent of “space weather” instruments that take images of the Sun and track magnetic and radiation levels in space around them.

Other orbital “sweet spots,” just beyond high Earth orbit, are the Lagrange points. At the Lagrange points, the pull of gravity from the Earth cancels out the pull of gravity from the Sun. Anything placed at these points will feel equally pulled toward the Earth and the Sun and will revolve with the Earth around the Sun.

Of the five Lagrange points in the Sun-Earth system, only the last two, called L4 and L5, are stable. A satellite at the other three points is like a ball balanced at the peak of a steep hill: any slight perturbation will push the satellite out of the Lagrange point like the ball rolling down the hill. Satellites at these three points need constant adjustments to stay balanced and in place. Satellites at the last two Lagrange points are more like a ball in a bowl: even if perturbed, they return to the Lagrange point.

The first Lagrange point is located between the Earth and the Sun, giving satellites at this point a constant view of the Sun. The Solar and Heliospheric Observatory (SOHO), a NASA and European Space Agency satellite tasked to monitor the Sun, orbits the first Lagrange point, about 1.5 million kilometers away from Earth.

The second Lagrange point is about the same distance from the Earth, but is located behind the Earth. Earth is always between the second Lagrange point and the Sun. Since the Sun and Earth are in a single line, satellites at this location only need one heat shield to block heat and light from the Sun and Earth. It is a good location for space telescopes, including the future James Webb Space Telescope (Hubble’s successor, scheduled to launch in 2014) and the current Wilkinson Microwave Anisotropy Probe (WMAP), used for studying the nature of the universe by mapping background microwave radiation.

The third Lagrange point is opposite the Earth on the other side of the Sun so that the Sun is always between it and Earth. A satellite in this position would not be able to communicate with Earth. The extremely stable fourth and fifth Lagrange points are in Earth’s orbital path around the Sun, 60 degrees ahead of and behind Earth. The twin Solar Terrestrial Relations Observatory (STEREO) spacecraft will orbit at the fourth and fifth Lagrange points to provide a three-dimensional view of the Sun.

Medium Earth Orbit

Closer to the Earth, satellites in a medium Earth orbit move more quickly. Two medium Earth orbits are notable: the semi-synchronous orbit and the Molniya orbit.

The semi-synchronous orbit is a near-circular orbit (low eccentricity) 26,560 kilometers from the center of the Earth (about 20,200 kilometers above the surface). A satellite at this height takes 12 hours to complete an orbit. As the satellite moves, the Earth rotates underneath it. In 24-hours, the satellite crosses over the same two spots on the equator every day. This orbit is consistent and highly predictable. It is the orbit used by the Global Positioning System (GPS) satellites.

The second common medium Earth orbit is the Molniya orbit. Invented by the Russians, the Molniya orbit works well for observing high latitudes. A geostationary orbit is valuable for the constant view it provides, but satellites in a geostationary orbit are parked over the equator, so they don’t work well for far northern or southern locations, which are always on the edge of view for a geostationary satellite. The Molniya orbit offers a useful alternative.

The Molniya orbit is highly eccentric: the satellite moves in an extreme ellipse with the Earth close to one edge. Because it is accelerated by our planet’s gravity, the satellite moves very quickly when it is close to the Earth. As it moves away, its speed slows, so it spends more time at the top of its orbit farthest from the Earth. A satellite in a Molniya orbit takes 12 hours to complete its orbit, but it spends about two-thirds of that time over one hemisphere. Like a semi-synchronous orbit, a satellite in the Molniya orbit passes over the same path every 24 hours. This type of orbit is useful for communications in the far north or south.

Low Earth Orbit

Most scientific satellites and many weather satellites are in a nearly circular, low Earth orbit. The satellite’s inclination depends on what the satellite was launched to monitor. The Tropical Rainfall Measuring Mission (TRMM) satellite was launched to monitor rainfall in the tropics. Therefore, it has a relatively low inclination (35 degrees), staying near the equator.

Many of the satellites in NASA’s Earth Observing System have a nearly polar orbit. In this highly inclined orbit, the satellite moves around the Earth from pole to pole, taking about 99 minutes to complete an orbit. During one half of the orbit, the satellite views the daytime side of the Earth. At the pole, satellite crosses over to the nighttime side of Earth.

As the satellites orbit, the Earth turns underneath. By the time the satellite crosses back into daylight, it is over the region adjacent to the area seen in its last orbit. In a 24-hour period, polar orbiting satellites will view most of the Earth twice: once in daylight and once in darkness.

Just as the geosynchronous satellites have a sweet spot over the equator that lets them stay over one spot on Earth, the polar-orbiting satellites have a sweet spot that allows them to stay in one time. This orbit is a Sun-synchronous orbit, which means that whenever and wherever the satellite crosses the equator, the local solar time on the ground is always the same. For the Terra satellite for example, it’s always about 10:30 in the morning when the satellite crosses the equator in Brazil. When the satellite comes around the Earth in its next overpass about 99 minutes later, it crosses over the equator in Ecuador or Colombia at about 10:30 local time.

The Sun-synchronous orbit is necessary for science because it keeps the angle of sunlight on the surface of the Earth as consistent as possible, though the angle will change from season to season. This consistency means that scientists can compare images from the same season over several years without worrying too much about extreme changes in shadows and lighting, which can create illusions of change. Without a Sun-synchronous orbit, it would be very difficult to track change over time. It would be impossible to collect the kind of consistent information required to study climate change.

The path that a satellite has to travel to stay in a Sun-synchronous orbit is very narrow. If a satellite is at a height of 100 kilometers, it must have an orbital inclination of 96 degrees to maintain a Sun-synchronous orbit. Any deviation in height or inclination will take the satellite out of a Sun-synchronous orbit. Since the drag of the atmosphere and the tug of gravity from the Sun and Moon alter a satellite’s orbit, it takes regular adjustments to maintain a satellite in a Sun-synchronous orbit.

Achieving and Maintaining Orbit

The amount of energy required to launch a satellite into orbit depends on the location of the launch site and how high and how inclined the orbit is. Satellites in high Earth orbit require the most energy to reach their destination. Satellites in a highly inclined orbit, such as a polar orbit, take more energy than a satellite that circles the Earth over the equator. A satellite with a low inclination can use the Earth’s rotation to help boost it into orbit. The International Space Station orbits at an inclination of 51.6397 degrees to make it easier for the Space Shuttle and Russian rockets to reach it. A polar-orbiting satellite, on the other hand, gets no help from Earth’s momentum, and so requires more energy to reach the same altitude.

Maintaining Orbit

Once a satellite is in orbit, it usually takes some work to keep it there. Since Earth isn’t a perfect sphere, its gravity is stronger in some places compared to others. This unevenness, along with the pull from the Sun, Moon, and Jupiter (the solar system’s most massive planet), will change the inclination of a satellite’s orbit. Throughout their lifetime, GOES satellites have to be moved three or four times to keep them in place. NASA’s low Earth orbit satellites adjust their inclination every year or two to maintain a Sun-synchronous orbit.

Satellites in a low Earth orbit are also pulled out of their orbit by drag from the atmosphere. Though satellites in low Earth orbit travel through the uppermost (thinnest) layers of the atmosphere, air resistance is still strong enough to tug at them, pulling them closer to the Earth. Earth’s gravity then causes the satellites to speed up. Over time, the satellite will eventually burn up as it spirals lower and faster into the atmosphere or it will fall to Earth.

Atmospheric drag is stronger when the Sun is active. Just as the air in a balloon expands and rises when heated, the atmosphere rises and expands when the Sun adds extra energy to it. The thinnest layer of atmosphere rises, and the thicker atmosphere beneath it lifts to take its place. Now, the satellite is moving through this thicker layer of the atmosphere instead of the thin layer it was in when the Sun was less active. Since the satellite moves through denser air at solar maximum, it faces more resistance. When the Sun is quiet, satellites in low Earth orbit have to boost their orbits about four times per year to make up for atmospheric drag. When solar activity is at its greatest, a satellite may have to be maneuvered every 2-3 weeks.

The third reason to move a satellite is to avoid space junk, orbital debris, that may be in its path. On February 11, a communication satellite owned by Iridium, a U.S. company, collided with a non-functioning Russian satellite. Both satellites broke apart, creating a field of debris that contained at least 2,500 pieces. Each piece of debris was added to the database of more than 18,000 manmade objects currently in Earth orbit and tracked by the U.S. Space Surveillance Network.

NASA satellite mission controllers carefully track anything that may enter the path of their satellites. As of May 2009, Earth Observing satellites had been moved three separate times to avoid orbital debris.

The debris field generated by the Iridium collision is of particular concern to the Earth Observing System because the center of the debris field will eventually drift through the EOS satellites’ orbits. The Iridium and Russian satellites were 790 kilometers above the Earth, while EOS satellites orbit at 705 kilometers. Many pieces of debris from this collision were propelled to lower altitudes and are already causing issues at 705 kilometers.

Mission control engineers track orbital debris and other orbiting satellites that could come into the Earth Observing System’s orbit, and they carefully plan avoidance maneuvers as needed. The same team also plans and executes maneuvers to adjust the satellite’s inclination and height. The team evaluates these planned maneuvers to ensure that they do not bring the EOS satellites into close proximity to catalogued orbital debris or other satellites. To peek in on a day in the mission control center during one such maneuver, see the related article Flying Steady: Mission Control Tunes Up Aqua’s Orbit.

• J-Track 3-D
• Eyes on the Earth 3D
• Air University. (2003, August). Orbital Mechanics. Space Primer. Accessed May 22, 2009.
• Blitzer, L. (1971, August). Satellite orbit paradox: A general view. American Journal of Physics. 39, 882-886.
• Cornish, N. J. (2008). The Lagrange Points. Wilkinson Microwave Anisotropy Probe (WMAP), National Aeronautics and Space Administration. Accessed June 4, 2009.
• European Space Agency. (2009, February 12). What are Lagrange Points? Accessed June 4, 2009.
• Gleick, J. (2003). Isaac Newton. New York: Vintage Books.
• Hawking, S. (2004). The Illustrated on the Shoulders of Giants. Philadelphia: Running Press.
• Iannotta, B. and Malik, T. (2009, February 11). U.S. satellite destroyed in space collision. Accessed May 22, 2009.
• The James Webb Space Telescope. About JWST’s Orbit. National Aeronautics and Space Administration. Accessed June 4, 2009.
• Komoma GPS Satellite Orbits. Accessed May 22, 2009.
• Pisacane. V. (2005). Fundamentals of Space Systems, p. 568. New York: Oxford University Press US. [ Online ]. Accessed September 4, 2009.
• Solar and Heliospheric Observatory. (2006). SOHO’s Orbit. National Aeronautics and Space Administration and European Space Agency. Accessed June 4, 2009.
• About Orbits
• Planetary Motion
• Flying Steady

Remote Sensing

Orbits and Kepler’s Laws

Kepler's Laws of Planetary Motion

The story of how we understand planetary motion could not be told if it were not for the work of a German mathematician named Johannes Kepler. 

Kepler's three laws describe how planets orbit the Sun. They describe how (1) planets move in elliptical orbits with the Sun as a focus, (2) a planet covers the same area of space in the same amount of time no matter where it is in its orbit, and (3) a planet’s orbital period is proportional to the size of its orbit.

Who Was Johannes Kepler?

Johannes Kepler was born on Dec. 27, 1571, in Weil der Stadt, Württemberg, which is now in the German state of Baden-Württemberg.

As a rather frail young man, the exceptionally talented Kepler turned to mathematics and the study of the heavens early on. When he was six, his mother pointed out a comet visible in the night sky. When Kepler was nine, his father took him out one night under the stars to observe a lunar eclipse. These events both made a vivid impression on Kepler's youthful mind and turned him toward a life dedicated to astronomy.

Kepler lived and worked in Graz, Austria, during the tumultuous early 17th century. Due to religious and political difficulties common during that era, Kepler was banished from Graz on Aug. 2, 1600. 

Fortunately, he found work as an assistant to the famous Danish astronomer Tycho Brahe (usually referred to by his first name) in Prague. Kepler moved his family from Graz, 300 miles (480 kilometers) across the Danube River to Tycho's home.

Kepler and the Mars Problem

Tycho was a brilliant astronomer. He is credited with making the most accurate astronomical observations of his time, which he accomplished without the aid of a telescope. He had been impressed with Kepler’s studies in an earlier meeting. 

However, some historians think Tycho mistrusted Kepler, fearing that his bright young intern might eclipse him as the premier astronomer of his day. Because of this, he only let Kepler see part of his voluminous collection of planetary data.

Tycho assigned Kepler the task of understanding the orbit of the planet Mars. The movement of Mars was problematic – it didn’t quite fit the models as described by Greek philosopher and scientist Aristotle (384 to 322 B.C.E.) and Egyptian astronomer Claudius Ptolemy (about 100 C.E to 170 C.E.). Aristotle thought Earth was the center of the universe, and that the Sun, Moon, planets, and stars revolved around it. Ptolemy developed this concept into a standardized,  geocentric model (now known as the Ptolemaic system) based around Earth as a stationary object, at the center of the universe.

Historians think that part of Tycho’s motivation for giving the Mars problem to Kepler was Tycho's hope that it would keep Kepler occupied while Tycho worked to perfect his own theory of the solar system. That theory was based on a geocentric model, modified from Ptolemy's, in which the planets Mercury, Venus, Mars, Jupiter, and Saturn all orbit the Sun, which in turn orbits Earth. 

As it turned out, Kepler, unlike Tycho, believed firmly in a model of the solar system known as the heliocentric model, which correctly placed the Sun at its center. This is also known as the Copernican system, because it was developed by astronomer Nicolaus Copernicus (1473-1543). But the reason Mars' orbit was problematic was because the Copernican system incorrectly assumed the orbits of the planets to be circular.

Like many philosophers of his era, Kepler had a mystical belief that the circle was the universe’s perfect shape, so he also thought the planets’ orbits must be circular. For many years, he struggled to make Tycho’s observations of the motions of Mars match up with a circular orbit.

Kepler eventually realized that the orbits of the planets are not perfect circles. His brilliant insight was that planets move in elongated, or flattened, circles called ellipses. 

The particular difficulties Tycho had with the movement of Mars were due to the fact that its orbit was the most elliptical of the planets for which he had extensive data. Thus, in a twist of irony, Tycho unwittingly gave Kepler the very part of his data that would enable his assistant to formulate the correct theory of the solar system.

Basic Properties of Ellipses

Since the orbits of the planets are ellipses, it might be helpful to review three basic properties of an ellipse:

• An ellipse is defined by two points, each called a focus, and together called foci. The sum of the distances to the foci from any point on the ellipse is always a constant. 
• The amount of flattening of the ellipse is called the eccentricity. The flatter the ellipse, the more eccentric it is. Each ellipse has an eccentricity with a value between zero (a circle), and one (essentially a flat line, technically called a parabola).
• The longest axis of the ellipse is called the major axis, while the shortest axis is called the minor axis. Half of the major axis is termed a semi-major axis. 

After determining that the orbits of the planets are elliptical, Kepler formulated three laws of planetary motion, which accurately described the motion of comets as well.

Kepler's Laws

In 1609 Kepler published “Astronomia Nova,” which explained what are now called Kepler's first two laws of planetary motion. Kepler had noticed that an imaginary line drawn from a planet to the Sun swept out an equal area of space in equal times, regardless of where the planet was in its orbit. If you draw a triangle from the Sun to a planet’s position at one point in time and its position at a fixed time later, the area of that triangle is always the same, anywhere in the orbit. 

For all these triangles to have the same area, the planet must move more quickly when it’s near the Sun, but more slowly when it is farther from the Sun. This discovery became Kepler’s second law of orbital motion, and led to the realization of what became Kepler’s first law: that the planets move in an ellipse with the Sun at one focus point, offset from the center. 

In 1619, Kepler published “Harmonices Mundi,” in which he describes his "third law." The third law shows that there is a precise mathematical relationship between a planet’s distance from the Sun and the amount of time it takes revolve around the Sun.

Here are Kepler’s Three Laws:

Kepler's First Law : Each planet's orbit about the Sun is an ellipse. The Sun's center is always located at one focus of the ellipse. The planet follows the ellipse in its orbit, meaning that the planet-to-Sun distance is constantly changing as the planet goes around its orbit.

Kepler's Second Law: The imaginary line joining a planet and the Sun sweeps out – or covers – equal areas of space during equal time intervals as the planet orbits. Basically, the planets do not move with constant speed along their orbits. Instead, their speed varies so that the line joining the centers of the Sun and the planet covers an equal area in equal amounts of time. The point of nearest approach of the planet to the Sun is called perihelion. The point of greatest separation is aphelion, hence by Kepler's second law, a planet is moving fastest when it is at perihelion and slowest at aphelion.

Kepler's Third Law: The orbital period of a planet, squared, is directly proportional to the semi-major axes of its orbit, cubed. This is written in equation form as p 2 =a 3 . Kepler's third law implies that the period for a planet to orbit the Sun increases rapidly with the radius of its orbit. Mercury, the innermost planet, takes only 88 days to orbit the Sun. Earth takes 365 days, while distant Saturn requires 10,759 days to do the same.  

How We Use Kepler’s Laws Today

Kepler didn’t know about gravity, which is responsible for holding the planets in their orbits around the Sun, when he came up with his three laws. But Kepler’s laws were instrumental in Isaac Newton’s development of his theory of universal gravitation, which explained the unknown force behind Kepler's third law. Kepler and his theories were crucial in the understanding of solar system dynamics and as a springboard to newer theories that more accurately approximate planetary orbits. However, his third law only applies to objects in our own solar system. 

Newton’s version of Kepler’s third law allows us to calculate the masses of any two objects in space if we know the distance between them and how long they take to orbit each other (their orbital period). What Newton realized was that the orbits of objects in space depend on their masses, which led him to discover gravity.

Newton’s generalized version of Kepler’s third law is the basis of most measurements we can make of the masses of distant objects in space today. These applications include determining the masses of moons orbiting the planets, stars that orbit each other, the masses of black holes (using nearby stars affected by their gravity), the masses of exoplanets (planets orbiting stars other than our Sun), and the existence of mysterious dark matter in our galaxy and others.

In planning trajectories (or flight plans) for spacecraft, and in making measurements of the masses of the moons and planets, modern scientists often go a step beyond Newton. They account for factors related to Albert Einstein’s theory of relativity, which is necessary to achieve the precision required by modern science measurements and spaceflight. 

However, Newton’s laws are still accurate enough for many applications, and Kepler’s laws remain an excellent guide for understanding how the planets move in our solar system.

Johannes Kepler died Nov. 15, 1630, at age 58. NASA's Kepler space telescope was named for him. The spacecraft launched March 6, 2009, and spent nine years searching for Earth-like planets orbiting other stars in our region of the Milky Way. The Kepler space telescope left a legacy of more than 2,600 planet discoveries from outside our solar system, many of which could be promising places for life.

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The Great Observatory for Long Wavelengths (GO-LoW) proposal

by Mary Knapp, NASA

Humankind has never before seen the low frequency radio sky. It is hidden from ground-based telescopes by the Earth's ionosphere and challenging to access from space with traditional missions because the long wavelengths involved (meter- to kilometer-scale) require infeasibly massive telescopes to see clearly.

Electromagnetic radiation at these low frequencies carries crucial information about exoplanetary and stellar magnetic fields (a key ingredient to habitability), the interstellar/intergalactic medium, and the earliest stars and galaxies.

The Great Observatory for Long Wavelengths (GO-LoW) proposes an interferometric array of thousands of identical SmallSats at an Earth-Sun Lagrange point (e.g., L5) to measure the magnetic fields of terrestrial exoplanets via detections of their radio emissions at frequencies between 100 kHz and 15 MHz. Each spacecraft will carry an innovative Vector Sensor Antenna, which will enable the first survey of exoplanetary magnetic fields within 5 parsecs.

In a departure from the traditional approach of a single large and expensive spacecraft (i.e., HST, Chandra, JWST) with many single points of failure, we propose an interferometric Great Observatory comprised of thousands of small, cheap, and easily-replaceable nodes.

Interferometry, a technique that combines signals from many spatially separated receivers to form a large "virtual" telescope, is ideally suited to long wavelength astronomy. The individual antenna/receiver systems are simple, no large structures are required, and the very large spacing between nodes provides high spatial resolution.

In our Phase I study, we found that a hybrid constellation architecture was most efficient. Small and simple "listener" nodes (LNs) collect raw radio data using a deployable vector sensor antenna. A small number of larger, more capable "communication and computation" nodes (CCNs) collect data from LNs via a local radio network, perform beamforming processing to reduce the data volume, and then transmit the data to Earth via free space optics (lasercomm).

Cross correlation of the beamformed data is performed on Earth, where computational resources are not tightly constrained. The CCNs are also responsible for constellation management, including timing distribution and ranging. The Phase I study also showed that the LN-CCN architecture optimizes packing efficiency, allowing a small number of super-heavy lift launch vehicles (e.g., Starship) to deploy the entire constellation to L4.

The Phase I study showed that the key innovation for GO-LoW is the "system of systems." The technology needed for each individual piece of the observatory (e.g., lasercomm, CubeSats, ranging, timing, data transfer , data processing, orbit propagation) is not a big leap from current state of the art, but the coordination of all these physical elements, data products, and communications systems is novel and challenging, especially at scale.

In the proposed study, we will

• Develop a real-time , multi-agent simulation of the GO-LoW constellation that demonstrates the autonomous operations architecture required to achieve a large (up to 100k) constellation outside of Earth's orbit
• Continue to refine the science case and requirements by simulating science output from the constellation and assessing major error sources informed by the real-time simulation
• Develop appropriate orbital modeling to assess propulsion requirements for stationkeeping at a stable Lagrange point
• Further refine the technology roadmap required to make GO-LoW feasible in the next 10–20 years.

GO-LoW represents a disruptive new paradigm for space missions. It achieves reliability through massive redundancy rather than extensive testing. It can evolve and grow with new technology rather than being bound to a fixed point in hardware/software development.

Finally, it promises to open a new spectral window on the universe where unforeseen discoveries surely await.

Provided by NASA

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A unique halo orbit is the road less traveled around the Moon.

As NASA prepares for humanity’s long-term return to the lunar surface through the Artemis missions , the agency is introducing novel concepts – backed up by science and decades of experience in human spaceflight – to blaze new trails on and around the Moon.

An international collaboration, Gateway is a human-tended, small station that will orbit the Moon. The lunar outpost is specially designed to enable deep space exploration with many capabilities for maintaining a sustained presence in space and conducting research in a deep space environment. Features like a human habitat, multiple docking ports for a variety of spacecraft, including Orion , and the ability to host experiments that will study space weather will all help contribute to future exploration efforts. Similarly, Gateway’s unique near-rectilinear halo orbit, or NRHO, was specifically chosen to help ensure the success of future Artemis missions.

There is no shortage of options for how a spacecraft could orbit the Moon, but two in particular – low lunar orbit and distant retrograde orbit – are helpful for understanding why NRHO is the right fit for Gateway.

A spacecraft in low lunar orbit follows a circular or elliptical path very close to the lunar surface, completing an orbit every two hours. Transit between Gateway and the lunar surface would be quite simple in a low lunar orbit given their proximity, but because of the Moon’s gravity, more propellant is required to maintain the orbit. Therefore, low lunar orbit is not very efficient for Gateway’s planned long-term presence at the Moon – at least 15 years.

Meanwhile, a distant retrograde orbit provides a large, circular, and stable (or more fuel-efficient) orbit that circles the Moon every two weeks. However, what Gateway would gain in a stable orbit, it would lose in easy access to the Moon: the distant orbit would make it harder to get to the lunar surface.

A third option, NRHO, is just right for Gateway, marrying the upsides of low lunar orbit (surface access) with the benefits of distant retrograde orbit (fuel efficiency). Hanging almost like a necklace from the Moon, NRHO is a one-week orbit that is balanced between the Earth’s and Moon’s gravity. This orbit will periodically bring Gateway close enough to the lunar surface to provide simple access to the Moon’s South Pole where astronauts will test capabilities for living on other planetary bodies, including Mars. NRHO can also provide astronauts and their spacecraft with access to other landing sites around the Moon in addition to the South Pole.

The benefits of NRHO don’t end with surface access and fuel efficiency. NRHO will allow scientists to take advantage of the deep space environment for a new era of radiation experiments that will inspire a greater understanding of potential impacts of space weather on people and instruments. NRHO will also give Gateway a continuous line of sight, or “view”, of Earth, translating to uninterrupted communication between Earth and the Moon.

NASA is preparing to launch the Cislunar Autonomous Positioning System Technology Operations and Navigation Experiment, or CAPSTONE mission , that will use a 55-pound cube satellite to gather data on the characteristics of NRHO ahead of Gateway’s expected launch in late 2024.

Check out this infographic to learn more about NRHO and what it looks like:

For more on Gateway, visit www.nasa.gov/gateway

For more on Artemis, visit www.nasa.gov/specials/artemis/