What is the X-37 for?

[Nibb31]

Reading between the lines a bit, I think it's a satellite killer

- No need to bring back a satellite killer. You'd be better off with something like MiTEx

possibly able to capture a satellite and return it to Earth for analysis.

- Too small.

- Capture of an uncooperative ennemy asset is impractical.

Possibly a small high-class orbiter I mean sure the cargo bay is that small but that could fit one or two EVA suits. I am sure a rich person wouldn't mind paying a sum of money to go to space.

- Too small for 2 EVA suits. You could probably fit one empty.

- Not enough supplies to loiter in orbit for over a year as it currently does.

A Traditional spy sat has one major drawback, once it is in place it is relatively fixed in orbit. An enemy can track it, and just pack up and wait while it passes overhead. The X37 however is mobile enough that astronomers that were tracking it after launch lost it when it dramatically adjusted orbit, something a normal spy satellite could not do. So it's purpose is to get the same imaging of a spy satellite anywhere, anytime, with no warning.

- No reason to bring back a spy sat.

- Too small for advanced optics.

- Cheaper to build a permanent spy sat with more fuel.

- If you can build one small enough to fit inside the cargo bay of an X-37, you could send up swarms of disposable ones in a single launch.

The payload bay is only 2x1 meters, so whatever it's carrying is small and probably light. It's must also be super valuable and delicate if they need to waste 5 tons of precious Atlas V payload just for hardware to bring it back.

Edited March 4, 2014 by Nibb31

[Rakaydos]

Airforce gets the big money nasa doesnt, but can only spend it on "defence related activities."

So if they need to test their classified spysat tech and the like, instead of waiting for nasa's next launch and letting all and sundry see the payload on the way up, they have their own private launch platform, one that can stay in space for YEARS doing operational tests, then return the payload to the engineers for analysis.

[jwenting]

See the big X in front of the number? That means eXperimantal.

Meaning it's NOT intended to be some super secret space weapon or next generation shuttle but a test vehicle.

Giving it a payload bay like that makes swapping out equipment packages between flights a lot easier, that's all.

And if you can open the doors in space, you could even use it to run experiments that need to be exposed to hard vacuum or need to have unobstructed view of say the sun.

[Kryten]

See the big X in front of the number? That means eXperimantal.

Meaning it's NOT intended to be some super secret space weapon or next generation shuttle but a test vehicle.

Really? Like the X-32 and X-35 'test vehicles'? They've also had the X-11 and X-12, which were prototype Atlas missiles, and the X-20, which was explicitly intended to be an operational vehicle.

[SargeRho]

Yes. The X-35 was also a prototype for the F-35. Same for the YF-22.

[Skyrunner27]

Could it possibly change orbits of already found sats. Also it could do the whole manless secret repair tool.

[Rocketscience101]

The air force is going to do what the air force does in space. Its not manned it's just designed to save money, by using the old idea of the re-usable space plane to launch satellites. These can be communication satellites spy satellites, and satellite recovery.

[TheBedla]

Originally that came from a forum post. Googling that phrase gives me...the same forum post and some stuff about pipes. Digging a bit deeper, this document gives a centre-of-gravity range for the finished vehicle of 2.5% body length, which comes out to about 30 inches, so it seems to be about right.

That's very interesting. So bringing foreign assets is probably not feasible.

See the big X in front of the number? That means eXperimantal.

Meaning it's NOT intended to be some super secret space weapon or next generation shuttle but a test vehicle.

Giving it a payload bay like that makes swapping out equipment packages between flights a lot easier, that's all.

And if you can open the doors in space, you could even use it to run experiments that need to be exposed to hard vacuum or need to have unobstructed view of say the sun.

It obviously is a test vehicle, but testing for what? X-35 was a test vehicle as well, but its purpose was to test next-gen fighter capabilities. I could rephrase the question slightly to "what is the purpose of the final vehicle that comes from the X-40/X-37 programme?", but that would be quite cumbersome. I also realize that the final version will be larger, and transporting astronauts will be part of its mission.

If it were a purely experimental vehicle, I doubt its missions would be run by the USAF and be classified, don't you think?

[Nibb31]

Its not manned it's just designed to save money, by using the old idea of the re-usable space plane to launch satellites.

That would make it the world's most expensive payload shroud. How does it save money to launch 200 Kg satellites on an Atlas V ?

[Kryten]

I also realize that the final version will be larger, and transporting astronauts will be part of its mission.

Extremely unlikely. Boeing's scaled-up crewed X-37 concept (X-37C) received effectively no interest and was cancelled, and they're highly unlikely to restart it now they've got CST-100 well into development.

[Nibb31]

And again, for crew launches, what's the point of launching a small reusable spaceplane on a large expendable rocket instead of launching a small reusable capsule on a medium expendable rocket?

[Lexif]

Another use would be for orbital manufacturing of some very valuable high-tech materials. For example, it could be used to grow new cristals in microgravity for later use in weapon or observation systems.

I think this is the most likely use for the X-37, it's basically the only thing that can't be done by other systems cheaper or better. I would have guessed it's just a scaled-down test vehicle, but it seems to me they are using it for something, or why would the leave it up there for so long? I'm very curious what it is they are manufacturing or testing, I hope we will find out some day.

Unless, of course, they are just toying around with it because they have a lot of money to burn that they can't direct back into non-secret projects.

[NASAFanboy]

The X-37 will likely NOT evolve to have manne capabilities, due to the fact that Boeing is well into the CST-100 stage, and the CST-100 has capabilities that far exceed that of the X-37 (Such as capability to host a crew of seven, X-37c could host crew of three at most, and the CST-100 relies on a cheaper carrier rocket than the X-37c). The X-37 is likely nto carrying rod-of-gods, and is likely not carrying anything else of any sort..however, DARPA is working on the SR-72 and an satellite launcher spaceplane.

The most likely use for the X-37, like Nibb said, is for testing software, for performing experiments with potiental for military use, and exposing small-scale equipment to space conditions. That would explain the orbital manuveurs and its behavior over the past year.

[Rakaydos]

If it were a purely experimental vehicle, I doubt its missions would be run by the USAF and be classified, don't you think?

From this statement, I make the assumption that you've never worked with a goverment agency.

[visiontranstech]

X37 operated for a orbital spaceflight mission intended to demonstrate reusable space technologies.

[Idobox]

The whole point of having a space-plane rather than a capsule is cross range capacity. You don't need that for exposing stuff to space or low-g manufacturing.

This thing is built to be able to go on pretty much any orbit you can think of, deorbit and land on a US base. Interfering with enemy satellites is one of the few missions that require this cross range capacity. I imagine they could use it to observe and tamper spy satellites rather than blow them up. If the satellite in question is illegal (for example if it's weaponized), or the owner doesn't detect the tampering, they will not raise a fuss.

They could also use it as a way to deliver something very quickly anywhere in the world. I'm thinking of very specific equipment that you want to keep secret, or deem to expansive or dangerous to keep on many ships just in case. It could also be something that would useful to a secret, behind-the-lines commando that's too large to be easily smuggled (an airdrop from a plane still looks an easier and cheaper way to do that without being detected).

I'm thinking of things the US isn't supposed to have, like biological weapons, neutron bombs, a working anti-missile laser. Something they might want to be available by one their fleets in case of WW3, but don't feel carrying around on every aircraft carrier.

[Nibb31]

The whole point of having a space-plane rather than a capsule is cross range capacity. You don't need that for exposing stuff to space or low-g manufacturing.

A spaceplane also provides a gentler re-entry and landing, which is pretty important for anything delicate enough that it needs to be manufacturing in microgravity.

This thing is built to be able to go on pretty much any orbit you can think of, deorbit and land on a US base. Interfering with enemy satellites is one of the few missions that require this cross range capacity. I imagine they could use it to observe and tamper spy satellites rather than blow them up.

Why would you need cross-range to interfere with hostile sats ? Why would you even need to re-enter for that matter ?

You're not going to takes parts off of an enemy sat or capture it because:

- The other party would take that as a casus-belli and you risk retaliation on your own sats.

- You have to assume that any military sat is equipped with some sort of anti-tamper system that would incapacitate your own spacecraft.

- Why go through so much hassle? If you want to disable it, there are easier ways. If you want intelligence, just take pictures.

They could also use it as a way to deliver something very quickly anywhere in the world. I'm thinking of very specific equipment that you want to keep secret, or deem to expansive or dangerous to keep on many ships just in case.

Fedex is cheaper. At any rate, most military and diplomatic services have their own courier services and transportation methods. Going all the way to orbit just to deliver a 200 Kg parcel makes no sense at all.

And there is nothing "quick" about integrating and launching an Atlas V payload. It takes literally months to prepare a launch from Vandenberg.

It could also be something that would useful to a secret, behind-the-lines commando that's too large to be easily smuggled (an airdrop from a plane still looks an easier and cheaper way to do that without being detected).

Again, there is nothing stealthy about a straight-line orbital re-entry and landing. It's highly visible from hundreds of kilometers away, and an easy hot target. The launch, orbital maouvers, and re-entry of the X-37 are easily tracked by amateurs with telescopes all over the world.

I'm thinking of things the US isn't supposed to have, like biological weapons, neutron bombs, a working anti-missile laser. Something they might want to be available by one their fleets in case of WW3, but don't feel carrying around on every aircraft carrier.

They'd be better off delivering them with a nuclear submarine, an unmarked van or a go-fast speedboat... Launching them to orbit is too risky and too obvious.

Edited March 6, 2014 by Nibb31

[Idobox]

A spaceplane also provides a gentler re-entry and landing, which is pretty important for anything delicate enough that it needs to be manufacturing in microgravity.

Is there really a big difference during re-entry?

If you use shock absorbers, and retrorockets, you can get a very smooth landing for less mass.

Why would you need cross-range to interfere with hostile sats ? Why would you even need to re-enter for that matter ?

You're not going to takes parts off of an enemy sat or capture it because:

- The other party would take that as a casus-belli and you risk retaliation on your own sats.

- You have to assume that any military sat is equipped with some sort of anti-tamper system that would incapacitate your own spacecraft.

- Why go through so much hassle? If you want to disable it, there are easier ways. If you want intelligence, just take pictures.

Let's say you want to interfere with a Russian military communication satellite in a Molniya orbit, for example to feed fake information. The thing is going to have counter-measures and various protections, so you will need some pretty high-tech stuff up there, maybe even human operators, so you want to retrieve them. But re-entry from a Molniya orbit would happen very far from US soil, so you need either a lot of deltaV to change your orbit, or a way to come back home when you re-enter in the middle of nowhere.

There are easier ways to incapacitate a satellite, sure. The most obvious would be to mechanically destroy it, but it's very visible. You can also try to blind it or destroy its power source, but I have no idea what you could do to discretely damage a RTG powered telecom satellite.

Fedex is cheaper. At any rate, most military and diplomatic services have their own courier services and transportation methods. Going all the way to orbit just to deliver a 200 Kg parcel makes no sense at all.

And there is nothing "quick" about integrating and launching an Atlas V payload. It takes literally months to prepare a launch from Vandenberg.

They'd be better off delivering them with a nuclear submarine, an unmarked van or a go-fast speedboat... Launching them to orbit is too risky and too obvious.

The idea would be to keep the cargo up there for months or years. When you need it, it can be delivered in less than an hour anywhere on the planet. Nothing can beat that.

Now, it would be very expensive, and everybody could see the delivery, so there aren't a lot of cases where an ICBM or more classical delivery couldn't do the job. Because the main advantage of the system is speed, it would be scenarios where reaction time is crucial.

For example, the best way to stop ICBMs is to detonate the biggest bomb you have as close as possible during the ascent phase. But you have minutes to react, and ICBM would take hours to get there, and the launch facility is likely to be in a place your planes can't reach quickly and easily, or in the case of a submarine, unknown.

So, once you have detected a launch, how do you deliver your bomb?

The only solution is to have a few of them lying in orbit, so that you can deorbit the first one that enters the window. And if you put wings on your bomb, you can steer it, which means you need much less to cover all possible targets. And if you're going to detonate a H-bomb to stop a nuclear attack, discretion is not an issue.

Talking about that, I had another idea.

Imagine the USAF really wants a suborbital troop transport, and also need to do some experiments in orbit. If you have two projects, it will be pretty obvious what their goals are. But a bigger X-37 could do both, and because it's highly over-engineered for these two tasks, it would confuse people about its mission.

The simple fact we're talking and wondering what such a craft could be used for, and the fact nobody else is working on a similar concept are proof that its mission isn't clear. Sure, military analysts probably have more information and competences to figure it out, and that would be a very expensive deception, but we're talking of the US military, they have an history with this kind of things.

[Lexif]

Is there really a big difference during re-entry?

If you use shock absorbers, and retrorockets, you can get a very smooth landing for less mass.

If we are talking about sustained g-forces, shock absorbers are useless.

You can also try to blind it or destroy its power source, but I have no idea what you could do to discretely damage a RTG powered telecom satellite.

You can try everything that's indistinguishable from a micro meteorit impact or maybe a collision with space debris. But the problem is that everyone will see that you maneuvered your vehicle to get close to the target. If there's a way to get it done without being detected, then you can just use a simple, high-dv satellite with something very similar to a shotgun instead of an X-37. And if you don't care if they detect you (WW III just broke out), you just do the same.

For example, the best way to stop ICBMs is to detonate the biggest bomb you have as close as possible during the ascent phase. But you have minutes to react, and ICBM would take hours to get there, and the launch facility is likely to be in a place your planes can't reach quickly and easily, or in the case of a submarine, unknown.

So, once you have detected a launch, how do you deliver your bomb?

I think deorbiting an X-37 somewhere specific on short notice still takes too long for the scenario you describe. There's no way you can deliver anything from a specific orbit to some random place on earth in less then an hour. Also, again, why spaceplane? To nuke something, wouldn't we just use the reentry vehicles we have? Those are certainly precise enough.

[SargeRho]

If you want to wreck a LEO sattelite, park an AEGIS cruiser in the middle of the Pacific and fire an ASAT missile at it. Or use a laser. So that's probably not it. My guess is still that it's simply a development prototype, with no purpose other than testing technology. That is, the X-37B. I can't say anything on the X-37C or possible successors.

[Nibb31]

Is there really a big difference during re-entry?

If you use shock absorbers, and retrorockets, you can get a very smooth landing for less mass.

Shock absorbers do nothing against high Gs.

Let's say you want to interfere with a Russian military communication satellite in a Molniya orbit, for example to feed fake information. The thing is going to have counter-measures and various protections, so you will need some pretty high-tech stuff up there, maybe even human operators, so you want to retrieve them. But re-entry from a Molniya orbit would happen very far from US soil, so you need either a lot of deltaV to change your orbit, or a way to come back home when you re-enter in the middle of nowhere.

There are easier ways to incapacitate a satellite, sure. The most obvious would be to mechanically destroy it, but it's very visible. You can also try to blind it or destroy its power source, but I have no idea what you could do to discretely damage a RTG powered telecom satellite.

X-37 can't reach a Molniya orbit without everyone noticing. Plus, it would take days or weeks to reach it, which would give the Russians ample time to shoot down every US bird from the sky. And I don't think the X-37 has that much delta-V.

To incapacitate a sat, all you need to do is spray it with black paint or a goo-like substance. That will mess with the optics and comms and will make it overheat and die.

But you specifically don't want a reusable vehicle for that. A small minisat with a spray can is enough. The smaller the better actually, because it would be undetectable.

The idea would be to keep the cargo up there for months or years. When you need it, it can be delivered in less than an hour anywhere on the planet. Nothing can beat that.

Now, it would be very expensive, and everybody could see the delivery, so there aren't a lot of cases where an ICBM or more classical delivery couldn't do the job. Because the main advantage of the system is speed, it would be scenarios where reaction time is crucial.

That would be rather convoluted way of sending a package to troops on the ground. It has far too many limitations:

- They need to be near long runway where the X-37 can be retrieved and brought back on a C-17, so why not send a C-17 anyway?

- It takes lots of delta-v for a satellite to get itself into the proper inclination, and then multiple orbits to get that inclination over the target. Each Earth orbit is ~90 minutes. If you're going to spend days to preposition your sat into a proper delivery orbit, then again, you might as well put your package on a C-17 and fly direct.

- There is no need for any sort of package to loiter on orbit for months.

For example, the best way to stop ICBMs is to detonate the biggest bomb you have as close as possible during the ascent phase. But you have minutes to react, and ICBM would take hours to get there, and the launch facility is likely to be in a place your planes can't reach quickly and easily, or in the case of a submarine, unknown.

So, once you have detected a launch, how do you deliver your bomb?

The only solution is to have a few of them lying in orbit, so that you can deorbit the first one that enters the window. And if you put wings on your bomb, you can steer it, which means you need much less to cover all possible targets. And if you're going to detonate a H-bomb to stop a nuclear attack, discretion is not an issue.

Ignoring the fact that it's against international treaties, it's still much easier to shoot down than an ICBM reentry vehicle and it takes more time to reach its target than a SLBM. Orbital bombing has been proven to be ineffective.

Talking about that, I had another idea.

Imagine the USAF really wants a suborbital troop transport, and also need to do some experiments in orbit. If you have two projects, it will be pretty obvious what their goals are. But a bigger X-37 could do both, and because it's highly over-engineered for these two tasks, it would confuse people about its mission.

The simple fact we're talking and wondering what such a craft could be used for, and the fact nobody else is working on a similar concept are proof that its mission isn't clear. Sure, military analysts probably have more information and competences to figure it out, and that would be a very expensive deception, but we're talking of the US military, they have an history with this kind of things.

What kind of rocket would be needed to launch a troop transport X-37 variant? X-37 fits on an Atlas V with a payload of 200Kg. An X-37C would need a much larger rocket. It already takes months to integrate a payload and prepare for an Atlas V launch, and the X-37 needs a runway to land. How would that be any better than flying your troops to that runway in a business jet or one of those stealth Black Hawks they used to get Bin Laden?

[magnemoe]

If you want to wreck a LEO sattelite, park an AEGIS cruiser in the middle of the Pacific and fire an ASAT missile at it. Or use a laser. So that's probably not it. My guess is still that it's simply a development prototype, with no purpose other than testing technology. That is, the X-37B. I can't say anything on the X-37C or possible successors.

Yes, it might also be used to test and return various technologies, lots of the early shuttle missions had equipment in the bay.

As other point out X- is for experimental, not anything who is in use.

---

The cruiser missile launch would probably be detected by early warning satellites, still it would work against non Russian birds, might still work in south pacific.

Yes you might do it with an small secondary payload satellite, this will be far easier to hide.

[Rakaydos]

What kind of rocket would be needed to launch a troop transport X-37 variant? X-37 fits on an Atlas V with a payload of 200Kg. An X-37C would need a much larger rocket. It already takes months to integrate a payload and prepare for an Atlas V launch, and the X-37 needs a runway to land. How would that be any better than flying your troops to that runway in a business jet or one of those stealth Black Hawks they used to get Bin Laden?

Not to mention, it would be easier to simply put a lander capsule directly on an ICBM without bothering wih the spaceplane or orbit-loitering capability.

[Red Iron Crown]

Reading through this thread, it's starting to look like there is no use case for the X-37 that cannot be done better/cheaper by some other method.

The long loiter in orbit and high amount of delta-V makes me think it's a standby orbital interceptor (doesn't matter how long a launch prep takes if there's always one or more already in orbit). But why have it be returnable, and as a spaceplane at that?

[Fuzzy Dunlop]

Firstly, it's likely that the X-37 has more than one purpose - the USAF loves its multi-role vehicles.

The most obvious use is reconnaissance. Traditional spy satellites have two issues. The first is that they are predictable, they tend to overfly the same area at the same time every couple of days, so if you're smart you can often hide your activities. You can get around this by altering the orbit, but you have limited amount of fuel, so you can't do this too often (most observed satellites do this 4 or 5 times during their mission). The second issue is that they're staggeringly expensive, a single KH-11 is belived to cost about $4.5 billion - as a single piece of equipment only a Nimitz class supercarrier is more expensive.

So there is a clear case for re-use, so you can change orbit frequently and once you run out of fuel you can just land, gas up and re-lauch - without having to shell out billions in new optics.

Now the X-37 is far too small for a fully fledged KH-11 (think a heavily upgraded Hubble) but it's cargo bay could accomodate the optics of ORS-1 (a small reconnaissance satellite the USA recently launched to provide intelligence in Afghanistan) which is still quite useful.

During the first X-37 mission USA-212 the craft frequently shifted orbits, and all of it's orbits were precisely in sync with the earth's rotation so that the X-37 was in exactly the same place, at the same time of day, every 2 or 3 days. That's a clear pattern that indicates earth observation was a mission objective.

Of course there are likely other uses - the USAF has launched a number of small experimental sattelites, including reconnaissance sattelites operating in unusual spectra, that the X-37 could be useful in prototyping.