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Secretive military spaceplane lands in Florida after record-long orbital flight (reuters.com)
238 points by anigbrowl 17 days ago | hide | past | web | favorite | 183 comments

My trusted close relative used to do classified work on "Buran", the Soviet Union's answer to the United States Space Shuttle program.

According to him, the USSR military developed Buran to match what they saw as the space warfare capabilities that USA gained with the Shuttle. Unlike the ICBMs, the shuttles decoupled the event of the payload launch from event of the payload delivery, i.e. bombing. The early shuttle missions demonstrated the ability to "dive" to an orbit from which they could deliver a nuke directly to Red Square and then return back to the low Earth orbit. Shuttles could also perform attack missions against targets in the Earth's orbit, approaching and destroying USSR's satellites as a prelude to a nuclear war.

Buran was designed to perform both of these missions. Unlike the shuttles, Buran could perform them while 100% unmanned. Until this X-37B flight, US did not have a public demonstration of a technology matching what USSR had with Buran in the late 1980s. Given the "hot peace" nature of the contemporary relationship between US and Russia, it is not surprising that US would want to demonstrate that it went above and beyond what USSR accomplished in space warfare. X-37B does that.

If you are wondering about the 2-year mission for X-37B: when Buran launched in 1980s US immediately started speculating that the "unmanned" capability of Buran was just another lie by USSR. Can't say the same about about X-37B considering that it was in orbit for twice the time of the longest manned mission.

Your friend is mixing together some stuff in telephone game style.

While there were some military applications to the space shuttle, it rather emphatically was not some sort of covert space bomber. It's ability to glide and boost itself back into orbit is very limited as it can't store a ton of propellant. While gliding it needs to be in a level slightly nose up posture. How do you think it's supposed to release a bomb in that pose? It rather plainly has a thermal protection system on the bottom, and nothing usable as a bomb bay.

The whole idea is just preposterous.

The military applications of the shuttle were the ability to launch and capture satellites, as well as to potentially act as a reconnaissance platform. The X-37B largely continues those same missions.

You are correct (AFAIK) about the real military capability of the STS. But the Russians, when analyzing the program, came to the conclusion that the stated reason the shuttle was being developed was bogus. They believed that it would never be cheaper to launch satellites using the shuttle than using regular expendable rockets, and so if the stated reason is bogus they concluded it's a cover for a military program. And then they invented military applications that such a system can have, even if you need to slightly modify the shuttle to achieve them. And then they decided to build their own to achieve parity with the West.

The US military's idea of military capability of the shuttle was to covertly launch a spy satellite from California going south, release it over the pole and land without completing a full orbit. This would, hypothetically, evade Soviet radar. Because the Earth rotates under the shuttle while this happens, the shuttle comes over far away from the launch site (and from the runway), and so it needed the large cross range ability (1100 miles) and this required the wings, etc.

AFAIK, the Soviets said they booby-trapped their military satellites so retrieving them from orbit would be hard.

Shooting at satellites from the shuttle is weird - a first strike requires shooting down many satellites, so you would need your weapons platform in many orbits at once. Just shoot from the ground or use something like the ASM-135 ASAT.

Bart Hendrickx and Bert Vis, Energiya-Buran: The Soviet Space Shuttle, 2007

>The IPM studies were conducted under the leadership of Yuriy Sikharulidze and Dmitriy Okhotsimskiy, two of its leading scientists.

>The IPM studies focused on the Shuttle’s possible use as a bomber, more particularly its capability to launch a nuclear first strike against the United States. Efraim Akin, one of the institute’s scientists, later recalled:

>“When the US Shuttle was announced we started investigating the logic of that approach. Very early our calculations showed that the cost figures being used by NASA were unrealistic. It would be better to use a series of expendable launch vehicles. Then, when we learned of the decision to build a Shuttle launch facility at Vandenberg for military purposes, we noted that the trajectories from Vandenberg allowed an overflight of the main centers of the USSR on the first orbit. So our hypothesis was that the development of the Shuttle was mainly for military purposes. Because of our suspicion and distrust we decided to replicate the Shuttle without a full understanding of its mission. When we analysed the trajectories from Vandenberg we saw that it was possible for any military payload to re-enter from orbit in three and a half minutes to the main centers of the USSR, a much shorter time than [a sub-marine-launched ballistic missile] could make possible (ten minutes from off the coast). You might feel that this is ridiculous but you must understand how our leadership, provided with that information, would react. Scientists have a different psychology than the military. The military, very sensitive to the variety of possible means of delivering the first strike, suspecting that a first-strike capability might be the Vandenberg Shuttle’s objective, and knowing that a first strike would be decisive in a war, responded predictably” [14].

On other hand, US had own intelligence screwups that ended with "self disinformation."

USSR military planners had a plan to very intentionally design Alfa and Papa class submarines with very bizarre specs, and uncertain strategic role with an intent to set American strategic planners on a wrong path.

They were intentionally let to sail close to population centres, with a lot of subassemblies given to civilian manufacturers to encourage leaks.

Amazingly, 30 years later we got to know that the plan actually worked for them. From what is known now, news of Alfa's existence truly did set the military, CIA, and the executive branch into a contention in late seventies.

> Your friend is mixing together some stuff in telephone game style.

Are they? They said:

>> developed Buran to match what they saw as the space warfare capabilities that USA gained with the Shuttle

"what they saw" being the important part. Everything that follows is a seemingly legit interpretation of what the Shuttle can do, if you (reasonably) assume the U.S. wasn't fully disclosing all capabilities and purposes.

Even if they were wrong about the capabilities of the shuttle (I'm in no place to say) that doesn't mean that the friend was at all inaccurate in what they reported.

> While gliding it needs to be in a level slightly nose up posture. How do you think it's supposed to release a bomb in that pose?

With a little imagination? Shuttle positions rocket in orbit like a satellite and then ignites engine? Shuttle abandons its usual "slightly nose up posture" in preference for a nose-on-target posture; turning into a nuclear armed ICBM toting kamikaze.

>With a little imagination?

Space is surprisingly good at punishing 'imagination'. The nose up posture is related to the aerodynamics of reentry. You can't blow through the atmosphere at Mach 25 dead on and have anything but a scorched hulk left afterwards. Those thermal tiles, and that particular reentry profile are required to allow the atmosphere to safely absorb the kinetic energy of a re-entering craft, while keeping the entire thing safe from becoming part of the exotic and exciting chemistry such a process involves and giving some level of control over the down range trajectory through adjusting the lift vector. That lift vector was engineered to be workable in the hypersonic regime, but once you got to subsonic, it was a bit like flying a brick as I recall.

Could a nuclear payload be lifted by the shuttle? Yes. Would the size of the resulting payload make it as effective as a rocket launched warhead? Not so much.

The Space Shuttle was an interesting effort in engineering extremes that only really got off the ground I think due to the unique situation of the time. The Apollo missions were a success, but Vietnam, and a souring disposition toward manned space programs really put the kebash on what the Shuttle was just meant to be one piece of.

I wish I could remember the exact name of NASA's solar system colonization plan back then, but it was truly a glorious thing to read. Politically impossible. Probably economically ruinous given the wars we'd get entangled in over the next 50 years. But a beautiful dream at least.

Interestingly enough, I think it was really a necessary fumble to make in order to realize that reusable rocketry was the more economic launch paradigm to go for.

Sadly, Buran only launched once. That flight was unmanned, and it completed two orbits before successfully landing.

And that was in 1988!

Shuttle had the capability to land unmanned from the beginning.

It just happened that it flew real missions with astronauts on board, so it wasn't used.

At best they could have skidded it down the runway, because opening the landing gear doors was purposely impossible without human intervention.


It would be quite deadly if they opened early. There was no need for automation.

Some time after the second wreak, NASA added the ability to run a cable for that. The idea was that a rescue mission would be launched, and the cable would be installed in the abandoned shuttle to allow a landing attempt.

BTW, the first mission was flown manually. I don't think the landing software could have been written without data from the first flight.

They could have installed remote control landing gear if they ever needed it.

More discussion of the relationship of the Space Shuttle to Braun here: https://idlewords.com/2005/08/a_rocket_to_nowhere.htm

> Until this X-37B flight, US did not have a public demonstration of a technology matching what USSR had with Buran in the late 1980s.

Nitpick, but the first flight of the X-37B program already demonstrated this back in 2010.

Yes, you are correct. And it would appear that the US was unwilling to shelve the Space Shuttle, despite the known problem of them blowing up every one out of fifty launches, didn't shut down the Space Shuttle until 2011, after confirmation that the X-37B could replace the military needs of the Space Shuttle.

I think the key difference was the USA preferred people on the space shuttle missions. It wasn't for lack of technology, which the whole system was computer assisted anyway, but manned missions are hard and require more engineering and technology. It was political and memorable, that was part of the demonstration and triumph.

It's very cool that the Buran completed a single 3 hour trip unmanned, it went down as the first unmanned space flight that not many people know about. There's nothing much more to say other than that, which is disappointing.

The X-37B and its predecessors have been flying for nearly 10 years. I've been following these programs for apparently a lot longer than I realized. The take away with this program is they are launching these missions without much fan fair and the only brag is the incredible amount of time these missions are active in space. Literally every mission I've seen has the same information being released which is a picture of the vehicle touched down and the time spent in orbit... that's it. As with the last mission, this will be forgotten, another will go up to space and in a couple years we will get another press release.

Certainly Sputnik was the first unmanned spaceflight?

That's pretty silly.

Considering the huge amount of effort to launch one, the short duration a shuttle can remain on station and the limited number of them we could have ever built and put in orbit, what would be the point? Let's assume for a moment we (well...US leadership) lost our collective minds and decided that we wanted to swoop down and nuke Red Square for the LoLs. Hell, let's assume we had every Space Shuttle up and each one swooped down and toasted a city. It's nowhere near the capability to prevent the next action being the retaliatory strike which would incinerate the US. 10x the number of Space Shuttles wouldn't prevent that. And we'd have to plan months in advance for this 'first strike', and prevent anyone from knowing we were loading nukes in the shuttles.

Maybe your 'Trusted close relative' really believed all that stuff. Crazier crap was taken as truth in the Cold War. But in reality, that's not what the Space Shuttle was for.

ICBMs can do that too; the MIRV capable ones carry enough delta-V when stripped to a single warhead for orbital insertion and ejection, albeit on crappy trajectories. That's why you can repurpose them for generic satellite launches. Parking a nuke in orbit violates the Outer Space Treaty though so countries don't (publicly) do it.

The thing with a shuttle is it's easier to stealthily violate the treaty than launching a bunch of suspiciously poorly built cylindrical tubes and calling them defunct space telescopes.

The premise of using a shuttle like this seems like a reinvention of fractional orbital bombardment: https://en.wikipedia.org/wiki/Fractional_Orbital_Bombardment...

Not the cheapest way to do it by any means, but I suppose masquerading as a harmless civilian space plane gives you some degree of plausible deniability, since it would be violating a few treaties to have such a system.

> USSR military developed Buran to match what they saw as the space warfare capabilities that USA gained with the Shuttle.

For more info on this, Mustard's documentary on the Buran: https://youtu.be/CwLx4L5NRU0?t=175

I remember seeing a classified US military publication in 1984 called "Soviet Military Power 1984" and there were pictures of this smaller soviet space shuttle being hoisted from the ocean onto a barge.

You forgot to mention that "Bor" was inspired by USAF program X-20 Dyno-Soar.

"The statement that this @usairforce X-37 flight deployed small satellites is alarming, since the US has not reported those deployments in its UN Registration Convention submissions. This would be the first time that either the USA or Russia has blatantly flouted the Convention."

I'm also alarmed by this. I wouldn't want Star Wars (neither Lucas's nor Reagan's) to become our future.

It may be that those deployments were replacing existing satellites. I'm sure other nations know when the vast majority of satellites were originally deployed, which gives them a rough estimate of what technology they might have. Being able to subvert this assumed knowledge by changing what the satellite is is quite possible more useful than launching a new one and having them both up. Even if what the space plane did was tracked so there's not likely to be any surprises, in-place upgrades might have their own uses.

If that's the case, and it's just replacing existing satellites, they're still tracked accurately under that convention. Not that the USAF would say either way unless pressed by national powers, as the ambiguity helps their mission. It also helps internet blow-hards that like to take relatively small amounts of information and construct narratives they can lambast. It's entirely possible the USAF deployed new satellites, or replaced some satellites, or did nothing like that and the messaging is posturing or disinformation.

If it was doing stuff with satellites, I'm actually more interested in how it got inventory to do so over a two year time span. Did it drop to lower altitudes to refuel and get more satellites to deploy/replace/upgrade?

> If it was doing stuff with satellites, I'm actually more interested in how it got inventory to do so over a two year time span. Did it drop to lower altitudes to refuel and get more satellites to deploy/replace/upgrade?

1) CubeSats can be very tiny, and perhaps it was only releasing babysats for part of the mission, or at long intervals

2) surely we'd have noticed if there was a space fuel depot,

2b) if there was, why would it need to find it at a lower altitude?

> 2) surely we'd have noticed if there was a space fuel depot

> 2b) if there was, why would it need to find it at a lower altitude?

Well, it's a space plane, so I was thinking of a more exotic variation of conventional air refueling, but upon further thought that seems very unlikely as if it was that easy to get from land to the refueling point and from the refueling point to space, we'd see that as the usual way to get to orbit instead of rockets (or rocket attached ships). I don't spend a lot of time thinking about rocketry and orbit unless in a discussion about it, so this wasn't immediately obvious to me initially.

That said, it's possible that some satellites actually contained extra fuel for future use when deployed, either in them or as a separate attached payload. In that case, there wouldn't be one large space fuel depot, but possibly many small ones.

I know that amateur astronomers have tracked the position and trajectory of X-37B so surely countries with advanced space programs (Russia, China) would be able to do this with ease? I think a rendezvous with a known satellite would be detectable.

Probably. At the same time, two years is a lot of time, and maybe enough to spend some time around many satellites such that it's hard to tell what's upgraded and what isn't. For hedging opponent behavior, it may be more beneficial to have 100 satellites with a 10% chance of being upgraded than 10 satellites with a 100% chance. And that's assuming that's even what it did, there's a lot of possibilities. When it comes to surveillance capabilities and maintenance/upgrades of that system, I would consider anything from an official source as an "unreliable narrator."

Casually announcing that your secret space plane has deployed even more secret mini-sats in unknown orbits is a pretty weird thing to do and it makes me wonder why they announced it.

International posturing, probably

I guess, but "spooky spaceplane that could be doing ~~anything~~" has its own value just by being spooky- what is it doing? Nobody knows! Except (maybe) now we do, and the next time we put it up in space there's going to be lots of questions about stealthy CubeSats.

So it makes me wonder why they chose to announce it rather than keeping it vague and spooky, which is a different kind of international posturing.

Search for "Sputnik Inspektor". Enjoy your anxiety :-) .

Sorry, looking for context, where is this quote from? Not finding it in the article.

Oh, sorry, I originally commented in another thread based on this npr submission which was marked as a duplicate: https://www.npr.org/2019/10/28/774010986/secret-air-force-sp...

the UN, at least in security, is a joke. I wouldn't be alarmed by this.

I think it's more about the principle of the thing.

It's definitely a bad thing to have satellites up there that no one knows are there (because of collision risks, etc.), and the US not registering theirs opens the door for other nations/entities to see what we're doing and choose to do the same, which would be bad for everyone.

Given Reuters cite the air force as their source, would anyone hazard theories as to why they're so happy to announce the movements of a supposedly secret plane? It's pretty much in the news every time anything happens involving it, which seems quite intentional.

Is it perhaps just some kind of announcement of a capability to foreign countries?

Anything in orbit can (and is) actively tracked by amateur and professionnal astronomers around the world. The secret aspect of the X37B plane is it's mission. Nobody knows what it was doing up there. Hypotheses range from carrying weapons, spying, or doing experiments. In any case, it is certainly also used as propaganda, a show of strength.

And I believe even the pro trackers lost it at least once, until it was rediscovered by accident. Which adds intrigue.

Not counting foreign intelligence, obviously.


A reasonable theory, given that weapon strikes from orbit are extremely subtle and stealthy, and matches have not been invented yet.


I know that when I secretly test weapons, I do it in a way that makes sure the effects will be in the news 24 hours a day for weeks and months.

Version 1:

"Did it work?"

"We, uh, dunno. We can't find what it hit."

Version 2:

"Did it work?"

<Turns on CNN> "Yup."

Kind of a shit weapon if you have no idea what you are hitting with it innit.

Some people believe the Earth is flat, too.

>Anything in orbit can (and is) actively tracked by amateur and professionnal astronomers around the world.

Indeed, I follow a guy on twitter that has photographed it.

Quickest link I could find to one of the photos https://www.space.com/x-37b-space-plane-skywatcher-photo.htm...

And here is his account where he also has photos of stuff like the ISS https://twitter.com/ralfvandebergh

Agreed with you regarding a show of strength. I can imagine that any release of information is carefully calibrated. After all, the picture in the article with men in spacesuits circling the aircraft is pretty cool. I doubt this is a "leaked" pic...

Is this really something they could effectively hide otherwise from other space powers? If not, telling the world about it doesn't hurt much, is good PR, might make running the mission easier (if it was known during the flight and coordinated with other users of space), and the question of what it did is probably more interesting anyways.

EDIT: looked it up a bit: both the start of this and previous missions had media coverage, and amateurs temporarily tracked the plane, so no point in secrecy.

> It's pretty much in the news every time anything happens involving it

It's in the news every time they decide to put it in the news. Many other things could happen in secret.

Anything for good PR for a military budget.

Because Trump bragged about it with the whole "we're gonna have a space force!" rant. Probably just made sense to make it public now.

It was spying on Baghdadi personally this whole time maybe.

The US military is not actually very good at war — the nuts and bolts of combat and conquest. They maintain an aura of invincibility through PR which is questioned every time they fail at war (the majority of the times since World War II) or fail to carry out the basic actions of war making, like driving ships: https://www.navytimes.com/news/your-navy/2017/08/27/navy-swo... .

You don’t have to be good at war, you just have to be better than everybody else. And that’s what sets the US military apart.

Having more helps too!

More military or war?

More of everything, especially guns.

> The US military is not actually very good at war

How do you define "good" at war? By the time you've reached "war" as a solution, "good" really isn't on the table.

Pretty much the only way to be "good" at war is to be willing to kill every single person in the theatre--civilians included. You are "good" at war and "win" in that case--there is no enemy left.

We also have a word for that--genocide. And we view that very negatively for good reason.

Where do you get the idea that the end-goal for use of military force is inevitably genocide?

You win a war when the outcome lets you plausibly declare victory.

How about their own metrics? Losing a carrier group to a bunch of speed boats and missiles in their own war games.


Isn't that article misleading though? For example the motorcycle messengers had "instantaneous communication" iirc.

[citation needed]


the same article linked in the wiki article that mentions motorcycle use.

That doesn't say that the motorcycle messages were instantaneous.

I mean you have this massive small-town sized ship (6000~ crew) and it's support ships, and then you have a bunch of agile, fast moving, speedboats that present very small targets that bounce across the waves that are capable of carrying enough explosives to put a hole in the hull...

Obviously the swarm of small things that are effectively man-piloted missiles are going to be able to take out the slow 200 million pound behemoth that requires 3-5 miles to turn around.

Carrier groups are specifically designed to combat these kinds of threats. That's why "carrier killer" missiles like China's DH-26 are hypersonic; it's because that's what you're supposed to have to do to overwhelm a carrier group.

Carrier groups are meant to take out proper ships, not small speedboats. You can have a hypersonic missile all you want, but when a speedboat can rapidly change speed and direction unlike even something small like cyclone-class patrol craft.

Change generic speedboat to fastboat and you have something that can do 30-90mph (50-80 knots) depending on wave conditions while the previously m entioned cyclone-class tops out at 40mph (35 knots).

Carrier groups aren't exactly in a tight circle around an aircraft carrier either and then you have to consider friendly fire (with deck guns/artillery) so enough much smaller craft can come zooming in and easily overwhelm any defensive capabilities.

Depending on distances and angle you might be firing a 62 caliber projectile directly at your own ships with a craft randomly adjusting course, in choppy waters. Software is only going to do so much to increase the odds of hitting your target and something like a deck gun is going to be used long before anti-ship missiles that cost many hundreds of thousands of dollars well into million dollar plus range a pop. Especially if you have a half dozen, a dozen, two dozen cheaply acquired speedboats/fast boats coming at you.

Naval warfare isn't much different now than it was hundreds of years ago for proper ships. Sure the projectiles can be laser guided and carry way more destructive potential while the ships can move under their own power but you're still talking about incredibly heavy ships that move slow and are bobbing up and down in the water.

Similarly put a dozen guys on performance dirt bikes and give them explosive backpacks and throw them at an M1 Abrams and unless you have one hell of a lucky gunner, one of those dozen people is going to get right up on that tank and at a minimum will render it immobile.

Naval ships are meant to fight other ships and in the case of the aircraft carrier itself, simply support a small fleet of aircraft. They are not designed, or intended to, fight multiple much smaller craft. Speedboats have very limited ranges, rarely leave coastal waters and can't carry any weapon system that poses a risk to naval vessels EXCEPT for shoulder-fired rockets and by acting as suicide man-piloted missiles laden with explosives.

I'm not sure where you're getting your information. Naval warfare has had more changes in the past 100 years then nearly any other point history. Like 100 years ago they didn't have aircraft carriers, the keel of the first one was laid 1924, and it wouldn't be until near the end of the Pacific theater that the supremacy of the carrier group was proven.

Like, your whole argument is equally applicable to torpedoes, except those are even harder to hit.

>Like, your whole argument is equally applicable to torpedoes, except those are even harder to hit.

Torpedos can cost a million bucks each, a stolen/commandeered/seized speedboat is free.

Torpedos are covered under ITAR and require quite a bit of sophistication to manufacture and are effectively limited to nations. Anyone can obtain a speedboat, or a dozen speedboats, and deploy them. Kinda like when the USS Cole was successfully attacked, leaving a 40x60 foot hole in the side, by a small fiberglass boat carrying several hundred pounds of explosives and modern day pirates usually use small fishing boats.

The Cole was literally moored for refueling, not quite at peak readiness, and not really what we're talking about here.

But the whole point of how carrier defenses work is to not wait until they're literally on top of you (like on your example of shooting your own ships). Speed boats are stupid loud on SONAR, so you should detect and destroy them before they can even see the carrier group.

There was this amazing article in 2010 about "chemical compounds i will not work with". Tetrafluorohydrazine was one of them:


and mentions briefly that hydrazine is produced at los alamos for national security purposes.

Almost all spacecraft (including satellites) use hydrazine (MMH, UDMH or Aerozine 50) for rotating around itself to keep pointing in the right direction (see attitude control, reaction control system).

When used as a bi-propellant, hydrazine is usually combined with N2O4, which is also super toxic.

It is not just the military that uses these things. Everyone uses it because it is the best performing high thrust (not ion engine) non-cryogenic (storable) propellant. It being hypergolic (self igniting) is a bonus for reliability.

The military actually switched to solids for ICBMs and SLBMs.

The F-16 has a hydrazine APU, and I would not be surprised if the F-35 does the same thing.

> The F-16 has a hydrazine APU, and I would not be surprised if the F-35 does the same thing.

The F-16 has an EPU not an APU, i.e. an Emergency Power Unit vs an Axillary Power Unit. Lacking an APU is an exception when it comes to jet aircraft and necessitates a few changes. Relevant here is that an APU can provide power in an emergency, so the role is played by the hydrazine powered EPU for the F-16.

This makes hydrazine somewhat more of a rational choice for something you expect to use rarely. If it were expected to be frequently used then it would have to be frequently refilled and that would necessitate all ground crew wearing the full body hazmat suits you see in the photo for the X-37b here as well as many other complex safety precautions.

The F-35 has a conventionally jet fuelled APU[0] so it has no need for an EPU or hydrazine.

Interestingly Concord didn't have space for an APU (due to the shape of the empennage and placement of a rear fuel tank). I have seen pictures of a hydrazine powered EPU on one of the prototypes, but this was never going to make it into service as certifying carrying something as toxic as hydrazine - even back then - would be nigh on impossible. This is the question that starts the most epic thread about Concord[1] (warning - you may get sucked into reading all 103 pages!)

[0] http://www.f-16.net/forum/viewtopic.php?f=60&t=12192

[1] https://www.pprune.org/tech-log/423988-concorde-question.htm...

I think you meant "Auxiliary Power Unit," not "Axillary Power Unit." Most planes lack armpits :)

Ah yes, good spot! And I got to learn a new word[0] today :)

[0] https://en.wikipedia.org/wiki/Axilla

The EPU on the F-16 is actually quite interesting itself and is a good fit for what is needed with 70s technology.

Redundant systems are normal on aircraft and the F-16 has a particular need for hydraulic and electrical power as its inherently unstable airframe needs various onboard systems to keep it stable and flyable.

If the main generator disconnects from the bus or the hydraulic pressure drops[0] the EPU will automatically operate to provide electrical and hydraulic power. It can run from engine bleed air, but if the (single) engine has failed then pressure will be provided from the hydrazine system.

It achieves this using a 70% solution of hydrazine in water as a monopropellant, which is decomposed over an iridium catalyst. The water helps keep it stable, and cools the catalyst when it boils, keeping it around 850C and the high pressure gasses are fed into the EPU.

This has the advantage of being light (25L of hydrazine and simple as only a single liquid), reliable and fast acting (~2s to max power).

[0] https://www.slideshare.net/matheusgaldino355/usaf-flight-man... (section 1-101)

Re: Concorde forum link: what a treasure trove of information!

pprune is the goto site whenever anything interesting happens in aviation (and the pro's there are very aware that it's where the journalists will start looking when there's an incident).

I suspect the F-35 does not use hypergolics, because they land on aircraft carriers. There's only so much risk you can tolerate on such a large, high-value asset. Nukes, sure. Hydrazine? Do we absolutely have to? If not, take a pass.

F-16s also land on carriers though.

Rocket fuel typically uses either monomethylhydrazine (MMH) or unsymmetrical dimetehalhydrazine (UDMH - the more common of the two).

The link you're responding to is about tetrafluorohydrazine, which is some kind of hydrazine and fluoride. I think it's mentioned in Ignition! but I can't remember. I just remember John Clark (the author of Ignition!) being very very hesitant and even frightened of working with fluoride based fuels.

I'm not really sure how how it's tetrafluorohydrazine is relevant to the X37-B though.

You remember the Crew Dragon test that exploded? The orangeish smoke cloud? Don't breathe that. That uses NTO + MMH.

"On 24 July 1975, NTO [dinitrogen tetroxide] poisoning affected three U.S. astronauts on the final descent to Earth after the Apollo-Soyuz Test Project flight. This was due to a switch accidentally left in the wrong position, which allowed the attitude control thrusters to fire after the cabin fresh air intake was opened, allowing NTO fumes to enter the cabin. One crew member lost consciousness during descent. Upon landing, the crew was hospitalized for five days for chemical-induced pneumonia and edema."


>There was this amazing article in 2010 about "chemical compounds i will not work with". Tetrafluorohydrazine was one of them:

I remember reading that article it was interesting. But it's funny that hydrofluoric acid (HF) was not mentioned since it seems to be incredibly dangerous.

Periodic Videos on Youtube has a new video about hydrofluoric acid. Professor Martyn Poliakoff mentions HF is feared by people working in chemistry. He also said that even a small drop of HF on skin will cause a heart attack (and eat through your skin).


> He also said that even a small drop of HF on skin will cause a heart attack

I really wish people in the know wouldn't spread stuff like this.

HF isn't untreatably deadly like dimethylmercury.

HF is a strong acid and should be treated as such. Most effects of HF are quite treatable as long as you haven't managed to somehow convert it into elemental fluorine gas.

They key is that you have to know that you've had an HF incident.

What IS nasty is that an HF burn probably doesn't hurt until far too late. HF reacts with calcium and can inactivate pain neurons. And, while a small droplet won't do it, a large HF burn can cause a heart attack because it soaks up a lot of the free calcium in your bloodstream.

So, when you go in for treatment for an HF burn the doctor needs to start giving you calcium gluconate in order to resupply your calcium.

HF is nasty, but not so nasty that semiconductor fabs work terribly hard to get rid of it. Piranha etch (HF and HNO3 at 70C) is bog standard and people work with it every day.

Constrast this to Arsine gas (AsH3--flammable and toxic--oh, the joy!) which everybody works to get rid of.

Not just flammable but even pyrophoric! (re Arsine)

Hydrofluoric acid is nasty stuff that strips the calcium from your bones

My brother works in a oil refinery lab and had a HF acid escape.

Procedure for escape is jump in the lab shower, strip off and lather yourself with calcium based cream

Turning on the shower activates the lab alarm, and the medical and emergency crews turn up shortly after.

When things have settled there's a health and safety investigation / review of the incident.

Yet, you can buy it in 1% solution at your neighborhood hardware store.

Concentration matters.

I don't believe I've ever been in any hardware store that sold hydrofluoric acid in any concentration. Care to expand on what you meant?

Now - hydrochloric acid or sulfuric acid - both those (and some other relatively nasty chemicals) can be easily purchased at many hardware (and other) stores; the first is commonly known as "muriatic acid" (pool acid), while the second is sold (usually at auto parts stores, but there are some hardware stores that sell it too) for lead-acid battery "replenishment" (if the acid in them becomes too diluted from "topping up" with distilled water over time).

But HF? No - I certainly can't see where that would be allowed to be sold in any concentration to the ordinary public...

In low concentration, it's in various cleaning products, rust removers, that kind of thing. In some places, you can buy glass etching cream which also contains HF.

Dumb question from someone who knows very little chemistry; is it possible for a malicious actor to use some sort of distillation process to take that 1% solution and concentrate it into something much more dangerous?

It's probably going to be more dangerous to the amature chemist than thier intended victim.

Yes but it's way cheaper and easier to just use drain cleaner for those kinds of malicious things.

The fun part in the video is when they neutralized the HF with sodium carbonate to make sodium fluoride which is used in toothpaste. Keeping in mind the concentration again.

HF is a weak acid and less dangerous than hydrochloric acid and sulfuric acid. If you really want bad news make piranha solution.

It's acidic, not less dangerous. If you get one of those other acids on you, you will know, immediately. Whereas HF will just absorb through your skin without appearing to cause any damage, but will kill all the tissue in it's path and start dissolving your bone underneath.

Don't get it under your fingernails, however.

Or store it in a glass container.

One of the near misses in terms of potentially fatal spacecraft accidents involved fumes from hydrazine and dinitrogen tetroxide entering the cockpit of the Apollo capsule returning from the Apollo-Soyuz docking in 1975. The astronauts survived after two weeks of hospitalization, thankfully.

Dr. Lowe's Things I Won’t Work With is on the top 10 best blogs out there. What an utter joy! His writing style is a breath of fresh air for the sleepy journal-club style articles. He is funny, informative, and interesting. A great addition to the world of science advocates. I love his blog. Some favs:

Can’t Stop the Nitro Groups :"... this new paper’s introduction includes the phrase “In our continuing efforts to introduce as many nitro groups associated with a tetrazole ring as possible. . .” and to most organic chemists that’s roughly equivalent to saying something like “In our continuing efforts to spray as much graffiti on the snouts of salt-water crocodiles as possible. . .”[0]

Sand Won't Save You This Time: "It is, of course, extremely toxic, but that’s the least of the problem. It is hypergolic with every known fuel, and so rapidly hypergolic that no ignition delay has ever been measured. It is also hypergolic with such things as cloth, wood, and test engineers, not to mention asbestos, sand, and water-with which it reacts explosively."[1]

Hexanitrohexaazaisowurtzitane: "Hexanitro? Say what? I’d call for all the chemists who’ve ever worked with a hexanitro compound to raise their hands, but that might be assuming too much about the limb-to-chemist ratio." [2]

Dioxygen Difluoride (aka FOOF, aka "Satan's Kimchi")[3]


[1] https://blogs.sciencemag.org/pipeline/archives/2008/02/26/sa...

[2] https://blogs.sciencemag.org/pipeline/archives/2011/11/11/th...

[3] https://blogs.sciencemag.org/pipeline/archives/2010/02/23/th...

I don’t see a mention of hydrazine in the link you shared.

People ask why the people servicing it after landing (in the photos) are in hazmat suits. It's because of the hydrazine and N2O4.

Yeah, it's an amusing article but it's not about Tetrafluorohydrazine and there don't seem to be any others in the series that are. Tetrafluorohydrazine also doesn't seem to be the same thing as hydrazine which is used as a fuel in some spacecraft.

The article does mention tetrafluorohydrazine being added to FOOF which is the actual subject of the article and a comment mentions tetrafluorohydrazine being used as an oxidizer for rocket fuels.

the article mentions hexafluoride. but LANL did (and probably still does) hydrazine. source:


(used to intern, and subsequently work there, although not as a chemist, of course. i'm not that smart)

and if you want to pedant that the patent wasn't issued to los alamos nat'l laboratory... well, in '54 things were different :)

There's been some work recently on using Hydroxylammonium nitrate (HAN) as a less toxic and better performing replacement for Hydrazine.



SpaceX webcast of the launch in 2017 [1]

Some info on the payload at 6:30 mark

[1] https://www.youtube.com/watch?v=9M6Zvi-fFv4

Why do the ground crew in picture have hazmat suits?

The Reaction Control System (RCS) [1] uses hypergolic fuels [2] which are highly toxic. Such fuels are desirable in this application because they combust whenever the fuel and oxidizer are brought in contact. There's no need to an ignition system, which reduces the chance for failure.

[1] https://en.wikipedia.org/wiki/Reaction_control_system

[2] https://en.wikipedia.org/wiki/Hypergolic_propellant

Hydrazine is one nasty substance and that's whats being used for maneuvering in orbit[1].

[1]: https://en.wikipedia.org/wiki/Hydrazine#Occupational_hazards

As others have said, the hydrazine / nitrogen tetroxide propellant for the reaction control system is highly toxic. The retired space shuttle used the same type of propellants in its RCS, auxiliary power unit (APU) and orbital maneuvering system (OMS), so it was also met upon landing by a hazmat suited service crew.

This NASA safety video from the Apollo era is incredible.


Most likely they're working with very hazardous fuels and oxidisers like hydrazine[0].

Edit: it seems that the orbiter was upgraded to use hydrazine and nitrogen tetroxide[1] from the somewhat less toxic hydrogen peroxide/JP-8 combination originally specced for its AR2-3 engine.

[0] https://en.wikipedia.org/wiki/Hydrazine

[1] https://www.airspacemag.com/space/spaceplane-x-37-180957777/

Hydrazine is hella toxic

From Wikipedia:

"The hydrazine antidepressants...were discovered and initially marketed in the 1950s and 1960s. Most have been withdrawn due to toxicity..."

Andromeda Strain?

Not sure if anyone has noticed, but these things seem to be setting 2+ year records every few months. So ... how many are up there?

"There have been five X-37 orbital missions. The spaceplane's first mission, USA-212, was launched in April 2010 and returned to Earth in December 2010. A second X-37 was launched on mission USA-226 in March 2011 and returned in June 2012. The third mission was USA-240, which launched in December 2012 and landed in October 2014. The fourth mission, USA-261, launched in May 2015 and landed in May 2017. The fifth and latest X-37 mission, USA-277, was launched on 7 September 2017, and broke the record for the longest X-37 mission, after 718 days in orbit, on 27 August 2019, finally landing on 27 October 2019 after 780 days in orbit."


Can you point to the last time one landed? May 2017 is what I'm tracking, so a few months before this one launched.

There are 2 known X37Bs, but I don't think they've been up at the same time.

Two have been manufactured for flight, one for aerodynamics testing.

I imagine they fly one and perform refurbishment and re-equip the second one while the first is flying.


Lots of theories about what that vehicle does... the one I like the best is that it intercepts "enemy" satellites and reprograms them. Of course, what comes around goes around and it would only be a matter of time before the Chinese do that to us if that's actually one of this vehicle's missions. A more likely scenario is that it is doing maintenance on and/or bringing home some of our own stuff -- as well as being an observation platform in its own right.

I don't know about reprogramming satellites but its possible it just grabs them and forces them to fall out of orbit. That's easier and quite effective.

Or it's just a moveable spy satellite that can hover over whatever it needs to.

Funny you mention the Chinese doing that to us. I just finished Snowden's book and he mentioned how he only learned what the NSA was doing after having to research what the Chinese were doing. Turns out, same thing!

The only place a satellite can 'hover' is directly above the equator in a geostationary orbit. Anywhere else and the best you can do is a highly eccentric orbit with a high inclination so you get lots of "hang time" over the target area, but that also means being very high up. From what I understand the X-37b was tracked by amateur astronomers to have a reasonably high inclination this time around, but an almost circular orbit.

Traditional spy satellites have very high inclinations because this lets gives them coverage of more of the planet (as the planet rotates beneath them.) The X-37 has thusfar to my knowledge not flown at a severely high inclination, from what I understand the most recent launch was somewhere around 54 degrees, and previous flights were lower. For reference the ISS is around 52 degrees.

The figures are all imprecise and the X-37b supposedly has the delta-v budget for relatively dramatic inclination changes, but even so 54 degrees is very far away from where earth-observing spy satellites traditionally are.

> its possible it just grabs them and forces them to fall out of orbit. That's easier and quite effective.

Honestly that seems neither easy, effective, nor subtle. To grab and deorbit something like that you'd need to grab it in such a way that let you thrust through it's center of mass which doesn't seem easy to do for a few reasons (not least because the distribution of mass inside the target satellite may not be known.) And since spy satellites can be massive, you'd need to burn a lot of fuel to do it. It's conceivable they're doing something a bit trickier, like slapping a time delayed ion thruster onto the side of victim satellites which would then slowly deorbit the target after the X-37 is long gone, but I'd still wager on the victim figuring out what was going on. Such anomalous thrust is something that would be noticed.

De-orbiting satellites I could see, but hijacking them seems more unlikely. Either they’re doing something physical to the satellite to hijack it (keep in mind every satellite is different, and this is an unmanned vehicle) or its over radio waves so why not do it from the ground?

Installing a modchip on a foreign satellite via robotic manipulation seems near impossible on the surface. Watching the Hubble service missions for example gives you an idea of just how much of a pain in the butt it is to service something in orbit, even when you have fully capable human beings doing the work. Building a robot to handle all of the unexpected hurdles of attempting such a task seems outside of our current capabilities. Even a waldo unit is a big ask.

>Even a waldo unit is a big ask.

why? the x37b has a shuttle bay at-least big enough for a solar array, i've seen pretty small waldos before.

Mostly because they aren't good enough yet. The manipulators struggle to balance small size, light weight, good grip, adequate cooling, and high strength. Getting the force feedback on the control solution correct is also difficult. And then you have to deal with communication delay as your bird is whipping around the world in LEO, constantly handing off between different ground stations, or worse, jumping through a sequence of Geo birds.

On the other hand, sometimes the government is willing to go to extreme lengths for intel purposes. The Glomar Explorer was outrageously ambitious, although ultimately only partially successful.

Even then you'd need intricate knowledge of the target satellite to hijack it - somehow opening and making electrical connections to a satellite you've never seen before seems rather infeasible - not even getting to the software side.

Nah I think it's far more likely it really was just a research vessel for more classified experiments they didn't want on the ISS.

Even just getting up close to another country's spy satellites would have value. The US keeps even the look of their current series of spy satellites classified; they're believed to be a lot like Hubble.

Apparently there was a quantity discount if nasa ordered one like Hubble.

> "Working with the LST science groups and contractors, the team reduced the telescope’s primary mirror from a 3-meter aperture to 2.4 meters. This major change mainly resulted from new NASA estimates of the Space Shuttle’s payload delivery capability; the Shuttle could not lift a 3-meter telescope to the required orbit. In addition, changing to a 2.4-meter mirror would lessen fabrication costs by using manufacturing tech- nologies developed for military spy satellites."


Hubble's mirror is probably the same [size] as a KH-11: https://en.wikipedia.org/wiki/KH-11_Kennen#Size_and_mass

Myself, I think it shot down the Cara Delevigne selfie satellite

This is my take away: “The sky is no longer the limit for the Air Force and, if Congress approves, the U.S. Space Force”

I used to be worried that the current trendiness of Space in the media would be a fad, gone by 10 or even 2 years from now. Such statements make me hope that —finally— people who matter have recognized both the value and inevitability of space. After that, it's all just a matter of time... wink@sagan

The Space Force/Core is not a proposal to significantly change US national security capabilities in space. It is merely a re-org of the command structure to put the existing infrastructure under a more specialized chain of command. Such command re-orgs can have practical implications, of course, but it is in no way some sort of novel realization that space is important for the military.

Thanks a lot for the explanation / clarification, helps me qualitatively appreciate events.

> it is in no way some sort of novel realization that space is important for the military.

I know, and didn't mean to imply that it was; I said "used to" because my fear is long gone, and such statements now pile up, like +1's I guess. (Upvotes are currently winning by a fair margin!)

I would however suggest that having a centralized Space command is a great leap towards building presence, solving big problems. Speaking as an EU citizen; but I'd vote for that, and with my wallet too.

My worry isn't that it is some trendy fad, or recognition of the value/inevitability, rather there is some other piece of information that the general public doesn't know. Maybe something not quite catastrophic as of yet, but is quitely driving the powers that be towards an unknown goal. Domination of space is of course going to be an important goal for any of the world powers, but the cost seems too high without a tangible asset/commodity that can provide wealth to keep the economic engines turning.

So what do you called an unmanned spacecraft? We've got unmanned aerial vehicles (UAVs), and unmanned submersible vehicles (USVs), and and unmanned land vehicles (ULVs), are they "unmanned orbital vehicles" (UOVs?) or maybe unmanned rocket vehicles? (URVs?)

Since you bring up naming, man/unmanned really needs to be dropped for crewed/uncrewed. NASA technically adopted this in 2006, but they still mess it up. Here's more info on their terminology, as well as other options you brought up:


Thank you for that, pretty much exactly what I was wondering.

Presuming "uncrewed" gets added to the dictionary I would expect that to prevail as the antonym for "crewless" might reasonably be "crewful", which also sounds weirder than "uncrewed"/"crewed".

Satellites. Voyager. Spirit Mars rover.

"Space ship" works. :)

It's fairly generic though. If I needed a more specific term for space planes like this, I'd probably go with orbital drone", based on terminology used in various sci-fi franchises.

Most spacecraft are already unmanned. It's redundant.

A reusable space plane has always been popular with the military. There were several secret military space shuttle missions. At times the military talked of owning one of the shuttles. They keep this dream alive with unmanned space planes.

People may be overthinking why the USAF flies the thing. If it's in active service, the USAF flies it once in a while. Otherwise they mothball it or retire it. Aircraft which just sit there don't stay in operating condition.

I mean, it's been in orbit for more than two years. That doesn't really lend itself to a test flight to make sure it works.

Unless they're testing it's durability?

Or more likely slowly taking high resolution photos of foreign satellites and/or trying to sniff any RF coming off of them.

Most of the cost is in the launch. Once it's up there, it may as well stay up there and do something.

A time record of an uncrewed vehicle and orbit is... not really news worthy.

I mean, you put it up there, and if the orbit is high enough, it simply stays there, no action required.

This doesn't seem to be much more impressive than a satellite that stays operational for 10+ years in orbit (and there are quite many of those).

And those satellites burn up in the atmosphere when their useful life has expired. This is notable because it returned to Earth in one piece.

Yes, but that has been done before.

The newsworthy portion seems to have been that it's been longer in orbit than before, and then returned.

Is it really all that impressive that it stayed 2 years in orbit before returning, instead of 1.5 years?

I'm sorry, I just don't see what the story is here.

I think the important part is the "spooky factor" of "this highly maneuverable space plane can stay on orbit for two years doing who knows what".

The implication is that the US military has a vehicle that can stay on orbit for as long as they want and move around to do anything from deploying secret satellites to spying to disabling enemy spacecraft without anyone else necessarily knowing what happened.

> I'm sorry, I just don't see what the story is here.

That's OK. I still found it interesting even if it wasn't some kind of superlative.

That ship looks incredibly cool. I assume it's un-manned.

Unmanned, yes. It looks like it would be a pretty miserable two years of your life if it were!


> The X-37B Orbital Test Vehicle, or OTV, is an experimental test program to demonstrate technologies for a reliable, reusable, unmanned space test platform for the U.S. Air Force

> Unmanned, yes. It looks like it would be a pretty miserable two years of your life if it were!

Nothing a Kerbal couldn't handle.

After a record-breaking 780 days circling the Earth, the U.S. Air Force's mysterious X-37B unmanned space plane dropped out of orbit...

-- FTA


The rest of us not obsessed with trump and turning everything into a trump issue wish you would be launched into space as well.

I'm glad we could find common ground.

I wouldn’t have brought up the President here because he’s simply not relevant, but I would love to understand better the privilege of folks who can get away with “not caring” about the commander in chief.

Not being obsessed != not caring.

People who are obsessed do bring it whenever it is relevant or not.


"Delusion"? Some 50+% of Americans want the man impeached and removed from office.

This isn’t a political discussion board. Please leave me alone little corner of peace and sanity.


The most succinct way I have seen it put thus far is "Trump Derangement Syndrome" or TDS for short.

The real "Trump Derangement Syndrome" is believing all of this is normal.

It may very well not be normal, however for three years now I have heard people screaming some variation of wolf ad nauseam. Whether it be a russian wolf, an orange wolf, a ready to start WW3 wolf or whatever else you can think of. It is just so incredibly tiring because as of yet there has been no wolf to speak of..

“Unwell”? Being concerned about our commander in chief makes me a patriot, not “unwell”.

Your pivot to “fake statistics” is telling.

No your obsession and demand that everyone care about the things you care about and have your opinion is delusional and unwell.

Your statistics were fake and unsourced and unrelated to the issue at hand.

You need help.


If only a crime was a vote instead of investigation. People won't look kindly at this period but I'm afraid it will not be as you claim - the virulent insanity will be remembered for a long time.

"Not turning everything into a Trump issue" is not the same thing as "the privilege of folks who can get away with 'not caring' about the commander in chief".

Is me setting my alarm for 630am "a Trump issue"? If I think it is not, am I "privileged" and "don't care about the commander in chief"? If it is, why am I "so obsessed with Trump and//or the commander in chief?

Yes, my example is ridiculous -- and you see my point. Not everything is "Trump" or "who the president is", being able to tell the difference doesn't necessarily make someone privileged or not.

It sure would have been nice to be off planet for the majority of this nightmare.

I think the secret has been so far that they had a driverless plane? That means the plane itself could be used as a weapon?

Previous long-term missions of it also had media coverage, so not a secret.

This seems like an unlikely coincidence — if I’m reading this other link right, it had been flying over Syria.


Edit: obviously I read it wrong. Still a strange coincidence though.

It's in low earth orbit so ground track changes every ~90 minute orbit. It flies over all countries with latitudes.

I always assumed it had an ability to relocate. I guess sustained movement in a 2y mission is hard, you have to budget for non-replaceables to make thrust work, ion thrusters consume stuff too.

I kind-of get it, that for a sufficiently timed orbit, it sees all places.. eventually. Being able to relocate means you can be where you want to be, without predictable periodicity.

It's hard to explain without calling out to Kerbal Space Program, but it's really hard to figure out what you mean by 'able to relocate' in the context of orbital flight.

Your orbital period is determined by size of your orbit, and the difference between that and the earth's rotation causes your land track to precess. For most this means your land track will eventually be over every possible point. Raising or lowering your orbit will let you find a 'flyover' intercept in fewer orbits, but it will still take time to get there. Hard to do accurately and you normally want to keep that fuel around for boosting your orbit when it degrades due to atmospheric drag.

Other kinds of orbital manoeuvres could be used, but they are even more expensive and less likely to get you were you want to be (as long as you are in an inclination that passes over your desired target).

The main reason for this is that orbits are characterised (pretty much exactly) by your position/velocity pair. Every orbit your position and velocity will repeat, absent any external forces. Modelling any acceleration as instantaneous (which is pretty close) you can see that you can only ever directly change your velocity. Accelerate prograde and your orbit will be raised on the other side of your orbit; when you complete one of your new orbits you will be back in the exact same location, but with your new speed.

but it's really hard to figure out what you mean by 'able to relocate' in the context of orbital flight.

I mean make a change of plane in unpredictable ways. You can't just scoot sideways for no apparent reason, clearly orbit means what it says. But the point would be to make changes of orbit at cost, to get somewhere faster than waiting for the orbit you are in, to get there.

(height and speed over a point on the ground being assumed to be less important than actually being over it, when you want it to be over it)

That TLE is from 2014. It's for OTV-3, eleven days before landing.

Ah, where’s the latest orbital data?

NORAD doesn't publish TLEs for X-37, but here's a spot from April 2018: http://www.satobs.org/seesat/Apr-2018/0065.html

Here's a TLE from Oct 17: https://www.n2yo.com/satellite/?s=42932

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