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Unmanned U.S. Air Force space plane lands after secret, two-year mission

reuters.com

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Re: Unmanned U.S. Air Force space plane lands after secret, two-year mission

#31

Post by SAI_Peregrinus »

azinman2 wrote: post #10
Animats wrote: post #5

Earlier quoted context omitted.

Toxic propellants. Nitrogen tetroxide / hydrazine. Both components are highly toxic. The big space shuttle used those for its maneuvering propulsion, and ground crews had to wear all the protective gear after landing until the propellant had been drained.

Is it all combusted perfectly, or do they lose some and just leave droplets of toxic liquid propellant in their paths as they fly?

You hope it's all combusted perfectly, but there's no reason to take the risk based on a hope. And the combustion byproducts aren't that much less toxic than the fuel. Also not all of the fuel will be used, so there's some in the tanks. That needs to be removed, and could leak if there was any damage.

Re: Unmanned U.S. Air Force space plane lands after secret, two-year mission

#33

Post by wolf550e »

bediger4000 wrote: post #26

I like the semi-gibberish official explanation: The orbiters "perform risk reduction, experimentation and concept-of-operations development for reusable space vehicle technologies," the Air Force has said without providing details. The cost of the program is also classified. How, pray tell, does anything "perform risk reduction"? Does that phrase have any meaning in English, or any other terrestrial language? "The co…

Risk reduction is a completely normal term in R&D. It just means experiment to raise confidence in a particular proposed approach, before going full scale production. It is meant to raise the TRL[1] of a technology, to gain experience with it.

In my software day job, we write throw away code to test out an idea, and we call it proof of concept. It is used to find out early if the schedule for a feature is too optimistic by demonstrating that the approach doesn't work.

1 - https://en.wikipedia.org/wiki/Technology_readiness_level

Re: Unmanned U.S. Air Force space plane lands after secret, two-year mission

#34

Post by ShannonAlther »

bediger4000 wrote: post #26

I like the semi-gibberish official explanation: The orbiters "perform risk reduction, experimentation and concept-of-operations development for reusable space vehicle technologies," the Air Force has said without providing details. The cost of the program is also classified. How, pray tell, does anything "perform risk reduction"? Does that phrase have any meaning in English, or any other terrestrial language? "The co…

> How, pray tell, does anything "perform risk reduction"? Does that phrase have any meaning in English, or any other terrestrial language?

This may not be what you meant, but suppose that my sister Alice is an alcoholic, and drinks during the day at her job (they're very tolerant). I am concerned that she will cause a traffic accident, so I encourage her to enroll at Alcoholics Anonymous, or I offer to pay her taxi fares or buy her a bus pass. Ta-da, risk reduced!

In this instance, I think they're either referring to the risk of crashing the plane or something conveniently censored by government classification.

Re: Unmanned U.S. Air Force space plane lands after secret, two-year mission

#35

Post by fake-name »

bediger4000 wrote: post #26

I like the semi-gibberish official explanation: The orbiters "perform risk reduction, experimentation and concept-of-operations development for reusable space vehicle technologies," the Air Force has said without providing details. The cost of the program is also classified. How, pray tell, does anything "perform risk reduction"? Does that phrase have any meaning in English, or any other terrestrial language? "The co…

I work for a gov contractor. "Risk Reduction Tests" are a common thing. What they mean is a test done partway through a program, to validate that the base assumptions for the program are correct and there haven't been any glaring oversights in terms of the feasibility of the project.

Basically, when contractors (Boeing, in this case) win a job from a bid, they don't then just go off for the duration of the contract, and return to the government at the end of the contract and hand over a delivery. There are generally a series of incremental deliverables and tests during the contract to validate that the contractor is actually working on the contract. Risk reduction tests are one of the mid-program deliverables.

Re: Unmanned U.S. Air Force space plane lands after secret, two-year mission

#36

Post by JshWright »

jcims wrote: post #12
Animats wrote: post #2

Whatever the X-37B does, it seems to do it very well. This is its fourth mission. Missions - that don't need people - are the luckiest missions in the world..

I always imagine it creeping up on unsuspecting satellites like some kind of space puma. All up close and personal like, giving them a sniff and then slipping away undetected.

It's tough to be sneaky in space...

Re: Unmanned U.S. Air Force space plane lands after secret, two-year mission

#37

Post by nyolfen »

jfoutz wrote: post #14
hendzen wrote: post #6

Earlier quoted context omitted.

Probably a space equivalent of the USS Jimmy Carter - i.e. hacking/surveilling unfriendly satellites.

My guess was to refuel spy satellites. I imagine those sats are tough and can survive a long time. But when they get low on gas they can only do station keeping. If you can count of fuel coming, there's a lot more freedom to shift the track a half a degree as needed. It may be all electronic surveillance. I guess, you can count on satellites not changing after they're launched, so the electronics package would be goo…

i don't think it's refueling anything. for one it has a pretty small payload, but more importantly it has a low orbit (~320km). there's some decent speculation here:

http://www.airspacemag.com/space/spaceplane-x-37-180957777/

tldr possibly a test bed for new smaller electronics packages designed for new smaller satellites

Re: Unmanned U.S. Air Force space plane lands after secret, two-year mission

#38

Post by schiffern »

blackguardx wrote: post #17
jessriedel wrote: post #15

Earlier quoted context omitted.

Yea, wings on spacecraft are about as elegant as parachutes. They can make sense for certain uses, but, as a rule of thumb, they are inelegant and not futuristic.

Technically, the space shuttle and this space plane are lifting bodies, which I think is pretty cool and elegant.

Capsules are lifting bodies too. Apollo had a L/D of 0.368 and "steered" by rotating. Dragon uses the same technique (albeit with a slightly lower L/D), and Dragon 2 will have a tungsten ballast sled so it can change its angle of attack dynamically during re-entry.

Even simple cylinders can be lifting bodies. Shuttle and Falcon 9 both have a L/D of 1.[1] On Falcon 9 the first stage acts as a lifting body, using the grid fins to "trim" the big cylindrical body making it act like a wing.

In the SpaceX landing videos you can see the stage pitch up on reentry. This is no accident. Upward lift = more atmosphere traveled through = more drag = less landing fuel needed = more payload to orbit. A nice optimization by the SpaceX team!

>you don't actually need wings by the way, it's kind of a common misconception around, you just need some lift over drag number, or lift vector - and steer back to the launch pad --- Elon Musk[2]

[1] https://spaceflightnow.com/2017/04/04/musk-previews-busy-yea...

[2] http://shitelonsays.com/transcript/npc-luncheon-with-elon-mu...

Re: Unmanned U.S. Air Force space plane lands after secret, two-year mission

#39

Post by compton_effect »

tammer wrote: post #20

Surprised nobody's mentioned this possibility as it usually comes up re: the X-37B. Terrifying but I think not out of the question given the strategic potential of such a weapon. https://en.wikipedia.org/wiki/Kinetic_bombardment

cool idea but I'm gonna assume its a lot more expensive to send up an X-37 and have it crash back down then it is too just send a few nukes at your target.

Re: Unmanned U.S. Air Force space plane lands after secret, two-year mission

#40

Post by justin66 »

azinman2 wrote: post #10
Animats wrote: post #5

Earlier quoted context omitted.

Toxic propellants. Nitrogen tetroxide / hydrazine. Both components are highly toxic. The big space shuttle used those for its maneuvering propulsion, and ground crews had to wear all the protective gear after landing until the propellant had been drained.

Is it all combusted perfectly, or do they lose some and just leave droplets of toxic liquid propellant in their paths as they fly?

There was at least one mishap during Apollo capsule reentry where astronauts were exposed to fumes from hypergolic fuel, after forgetting to purge the thrusters at the proper time: https://en.wikipedia.org/wiki/Apollo%E2%80%93Soyuz_Test_Proj...

That brief exposure, before they got their oxygen masks on, put them in the hospital for a couple of weeks. It really could have been worse.

I believe the technical procedure for unprotected ground crew dealing with a leak of this stuff is, roughly, "turn around and run for your life." Hence the guys in funny-looking suits.

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