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Minor Technical Issue Aboard Shuttle Discovery
IZ Reloaded writes "Space Shuttle Discovery has a problem with the pipeline for an auxiliary power unit that controls the shuttle's hydraulic steering and braking maneuvers. CNN reports that the pipleline is leaking 'fuel' at about six drops per hour." From the article: "The leak is more likely nitrogen, but there is no way of knowing that, so NASA is treating the problem as if the leak were fuel ... If it is fuel, the current rate is still 100,000 times slower than what would cause a fire ... Just in case, NASA will turn on the power unit with the leak early Sunday as part of its normal testing and then see if the leak rate changes. If it does, NASA may burn off the hydrazine and shut down the power unit before the shuttle returns to Earth to eliminate any fire hazard.'"
Two words: Duct tape.
There are pipelines in space now? Cool.
The leak is more likely nitrogen, but there is no way of knowing that.
Excuse me? The shuttle must be one of the most redundantly-instrumented efforts ever built and they don't know what's leaking?
Hydrazine is nasty stuff but it is just one of the dangerous checmicals aboard the shuttle.
When Columbia broke up, it was the possible presence of Hydrazine from the APUs that make the Texas Dept of Health issue warnings about approaching shuttle debris.
The problem with spaceflight is that everything is so close to the edge. Performance requirements that can still leave a good safety margin mean that simpler and safer methods are often inadequate. Consumers don't have the same risk/reward ratio as people who sit on top of rockets for a living.
-M
# grep slashdot access.log | grep html | sort | uniq | wc -l 2604
Seems off that only APU1 drives the landing gear, with a backup of pyrotechnics...
1 4mplm/
"APU 1 is the only hydraulic system that can deploy the shuttle's landing gear. If APU 1 is out of action, pilot Mark Kelly would have to manually fire pyrotechnic charges to deploy the gear."
http://www.spaceflightnow.com/shuttle/sts121/0607
STS-9 came in with an APU on fire. Here is a video.
Suddenly, the hairy finger of a familiar monkey tapped me on the shoulder. It was time.--G. T.
NASA is crippled. Rather than cover the achievements of each mission, they cover the lack of failures. It's a no-win situation. If they screw up ANYWHERE, they look terrible. If they make it back ok, they wasted a ton of money on... what again?
In the media, I've heard all about how they made sure the stupid thing can land, on at least 3 media sources. But WTF is the reason they launched? What are they up there for, other than to make it back alive? I could do that on a Mooney for alot less money and with alot less stress!
This is being handled all wrong. They shoulda spun this as "making real forward progress sometimes hurts - there's risk in growth - DEAL WITH IT" - but instead they're trying to make it seem like it's a big deal to launch into low-earth orbit and make it back alive.
How stupid!?!?!? We've been able to do THAT since the 1960s.
This is a PR ball that's being dropped, and NASA is now neutered. It's a worthless waste of time. Send everybody home, take the (piddling, thanks to terrible PR management) amount of money that was being spent there, and give it to an organization that can LOOK FORWARD again...
Give me a reason to get excited, or stop spending my damned tax dollars. (Oh, and don't mention Iraq, I marched in the streets with signs over that one!)
I have no problem with your religion until you decide it's reason to deprive others of the truth.
A leak in a "gas tank" is a minor technical issue? :p
"Hey there cowboy, word goes around that there's something wrong with my car."
"Nah sir, just a little scratch."
"Ah if it's just a scratch then I can live with it."
"Yes sir, just a bit of gas leaking through that "scratch", so you might want to cut down on that smoking sir."
The write-up missed the important angle that if they decide to power down the possibly leaky APU, they'll have to use explosive bolts to lower the undercarriage. That's never been used in flight before. That doesn't mean it won't work, of course, but it will make the re-entry and landing a little more interesting than usual.
Everything I needed to know about life, I learnt from Blake's Seven
I had an undetected small leak in a Diesel system for some time because it only leaked under feed pump pressure, which meant the engine was running, and the heat volatilised the fuel which was then sucked into the air inlet above the leak. It may have been there for several years undetected.
Despite all the fuss about it being hydrazine, it may be safer and easier to ignore it because any attempt to fix the leak may simply make it worse.
Pining for the fjords
The shuttle has 3 auxillary power units. One is necessary to land. They are routinely tested while in space. If one fails they land as soon as possible. The APUs are not small, they are powered by a 100 horsepower turbine which is turned by decomposing hydrazine over a catalyst. Sometimes on good movies of the shuttle after it has landed you can see the heat waves from the hot gases (nitrogen, hydrogen, and a little ammonia) from the decomposing hydrazine coming straight up from the shuttle.
The larger thrusters and the rocket engine used by the shuttle in space are powered by methyl hydrazine reacting with nitrogen dioxide. These are hypergolic (burn on contact with each other) so no possiblity of them failing to ignite for a second or two then going boom which is possible with other fuels like hydrogen and oxygen. They are liquids at ambient temperatures so don't require cryogenic storage.
Hydrazine, N2H4, is a great rocket fuel. It is a liquid with similar boiling and freezing points to water -- but can explosively decompose (it is dangerous to measure its boiling point), is toxic at ppm levels, is carcinogenic (ie all the rats that breathed it got nasal cancer), causes skin burns. Like most amines it smells like rotten fish. Believe it or not there are people who believe that low levels in the blood is an anti cancer agent.
Hydrazine reacts in the precense of a catalyst such as silver or iridium, which is why combustion chambers of many reaction control rockets are lined with such. Hydrazine is semi-stable. It will breakdown in the precense of the catalyst or if it warms up to the proper point. If neither happens, you're fine. The engineers who actually know how the system is designed (ie, not you), and know where stuff can get into, where it might come into contact with a catalyst, or where it might warm up are the ones qualified to analyze the risk.
As for the risk of explosion, well that's poorly written, but if you don't have enough to cause a pressure increase of damaging magnitude, well then there's nothing to worry about. In this case they have a lot less. That suggests to me they looked it over and decided it must be leaking in a way that there's no place for it to accumulate.
Furthermore, according to NASA, they don't actually use pure hydrazine in the shuttle RCS jets. They use nitrogen tetraxide and monomethyl hydrazine (add on a carbon atom), which are hypergolics. They're more stable but they react spontaneously in each others presence.
Of course, the shuttle engineers don't have a clue about any of this. They like playing dice with their co-workers lives.