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NASA Scrubs Launch Due to Faulty Fuel-Tank Sensor
VUSE g-EE-k writes "NASA has scrubbed Wednesday's launch of Discovery due to a faulty fuel-tank sensor in the external fuel tank. They are going to begin the troubleshooting process. They have not released details as to how long this delay will last. The crew have begun to get off the shuttle. For more information, see the NASA TV site. Drudge Report has some initial coverage of the scrub."
Reader adefa adds a link to NASA's Space Shuttle launch page with more info.
Anybody know how big their launch window is? I was under the impression they had a very small amount of time to be able to meet the ISS.
They had a fuel low level sensor fail. This was some sort of instrumentation and control equipment or sensor fault. The possible causes could be that the actual sensor failed (which might require replacing the liquid fuel tank) or there was an instrumentation fault. Since they were using a test circuit to simulate a low level (since the tank is actually full), an instrumentation failure could be either a failure in the normal instrumentation circuitry or a failure in the test circuitry. Either of these two cases should be easy to fix.
As someone who has worked extensively on I&CE operation, maintenance, and repair on nuclear reactors, I fully understand why they scrubbed the launch. Redundancy is for faults in operation, not to compensate for damaged equipment prior to operation. From my experience, it is probably the test circuit that failed. Then the instrumentation circuitry. Then, in the most unlikely case, the sensor itself.
An astronaut on NASA TV explained that the there is a coincidence circuit if two low level alarms trigger that will cause an automatic engine turnoff. If this did not happen and the tank completely emptied, he said that it could cause major damage to the shuttle's main engines. I'm not sure exactly how, perhaps because either without liquid hydrogen, only the oxygen would flow through the engine and no chemical reaction would occur, cooling parts of the engine below their specifications? Or flow characteristics wouldn't be predictable?
Suddenly, the hairy finger of a familiar monkey tapped me on the shoulder. It was time.--G. T.
If you tried to run the engines without any fuel in them, it would be like putting your foot to the floor when the transmission is in neutral. Without a load the engine spins faster and faster until parts start flying off.
On the shuttle, the turbines are large enough that a catostrophic failure would probably destroy most of the equipment in the tail end of the craft. This includes the orbital maneuvering system, the hydrolic system, several fuel cells, and the rearmost parts of the cargo bay. You also run an outside risk of damaging the tail and flight surfaces on the wings.
Not a fun thought at all.
"Learning is not compulsory... neither is survival."
--Dr.W.Edwards Deming
About this time someone says "get on the shuttle, get on the shuttle"
I say "FUCK YOU I'm getting IN the Shuttle! Let Lance Bass ride ON the shuttle."
Good point- although I wish to take it a step further. Yes any vehicle a few decades old will show some bumps, even if maintained (My grandmother's 78 Caddy, only 32,000 miles, but a few bumps), but even well maintained vehicles (My Pick Up, Used to plow snow for extra money in winter- beat to heck- well maintained though). The severity of what the shuttle goes through is also a huge factor I imagine. Amazing temps and pressures. I don't pretend to have the knowledge about rocket science others here do, but I do know the shuttle goes through some majorly extreme stress and conditions...
It isn't "funny," as nothing that has to do with lefe and death of the crew members is funny, however, I feel like NASA keeps having these setbacks in an almost tragicomic way. I mean, a cover falling off a window and damaging heat tiles? I read that the cover is to prevent dust- so why does it need to be made of something hard that can damage the shuttle? Wouldn't cotton have done as nicely? If someone knows, I really am curious, I am not being a jack-a##
And All I Ask is a Tall Ship And a Star to Steer Her By
Risk-taking is a part of life. If airplanes had been invented under the current regulatory climate noone would get off the ground.
NASA cowboyed the Challenger launch over the heads of the engineers who BUILT the damn SRBs
If the engineers who built the things say "its not safe" and you ignore them that is pointless risk.
However what is acceptable risk? Assume they had 12 fuel sensors, needed 2, but only 11 worked. I bet they'd STILL delay the launch...
Another thing to think about, how is it that we can have a couple thousand ICBM's ready to launch hot molten death on a few minutes notice,
but don't have a space program capable of launching humans every few days?
Service guarantees Citizenship! Questions Guarantee GITMO.... Amerika Uber Alles!