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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.
I'm still confident they'll launch before DNF or Longhorn are released.
I have a faulty fuel sensor in my car. My solution: just fill up every few days to make sure I don't run out of gas. Why can't these "genius" rocket scientist just have the crew stop off and get gas half way up, and again when they come back down?
Dammit, *I* should be in charge of NASA.
(please note, that this post is as insightful as most of the other Slashdot 'advice' to NASA. please mod accordingly)
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I had to laugh though... Drudge Report had some initial coverage
I have a few friends that work in the Public Information/Media Relations department at KSC. I'll check to see if Drudge was issued a press credential.
Drudge Report, where I go for all my hard-hitting science news.
NASA has through July 31 to launch Discovery or else wait until September 9 due to the need to lift off and separate the external tank in daylight.
The external fuel tank burns up in the atmosphere after launch. They are never reused or AFAIK even recovered. The external fuel tank on the pad now, and every part in it, is brand new.
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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?
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True, back in the 60's in the Apollo days, they tested the bejezus out of everything; that's because they were pushing stuff to almost beyond what technology of the time would do, and they had to have the best of the best to have a chance in hell of pulling off the mission.
They just don't have the budget for that now. I think they just ignored a lot of stuff and got lucky most of the time. They are going to be super-careful this time; they can NOT afford a failure on this launch.
Remember when the air force told NASA to expect something like 1 in 20 missions to blow up, because that was their record with SRBs? NASA has been doing WAY better than that.
These days they're scrubbing when they notice something outside of nominal. I'm happy they are. The Challenger was lost when they were operating outside of nominal and figured they could get away with it. After that event, investigations showed that they were ignoring a WHOLE LOT of stuff. I keep hoping they'll stop ignoring their own rules; we'll see.
There's a daily lauch window of about 10 minutes when the ISS is in the right place. Those 10 minutes occur during the night between July 31st and September 9th.