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July 17, 2006
Shuttle lands safely, reporters wring hands over the baggage retrieval system at Heathrow.
From the AP, as posted on FOX.
Toward that end, Discovery's astronauts and flight controllers kept close watch on a slightly leaking power unit that tested out fine a day earlier in orbit.
NASA did not know whether harmless nitrogen gas or flammable hydrazine was dripping from the auxiliary power unit, one of three needed to drive the hydraulic landing systems. The leak was small, managers said. If it worsened during re-entry — considered unlikely — the unit would shut down automatically and Discovery would become the first shuttle to land with only two functioning auxiliary power units.
Now, I freely admit that I am not a shuttle engineer. But I'm a bit of a fanatic on "Manned Spaceflight" and know a thing or two about the shuttle's systems. Let us ignore the flammable carcinogenic rocket fuel hydrazine and assume that anything routed by that substance took that fact into consideration as it was being designed.
If memory serves me correctly (appologies to Kaga) ALL, did I say that emphatically enough? Make that * * * A L L * * * critical shuttle systems are triple redundant. As in there are THREE wires leading to everything. If one wire says something different from the other two, that wire is henceforth IGNORED. There are THREE hydrolic systems to move each flap on the wings and tail, each with enough oomph needed to move said flap. If one of the three wants to push the wrong way, the other two will easily muscle it to the right position.
So. If one of the power units to drive the hydrolic landing gear is crap... the other two will still do the job. Easily.
Oh. And I failed to stress one more thing. This was the *AUXILIARY* power unit.
I consider this the equivalent of reporting that someone on the shuttle gave the guys on the ISS the spare roll of toilet paper that they keep hidden in the back of the cupboard. Cause, you know, they just CONCEIVABLY MIGHT NEED THAT SPARE ROLL OF TOILET PAPER.
Posted by paul at July 17, 2006 10:27 AM