STS 122, Colombus to the ISS Options

[climber]

Here we are with another Shuttle launch. Only another 1000 days to go. We're going to miss that.
HD television is available @nasa new web site but not for live videos unfortunately. May be one day on the net.
On top of Colombus delivery, when Atlantis will leave the ISS, we'll have the 3rd version (out of 4 scheduled) of the 16's ISS expedition crew as follow :
Witson - Malenchenko - Anderson
Witson - Malenchenko - Tani
Witson - Malenchenko - Eyharts
Witson - Malenchenko - Reisman
It's nice that (the) Atlantis will deliver Colombus (remind me of something)

[ilbasso]

One thing I have never done is witnessed a Shuttle launch. I realized this week that I had better get my act in gear if I want to catch one! Anyone for a UMSF Discovery party on April 24?

[jaredGalen]

24 hour scrub called due to ECO sensors in the fuel tank indicating dry when wet.

http://www.nasa.gov/mission_pages/shuttle/main/index.html

[blobrana]

The launch has been rescheduled for Saturday 20:43 GMT, (3:43 pm EST), 8th December.

[nprev]

Mixed feelings about the potential decision to fly as-is with the empty tank sensor malfunction. Since all three are out (one's showing dry tank when immersed, the other two are showing open-circuit indications), either there's a multi-wire harness problem, which in my experience is a result of either miswiring or physical damage, or that the multiplexing device that's interpreting & relaying the signals to the rest of the vehicle isn't feeling very well. A third possibility is that one sensor's failed and some other event happened to the other two, which share an unexpected single-point vulnerability. Coincidental compound malfunctions begin to occur late in a system's life-cycle, where the Shuttle's definitely at...and, boy, are they ever a pain to troubleshoot.

Since it is a backup system, the temptation will be there for managers to fly it using a workaround, which is exactly what's being discussed. Saw this happen many times on USAF aircraft with no ill effects (esp. during Desert Storm) save piling up the maintenance discrepancies & increasing downtime after the mission. What I don't like is that an inflight abort for the Shuttle is incredibly more risky than that for an aircraft. I'm also quite concerned about the possible wire harness damage failure mode I mentioned; are there any wires for other critical systems bundled in there as well?

There's an old Air Force aircraft maintenance acronym--FIFIFIL, which, cleaned up for a G-rated audience means "Fudge it, fly it, fix it later". Suffice to say that it's generally a bad paradigm to apply to spaceflight. I'm thinking that the best choice may be to bite the bullet, fix the problem, eat the holiday overtime, and shoot for the 2 Jan launch window.

[stevesliva]

Is it a "backup system?" Perhaps "failsafe" is a better term? It sounds like it's an automatic failure-detect system that shuts off the engines if and only if there is some sort of anomaly that empties the tank faster than anticipated. I don't know that there's another automatic system that it's a backup for.

I imagine they're developing protocol to implement the failure-detect manually, and hit the big red button manually. The big question is whether they can assure themselves that they'll have the process in place to react correctly and in time.

It would be an unprecedented event in that with the system either working right or disabled they might be doing an abort-to-earth. I wonder if the system engaged when the Challenger's ET disappeared.

[David]

The launch has been rescheduled for Saturday 20:43 GMT, (3:43 pm EST), 8th December.

It's been pushed back further, to 3:21 p.m. EST on Sunday, December 9 -- at the earliest.

[nprev]

I don't know that there's another automatic system that it's a backup for.

Believe that you're right. I was thinking of it as an additional cue to the flight computers, which really shouldn't need it if the flight profile is nominal. If it's a fail-safe, then that's an even more powerful argument for fixing it instead of flying as-is.

[ugordan]

I'm not sure I got the story straight, but AFAIK the 4 cutoff sensors aren't part of any backup system. In a normal ascent profile they shouldn't be triggered, because you don't want to plan your payload capacity based on running the tanks completely dry.

As far as I'm aware, there's been one problematic flight, STS-93 where there was a hydrogen leak (among other problems, ironically; you can actually see the leak in tracking footage!) leading up to a couple-of-second-early MECO. It was triggered by those same fuel sensors because the shuttle didn't have enough fuel for a nominal MECO before the tanks ran "dry". It was IIRC the oxygen tank that got depleted (counterintuitive because it was an LH2 leak). MECO is forced probably when more than 2 of those sensors (in either tank?) register "dry". Had there been no such sensors, the SSMEs would have run out of propellant and the turbopumps would probably have failed catastrophically.

[nprev]

Thanks, Gordan. Bottom line is that this looks like a must-fix problem.

[Jim from NSF.com]

There's an old Air Force aircraft maintenance acronym--FIFIFIL, which, cleaned up for a G-rated audience means "Fudge it, fly it, fix it later". Suffice to say that it's generally a bad paradigm to apply to spaceflight.

The USAF spaceflight version is just FIFI

[nprev]

Oooo....burn!!!!

[jmjawors]

Well.... the decision has been made to fly tomorrow with a caveat; 4 good sensors at launch. The flight rule previously had been 3/4 sensors. Rationale is that in all previous cases (at least, in my memory, since return to flight) the sensors behaved during subsequent tankings.

And ugordon, well called on STS-93. That specific flight was referenced today at the presser.

[nprev]

Tank fuel upload set to begin now (1100 GMT); should know shortly whether the sensors are working:

http://www.nasa.gov/mission_pages/shuttle/main/index.html

http://www.nasa.gov/multimedia/nasatv/

[djellison]

Sensor 3 has just failed. Game over for today.

Doug