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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. sad.gif

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
QUOTE (blobrana @ Dec 7 2007, 07:15 PM) *
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
QUOTE (stevesliva @ Dec 7 2007, 12:58 PM) *
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
QUOTE (nprev @ Dec 7 2007, 02:50 PM) *
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!!!! laugh.gif
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
nprev
Yep.

This has gotta be a wiring problem; weird, intermittent sensor malfunctions almost invariably are. Thermal contraction at an interface point once the LH2 hits it?
blobrana
A preliminary launch date has now been set for 2 January, 2008.
nprev
Good call. They've learned the lesson of Challenger well, then. I was more than a little concerned about the time pressure causing hasty decisions.
dvandorn
As a tech support rep for Comcast, I can tell these guys exactly how to fix their problem:

1) Unplug everything.

2) Leave everything unplugged for a good 30 seconds.

3) Plug everything back in, in sequence from upstream to downstream (in terms of signal flow).

Works every time... rolleyes.gif

-the other Doug
djellison
It worked for our little network here at work - if I did it any other way, we wouldn't get gbit networking throughout.

Doug
nprev
Bloody cable & computer guys... tongue.gif

Believe it or not, fuel quantity sensing systems are almost always the most difficult things to troubleshoot on aircraft. These level sensors probably aren't so bad, but I wish I knew their operating principle.

AC-excited capacitive sensors are the worst by far; any little cable or shielding fault often screws things up royally or causes an endless series of intermittent, difficult-to-duplicate problems. I've been in situations where it was actually easier to rewire an entire tank then to spend time finding the actual fault.
dvandorn
The ECO sensors are indeed capacitance sensors. I don't have data at the moment as to whether or not they're AC-excited, but they're definitely capacitance sensors.

-the other Doug
nprev
Oh, lovely (not)... sad.gif Hopefully, then, they're DC-excited; these are much easier systems to troubleshoot since the cable shielding isn't part of the overall signal path. Given the age of the Shuttle, though, I suspect that they're AC after all.
lyford
And now... this:

A giant spider attacks the shuttle Atlantis.

Click to view attachment
ugordan
zOMG, look how many strap-on boosters that thing has!!11
Stu
Now that's what I call a serious software bug problem... ohmy.gif
climber
Tintin get the same trouble once, but it was on "L'étoile mystérieuse" not "Objectif Lune"...
Doc
Hi, im new here. Just joined yesterday. Its hard to get connected to the rest of the world when yer in the middle of Africa.....Tanzania, Dar es Salaam to be precise. Any way im sure all of of us hav one thing in common.....the postponed launch of STS-122. I mean c'mon, i'v watched most of the shuttle launches since "Discovery's Return to Flight" mission but this has got to be one of the most frustrating missions i hav ever had the pleasure to witness.


Anyway, safety coms first i suppose. I didnt notice that spider picture posted by lyford!
It kind of reminds me of Tintin in "The Shooting Star".

Here's to a succesful launch on 2nd January.
centsworth_II
QUOTE (Doc @ Dec 12 2007, 06:10 AM) *
...this has got to be one of the most frustrating missions i have ever had the pleasure to witness.

Ironically it looked like one of the smoothest up to the point where the current problem occurred.
Having lived a two hour drive from The Cape the entire life of the Shuttle program, this was going
to be the first time I made the drive to see a launch. All the stars were in alignment: Beautiful
weather, no serious problems being worked, wife and I both finagled time off from work.... Oh, well.
Airbag
All kinds of ECO sensor info (but no sensor AC/DC info) at:

http://www.nasa.gov/returntoflight/news/ECO_graphics.html

Airbag
hendric
Well, no wonder they are having problems with fuel level sensors in the external tank. That giant spider is sucking out all the fuel! I for one welcome our new arachnid overlords! biggrin.gif
nprev
(You suck-up! tongue.gif )

Just an obervation, but an external tank would make one hell of a can of Raid...
nprev
Looks like this is gonna stretch on a bit; they've decided to replace a tank boundary connector.

Definitely an AC-capacitance system. Open shielding in these systems causes an off-scale high indication, which is completely anethemic to the intent of these sensors, since there would be no cutoff signal for the engines if the tank ran dry. (An open center conductor would cause an off-scale low indication, which would cause premature engine cutoff--also not good.)

This is quite literally Monday-morning quarterbacking, but I have to wonder why they chose capacitive sensors for a discrete signal function. C-5 aircraft, which entered production in 1966, have tank low-level sensors as well, but they use thermistors--if the fuel's gone, they heat up & change their resistance, turning on a warning light. Guess that this might have been deemed too risky for LH2, but still...
kspace
Launch date set for Feb. 7th

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

Jan. 11

NASA Friday announced Feb. 7 as the target launch date for shuttle Atlantis' STS-122 mission to the International Space Station and mid-March for the launch of Endeavour on STS-123. Liftoff of Atlantis from NASA's Kennedy Space Center, Fla., will be at 2:47 p.m. EST.

A decision by the Russian Federal Space Agency to move up its Progress launch from Feb. 7 to Feb. 5 enables both STS-122 and STS-123 to launch before the next Russian Soyuz mission in early April. This allows astronauts assigned to the space station's Expedition 16 crew to complete the tasks they have trained for, including support of the launch and docking of Jules Verne, the first European Space Agency Automated Transfer Vehicle. Targeting Feb. 7 also allows time to complete modifications to the engine cutoff sensor system that postponed two shuttle launch attempts in December.
dvandorn
Yes, and the solution to the ECO sensor problem? Solder the pin connectors! This is apparently a fix that people came up with for a very similar problem in Centaur upper stages nearly 40 years ago. It took this amount of time and effort for someone to check another program's Lessons Learned Book... *sigh*...

-the other Doug
nprev
I hear ya, but can't get too mad at them for it. Fuel quantity sucks!!!

There are a few avionics systems that are always very peculiar (in terms of design) to specific aerospace vehicles: G&C, and fuel quantity sensing systems are usually the biggies. This fact tends to channelize thinking when troubleshooting, since drawing analogies to equivalent systems on other platforms often isn't practical, at least down into minutae like connector designs. I just hope that it works.
Doc
With the launch of STS-122 approaching, I thought it right to ressurect this thread.

Weather is not looking too good but other than that, no technical faults to talk about.(30% chance for launch).

Latest radar of the area-->
http://radar.weather.gov/radar.php?rid=mlb...111&loop=no
MahFL
QUOTE (dvandorn @ Jan 12 2008, 06:14 PM) *
Yes, and the solution to the ECO sensor problem? Solder the pin connectors! This is apparently a fix that people came up with for a very similar problem in Centaur upper stages nearly 40 years ago. It took this amount of time and effort for someone to check another program's Lessons Learned Book... *sigh*...

-the other Doug


And what might happen if the solder cracks ?.....
Doc
QUOTE (MahFL @ Feb 7 2008, 03:06 PM) *
And what might happen if the solder cracks ?.....


May the Almighty forbid that!
djellison
I think that's an issue that was sorted years ago. There is soldering on so many components of LV's - that I'm sure specific ways, means and methods for avoiding that problem have been addressed for decades.

Doug
nprev
I'm sure that they're using something radically different in composition then conventional solder. For example, high-temp connections such as jet engine thermocouples use silver solder; presumably there is a cryogenically-resistant equivalent, but don't know what it might be.
paxdan
I'm gonna be in the chat room if anyone is about for the launch
djellison
And away she goes smile.gif
djellison
STUNNING ET sep shots - a whole swathe of back lit plasmarey, RCS-exhaustey lovely stuff.

It's been a long time, but Columbus is in space.
K-P
Oh man... Sometimes I feel REALLY stupid... unsure.gif

I tried to get NASA TV working via internet as usual when watching shuttle launches and there were some problems this time to see broadcast. I was like grrr....... Is it now just watching text-updates on spaceflightnow.com smile.gif NO WAY! Still trying to resolve problem, no... no broadcast on my screen, T- 2minutes... shiteshiteshite....! Whattodoo?!?!? Then I got it. TELEVISION! (remember that old grey non-interactive box?). Quickly CNN. "T- 10seconds, 9,8..." phew! Oh man... I felt SOO stupid. biggrin.gif

Nice launch anyway, and finally we Europeans have our own little module in space. And then we separate it as independent station and then we fly our own Hermes-shuttle there and... .... ...then I woke up and changed dry underwear.

blink.gif

No, really, great, this has been a long time coming, let's say half of my short but prosperous and impressive life.

Over and out.

djellison
Fortunately, Sky News in the UK often carries Nasa TV for 20 or so minutes during a shuttle launch. I wish someone could put together a business plan to have Nasa TV on Sky TV in the UK at, say, £10 a month.

Doug
Sunspot
I'm having trouble viewing the launch on the NASA website and viewing NASA TV online. Firefox completely locks up and freezes for maybe 6-7 seconds. Or maybe my computer isnt up to the job lol

Anyone else having these problems?

http://www.nasa.gov/multimedia/nasatv/index.html
helvick
No problem for me with Firefox (under Vista at any rate). Firefox's default settings for handling Windows Media on my machine seem to prevent the launch of a separate instance of WMP to make it possible to run in full screen mode, it did work fine under IE though.
djellison
I just open http://playlist.yahoo.com/makeplaylist.dll?id=1368570 in Quicktime (with flip4mac on OSX)

Doug
Sunspot
The whole computer freezes too...I noticed the seconds no longer tick by on the clock in the task bar, so maybe the computer just isn't up to the job of handling these files.. Sigh, I need a new computer lol huh.gif ... still waiting for that updated Mac Mini.
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