Launch Scrubbed for today

rvsm410

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discovery will not happen today...low fuel pressure sensor failure in the ET...They will de-tank and examine the sensors and or replace....dont know how long this will take...tomorrows window will be at 15:28 Friday will be at 15:08...


Safe than sorry....good call...
 

RockyMnt1

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How do they find this stuff? Do they have sensors sensing the sensors?? Most of the no-go items that I find are usually very obvious by the time I find them (puddles of oil/fuel/hydraulic fluid). I would have no clue that the low fuel pressure sensor is broken unless it was on/abnormal all the time. I am thinking that there must be a self test/full cycle feature built into the sensor.
 

U of I Tweak

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Test circuit

RockyMnt1 said:
How do they find this stuff? Do they have sensors sensing the sensors?? Most of the no-go items that I find are usually very obvious by the time I find them (puddles of oil/fuel/hydraulic fluid). I would have no clue that the low fuel pressure sensor is broken unless it was on/abnormal all the time. I am thinking that there must be a self test/full cycle feature built into the sensor.


One of the speculations on the NASA channel was that it was a problem with the test circuit for the sensor; which supports the conclusion that there is a self test feature built into it.
 

9GClub

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RockyMnt1 said:
How do they find this stuff? Do they have sensors sensing the sensors?? Most of the no-go items that I find are usually very obvious by the time I find them (puddles of oil/fuel/hydraulic fluid). I would have no clue that the low fuel pressure sensor is broken unless it was on/abnormal all the time. I am thinking that there must be a self test/full cycle feature built into the sensor.

My understanding is that two of four low-fuel-level sensors were indicating low hydrogen levels in the recently topped-off tank, which of course doesn't make sense. According to CBS news:

"The sensors let the computers know when the tank is dry and they can shut the engine down. If the engines were to continue running at high speed without fuel, it could lead to a catastrophe. It was not the first time these sensors malfunctioned. During a fueling test of Discovery's original tank in April, some of the sensors gave intermittent readings. NASA could not ascertain the exact reason for the failure but replaced the tank for other reasons."

Sounds like they were aware of a potential problem in April but didn't address it. According to ABC news:

"Shuttle managers considered conducting a fueling test at the launch pad on the replacement tank, but ruled it out to save time, saying that the actual fueling on launch day would be the ultimate test."

Sure was.

Gotta hand it to those guys and gals, though.... they're literally monitoring 20,000 (twenty thousand) parameters prior to a launch.

Full articles:
http://abcnews.go.com/Technology/wireStory?id=935773
http://www.cbsnews.com/stories/2005/07/13/tech/main708664.shtml
 

RockyMnt1

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I sure hope that the guy making the fix is an A&P and that they get an IA sign off before flight!! GOtta keep the FAA happy. Of course, the log books must be updated too. I would sure like to see the airworthiness certificate for this thing.
 

EagleRJ

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If the engines were to continue running at high speed without fuel, it could lead to a catastrophe.


Typical media Nonsense. How can an engine- any engine- continue to run without fuel? Hello?

All four of the sensors are required for flight, and two of them were periodically giving false empty readings. They sense when the External Tank is empty, and tell the computer when to shut the engines down. If they were to give a false reading during the main engine burn, the shuttle might have too much energy to return to the Cape, and too little energy to reach the abort fields across the Atlantic. In that case, the crew would have to bail out and go for a swim, and we would lose the orbiter.
Probably a good idea to scrub the mission, but still, those sensors should have been changed at the first sign of trouble.
 

rvsm410

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Please remember one thing....for all these years I have worked on the orbiters, and since i left the program in 99', the media has got to find a way to hipe up the story line...many times they just get it wrong, mis-quote, or make assumptions....

As to the sensors....I can only tell you in general, that every single inch of wiring, sensors, avionics, and all the systems have redundant backups that run ongoing diagnostics all the time by the GPC's (general Purpose Computers) I believe there are 4 of these on board.....I am sure they would know who, when, where and how long one of the astronauts pass wind!

Bottom line, NOTHING is over looked, and on this mission, they are being extra careful that everything is in the green.....no exceptions...

Obviously 7 lives are at stake, but the whole program will be at risk everytime we/ they launch a Space Shuttle for the duration of this program....tens of thousands of jobs, billions to the economy, FL, TX, and many other states....
The early retirement of the program now scheduled for 2010, has everyone worried about our future employment....the follow on vehicle is still in the design phase, years away from reality.....there will be alot of down time, lost talent before another vehicle will be able to replace this one...

For all her fragility and downfalls, this has been one wonderful machine, a true marvel of mankind....its not Star-Trek, but it is the first steps to get there, the media and the American Public forget this all the time...Space is always going to be an all or nothing proposition......there is no room for errors there......
 

9GClub

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EagleRJ said:
Typical media Nonsense. How can an engine- any engine- continue to run without fuel? Hello?

Maybe they're concerned about spewing LOX all over the place without any hydrogen to mix with it......

This non-NASA-insider speculative crap is freaking awesome! People who actually know what they're talking about...... just go play with your slide rules or something whilst the rest of us project our Cessna and Piper paradigms onto the U.S. space program.
 

NookyBooky

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RockyMnt1 said:
I sure hope that the guy making the fix is an A&P and that they get an IA sign off before flight!! GOtta keep the FAA happy. Of course, the log books must be updated too. I would sure like to see the airworthiness certificate for this thing.



I wonder if the shuttle pilot has his glider licence...................
 

Fly_Chick

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paulsalem said:
How do they determine their "window" of time to launch within?

Based on having daylight for the entire lift-off and entry into orbit. Want to be able to see everything in case anything is out of the norm.

They also time this for when they will be able to reach the space station. The time will decrease by about 30 minutes each day. As of now, the latest is they will try again on Monday, and the time frame is for somewhere near 1:30 pm local.
 

EagleRJ

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9GClub said:
Maybe they're concerned about spewing LOX all over the place without any hydrogen to mix with it......

This non-NASA-insider speculative crap is freaking awesome! People who actually know what they're talking about...... just go play with your slide rules or something whilst the rest of us project our Cessna and Piper paradigms onto the U.S. space program.


?????

The sensors in question are intended to shut the engines down in the event the LH tank is depleted before the orbiter's computers command a shutdown at the normal time. Under normal conditions, the engines are shut down while there is still fuel in the ET- the burn time is carefully calculated based on vehicle weight, desired altitude, etc. If either the LH or LO were to be depleted while the turbopumps were still running, the engines would obviously quit, but there could be all sorts of other bad things going on- pressure surges, ruptured lines, and so forth.
The failed sensors are intended to prevent that, shutting down the engines before the LH tank is empty. If they were to suddenly indicate zero quantity before MECO, they could cause the aforementioned swim in the Atlantic for the astronauts.
The danger from this anomaly was not from "running an engine without fuel".

Typical clumsy reporting.
 
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9GClub

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Wiggling some wires

CBS news 7/15:

"The only way the shuttle would be able to fly on Sunday is 'if we go in and wiggle some wires and find a loose connection,' said [deputy shuttle program manager Wayne] Hale, who conceded that was unlikely."

Crap I can wiggle wires, can I work for NASA?
 

9GClub

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Ps

Is Collins actually a pilot......... or is she just a female?
 

mzaharis

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9GClub said:
Is Collins actually a pilot......... or is she just a female?

She's the commander. Translation - pilot, left-seat-occupier.

http://www.jsc.nasa.gov/Bios/htmlbios/collins.html


This biography gives her over 4700 hours in 30 types of aircraft - I know that number isn't too impressive to some of you, but not bad for a military career from 1979 to 1990, is it? She was attending the AF Test Pilot School when selected as an astronaut.

EDIT - Since this biography is a bit dated, she has presumably picked up a lot of T-38 time since them.
 

9GClub

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mzaharis said:
She's the commander. Translation - pilot, left-seat-occupier.

MZ,

HA! I know that, I was joking. Check out the "Hello, I'm Miss KittyKat" thread.

Last I heard, Collins has somewhere north of 6,200 hours of jet time. If I'm not mistaken, her primary ride in the AF was the -141.
 

mzaharis

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Sorry - should have put [Literal] and [/Literal] around my post. Hadn't read the MissKittyKat post first.

;)
Yeah, the bio lists mostly C-141 experience. I guess that Transport pukes also have a shot at a machine with a >1-to-1 thrust ratio.
 
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9GClub

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No prob, I read somewhere that her husband flew -141's too and that's how they met.
 
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