NASA may have isolated shuttle glitch

New Scientist.com ^ | July 21, 2005 | Kelly Young

[Thebaddog]

NASA officials think they have found the source of the problem that delayed the launch of space shuttle Discovery, and if they can fix the glitch in time, they could launch on Tuesday, 26 July.

A launch attempt on 13 July was called off when one of the four hydrogen fuel sensors at the bottom of the external tank failed a pre-launch test. These sensors read “wet” or “dry” to indicate whether there is fuel near the bottom of the tank, and trigger engine cut-off when the tank is empty. Since then, hundreds of engineers around the US have tried to hunt down the exact cause.

NASA is now looking at a slight electrical grounding problem within the fuel sensor system that could allow it to be affected by electromagnetic interference during the launch countdown. On Wednesday night, engineers and technicians tried to replicate the electromagnetic environment during the launch countdown. They will not truly know whether they have fixed the problem until the external tank is loaded with cryogenic fuel and all of the electrical systems are activated.

Heater trouble The interference could come from several sources, but a prime candidate is the new heater for the external tank - which reduces ice build-up on the outside of the tank. When this heater has been turned off, NASA has seen the fuel sensor reading return to normal soon after. This heater is relatively high up on the tank – where the tank attaches to the front part of the orbiter. During the countdown, managers will be closely watching the sensors.

“Every time we change something on the spacecraft we think might affect the sensors, we’re going to check the sensors again,” says John Muratore, NASA’s shuttle systems engineering and integration manager.

[Thebaddog]

Interesting.

[ARCADIA]

We are fying a decrepid antique; I hope those astronauts have purchased extra life insurance.

[FinallyBackInNH]

NASA is now looking at a slight electrical grounding problem within the fuel sensor system that could allow it to be affected by electromagnetic interference

I don't know... this just reeks of one of those "little engineering annoyances we decided we could launch with" that we seem to hear about after accident investigation panels (a la O-rings and shedding insulation). Just somehow something disconcerting about those kinds of statements.

[Normal4me]

You're right. We had two whole years to build a completely new launch vehicle! Reminder: 112 sucessful launches and 2 failures.

[Rockitz]

With such low production rates on the components and no repair shops along their path, even the simple things are still rocket science. I'm in the business and am continuously amazed when it all works.

[dr_who_2]

Pops self on head. Of course! EMI in the high VHF bands was transmitted from the speaker wire running directly into the skin of the main tank and focused by the concave surface at the bottom of the tank. The power density was thus amplified 10^2+/-0.5 in the same region as the transducer, possibly generating a lethal static discharge that could cause a chain reaction that would destroy the entire shuttle on the launch pad, killing the crew and countless seagulls and pigeons.

You'd think they'd just go back to the Gemini program.

[dr_who_2]

Here I am floating in my tin can...

[Hurricane Andrew]

So, if their fuel gauge read empty halfway home, what were they going to do? Stop by the nearest "Shuttle Gas & Go" and fill up?

[Normal4me]

Ping

[Last Dakotan]

We are fying a decrepid antique; I hope those astronauts have purchased extra life insurance.

Then again, very little isn't known about the shuttles. I've had cars with 200k plus miles on them that I'd drive anywhere.

The operation of complex systems and engineering reliability are known and strict disciplines that usually function well when applied correctly. Thus the only errors in judgment are when politicians, lawyers or bureaucrats become involved. Let the engineers here be engineers.

[EUPHORIC]

"So, if their fuel gauge read empty halfway home, what were they going to do?"

Explode. If those sensors indicate a full tank when it is actually empty during flight the turbopumps which supply fuel will super-rev and come apart like fragmentation bombs.

Of course if they "just" cut out when there is plenty of fuel they could just crash...

[bill1952]

Arcadia, given the syntax and spelling of that statement I think I'll pass on your logic.

The Shuttle is still state of the art aeronautical technology that works in the real world.

Nothing else at this time even comes close.
Space travel is dangerous, and will remain so for the foreseeable future, IE, the next thousand years..

Engineering is not star trek, liberal wishful thinking nonsense.

It is centuries of hard work where progress is only possible by lifetimes of dedicated hard work by geniuses who push the frontiers of human knowledge only by standing on the shoulders of the giants who walked before us.

[ARCADIA]

The Shuttle is still state of the art aeronautical technology that works in the real world.

Yes, and composed of millions of parts which have been slowly decaying for 20 years. It is a complete waste of money, which should have been used to help develop its replacement.

[The Brush]

Pops self on head. Of course! EMI in the high VHF bands was transmitted from the speaker wire running directly into the skin of the main tank and focused by the concave surface at the bottom of the tank. The power density was thus amplified 10^2+/-0.5 in the same region as the transducer, possibly generating a lethal static discharge that could cause a chain reaction that would destroy the entire shuttle on the launch pad, killing the crew and countless seagulls and pigeons.

I was just thinking the same thing...

[Right Wing Assault]

B-52s are still flying and they are a bit older. Yes, same parts deteriorate but they know what to replace. It's not as if they totally ignore everything when they prepare for a launch.

[Chode]

so let me get this straight, a sensor worth only a few hundred$ is a "Crit-One" system with NO DOUBLE OR TRIPLE REDUNDANT BACK UP SYSTEM and is holding up billion's of dollars worth of launch???

is it just me or is this MORE than a little piss poor planing on nasa's part...

[ARCADIA]

I have been as proud of the space shuttle as anyone. But, this isn't a B-52. When a B-52 loses a system it is usually not flying at 20,000 MPH in the middle of nowhere, and the crew always has a chance to eject. But, more to the point maintaing a B-52 is a heck of alot cheaper then the shuttle program. It was a good program; but do we really need to continue to invest in three old shuttles?

[SirChas]

Pops self on head. Of course! EMI in the high VHF bands was transmitted from the speaker wire running directly into the skin of the main tank and focused by the concave surface at the bottom of the tank. The power density was thus amplified 10^2+/-0.5 in the same region as the transducer, possibly generating a lethal static discharge that could cause a chain reaction that would destroy the entire shuttle on the launch pad, killing the crew and countless seagulls and pigeons.

I was just thinking the same thing...

Silly me, I thought it was just the Flux Capacitor.

[benjaminjjones]

We are fying a decrepid antique

LOL!

[VRWC For Truth]

The B52 has redundant systems. For the first two minutes of flight the Shuttle is a projectile with no redundancy. One merely has to overcome gravity and windspeed ... the other gravitational forces and the atmosphere. Big differences.