Minor Technical Issue Aboard Shuttle Discovery

IZ Reloaded writes "Space Shuttle Discovery has a problem with the pipeline for an auxiliary power unit that controls the shuttle's hydraulic steering and braking maneuvers. CNN reports that the pipleline is leaking 'fuel' at about six drops per hour." From the article: "The leak is more likely nitrogen, but there is no way of knowing that, so NASA is treating the problem as if the leak were fuel ... If it is fuel, the current rate is still 100,000 times slower than what would cause a fire ... Just in case, NASA will turn on the power unit with the leak early Sunday as part of its normal testing and then see if the leak rate changes. If it does, NASA may burn off the hydrazine and shut down the power unit before the shuttle returns to Earth to eliminate any fire hazard.'"

Comments

solution

[Anonymous Coward]

Two words: Duct tape.

Terminology

[pipingguy]

There are pipelines in space now? Cool.

The leak is more likely nitrogen, but there is no way of knowing that.

Excuse me? The shuttle must be one of the most redundantly-instrumented efforts ever built and they don't know what's leaking?

Re:Terminology

[TrappedByMyself]

Excuse me? The shuttle must be one of the most redundantly-instrumented efforts ever built and they don't know what's leaking?

Obviously not. I guess some rogue foam disabled the giant blinking "HYDRAZINE LEAK" and "NITROGEN LEAK" signs, so they're lost up there. You better call NASA and tell em what's what.

Re:Terminology

[leathered]

There are pipelines in space now? Cool.

They're the tubes that makes the intarweb run, how do you think all that data gets to the satellites and back?

Re:Terminology

[NOLAChief]

There have been pipelines in space since the beginning of the use of liquid fueled rocket engines. Propellant has to get from the tanks to the engines somehow...

They mean it, there really is no way of knowing. They know there's a leak based on pressure readings. They know it's not an instrumentation issue because those pressure readings are redundant (i.e. if one sensor started trending down and it's backup didn't, then the sensor's bad). Based on those same pressure readings they know what the leak rate is (drops per hour was probably the guy's attempt at making it make sense to the layperson by analogy to a dripping faucet. Sadly that analogy seems to have fallen flat.) Since the fuel tank (hydrazine) is connected to the pressurant system (nitrogen), the entire system is at the same pressure, so since there is a leak, every pressure sensor monitoring the system is trending down.

(Time for my own bad analogy) Let's say you've got a Super Soaker with a pressure gauge in the water reservoir. You pump up the Super Soaker and put it in a box so that the only thing you can see is the pressure gauge. Now, somehow a hole forms in the reservoir. Because you can't see the reservoir, you don't know if it's your fuel (the water) or the pressurant (the air you pumped into the thing) that's leaking, but you know from the decreasing pressure reading that there's a leak present. That's essentially what's going on with Discovery. Hence, they're playing it safe and assuming the leak is fuel, when more likely it is the smaller nitrogen molecule that's escaping the system.

Getting rid of it is a good idea

[Megaport]

Hydrazine is nasty stuff but it is just one of the dangerous checmicals aboard the shuttle.

When Columbia broke up, it was the possible presence of Hydrazine from the APUs that make the Texas Dept of Health issue warnings about approaching shuttle debris.

The problem with spaceflight is that everything is so close to the edge. Performance requirements that can still leave a good safety margin mean that simpler and safer methods are often inadequate. Consumers don't have the same risk/reward ratio as people who sit on top of rockets for a living.

-M

Re:Getting rid of it is a good idea

[Ohreally_factor]

I'm trying to calculate the risk/reward ratio for those strapped underneath a rocket. So far, I keep getting divide by zero errors.

3 APU's yet only APU1 drives the landing gear ?

[Anonymous Coward]

Seems off that only APU1 drives the landing gear, with a backup of pyrotechnics...

"APU 1 is the only hydraulic system that can deploy the shuttle's landing gear. If APU 1 is out of action, pilot Mark Kelly would have to manually fire pyrotechnic charges to deploy the gear."

http://www.spaceflightnow.com/shuttle/sts121/06071 4mplm/

STS-9 APU Fire

[Aglassis]

STS-9 came in with an APU on fire. Here is a video.

Re:STS-9 APU Fire

[Aglassis]

But are you saying this makes it less or more worrying?...

I would say that it is less worrying for the astronauts, and more worrying for the engineers on the ground. The astronauts know that a fire has occurred before and that it wasn't deadly (though the circumstances are different). Mission control knows a fire has occurred before and doesn't want to take the chance again!

On a side note, the two APU fires (I miswrote in my previous post--there were two!) were minor issues for STS-9 compared to the 2 failed GPC's and failed IMU that almost killed the astronauts.

Re:Overconservatism

[Anonymous Coward]

You can't escape from taxes, and I'd rather see them spent on NASA than on Iraq.

Did you ever watch one of those news conferences held with the astronauts/mission management team representatives? ALL questions somehow related to a concern for safety and NONE are actually asking whatever the crew have done that day. NASA is surely making a big deal on re-entry, but it's the media is making it sound like it's gonna be another Columbia.

The overwhelming concern on safety is exactly what got me excited about these couple of "return-to-flight" missions. NASA is trying to MOVE FORWARD with the construction of the ISS while trying their best to keep the construction workers safe. If they slip and the program stalls it will not only be years and years of your and my tax dollars that go down the drain, but also investments from Russia, Japan, Europe and other international partners. It is ALREADY an international effort. It is a sunken-cost mentality and it is make-or-break for NASA.

Quit acting like you don't care about the lives of those astronauts if they are given in the name of "progress". Everything that NASA does to protect them IS "progress". You protested furiously about the not having any more dead soldiers in Iraq didn't you? What makes you think it is any different in space?

Minor technical issue?

[Seiruu]

A leak in a "gas tank" is a minor technical issue? :p

"Hey there cowboy, word goes around that there's something wrong with my car."

"Nah sir, just a little scratch."

"Ah if it's just a scratch then I can live with it."

"Yes sir, just a bit of gas leaking through that "scratch", so you might want to cut down on that smoking sir."

Explosive bolts

[OriginalArlen]

The write-up missed the important angle that if they decide to power down the possibly leaky APU, they'll have to use explosive bolts to lower the undercarriage. That's never been used in flight before. That doesn't mean it won't work, of course, but it will make the re-entry and landing a little more interesting than usual.

Re:Overconservatism

[icebrain]

FY06 NASA budget: $16.5 billion

US population: ~ 300 million

Total cost, per person: ~ $54.84

About 25-30% of the population is too young to pay taxes - that leaves around $71 per taxpayer.

To put this in perspective (albeit with 2004 numbers):

NASA budget allocation: $15.5 billion

Department of Education: $53.1 billion (29.4b for primary/secondary, 15b for higher ed., 1b for vocational)

Housing and Urban Development: $31.3 billion

IRS (tax collectors): $10.4 billion

Foreign aid: $17.1 billion

Department of Agriculture: $19.5 billion

And an interesting pictorial representation:

http://www.deviantart.com/deviation/9410862/