ISS May Have A Leak

Rio writes "The International Space Station is experiencing a slow, steady drop in air pressure, and American and Russian flight controllers are investigating possible causes of the leak. The Local 6 News report says Mission Control notified astronaut Michael Foale and cosmonaut Alexander Kaleri about the leak just before their bedtime late Monday afternoon. Mission Control first noticed the drop in pressure Jan. 1 and said the data showed a daily decline of about 2 millimeters of mercury. As of Monday, the pressure had declined a total of nine millimeters. That is equivalent to about one-quarter of a pound per square inch, said NASA spokesman James Hartsfield."

Comments

So .... what's their plan of action?

[NightSpots]

They say "There are no immediate concerns for the safety or health of the crew", but what are they doing about it?

When is it time to take action?
Do they have a way to leave?

They have a supply of Oxygen and Nitrogen to repressurize the station, but how long will that last?

It would be nice to sit in on the decision-making, just to observe...

Re:So .... what's their plan of action?

[lone_marauder]

They say "There are no immediate concerns for the safety or health of the crew", but what are they doing about it?

Looking for it.

When is it time to take action?

You mean, try to fix it, or abandon the station? Now for the former and when it gets about 1000 times worse and becomes a threat to life support for the latter.

Do they have a way to leave?

Yes. A Soyuz spacecraft is always docked to the station in the case of an emergency evacuation.

My approach would be thus: if the leak cannot be located, start sealing off compartments (this means effectively turning them off, I believe) If it gets that bad, though, I think it means abandoning the affected compartment. This combined with the November event concerns me greatly, but it isn't time to panic yet.

Re:So .... what's their plan of action?

[Wavicle]

Also, I suspect that a healthy man could be subjected to well below 0.5 atm, especially if the pressure were reduced so gradually.

When I was taking physics in college, one of the professors there was an ex-SR-71 pilot (it was a community college) and gave a talk about air pressure, air mix and breathing. (It was some years ago, so hopefully I remember the pertinent facts)

At the altitude the SR-71 flew, the air pressure was something like 1 or 2 millibars (I forget exactly, but it was really close to zero) and for entirely practical reasons the cockpit could not be pressurized, so the pilots sat in a "space suit" (it wasn't an actual space suit, but pretty close). However the space suit couldn't be pressurized to 1 atm or it would be too stiff for the pilot to move.

The obvious solution was to drop the pressure in the suit, but as it turns out if you drop the pressure too low, the partial pressure of CO2 in your lungs doesn't get high enough for it to send a signal to your autonomic nervous system to take a breath. It turns out that when the CO2 in your lungs reaches a partial pressure of about 5% of 1atm, your brain decides its time to take a breath.

What this all boils down to is, as the pressure drops, the relative concentration of oxygen has to increase to keep the balance of the partial pressure of oxygen and CO2 in your lungs, or you will start suffering symptoms of oxygen deprivation.

I believe in the case the prof was lecturing on, a pure oxygen mix at 3.5 psi was enough to keep you lucid while being low enough you could actually move around.

Re:So .... what's their plan of action?

[MemoryAid]

Here's a couple of thoughts:

1. Typical leaks are faster at higher pressure, so as pressure decreases, the leak rate decreases. I don't remember off the top of my head any equations for flow through an orifice, but the leak will taper off and approach zero psi (mbar, mmHg, whatever, zero is zero) asymptotically.

2. A rough rule of thumb that I have heard is that at 18000 feet, half of the atmosphere (by mass) is below you. I think that corresponds to 0.5 atmospheres, but I don't know that equation, either. And it's only a rule of thumb.

Re:So .... what's their plan of action?

[cluckshot]

Good report on the facts. I do believe they have space suits on the station...

Regards to this problem, the loss of this much air should impart a significant rate to the space station. This would make it tend to make the station spin or move a bit. As a result the location of the leak should be pretty easy to determine.

Re:So .... what's their plan of action?

[Rorschach1]

It gets a little more complicated than that... I think even with the hypercapnic respiratory drive suppressed you've still got the hypoxic drive. At least, normal healthy people should. See this document for more than you ever wanted to know about respiratory drive. But yeah, pure oxygen in the 3.5 to 4 psi neighborhood has long been used for spacecraft and pressure suits. Of course, you've got to either reduce the pressure very slowly or prebreathe pure O2 for a while first or risk getting the bends due to pressure change.

This could put ISS on ice

[fname]

Well, if they can't seal the leak, they'll need to send the astronauts home until Shuttle is back in service, which could be 2 years plus. Hopefully, they'll find the leak and fix it.

One possible cause of the leak is from a meteorite impact. I have a tiny bit of experience with this from my grad school days. During the design stage of the American module, there was some concern about what would happen if there was an impact from debris. Tests showed that if the impact object was the right size, the entire damaged section could "unzip" and the and essentially blow up, likely killing the astronauts and disabling ISS. The design was tweaked, and it was showed that the section would not unzip, instead it would leak (probably not as slow as what is described, though-- think hours to reach vacuum, not months or seconds).

I have no idea if that's what happened-- it might be a completely unrelated issue. But just wanted to point out that a tremendous variety of possible events are considered, and NASA really wants to assure that none of these could result in a catastrophic event.

Re:This could put ISS on ice

[fname]

Hmm... shoulda Googles before making that post. Anyways, here's the #1 hit for "ISS Leak" on Google. Fairly on-topic stuff.

Re:Visible?

[NightSpots]

There's even a cargo ship that's docked to the station ... they've been testing valves all night, I'm guessing they'll wait til that Russian ship leaves, and if the leak doesn't disappear, then they'll start to get concerned.

If you assume that the more complex a seal is, the better chance it has of leaking, then the docking hardware might be a good place to start looking.

Re:ok

[Exiler]

They could probally make some lather and cover the station in soap while spacewalking, that would help...

Another overlooked problem?

[Wister285]

I remember there was a Slashdot story a few days/weeks ago where the ISS crew heard a loud thud. They said there was nothing to worry about, but I think it is possible that this could turn into another Columbia style foam incident. Luckily though, this crew should be able to escape in time if there ever were a problem.

Re:There is indeed a Soyuz for emergency

[Eric Smith]

So if they had a crew of three, in a medical emergency, they would send two back to earth in the Soyuz, leaving one crewmember on the ISS? Seems like a strange plan. As I recall, NASA was very much opposed to trying to run ISS with only a two-person crew rather than the usual three, so having only one crewmember on board would *really* seem to be pushing it.

Of course, in an emergency, you do what you have to do.

NASA

[Raven42rac]

This is the last thing that NASA needs right about now. No matter what the root cause of the leak is, it will still cast a negative shadow on the space agency. The public can be a fickle bunch.

a few points(are we geeks or not)

[phrostie]

1. who remembers a few months back when they thought they heard something "hit" the station?

i would start looking in that direction.

2. there are a number of posts about watching objects(insert with balloons, pepsi, dr peper,,,) float thru the station and use that for an indicator of air flow.

as with other manned space programs the ISS has CO2 scrubbers(remember apollo 13) that keep the air clean. i was under the impression that the air is circulated thru these and that a flow already exists because of this. i also recall reading that with skylab this flow effect caused lose items to commonly be found at one end of the station.

3. newtons laws of motion and inertial navagation.
even though the ISS is in a fixed orbit, it still makes use of an inertial navagation system. it is required to keep the station from tossing and tumbling out of control when the astro/cosmo-nauts move around. each of their movements create a reaction which causes an equal and opposite reaction on the station. a computer is constatly making corrections to maintain pitch and attitude of the station. a log these corrections will show these reactions to be somewhat random with an almost noise quality.

with a contiuous leak of a known size in the iss, a constant known vector(except for location) is created. once the noise is removed the location should be able to be calculted from the log information.

in short, break out the slide rules!