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.

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: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.