NASA Schedules Space Walks to Fix ISS Pumps; Orbital Sciences Launch Delayed

The ISS has been operating at partial capacity after a coolant pump malfunctioned last week. NASA has now announced the repair mission: "NASA currently plans for two Expedition 38 astronauts to venture outside the space station Dec. 21, 23, and 25. NASA astronauts Rick Mastracchio and Mike Hopkins will remove a pump module that has a failed valve. They will replace it with an existing spare that is stored on an external stowage platform. The pump is associated with one of the station's two external cooling loops, which circulate ammonia outside the station to keep both internal and external equipment cool. Each of the three spacewalks will begin at 7:10 a.m. and is scheduled to last six and a half hours. NASA TV coverage will begin at 6:15 a.m." NASA TV will be airing a preview of the space walks at 3 p.m. EST. As a result of the coolant pump malfunction and the repairs, NASA has also delayed the launch of Orbital Sciences' cargo resupply mission until at least mid-January.

Comments

A question about space walks.

[Thanshin]

How dangerous is a space walk compared to, for example, a 100m depth scuba dive?

i.e.: If it wasn't so very expensive to send things up there, could space walking become a "leisure" activity?

Re:A question about space walks.

[Jjeff1]

I read a lot about space, and am a scuba diver, here's my take.

First, diving to 100 meters is going to be fairly dangerous, certainly not something your typical sport diver would do. Beyond 100 feet, you'll increasingly have issues with nitrogen narcosis (you feel drunk), and you'll definitely be in the realm of exotic air mixes (helium instead of Nitrogen, less than surface amounts of O2, etc...). At 100m using normal air, your partial pressure (think concentration) of O2 is 180% of surface level (been a while since I had to do that sort of math), which would be poisonous. Lets just compare to 100 FEET of depth, which a sport diver might do. You could remain at that depth for 10-15 minutes without having to decompress. Stay longer, and you need to sit at depth (say 20 feet) for a while to let the air dissolved in your blood to slowly come out of solution. Go up too fast and it's like opening a bottle of pop, but in your blood. Those bubbles can get caught in your joints, or worse spine, and cause paralysis. Divers that DO engage in deep diving are doing technical diving. Most of the gear is the same as a sport diver, you just carry more of it, particularly tanks and regulators.

But space is worse. First, space suits don't run at normal air pressure, they're down around 4.3 PSI (normal earth is 15). The ISS runs at the same pressure as earth, so donning a space suit is the same as rising UP from depth while diving, you'd get the bends as soon as you open the hatch and exit the ISS (opening the pop bottle). To solve this, when doing an EVA, astronauts breathe 100% O2 for an hour before donning and exiting the ISS.

Second, you have all sorts of cooling issues in space. Your body gives off a lot of heat, and in space, there is no place for that heat to go, so the cooling systems are far more elaborate than any warming systems (often just a hose with hot water being piped down from the surface if you were commercial diving) you might use underwater.

Christmas

[schneidafunk]

I heard about this on NPR this morning. The astronauts were saying they think they can finish it in two space walks instead of three and hopefully have the day off on Christmas.

Re:Christmas

[jandrese]

I know you're joking, but time off is something NASA takes very seriously. It didn't used to be this way, they used to work Astronauts to the bone for exactly the reason you mentioned, but after a semi-revolt on one mission they changed the policy to insure that the astronauts get enough rest.