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.

Re:A question about space walks.

[tlhIngan]

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?

I think it's quite dangerous - for many reasons. Hence for planned missions, they train extensively in the Neutral Buoyancy Lab - spending months practicing doing some task that will take them a day in space.

They even train for non-routine servicing - while they don't train for the specific scenario, they train hard on how to get around the ISS and all that so everyone is familiar (none more so than the commander).

Effectively, a spacewalk ends up being "routine" because the astronauts spent months practicing until it became routine. It's why it took over a week for this spacewalk - they had to come up with the scenario and figure everything out so it ends up still being well choreographed.

In effect, it's "safe" purely because everyone's done it before. And there are well know abort procedures - if something happens, abort immediately and return back to station. No "give me one more second and I'll have it" sort of things - abort means abort and get your ass back to the airlock.

I'm sure that 100m scuba dive could achieve similar results, had everything been practiced for months ahead of time and failure modes explored and abort modes followed. Of course, it sort of ruins the whole spontaneity of the thing and a lot of the fun in doing it goes away. (Plus, they're trained astronauts, so they work as a team and consider that primary over self).