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

AE-35 unit

[Anonymous Coward]

"Roger your plan to go EVA and replace Alpha-Echo three-five unit prior to failure."

Re:AE-35 unit

[scuzzlebutt]

"Open the Pod Bay doors, HAL."

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.

[SuricouRaven]

How recreational is it? There's nothing to do - literally, nothing around you except the ship itsself. The equipment is cumbersome. I could see it working on the moon, possibly*, but not just in orbit. If you want to go floating free for fun, you'd be better off taking a huge inflatable structure of some sort so you can keep atmosphere in. Much more comfortable, and flexible enough for zero-g sports.

*There would, of course, be a golf course.

Re:A question about space walks.

[Trepidity]

So far they seem to be one of the safer parts of spaceflight, in that there have been 204 spacewalkers, and none died or suffered serious injuries. Whereas a number of people have died during take-off or reentry. On the other hand, they're typically planned for very carefully and not done that often. And 204 is too small a sample to reliably compare it to the safety of scuba diving, since serious scuba accidents, especially by professionals, are far less common than 1/200 dives.

Re:A question about space walks.

[Thanshin]

So, less dangerous than 250m scuba diving but probably more than 100m scuba diving.

So, no recreational even if it was cheap to send people up.

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).

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.

Re:6.5 hours x2 for a Cooling Pump

[perpenso]

Also, isn't there a Canadian robot up there that is suppose to do this stuff?

It gets Christmas and Boxing Day off. :-)