Moving about the ISS structure during an EVA

I was wondering why it is so difficult for space walkers to move around the ISS during its construction. Why do they need to use hand grips or the small cart on the external rail system?

Why havent NASA or someone else come up with a small thruster system fitted to a space suit or small vehicle to get around the station. They had a special EVA suit that they used a couple of times with the shuttle with a built in thruster system but they seemed to have abandoned the idea since then.

With such a system an astronaut could get to any part of the station relatively quickly where now it sometimes takes quite a few minutes.

One reason i can think of is that the eva suit with thrusters has a capability of just a few minutes of thrust. And spacesuits are allready bulky as they are so an addition to an allready bulky spacesuit, you would get an additional bulky thing on the suit.

But, in spacewalks where the repair itself costs hours, i don't think it's a big deal if it takes 5 minutes to get from A to B and back. And the size of the station itself is not that small anymore try walking on legs and arms accross an entire soccerfield. That takes a while

Safety rules that require them to avoid certain areas, like thruster nozzles, may cause some delays, but they can move very quickly using the hand holds from what I have seen in the videos.

I seem to remember an article I read saying it took something like 20 minutes to get from the Russian airlock (this was used because they were using Russian suits) to the work area on the US part of the station. I may be mistaken but this seems like a lot of time just getting to where you need to be and back again.

I do recall seeing video of astronauts outside the shuttle, before work started on the ISS, using the MMU, and they were moving SOOOOOoooooo slowly it was crazy. The back pack was giant too. It probably isn't worth the trouble. So they did have that capability and are choosing not to use it now. There must be good reasons, but I bet they aren't simple reasons.

I agree the suit used on the shuttle seemed far to cumbersum, I was thinking along the lines of a couple small thrusters mounted on the back of the astronaut's gloves with a limited amount of propellant. The user could direct thrust by moving the orientation of their hands. This would allow movement over larger distances and when the astronaut reached where they wanted to be they could revert to the usual hand holds.

It would also provide an extra measure of safety as astronauts would be able to fly back to the ISS if they became detatched.

The Shuttle MMU (Manned Manouvering Unit), worked fine, but they discovered the shuttle itself was incredibly manouverable, so it was easier to have a spacewalker stand on the end of the robot arm.

And if I was crawling around a complicated mess like the ISS, with no gravity, lots of sharp edges and only a thin suit keeping me from explosive decompression, I'd take my time too!

So I guess the answer to the original question is, they could not figure out a way to make it small. Ed White used a small hand held device on the first U.S. space walk during project Gemini, but it ran out of propellant too fast.

Here is a link to a NASA page on the subject.
http://nasaexplores.nasa.gov/show2_912a ... 050&gl=912

The bottom line seems to be that hand holds are just better, faster, easier, cheaper, safer or some combination of all of the above.

How about leaving the fuel for the device on the station? I bet they use lifelines anyway, so why not a strengthened fuel line serving as both?

I am watching today's space walk live on NASA TV and they only take a few seconds to go from place to place. But it seems like it takes forever to do everything else, like plug in a cable or whatever. I don't know what they are doing 99% of the time, but when they say there are going back to the air lock or whatever, it is really quick.