Space Station Spacewalkers Stymied By Stubborn Bolt

Hugh Pickens writes "Reuters reports that astronauts at the International Space Station ran into problems after removing the station's 100-kg power-switching unit, one of four used in a system that distributes electrical power generated by the station's solar array wings, and were stymied after repeated attempts to attach the new device failed when a bolt jammed, preventing astronauts from hooking it up into the station's power grid. Japanese Astronaut Akihiko Hoshide got the bolt to turn nine times but engineers need 15 turns to secure the power-switching unit. 'We're kind of at a loss of what else we can try,' said astronaut Jack Fischer at NASA's Mission Control Center in Houston after more than an hour of trouble-shooting. 'If you guys have any thoughts or ideas or brilliant schemes on what we can do, let us know.' Hoshide suggested using a tool that provides more force on bolts, but NASA engineers are reluctant to try anything that could make the situation worse and as the spacewalk slipped past seven hours, flight controllers told the astronauts to tether the unit in place, clean up their tools and head back into the station's airlock. NASA officials says the failure to secure the new unit won't disrupt station operations but it will force engineers to carefully distribute electrical power from three operating units to various station systems and says another attempt to install the power distributor could come as early as next week if engineers can figure out what to do with the stubborn bolt. 'We're going to figure it out another day,' says Fischer."

Re:loosen other bolts

[crmanriq]

Yes.

Yes.

Yes.

Can't tell you how many times this happens to me. You always leave bolts loose, and then incrementally tighten. Hell, you even do it when changing a tire.

Re:Come on, this is 2012

[jkflying]

Mechanical design is very different, I've done both. You're working with analogue systems, which means that everything has a tolerance - let's compare it to 'bits of accuracy'. You can go to a higher accuracy, but it becomes vastly more expensive. Unfortunately, every copy of the component is different, which is scary for CS people. Imagine if every time you created a copy of something, it was *guaranteed* to be slightly different.

So, you suggest doing something like 'unit tests'. Well, that's what they did, and that's what happened here, a unit test failed. They should be getting 15 turns, but are only getting 9. They're not sure why, so they're going to brainstorm and come up with a bunch of possibilities, discount as many as they can based on physics, design etc, and see if they can figure out what's wrong.

Perhaps it would be better if the summary included something like "a unit test failed", then the CS people would understand.

Re:Space WD-40?

[Anonymous Coward]

Anyone with a clue (engineers and mechanics alike) know that WD-40 worthless as a lubricant.
It was designed and works fine as a water displacer, but isn't good for anything else.

Re:Red Green solution

[morethanapapercert]

That leads me to an interesting question: Just how strong is capillary action in a vacuum? With the bolt blocking the hole, any lubricant has to have good wicking properties to get in around the threads. On the other hand, I'd imagine that anything with a low enough viscosity to wick well would also be something that would boil off pretty quickly in a vacuum. That would certainly rule out any of the aerosol graphite or lithium sprays.

I know there have been experiments that included capillary action in micro-gravity, astronauts playing with a globe of water and a straw for example. But as far as I know, all such experiments were in a pressurized, shirt sleeve environment. I'm not aware of any similar experiments with fluids in microgravity *and* vacuum.