Re: How do tools in space work?

This question is excellent, but fairly specialized. The number of people who have actually used, designed, fabricated, or even handled tools to be used in space is rather small -- and I am not one. Also, I have not succeeded in finding much information about the detailed design of tools that have actually been used in EVA's, so I will have to give a general answer, based on the basic facts of physics and zero gravity.

I know of two basic approaches to this problem. The first is to anchor the astronaut so firmly that the force transmitted from the tool to the astronaut's body does not cause it to move out of position. This can be done in various ways which differ in detail. One example would be adjustable tether lines, from the work area to the astronaut. At least two or three of these in different directions would typically be needed, and they have to be adjusted to be taut, so that the astronaut is braced against movement. Another example would be foot restraints, special fixtures on the outside of the spacecraft in areas where work is likely to be performed. The astronaut's boot mates with the fixture so that it is effectively locked in place, and cannot move. Such restraints have been used on the Space Shuttle remote manipulator arm. The effect is somewhat like working normally on Earth, except that gravity is replaced by the force from the fixture. An advantage is that the tool itself can be more like a standard earth tool. A disadvantage is that restraining fixtures cannot be placed everywhere that work may be necessary. Also, it may be quite tiring to resist forces in some directions using foot restraints only.

The other basic approach, which you suggest in your question, is to use tools specially designed not to transmit forces to the user. For example, a motorized screwdriver might have special pins around the central drive bit, and the screw would have to have a pattern of matching holes surrounding it. The astronaut would first insert the pins into the holes, so that the tool as a whole could not rotate. She would then slide the bit forward to engage the screw, and start the motor to turn the bit. An obvious disadvantage of this approach is that it requires a more complex tool, and can only be used if the screw-hole has been designed in advance with surrounding holes or some similar arrangement to hold the tool and take up the working forces before they are transmitted to the astronaut.

For a drill, the particular tool you mentioned, it is unlikely that mating holes would have been thoughtfully provided just where a hole was to be made. An adjustable clamp of some kind might be provided to clamp the tool to the work in such situations. Otherwise the first approach of anchoring the astronaut might be better.