|
||||||||||
|
A common estimate for EVA productivity is that it takes about 3 times longer to do something in space. I once advised a new test conductor, "Estimate the task time yourself, pantomime all the steps moving slowly, and give the task time the longest you can stand. Then double it." That turns out to be an uncannily accurate estimate.
Look at standard task times we use for EVA timelines; it'll be a real eye-opener:
To attach a safety tether: 30 seconds
To set up a portable foot restraint: 3 minutes
To ingress a portable foot restraint: 1 minute
It's not just the gloves. Part of the problem is that you're big and blind, and maintaining your body position in zero g is a constant effort. We try to do everything we can from a foot restraint; it's worth the extra time it takes to set it up and tear it down.
The gloves have very little dexterity. You can hardly move your thumb at all, and any task which requires you to open your fingers is just about impossible. The maximum diameter an astronaut can grip is 2 inches. (Not even 2-1/8 inches.) Worse yet, the gloves use fine muscle groups, so we try to design tasks which use major muscle groups--the upper arms and sometimes even the legs. Fatigue is a big problem on almost every EVA.
We've had a lot of discussion in the Artemis Project forums about using powered space suits to increase EVA productivity. Powered suits seem to be a popular notion -- they show up in quite a few science fiction stories (including mine), and even played a starring role in Robert A. Heinlein's Starship Troopers. The most difficult part of designing a powered suit with today's technology is storing the power. After that, we have the question of where to put the mechanisms that assist the astronaut--we don't want to put them where they'll inhibit the astronaut in working in the suit.
Since hand fatigue is a major problem for EVA, the first part of the suit where we'd like to provide a power assist is the hands. Never mind making the astronaut as strong as Superman; we just want him to be able to get out there and get his work done without rubbing his hands raw and coming home feeling like his forearms are on fire.
So let's consider adding some mechanisms to the gloves. We can't put much along the inside of the fingers; any mechanisms there would inhibit the astronaut's mobility even more than his bulky gloves already do. However, the back of the hand could become quite bulky without seriously affecting crew performance. We'd need to make sure not to design anything that requires reaching into a small space, but even designing to NASA criteria (8" clearance) gives us lots of space to work in.
The palm of the glove might be another target for power assist. For the palm restraint, we might consider a series linked rigid plates like the back of an armaldillo, with pads to press against the palm. The pads need not be constant volume; they could be filled with a working fluid which expands an elastic bladder to maintain constant pressure.
|
|
|