EVA Systems
Section 4.3.8.
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Gloves and Manipulators for EVA Tasks

Astronaut Buzz Aldrin in Space Suit on the Moon

The astronaut corps is pretty much dead set against robotic extensions in place of human hands because of the loss of manual dexterity. When I think of the tasks they have to do with those gloved hands, I'm inclined to agree. If you can do a task with a claw or other simple manipulator, you can probably do it with a teleoperated manipulator attached to a roving robot.

What astronauts do with the their hands

Imagine a typical EVA sortie, where you have to (a) operate tether hooks repeatedly, (b) translate to the work site by grasping handrails, (c) open and close snaps and Velcro enclosures to get to the equipment, (d) handle hand tools and a power tool like an electric drill, (e) stow and unstow small parts, bolts, clips, clamps, fastenters, and wires, (f) pull back spring-loaded thermal covers over connectors, (g) grasp an electrical connector, pull back its bail, move the connector to another plug without damaging the pins, (h) adjust the valves on the front of your space suit, (i) set up your foot restraint several times, (j) operate Pip pins [ball detent fasteners], and (k) stabilize yourself while moving and working in zero g. Astronauts have proven to be amazingly agile with their hands, especially considering the limitations their gloves impose on them.

Such a wide variety of tasks would be far more difficult to perform with only a remotely-operated claw. We could try to solve these problems by designing everything to be maintained by telerobotics, but so far this has proven to be a very expensive design solution; and about half the time we've found that it isn't even possible to design robot-compatible systems.

It might be different on the moon

Some of these operations are unique to the zero g environment. It may be possible to design equipment and tasks in the lunar environment where a claw is just the right grasping device for the job; but I expect that will come a little farther downstream when peole are thinking of building specialized suits for specialized tasks. But if the dexterity of a gloved hand is not required, we can probably do the task with a telerobot and save our crew for other work.

Divers Do It

JIM Suit

The deep-sea diver's JIM suit provides a good analog to replacing space suit gloves with claws. The JIM suit's hands are mechanical jaws, operated by the diver's muscle power. You do get some tactile feedback via the forces reacted through the mechanical linkage to the claw. Divers have used this arrangement for a lot of useful work in maintaining oil platforms, but it will be a while before we have a lot of roughneck work to do on the moon.

Once we get into heavy mining operations on the moon, we might have such tasks to do. However, I suspect that it's more likely we'll have robots doing the field work while the people spend their time maintaining the robots.

Robotic Hands

We may never see powered mechanical hands that look like human hands; at least not for real work. These things exist, but they're very complex mechanisms -- expensive, prone to break down, and weak.

Think of all those moving joints in your own hands. Note that the power to your fingers is supplied by muscles in your forearms which manipulate your fingers by pulling on tendons that move in self-lubricating, self-maintaining organic sheaths. A machine with as many parts as a human hand has an enormous number of failure modes. Each joint, mechanism, and bearing will eventually fail; and with so many of failure modes, the mean time between failures is just a few minutes.

If we could solve the tendency of these machines to break down, we would still be faced with their lack of power. Complex mechanisms the size of a human hand are too weak and too delicate to do the kind of work we do with our hands.

We will need major breakthroughs in mechancial technology before we can build robots with both the strength and dexterity of the human hand. This might happen some day, with self-repairing flexible polymers that contract in response to electrical pulses. However, such technology may never happen, and is far too speculative to include in baseline plans for the Artemis Project.

Stick with Gloves

Confronted by these problems with alternative designs for EVA suits, we will stick with human hands inside pressurized gloves, complete with all their knuckle-chafing, fatigue-inducing problems. It's the only solution we know that really works.

EVA Systems

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