trc@hou5a.UUCP (Tom Craver) (10/03/84)
The Two-toed Space Sloth It seems possible to do "space construction on a budget", by use of a tele-operated robot with minimal local intelligence. The following is an example of a special class of robot, used mainly for working on space commercial/industrial packages. The two-toed space sloth gets its name from its two "gripper toes". Rather than mounting these on a complex "leg", they would simply be tethered to the robot by cables that could be reeled in or out. These toes would be designed to grip special "toe-holds", but should be able to grip to edges of materials as well - simply to provide an emergency capability. They might be simple clips, or be a servo- actuated. To move over a package, the robot would normally grab one toe with its arm-hand, attach the toe to a toe hold, push off a bit, then reel in the toe while reeling out its other toe. Reeling in the toe and locking it down provides a secure base for leverage. The arm could be used to help guide the movement. [I am assuming here that the arm(s) would be relatively weak, though a hand (or a hand attachment) might be quite strong. Arms are used mainly for positioning stuff, and movement in space can be done with quite little strength.] For propulsion between packages, Tuto (Two-toe) would use "tether guidance - hop or pull" Essentially, the robot pushes off, then controls its flight direction and stops using the cables. The cables might also be used as a control signal path, for telling the robot what to do, and for sending back the robot's data, such as slow scan TV from its "eye". This "jump unit" might be a separate segment from the rest, so that it doesnt encumber the robot while it works. It would have a single toe to grab the package and hold on, while the robot steps off (keeping one toe on a toe hold on the jump unit, of course) onto the package. The main direction of flight would be set by aiming a launching platform before jumping. Then in-flight adjustments could be made by having three or four cables, and letting several reel out slower than the others. This would be fairly easy to control, since there would have to be motors to provide momentum to the cable as it is reeled out. Packages could simply be "dumped" with low relative velocity into orbit near the robot's base. The twotoe would jump out, and match the package's velocity more precisely by pulling on its cable, or by transferring velocity by bumping into it. For larger increments in velocity, it might toss off a mass that is also tethered to the central unit. Probably this would be a routine task, as packages slowly drift apart. Or, they might each have a cable to attach to the central station. The point of all this jumping, tossing, and pulling, is that it can be done mechanically, using electric power, which should be abundant, and without any non-reusable rocket fuels. The reason for using "toes, tethers and reels" is to avoid having many complex arms or legs, as well as to avoid accidentally "falling off". The reason for teleoperation is simply to avoid having to spend time developing "AI" when there is a plentiful source of cheap or *volunteer* "I" on earth, and to avoid the terrific expense of moving that "I" into space and taking care of it while there. Robots can live on just electricity - humans cant. Plus, (and here is where the "sloth" part comes in), a Tuto can get by on a relative trickle of electricity that is stored up over time - allowing smaller solar panels. It would simply sit idle for long periods of time, soaking up solar power. Meanwhile, on earth, its operators could plan its next move. A space station built along these lines would look like a collection of shuttle pallet shaped blocks in a spider's web. At the central block would be the robot communications relay, storage, the jump reels, etc. I guess that designing, building, and lofting such a twotoe spacloth and base would only cost a couple tens of millions for the first, and maybe under a million for the second - depending on how well the designers keep to a goal of low cost for the system. It would only take up a small part of a shuttle payload. By the way - for those of you who are "human chauvinists", and want to put Men out there instead of robots - consider this: Are you more likely to be one of the few who get to go into space, or of the many who would get to control a Tuto? And can you get more space structures built by sending up a few Men, or a lot of Tutoes? I think that by going with Tutoes, or something equivalent, we'll bring down the costs of building space structures, which will encourage building more of them, and in turn, lead to a need for some humans "on site". Further, the increased building will require either shipping lots of material from earth, which bodes well for improved lifting-craft; or use of lunar material, which cannot be easily done with teleoperated robots. Either way, it becomes easier for humans to get into space. Tom Craver hou5a!trc