From: hack@arabia.uucp (Edmund Hack)
Newsgroups: sci.space
Subject: Re: microbots for repair?
Summary: Hard to do. Maybe in the future.
Date: 9 Apr 1992 20:41:50 GMT
Organization: Lockheed ESC, Houston

In article <jchapin.702800597@Xenon.Stanford.EDU> jchapin@Xenon.Stanford.EDU (John M. Chapin) writes:
>Researchers such as Rod Brooks at MIT have been making good progress
>on extremely small insect-like robots (10-100 grams) that have enough
>battery power and intelligence on board to move around in complex
>environments.

My impression is that most of the MIT insectbots are much heavier.  Ghengis,
et.al. are in the kilograms range.

>
>Looking forward 5 years, would it be worthwhile to take ~1 Kg of an
>interplanetary probe for a half dozen robots and a recharging/
>programming station?  Then if something goes wrong that requires
>physical help (eg. Galileo, or perhaps micrometeorite impacts on
>the really long missions) the robots could crawl to the site and
>apply a small amount of force as directed.
         ^^^^^
This is a severe limit in doing any useful repair. 

>
>The risk is obvious--that a robot will go haywire and crunch itself
>in the middle of a previously-working part or die right at the
>aperture of an instrument.
>
>Still, this might be a valuable backup system to have if the
>mission is in jeopardy because of an unanticipated physical problem.
>
Most problems in spacecraft involve electronic or electromechanical failures.
With current electonic components, a microbot will not be able to exert enough
force to:
  - move aside a thermal blanket (if one is needed, or the 'bot is outside).
  - unfasten a coverplate (they have to be very well fastened down to survive
the acoustic/vibrational/gee force loads of launch (esp. on expendables))
  - hold the coverplate aside
  - unfasten a wiring harness (if applicable)
  - pull a card or module out of a card cage
  - pop out the defective component
(showstopper coming)
  - find a spare part and place back in (this is the biggie)
  - put the card/module back
  - rewire it
  - close the cage
  - put the thermal blanket back
  - stow the defective part

This will need to be done in the space environment, with all the problems that
it entails for power, thermal and mobility.

_If you have a spare part available_, it might be better to have in put it
inline as a spare string, giving you an additional redundant path.  This is
the current line of reasoning on self-repair.

In addition, if you don't do this by teleoperations, you have to train the
'bot to do the work in advance.  Note that NASA experience has shown that
even well trained, dextrous, autonomous, mobile biocomputers with stereo 
vision systems, tactile feedback and progammability (i.e. Astronauts on EVA)
found it hard to do a Orbital Replacement Unit swapout on a satellite 
designed for EVA repair (Solar Max).  It is possible that there will be a 
breakthru that will make microbots feasable, but if so, it isn't here yet.

Microbots will, IMHO, find their first extraterrestrial use as explorers.  In
fact, they are being considered as a payload for the Artemis mission (a.k.a.
Common Lunar Lander).

-- 
| Edmund Hack - Lockheed Engineering & Sciences Co. - Houston, TX
| hack@aio.jsc.nasa.gov    SpokesPersonp(Me,or(NASA,LESC)) = NIL
| "See the constellation ride across the sky.  No cigar, no lady on
| his arm. Just a guy made of dots and lines." - They Might Be Giants