Return-path: X-Andrew-Authenticated-as: 7997;andrew.cmu.edu;Ted Anderson Received: from beak.andrew.cmu.edu via trymail for +dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl@andrew.cmu.edu (->+dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl) (->ota+space.digests) ID ; Wed, 17 Oct 1990 01:26:10 -0400 (EDT) Message-ID: Precedence: junk Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Wed, 17 Oct 1990 01:25:37 -0400 (EDT) Subject: SPACE Digest V12 #462 SPACE Digest Volume 12 : Issue 462 Today's Topics: High-speed operations with feedback delay (teleoperators) Re: Challenges to nomenclature Reflexes (teleoperators) Re: You Can't Expect a Space Station to be Cheap Administrivia: Submissions to the SPACE Digest/sci.space should be mailed to space+@andrew.cmu.edu. Other mail, esp. [un]subscription notices, should be sent to space-request+@andrew.cmu.edu, or, if urgent, to tm2b+@andrew.cmu.edu ---------------------------------------------------------------------- Date: Tue, 16 Oct 90 15:23:20 EDT From: John Roberts Disclaimer: Opinions expressed are those of the sender and do not reflect NIST policy or agreement. Subject: High-speed operations with feedback delay (teleoperators) >From: visix!news@uunet.uu.net (Amanda Walker) >Subject: Re: Manned/unmanned tradeoffs >Another thing to keep in mind when thinking about time delays is >programmability. Even though humans have a closed-loop cycle time >of about 200ms, they can still perform tasks that require greater than >200ms precision. If a task (or subtask) can be performed ballistically >(open loop), or locally (closed loop but without having to go through >remote processing, such as a spinal reflex), the overall time delay >is less relevant. I suspect humans often do this by means of preprogrammed sequences of actions, which they can carry through without consciously verifying each step before going on to the next. For instance, before making a running broad jump, or some other complex action, you mentally rehearse what you're going to do. Playing a piano or typing on a keyboard can be accomplished similarly. The conscious mind can monitor the results (with a time delay), and in the case of the keyboard, give an alert if a wrong key has been struck and a word needs to be retyped. For a continuous operation such as riding a bicycle, it is possible that trained reflexes (spinal cord, brain stem, and other motor control sections operating below conscious level?) play a significant part. >I think it is naive to assume that teleoperated robots can't have the >equivalent of motor skills and reflexes. The operator doesn't have to be >consciously "in the loop" for every action, any more than they are >*with their own body*. Robots can be built and programmed to act in the same way. For the given example of a soldering operation, the robot could be instructed to hold the iron and solder to the connection point for a specified time, then back off and see whether a good joint was formed. A more sophisticated robot could use optical or thermal sensors for real-time feedback. >Amanda Walker amanda@visix.com >Visix Software Inc. ...!uunet!visix!amanda John Roberts roberts@cmr.ncsl.nist.gov ------------------------------ Date: Tue, 16 Oct 90 10:10:49 EDT From: John Roberts Disclaimer: Opinions expressed are those of the sender and do not reflect NIST policy or agreement. Subject: Re: Challenges to nomenclature >Date: 14 Oct 90 18:19:19 GMT >From: unmvax!nmt.edu!nraoaoc@ucbvax.Berkeley.EDU (Daniel Briggs) >Subject: Re: Magellan/Venus Info >I've got to side with Henry on the question regarding poles. What Ron >is assuming is essentially the IAU definition of 'North Pole'. (The >North pole of a planet points north of the ecliptic.) This definition >can cause violent controvery at meetings. Many people think that this >definition is just plain wrong. (Usually these are people whose job >includes studying the planet in question, rather than just cataloging >the orbital parameters. The IAU definition makes bookkeeping simpler, >at cost of screwing up the planetary physics.) Bottom line: Ron's >definition is the most common one, but it is by no means universal. >dbriggs@nrao.edu (Internet) As long as we're going to revolutionize the terminology for the sake of convenience, how about a few more changes: - Allow the use of the vernacular, such as for place names on other celestial bodies, rather than forcing the use of Latin or Greek. The prior convention made sense when Latin was the international language of science, but this hasn't been the case for over a century (perhaps much longer). - Admit that our ancestors were a bunch of geocentric idiots, and allow the prefix or suffix "ge" to be used in context to refer to any celestial body. Thus, a probe in orbit about another planet or the sun could still have an apogee and a perigee, a rock-formation specialist on the moon could still pursue geology, a mapmaker could lay out the geography, a mathematician could study geometry, and so on. With hundreds of named major and minor bodies in the solar system, coming up with and remembering the appropriate Latin or Greek terms for each would be a real headache, and serve no useful purpose whatever. The other alternative, looking for generic roots that are most consistent with the ancient languages, forces the use of awkward terms such as "apoapsis" and "periapsis". (Incidentally, if you wish to be true to the ancient traditions, for plurals you must use "apoapsides" and "periapsides", as in "the two orbits have different apoapsides".) The earth-centered terms came into use when the earth was the main object of interest. They have become widespread, and have tended to be the de facto terms applied to objects other than the earth. Only some twisted desire to get the teminology "right", so that Galileo, Newton, and Kepler would not be disappointed in us has produced this insistence on application of classical terms that threatens to throw space-related terminology into chaos. Sure, it's neat to know what "-ology" to use on each planet, moon, and asteroid, but what practical use does it have other than to drive youngsters away from learning the the subject? Either we should acknowledge that language has changed since the time of the Roman Empire, and avoid the complexities of the old usages, or we should go back completely to the "good old days": "Actioni contrarium semper et aequalem esse reactionem: sive corporum duorum actiones in se mutuo semper esse aequales et in partes contrarias dirigi." - Newton, Philosophiae naturalis principia mathematica John Roberts roberts@cmr.ncsl.nist.gov ------------------------------ Date: Tue, 16 Oct 90 15:01:58 EDT From: John Roberts Disclaimer: Opinions expressed are those of the sender and do not reflect NIST policy or agreement. Subject: Reflexes (teleoperators) >From: mcsun!i2unix!sixcom!garof@uunet.uu.net (Joe Giampapa) >Subject: Re: Manned/unmanned tradeoffs > Isn't this the description of the reflex arc? A human may touch a hot >object and pull away very rapidly before the temperature stress signal reaches >the brain. The input signal only travels to the spinal cord (analogous to >Daniel Mocsny's "large nerve ganglion") before the output "retraction" signal >is emitted. It is not completely uncontrollable either. A person may suppress >this reflex as well. I've often wondered about that. How can a conscious command from the brain suppress a reflex action that would normally be triggered before the stimulus even reaches the brain? If a robot probe were involved, the answer would be pre-loading of instructions into the local controller. Is this also the case with humans? If so, what is the extent of the complexity of instructions that can be downloaded? John Roberts roberts@cmr.ncsl.nist.gov ------------------------------ Date: Tue, 16 Oct 90 22:35:43 -0400 From: "Allen W. Sherzer" Subject: Re: You Can't Expect a Space Station to be Cheap Newsgroups: sci.space Cc: In article <1990Oct14.235219.3320@eagle.lerc.nasa.gov> you write: >So, my question is this. What does the LLNL scenario say about the >following systems: > - Power system The LLNL Earth Station power system will provide 60kWe. Power is generated by two 5 x 45 m arrays of flexibly magazine deployed amorphous silicon photovoltaic steets. One array will be on each of the habitation module triplets. The assumed weight is 1 kilo per KW. The NASA assessment says this is too optimistic. LLNL comes back with 1) they have samples of these sheets in house and 2) they can use what NASA says is the state of the art and still be below their weight budget. Energy storage will be with Nickel-hydrogen batteries using a common pressure vessel to reduce weight. Each module will have 20 kW at 10 kilos per kWh. Total weight: 1.2 T. Cables, power conditioning, monitoring and control add another .2T or so. Total Earth Station power system weight budget is 2.6T of which about 1.4T is used. This gives roughly a 2X margin of error. The LEO Gas Station uses about 200KW. > - Thermal Control System The Earth Station provides 20KW of cooling using six radiators. Each radiator is 3 meters high and goes around the station. An alternative is being examined which would put the radiators behind the solar cells. This should weigh about 2T plus .3T for pumps, coolant, corols, ect. > - Communications The central hub has an antenna. Don't have any more detail than that. > - Propulsion & attitude control I assume they will use the same system they plan to use for the artificial gravity. > - Data management Don't know. > - etc. The etc is that we can do it in about three years for less than what we will spend on Freedom this year alone (including HLV development). Anybody who doesn't believe this should consider Skylab an 'existance proof'. We did it before, we can do it again. Allen -- +-------------------------------------------------------------------------+ | Allen W. Sherzer | What should man do but dare? | | aws@iti.org | - Sir Gawain | +-------------------------------------------------------------------------+ ------------------------------ End of SPACE Digest V12 #462 *******************