PJS@GROUCH.JPL.NASA.GOV (Peter Scott) (01/26/89)
The current debate surrounding the opinions of Dr. Van Allen et al points up the fundamental conflict between manned and unmanned space missions, viz: unmanned missions, by virtue of their current economic ability to reach places that astronauts (or even cosmonauts) cannot explore, have more-or-less immediate return on investment. Even though the ROI is mostly limited to planetary scientists, it's still much more than the virtually non-existent return on space colonisation, since any other value returned from a manned mission has so far been something that could have been achieved with an unmanned mission (e.g., Skylab observations). Thus advocates of manned missions often find themselves grasping at straws (e.g. the zero-g pharmaceutical opportunity arguments). The ROI for manned missions qua manned missions is decades away (e.g., asteroid mining operations), but *that doesn't mean we shouldn't start now*. After all, we won't get there at all if we don't take the first step. I'm just not sure that it's a winning strategy for us manned mission advocates to try and compete with the immediate ROI currently available to unmanned missions. Question is, who on earth is prepared to undertake a venture that won't break even for thirty years? The classic response is, "Governments", and they've done similar in the past, so how come it's so difficult to get them to do it in space? Peter Scott (pjs@grouch.jpl.nasa.gov)
dietz@cs.rochester.edu (Paul Dietz) (01/30/89)
In article <890125100532.000004A2082@grouch.JPL.NASA.GOV> PJS@GROUCH.JPL.NASA.GOV (Peter Scott) writes: > The ROI for > manned missions qua manned missions is decades away (e.g., asteroid > mining operations), but *that doesn't mean we shouldn't start now*. > After all, we won't get there at all if we don't take the first step. I expect asteroid mining, when it starts, will be small scale and unmanned. Given the long travel time it makes little sense to send people when they are not absolutely required. It would make more sense, I admit, to have people in earth orbit (low or high) to process the returned material, and to maintain the mining vehicles. Unmanned asteroid mining could occur surprisingly soon, if anyone wanted to try. A really primitive mission, using an expendable chemical upper stage to inject to the asteroid and aerobraking to LEO could return 2.6 times the mass launched to LEO in asteroidal material. This goes up to 8 if the aerobrake is stored in HEEO and reused several times. Additional benefits can be attained by extracting water at the asteroid or by using solar-thermal rockets. No mass drivers are required. These numbers use 1982 DB as an example; more accessible asteroids almost certainly exist. We should start now. The first step is to find as many earth approaching asteroids as we can. Existing technology -- ground telescopes, computers and CCDs -- could find them in droves, if we tried hard. Current searches, while excellent, are shoestring operations. Upgrading to more/larger scopes with better detectors, computers and more staff would help immensely. The cost would be modest; the benefits, large. > I'm just not sure that it's a winning strategy for us manned mission > advocates to try and compete with the immediate ROI currently available > to unmanned missions. I suggest manned spaceflight advocates look for synergism with unmanned activities (and vice versa). Sending people anywhere beyond LEO would be much cheaper if asteroidally derived rocket fuels were available. Unmanned missions would be easier to justify, I think, as being precursors to manned activities. Paul F. Dietz dietz@cs.rochester.edu
leech@piglet.cs.unc.edu (Jonathan Leech) (01/30/89)
In article <1989Jan29.161750.29964@cs.rochester.edu> dietz@cs.rochester.edu (Paul Dietz) writes: >I expect asteroid mining, when it starts, will be small scale and >unmanned. Given the long travel time it makes little sense to send >people when they are not absolutely required. The scenario involving a Mars mission mining its return fuel from Phobos is another (slight) possibility. >We should start now. The first step is to find as many earth >approaching asteroids as we can. Existing technology -- ground >telescopes, computers and CCDs -- could find them in droves, if we >tried hard. Marsden's semi-automated searches are doing a good job. I suspect the hard part is getting more time on wide-field telescopes (on the other hand, Gene & Carolyn Shoemaker use the 18" Schmidt at Palomar, which might not get much use otherwise) -- Jon Leech (leech@cs.unc.edu) __@/ ``I have a fair amount of faith in American free press; oppression continues to surface, but justice will always triumph as long as enough money can be supplied.'' - Reed Waller