good@pixar.UUCP (Void where prohibited) (11/17/86)
In article <7325@utzoo.UUCP> henry@utzoo.UUCP (Henry Spencer) writes: >JPL is studying a mission dubbed TAU, Thousand Astronomical Units... >...propulsion system would be shed after fuel exhaustion, leaving the >11,000-lb spacecraft to continue on for up to 40 more years... > >[Mini-editorial: a probe with a 50-year mission will be passed by newer >probes with better engines long before the end of its mission. Planning >for such long missions needs to consider in-flight obsolescence. -- HS] Good point. But better engines will result, at least in part, from experience gained by flying the current idea of "new" engines. I also wonder if the probe might not return some data significant for the planning of a follow-up mission during the first few years. Perhaps this probe could wind up as a long-term, deep space exposure experiment when it is found by one of the later craft. Think of how much fun it would be to check it for dings and graffiti. -- --Craig ...{ucbvax,sun}!pixar!good
freeman@spar.SPAR.SLB.COM (Jay Freeman) (11/18/86)
In article <260@pixar.UUCP> good@pixar.UUCP (Void where prohibited) writes: >In article <7325@utzoo.UUCP> henry@utzoo.UUCP (Henry Spencer) writes: >>JPL is studying a mission dubbed TAU, Thousand Astronomical Units... >>...propulsion system would be shed after fuel exhaustion, leaving the >>11,000-lb spacecraft to continue on for up to 40 more years... >> >>[Mini-editorial: a probe with a 50-year mission will be passed by newer >>probes with better engines long before the end of its mission. Planning >>for such long missions needs to consider in-flight obsolescence. -- HS] > >Good point. But better engines will result, at least in part, from experience >gained by flying the current idea of "new" engines. I also wonder if the >probe might not return some data significant for the planning of a follow-up >mission during the first few years. > > > >-- > --Craig > ...{ucbvax,sun}!pixar!good Furthermore, there is reasonably good science to be done at order of 100 AU -- nominal distance for the (presumed) shock front at which the solar wind slows down abruptly due to interaction with the interstellar medium. A mission would presumably study this region, as well as study the nature of the unperturbed interstellar medium not far beyond. It is probably worth developing an advanced engine just to get to there, and if it doesn't cost too much more to make the vehicle last longer, so much the better. Besides, direct measurement of stellar distances benefits in proportion to the distance traveled. At 100 AU one would be only 10% as well off as at 1000 AU, but 50 times better off than here (our baseline is 2 AU, the diameter of the Earth's orbit). One might indeed need some of those interim measurements as an aid to mission planning for the interstellar missions to be launched with the advanced engines developed during the next 40 years ... -- Jay Freeman
eugene@nike.uucp (Eugene Miya N.) (11/20/86)
> Various comments about technological obsolesence. Space craft > overtaking one another. Oh yeah? Reminds of Achilles and the Tortiose. Tell me this the next time I go to Washington DC and I sit on the steps of the Capitol. (December/January) From the Rock of Ages Home for Retired Hackers: --eugene miya NASA Ames Research Center eugene@ames-aurora.ARPA (aurora's back up) "You trust the `reply' command with all those different mailers out there?" {hplabs,hao,nike,ihnp4,decwrl,allegra,tektronix,menlo70}!ames!aurora!eugene