Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cornell!rochester!dietz
From: dietz@cs.rochester.edu (Paul Dietz)
Newsgroups: sci.space
Subject: Re: Manned missions vs. Planetary Science
Message-ID: <1989Jan29.161750.29964@cs.rochester.edu>
Date: 29 Jan 89 21:17:50 GMT
References: <890125100532.000004A2082@grouch.JPL.NASA.GOV>
Reply-To: dietz@cs.rochester.edu (Paul Dietz)
Organization: U of Rochester, CS Dept, Rochester, NY
Lines: 42

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