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From: dietz@SLB-DOLL.CSNET (Paul Dietz)
Newsgroups: net.space
Subject: Re: Manned Mars Trip
Message-ID: <8512071719.AA10364@s1-b.arpa>
Date: Sat, 7-Dec-85 10:13:13 EST
Article-I.D.: s1-b.8512071719.AA10364
Posted: Sat Dec  7 10:13:13 1985
Date-Received: Sun, 8-Dec-85 03:05:52 EST
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The ARPA Internet
Lines: 42

A manned Mars trip should have low priority.  The following items
are more important:

   (1) Cheaper transport to low earth orbit
   (2) Reusable OTV's (robotic or remote controlled)
   (3) Storage areas in LEO and GEO for parts & fuel for OTV's
   (4) A LEO space station
   (5) A GEO space station
   (6) Visits to asteroids co-orbital with earth, if any exist
   (7) A lunar base
   (8) Visits to some Apollo/Amor asteroids

It really makes little sense to visit Mars until we can do so
economically.  This will require more infrastructure around earth
if we want to establish a base there at a reasonable cost.
The payback from asteroid visits is also likely to be higher,
if large amounts of mass can be returned to earth orbit.
Of course, there will be scientific benefits from a Mars mission,
but the results would be expensive, and more science could be done
on earth (in other fields) for the same money.

Of the eight points I listed above, (1) is the most important for
making a Mars mission practical.  A Mars ship will be heavy.  In
proposed Mars missions I've seen, the major cost has been bringing
the Mars ship and its fuel into orbit.

The rockets used in the Mars mission could be conventional LH/LOX
chemical rockets or NERVA-type nuclear rockets.
Some sort of beam-powered (microwave or laser) electric rocket
could also be practical, at least for the boost away from earth.

The first missions to Mars will probably establish bases on or near
Phobos and/or Deimos.  These moons are likely to contain water
and carbon compounds, and could be processed into air, food and fuel.

Probably the cheapest way to get to Mars in the near term is by
an Orion-type rocket.  It could be built in orbit to reduce fallout,
but this would again require cheap boosters to put its thousands of
tonnes of mass into space.  ET materials might be useful as shielding,
or for structural material, if a nickel-iron asteroid could be snared.
Water or carbon compounds from asteroids or the moons of Mars could be
used as reaction mass in the shaped nuclear charges.