To Mars and Back With Less Fuel

One of the facts about space travel, when done with rockets, is that if
you need to execute a manoeuver requiring a large delta-V in order to
come back from where you went, then the amount of fuel needed to send
you there has been multiplied many times over because your return fuel
had to be sent with you.

We are all familiar with the plan of Dr. Robert Zubrin to alleviate this
issue by sending only hydrogen to Mars, which can be used to produce
oxygen and methane by reacting with the carbon dioxide in the Martian
atmosphere.

NASA proposed a Mars Reference Mission, in which production of fuel on
Mars was scaled down, to just enough to launch a capsule into orbit to
rendezvous with the return craft.

Originally, I proposed a modification of Dr. Zubrin's original plan to
cut it up into smaller pieces. But now I think that a plan with even
smaller fuel requirements can be constructed using the Mars Reference
Mission as a basis.

The amount of fuel produced on Mars is increased, however; to a level
greater than that required to put a small ship into Mars orbit, but less
than that required to send a large ship, on which astronauts can be
provided life-support for the long journey home, on a Hohmann orbit back
to Earth.

I propose that the asronauts begin their journey home by using the fuel
produced on Mars to launch a small craft into an orbit that would return
it to Earth.

But in that craft, they would rendezvous with a larger craft, launched
*three years previously* from Earth, in a 1.5 year free-return orbit,
which would have the supplies they need to survive on the long journey
back.

This avoids sending to Mars the fuel needed to provide a large delta-V
to a large ship. It does pose risks, as making the return rendezvous is
critical. The fuel savings may be enough as not to be entirely offset by
launching two return ships.

John Savard
http://www.quadibloc.com/index.html
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