tentative hybrid design.

[Kevin C Houston <hous0042@maroon.tc.umn.edu>]

Kevin sees Brian's "pocket change" and rasies one dollar.  ;)

I don't have much time right now, so this will be short.

Here's the idea I'm thinking of.

the ship starts off as a hybrid structure.  a MARS-like front end, with 
an explorer-like backend.

the ship accelerates out of Sol System with a simple maser sail.  The 
large fuel tanks (used by the MArs as RM, but used by explorer like 
fuel)  on the MARS keep us shielded from interstellar speed-induced 
radiation.  As we approach the halfway point, (speed ~ .9905 C)
the two ships separate.  the MARS begins converting the masers to 
electricity, cutting it's photon derived thrust to ~5 m/s^2 (1/2 G)
under computer control, the fuel is thrust out the back end so that it's 
speed is just under the MARS's velocity.  The velocity of the and mass of 
the exhaust can be tailored to the needs of the explorer, since there 
will be no humans aboard the MARS

Meanwhile, the explorer spreads a large ram scoop out *behind* itself.  
This scoop grabs the (already) ionized fuel, (no containers, just gas) 
and fuses it, redirecting the exhaust at the retreating MARS.  The 
redirected exhaust protects the crew sections from erosion by the fuel.

The MARS continues along toward TC, getting closer and closer to the 
speed of light.  just before it enters Tau Ceti itself, hundreds of small 
probes luanch away (at perpendicular velocities) get some slight bending 
from the star, and streak away to fly-by various other stars.  The big 
tanks (now empty) and the lineac core crash straight into the star, and 
make nary a splash.

The crew deploys self-replicating robots (under some human direction) to 
construct the return masers, and a simple manufacturing plant handles the 
return sail (much like chicken wire)  the explorer, after ditching it's 
fusion motor, sails off back toward Sol, where the original masers sit 
waiting for our return.  :)

Kevin