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>From Brian
March 1, 1996

Here it is: the detailed design I promised (as detailed as I can make it at 
the moment anyway).  But first: does the "interstellar drive group" 
selection that I now see on my address book  now account for everyone in the 
discussion team?  Okay, on with the show.

Note that this is my first draft.  The lab is about to close and I have a 
lot more ideas to cover but they may have to wait a bit.  Things like sail 
shielding and mirror array design are among them.  Sill I'm going to send 
what I've got to let you all have some fun ripping it apart :)

MARS HYBRID DESIGN II (Kevin already submitted the first this morning)

Total mission time: 50+ years
Pathfinder(s) mission flight time: 40+ years
Asimov flight time: 24+ years
Asimov exploration phase time: Undetermined

     It is assumed for this mission plan that a high degree of robotic 
automation has already made possible the production of at least 1E18 W 
needed to power 1E7 masers without much human supervision.  It is also 
assumed that this maser array is totally dedicated to the mission and that 
the beam will be left throughout the mission.

     At least one heavy pathfider vessel will be sent before the Asimov 
using  maser sail to reach a terminal velocity of 1/3c.  Pathfinder carries 
several thousand, heavy duty, heavy weight, individually targetable, 
disassembled mirror arrays that will be deployed roughly 30 years later near 
TC (see reflectors in an upcoming posting).  These arrays (probably making 
an effective 1000 km+ wide reflector) will reflect maser energy back to the 
Asimov for the deceleration phase.  The Pathfinder may or may not have a 
crew depending on the level of automation available at the time of launch. 
 Also, it may or may not carry emergency supplies for the Asimov should they 
choose to match speed and dock during the deceleration phase.

     The  Asimov is maser pushed to a high %c terminal velocity.  It is 
hoped that the maser propulsion system will be efficient enough to push the 
Asimov to a speed at which the effects of time dialation will be useful to 
the crew.  At the very least, a max speed of .75c is assumed here.
     This ship will consist of an ion drive for in system shuttling around 
TC.  It will also carry the exploration team and their supplies for the 
mission.  Among the supplies already mentioned in other discusions are seed 
robots.  They will be used to start a robot workforce that will help 
construct, among other things, a precision mirror array to reflect the maser 
energy from Sol back to the Asimov's maser sail when the exploration phase 
is completed.

     The exact process has many variations.  If there are several 
Pathfinders, each, the one closest to the Asimov will deploy its reflector 
array and then move to a safe range from the beam path.  The array will 
enter the beam path and redirect the maser energy back to the Asimov.  The 
Asimov, of course, will have turned its sail around (a slow and delicate 
process).  It will also have moved slightly to the side the maser beam 
coming from Sol to prevent blocking of the array.
     Some method of periodic or even continuous course correction on both 
the Asimov's part and the array's will be required to correct for the angle 
at which the maser beam must be reflected.  The Asimov may simply angle its 
sail slightly with the edge furtherest from the Sol to array beam tilted 
back toward Sol.  The array will have to use built in rockets, or else tilt 
from time to time in the proper direction to allow vectorial force to push 
it back into the center of the beam.
     Now, assuming that the doplar effect will cause problems with 
reflection of the maser beam, another Pathfinder could deploy it's array and 
continue the decelation process.  Note that I don't know if  the most 
efficient thing that the Asimov can do with the redirected maser beam will 
be to simply bounce it back to space or to power a ion drive.   The exhaust 
from an ion drive would make for nice shielding against large particles.
     One final note.  As the Asimov and Pathfinder speeds reach equilibrium 
they have the option of docking (assuming the deceleration of the Asimov 
brought it close to the Pathfinder when speed equilibrium was reached.  At 
this point, any crew on the Pathfinder could cross over.  Note that the 
Asimov could dock with only one Pathfinder.

     The Asimov enters the Tau Ceti star system's Kupier Belt.  At this 
point it disassembles its sail and starts scouting for a low gravity, metal 
rich Kupier body that is not too far from the maser beam path.  Once such a 
body is located, the seed robots are deployed to begin a robot community. 
 Since the Kupier body will be too far away from Tau Ceti for solar energy 
collection, it is assumed that the robots will be powered by fusion reactor 
that must be brought along (in addition to the fuel).  Depending on the 
automation technology at the time of launch, these robots will at least be 
responsible for construction of a mirror platform needed for reacceleration 
to Sol.
     The Asimov leaves the Kupier outpost to continue its exploration of the 
star system.  Whatever number of crew is needed to oversee construction 
stays behind.  As the maser reflector nears completion.  The array must be 
somehow weighted down to keep it from flying off.  Keeping it tethered to 
something like the weight of Phoboes would be nice but then Sol would have 
to track it to keep the beam on target.  It will probably be better to 
simply give it enough weight to prevent it from blowing away too fast while 
reaccelerating the Asimov.  I only hope that the required weight won't be 
beyond out ability to put to space.  Also, this entire array will have to be 
able to maintain its position inside the maser beam which means some 
powerful rockets or some angling of the array as mentioned in Phase 3.

     This final phase is pretty self-explanitory.  The Asimov's sail (having 
been patched up from the flight to TC we hope) is redeployed is manuvered 
into the path of the redirected maser beam.  Again, it is hoped that a high 
terminal velocity will be possible.  As the Asimov nears Sol, the array is 
turned around and the masers focus straight on to the tatered sail.  Mission 
ends as the Asimov pulls into the local Starbase.