```
Subject   : Using the SIM

>I listed some assumptions on my Explorer Web page in LIT.  I think bottom
>assumption was a hydrogen atom every cubic centameter or 4.

Now the question what are we going to do with the hydrogen? First catch it
and decelerate a bit. Then use it both as fuel and reaction mass to
decelerate even more.
4 per cubic centimetre --> 4E6 per cubic metre

How much would we scoop? Total deceleration length: 2 ly = roughly 2E16
metres.
2E16*4E6*surface_of_the_scoop=8E22 hydrogen atoms per square metre of
scooping area during the total deceleration. Thats a little more than one
tenth MOL! and has a mass equivalent of: 0.0001 kilogram.
This value seems to be too small to be useful! Unless we are planning a
scoop of more than 1000 kilometres in radius. (Earth has a radius of 6500
kilometres)

===========================================================================

Subject   : Plasma mirror

>Sorry that won't work.  As the outer mirror moves away from the ship it has
>to continuosly reshape itself to refocus on the smaller catcher mirror/sail
>on the ship.

>> I don't think refocussing is necessary, the mirror itself can
>> be just a flat mirror so the reflected beam is nothing
>> different than the beam from Earth.

That would mean the catcher sail on the ship would be the same size as the
reflector mirror.  That would mean it would get more push forward from the
dirrect beam from earth, than push back from the reflected beam from the
mirror.  Assuming of course the mirror flies sideway slightly so it isn't in
the ships shaddow all the way to Tau.  Of course if its off to one side you
have to turn it so its reflections tracks the ship, so your back to the
tracking problem.

>Also without the anchor on the ship it will tend to flutter and
>shift off course due to slight variations in beam, ISM, mirror reflectvity,
>seperation torque, etc..  This of course ignores the fact the sail isn't
>rigid, and will tend to crumple once its free of the ship.

>> Of course the mirror has it's own "gyro-system" it can
>> compensate slight movements by using a small side
>> reflectors.  The same principle would be used when the
>> Asimov is accelerated by a beam.

With enough accuracy to hit the retro sail at a distence of light years?

==============================================================================
=

Subject   : nanoAI

>> About AI and nanotech. If AI and nanotech would be
>> small vessels could be send to TC all with their
>> own fuel to decelerate. These small vessels would
>> contain AI and nanotech or even a combination of both.
>> This nanoAI could build the same facilities on TC that
>> would "create" the energy for the Asimov on Earth.  The
>> advantage is that the small vessels would use much less
>> energy to make the trip.  After nanoAI has build the
>> facilities, accelerating and decelerating the Asimov
>> would be the same and make the whole design a lot easier.

We still have no drive idea that could get a bit or small ship to Tau C.

We've added the relyability problems of the AI and Nano systems to the
project.  After all, programs can crash, and nano's are made of complex
molecules that might break down in the high radiation in transite.  Assuming
they get there in tact, what do we tel them to use for resources in a system

How does a ship fly in two apposing beams?  You can't turn eiather off.
Since: you can't contact the ship to know what its doing in time, and don't
want to fly to a system in the hopes the A.I's will turn the beam on when you
expect.

We also have extended the time of the project to us sustainable levels.
Figure a quarter century after launch before a returning beam from Tau C.
announces the decel system is compleated.  Then a quarter century after that
(50 years from the launch of the first nano ship), a beam from your starship
announces you've started exploration.  If the projects going to take that
long you might as well wait untill you have a better drive system.

For that matter. If the A.I's are good enough to build the decel gear.  You
might as well have them do the exploration and skip the human ship.

```