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Engineering Newsletter

Who anyone who likes a physics comic, try:


It's about 14 Kbyte


ReplyTo   : Kelly
ReplyFrom : Timothy
Subject   : Plasma mirror

>>> 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

Hmm, yes, but there seems to have a similar problem with the plasma mirror.

But I've found a solution:

     A /    \ B        Two mirrors A and B at a perpendicular angle
 / ||          || \
   ||          ||
   ||          ||
   ||          /\
   \/        Beam from Earth
 Beam to Earth

This design makes the total mirror about 3 times bigger.
The beam from Earth should be directed mainly on mirror B so that the beam
to the Earth (or from TC) is reflected mainly from A. The final result is
that there are two beams next to each other, one is going up the other is
going down.

>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.

With this new design the biggest tracking problem is removed. Furthermore
the Asimov always has to follow the beam just as in the acceleration fase.

>>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?

10 ly, 30 ly does it really matter? The minimum is 10 ly for any kind of
beam-propulsion system. I wonder if an extra 20 ly makes that much difference.


ReplyTo   : Kelly
ReplyFrom : Timothy
Subject   : nanoAI

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

We have ideas, the biggest problem is the enormous amounts of fuel that are
needed. Lets say we use a take-all-fuel-with-you system. For
matter&anti-matter fuel the ratio fuel:ship would be about 20:1 for small
ships 1E4 1E5 kg this may be acceptable but for ships 1E8 or 1E9 kg its a
completly different story.

>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
>we don't know anything about?

Indeed things can go wrong and will go wrong. So will things happen on a
ship like the Asimov, only then people are endangered.
High radiation as a cause of error can easely be prevented by sufficient
We know that there will be asteroids and planets there. This means that all
the basic materials should be present, so our mini factories have to find
them an use them.

>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

The beams should be slightly from parallel. Halfway the should cross, and
the vessel using it has to change beams there. This means that it has to
move "side-way" some 100-1000 km or so. It should be like changing
rail-tracks by using a switch.

>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.

Supposing a significant better system is possible within 50 extra years, I
think its worth the waiting.

>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.

That is something completly different discussion: Why do we want to go there
anyway. I was having a discussion with Nick Tosh about that, until his
connection broke down. I can tell you, that I don't know why we want to go
there so soon anyway.
If you have an answer I'd like to know...

For the AI and nano, if they will be as unreliable and unadvanced as you
think, my guess is that the time isn't right for flying to TC anyway:
If anything, and I mean anything goes wrong in a system that uses 1E17 Watts
you are lost! It's not like you can cut the power any time you like. What I
wrote about overheating is just a small example of the problems that go with
these power streams. (And as far as I'm concerned that problem isn't solved yet)