```ReplyTo   : Kelly
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
>>>mirror.
>
>>Hmm, yes, but there seems to have a similar problem with
>>the plasma mirror.
>
>Not really, Since the ring sail & catcher mirror are in the same place
>(attached to the ship) the ring sial would be geting the same energy (no
>energy drop due to r^2 losses.)

But would the beam from Earth not strike the ring sail?
If not, please could you make an (ASCII)drawing, because then I don't
understand how where the ring-sail and catcher mirror and the plasma are
located.

I don't use a ring-sail AND a catcher mirror, during deceleration, I have
only one flat mirror directed to TC on the ship and a retro-mirror that is
not coupled to the ship.

A|----\
O-----------/

O           Earth

----------- Beam from Earth

\
/           Retro-mirror

----        Beam from TC (Beam from Earth reflected by the retro-mirror)

A|          Asimov with a flat mirror

>> 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.

It overcomes the problem you mentioned: tracking.
The only thing the Asimov has to do is move about 1000 kilometres to the
left after it has uncoupled the retro-mirror. The result is that the mirror
and the Asimov will move in the same direction during deceleration.

>Also you seem to asume the that the power beam will be as small as the
miror?  >It sould be thousands of miles across.

I indeed did, if the beam is much bigger than the mirror, that would really
be a waste. If the radius of the beam is twice as big as the radius of the
mirror that would mean a loss of 75% of the beam!
But to overcome this if the beam is misplaced or bigger than the mirror, my
design could be modified a bit:

Beam that missed the mirror
||
||
/      ||  \
A /        ||    \ B        Two mirrors A and B at a perpendicular angle
/__________________\        but at some distance from each other
/|____________________|\
/ ||           ||       || \
||           ||       ||
||           ||       ||
||           /\       /\
\/          Beams from Earth
Beam to Earth

Although the mirrors are further apart, they still would be connected to
each other, only the connections will not reflect much.

>>>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 phase.
>
>I don't understand what your going for.

See above. You said that a retro-mirror had tracking problems because it
always had to be at an angle with the Asimov. My new design overcomes this
problem

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

Subject   : nanoAI

>>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.
>
>Your taking hundreds of tons of antimatter!  That is a stagering amount to
>manufacture, or even hold on to!

My assumptions are that making anti-matter in 50 years will be about 50%
efficient. Of course I can't be sure of this, but why wouldn't it?
(Rethorical question)
Besides this efficiency, I wonder why you are so blaffed by these numbers.
These numbers are just the sum of the energy needed during 1 or 2 years of
acceleration.
If we build a maser beaming station, a similar amount of energy is needed.
The only thing you do when transferring energy to anti-matter is making it a
bit more permanent. It probably is the easiest way to store such amounts of
energy.

So the moral is, anti-matter is merely an amount of energy that is easier to
keep in storage.

>People are mentally much more adaptable and relyable than any current
>Nano/A.I. systems.

You can't compare adaptability and reliable to CURRENT systems. That would
be the same as to say that current engines would not work for our project
and thus that it was not possible.

>>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.
>
>Thats a big job if your the size of a virus.

>From this I can conclude that I have a more optimistic view about nanotech
and AI, then you do.
Of course nanotech and AI are now in an early stage, but if 50 years ago,
you had said what computers of today would be like, then they had laughed at
you also.

>>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...
>
>As I remember the idea of LIT was to see if we could think of some way we
>could build a starship in 2050 with probable technology of the day.  Tau C
>was selected as a target to focus the groups attention on.

I know that, but I thought it was interesting to figure out why we want to
go there. Is it just to have pissed on the ground there? Or is it because we
want to colonize it? Or is it for scientific reasons? Or maybe all of them?
All these things me be reasonable at first but, if you think a bit further,
they make not much sense anymore...

>Agreed. I remember a demo where a steelwool pad was throw in a radar beam.
> It burned away in secounds.  Very impresive!  Especially to someone who
>might be thinking of riding such a beam for a couple decades.

I wish I could have seen it. Bear in mind that what you saw there was
probably as very small example of what may be the case for the Asimov.

Timothy

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