Re: MIRRORS Argosy Class

[Brian Mansur <bmansur@oc.edu>]

Brian 3:10 PM CT 3/6/96

>Kelly
>>The washer sail focusing back on a smallar drag sail is a design Forward
>>used in his Dragon fly series.  Assuming you intended to drop the outer
>>sail as a retro sail?
>
>Brian
>I'm not sure if we understand each on the last sentence.  This washer sail
>design is ALL part of the Asimov.  The retro mirror has long since been
>launched to position separated.  The whole point  of the design is to let
>the maser beam go between the Asimov sails to the retro mirror.

>Kelly
>???  Over interstellar distences your expecting to  shoot between the sail? 

>Besides the beam diameter would be the size of jupiter or something, and
>fading out to almost forever.  You couldn't make a sail that has a hole
>bigger than the beam.

Brian
If we could refocus the beam periodically along the way with several 
refocusing  aparatus it would be possible.  Problem is with energy loses in 
the refocusing and in getting the blasted things in place.  This idea just 
keeps getting more complicated all the time.

>
>[text deleted]
>
>>Brian
>>Course corrections are a detail we are still working on.  I'm beginning to
>>think that the tugs that I've envisioned elsewhere might be replaced by 
the
>>ion engine of the Asimov.  It could be fired at angles although the 
exhaust
>>would probably be into the sail.  More thought needed.
>
>>Kelly
>>Rather than tugs, you could pull in one side of the sail to generate an 
off
>>angle thrust.  Otherwise if you tried to push with rockets the sai would
>>get twisted out of shape, or draged behind slightly.
>
>Brian
>Yes, I'd like to do that if possible.  This is where my limited
>understanding of engineering starts to get on my nerves.  I can give
>theoretical concepts, but I don't know if they can be done from an
>engineering standpoint for lack of classes like statics, calculus based
>physics, and so on.  So I don't know if angling the sail is going to be
>easier than a tug.  Some voice in the back of my head tells me that it 
would
>be.

>Kelly
>That would just involve SLOWLYYYY!, pulling in or letting out some line on
>the right support cables.

Brian
Since we don't want fast movement in any direction but forward and backward, 
and we shouldn't be needing too many or drastic course corrections, slowly 
is good.

>>Kelly
>>Of course trying to keep the retro mirror focused, or even out of the
>>shadow of the ships retro mirror is probably a lost cause.
>
>Brian
>See my idea in Mirrors round 3.
>
>>Brian
>>I noticed that for this sail to work, the diameter would be greater than
>>Jupiter's to let the beam through.  ARRGGHH!  On the other hand it doesn't
>>have to be as precisely shaped as the retro mirror.  Still not sure how to
>>correct retro-mirror's course and keep its shape.  I'm trying to figure if
>>there is a way to break it down into components that will reflect at the
>>slight angle needed to hit the new rig.

>Kelly
>While surfing a microwave fire house at near light speed?

Brian
Yep.  Kind of like riding the flames of hell (sounds like the source idea 
for a demonic quote ;).

>>Kelly
>>??????!!!!  Jupiter!
>
>Brian
>We could cut that down considerably with refocusing mirror aparatuses which
>I proposed when I first joined.  That was in fact what my ugly BMP file had
>on it: a very simple diagram to illustrate the point.  Fresnel lenses might
>work better.  Problem is that these things have to be unmanned and they 
will
>take time to get into place.

Kelly
>But then you'ld need to aim the refocused beam to interstellar optical
>precision.  Also you'ld need to be able to build a freznel lense the size
>of a planet and carry it to interstellar space, and have it automatically
>center itself on the beam and aim at the target star.

Brian
Necessary evils.  We "just" have to figure out how to make them work.  The 
refocusing mirror may be easier to aim because it could be constructed like 
the retro mirror I have in mind in Mirrors Round 3.