[ExI] Deceleration mirrors was Re: managing omnicidal maniacs

[Rafal Smigrodzki]

On Wed, Sep 9, 2015 at 8:25 PM, spike <spike66 at att.net> wrote:

>
>
> We have in our world today what looks a lot like a religion with a branch
> or subset espousing mass murder/suicide.  Tragic.
>

### Indeed, the Deep Green fanatics give me the collywobbles.

I was quite intrigued to read Anders' mention of chains of Fresnel lenses
for prolonging the acceleration phase of laser sail ships. It occurred to
me that optical devices could be also used for deceleration close to target:

Let's say we build a series of large mirrors and possibly Fresnel lenses
and send them into space in the direction of a planned ship cruise. Then we
send the sail ship, followed by a series of lenses focusing the laser beam
on the ship until midway to target, at maximum acceleration, and then
switch to the mirrors ahead of it, to effect deceleration. The mirrors
eventually crash into the target star or perhaps are left to sail forever
but the ship is rapidly slowed down to reach target in the shortest time.

This would be a complex scheme, and I am not sure if it would offer any
benefits over the alternatives. I feel that having a ship capable of
consuming its sail and using it as reaction mass in a plasma or ion
retro-rocket would still be overall faster and more reliable but future
starship builders should do the math on the deceleration mirror idea as
well.

It will be a glorious age. The Deep Green will not poison us.

Rafał
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