Re: Ravening Laser Death Station

On Aug 14, 1:32 am, Logan Kearsley <chronosur...@xxxxxxxxx> wrote:
On Aug 14, 12:03 am, IsaacKuo <mech...@xxxxxxxxx> wrote:

I'm thinking in terms of a FEL system which is maybe 100m to 1km
in overall length. It has two selectable wigglers for operations in
two different modes--a short range UV mode, and a long range
X-ray mode. In both modes, the beam starts off as a narrow cone.
This cone spreads out onto a large diameter lens drone, which
is far away. In UV mode, this lens is a fresnel lens which
efficiently focuses the laser light onto the target. In X-ray mode,
this lens is a zone plate which directly absorbs about 50% of the
laser light, but can be focused onto targets at far greater distances.

[...] For X-ray mode, I'm thinking about combat ranges
on the order of 1000 light seconds, so the drone is maybe 1 light
second away from the laser ship.

I'm not a big fan of physically separated components at long ranges. I
can overlook the 50% cut in efficiency, but it makes the whole set-up
more vulnerable and turns re-aiming into a Major Production, except at
fairly small angles.

Looking at it a little more closely, the cut in efficiency is actually
75%. You lose 50% of the light because that's absorbed by
the zone plate. Only 50% of the light which passes through is
focused onto the central diffraction spot. The remaining light
ends up in a larger diffraction pattern of concentric rings.

I suppose that isn't really much of a problem for an IPWM*, where all
of your targets are millions of kilometers distant, and if any of them
aren't in the same small patch of sky you've got a long time to re-
position everything. But it still seems.... unaesthetic.

You do need multiple drones, but there are some nice
benefits to the long distance between the drones and the
laser ship. The drones are relatively insensitive to vibrations
from battle damage, and making precise aim adjustments is
easy (motions are only amplified 1000x).

Hm. Perhaps one could build a very large ring of focusing components
(fresnel lenses / zone plates) on the surface of a moon or asteroid,
with the laser apparatus at the center, capable of rotating to fire at
any one of them. Preferably at the pole of a slowly rotating body
(like The Moon) so as to fire in the ecliptic, but one could simply
rely on the rotation of faster-spinning bodies to periodically point
the lenses the right way.

The distance I propose between the drone and the laser
engine is 300,000km. There is no moon or asteroid
sufficiently big for a ring 300,000km in radius.

For the short range UV mode, I propose a distance of
maybe 50-100km. But with a range of only maybe
100,000km, this mode needs to be able engage targets
from any direction, not just vaguely along the ecliptic.

Isaac Kuo

.

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