Re: Striking a Lunar target in the near future...

From: Ian Stirling (root_at_mauve.demon.co.uk)
Date: 08/19/04 

Date: 19 Aug 2004 12:01:43 GMT

In sci.space.policy Henry Spencer <henry@spsystems.net> wrote:
> In article <4123e2f0$0$2893$ed2619ec@ptn-nntp-reader03.plus.net>,
> Ian Stirling <root@mauve.demon.co.uk> wrote:
>>This would imply that contact fusing, even at 10Km/s or so impact speeds
>>is quite possible, as long as you have a few dozen cm of clearance.
>
> There are indeed reported to be contact fuzes in at least some
> ballistic-missile warheads -- when fine wires in the nose of that long,
> pointy reentry vehicle start to break, the bomb back in the thick tail is
> triggered -- although they may not be the only fuzes present. (For soft
> targets -- that is, almost anything except ICBM silos -- air bursts will
> typically do more damage.)
>
>>It'll depend on your target.
>>If it's a spread-out dome structure, you probably want to light the
>>blue touchpaper where the target is around 60 degrees across from the
>>bombs POV, so it causes maximum blast effect on the surface.
>
> Remember that there is very little *blast*, per se, in vacuum. Much of
> the bomb's energy comes out as soft X-rays. In air, that energy is
> promptly absorbed by the air -- that's what makes the fireball -- and that
> converts it, via incandescent air, to heat and blast. In space, it's the
> X-rays that hit whatever's in line of sight; if it's close, they vaporize
> its outer layers, and *that* makes any blast effect.

Sorry, speaking loosely.
The blast of course comes from the structure itself, not the air.

> The problem with a target on the Moon is that unless it absolutely has to
> be on the surface for some reason (antennas?), an awfully obvious way
> to protect it against temperature extremes, micrometeorites, radiation,
> and missile attacks :-) is to shovel a couple of meters of dirt over it.

We don't know what the target is, if it's something like greenhouses
for a race that don't mind temperature extremes or radiation, then
it might be appropriate.
Dug in structures are probably going to want to have a subsurface burst
as you say.

> That makes X-ray-based attacks rather iffy, especially if you aren't
> confident of a direct hit. (Bear in mind that the only *precision*
> lunar landing capability ever demonstrated involved starting from lunar
> orbit, not going straight in.)
>
> I would guess that you are better off fuzing for a surface burst, or even
> (warhead design permitting) a subsurface burst, which will excavate a
> sizable crater and pretty assuredly kill anything in or near the crater.

I suppose the lack of atmosphere will mean that the ejecta from the crater
proceeds outwards much faster than it otherwise would, as there is no
air to get in the way and be compressed by the expanding debris cloud.
So, two or three bombs dropped down the same hole might be possible.
You'd need to put them quite far apart to avoid the radiation pulse killing
the next one in the line.

It's going to depend on the target if you get best bang for the launch
weight going for one big bomb, several little ones to drill a hole for
the one big one, or lots of little ones spread out over an area.

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