Re: Missiles in Space Combat?

In article <Hi7_j.162244$rd2.79851@pd7urf3no>, bryan.derksen@xxxxxxx
says...
SolomonW wrote:
In article <262c2103-86ba-48b8-a6c5-e3388e32c5e2
@x1g2000prh.googlegroups.com>, lwcamp@xxxxxxxxx says...
In any event,
no, there isn't a minimum frequency (zero frequency EM "waves" are
common, we call them static electric or magnetic fields). If, as I
suspect, you are talking about a maximum frequency, there is no known
maximum frequency either. It is just that there is no known physical
mechanism to generate photons with such an absurdly high frequency.

Yet for a weapon designers, the shorter the pulse the better. In theory
he cannot do better then that.

Only when you're focusing solely on one single measure of "better". When
building a weapon system you have to consider many factors, and the
mechanisms necessary for cranking the quality of your laser pulse up to
such unreasonable levels will come at the expense of other things.



What factors are you thinking of? The energy level can be the same.


If you were trying to design an ideal bomb to maximize the amount of
explosive yield for its mass, as another example, you might say that it
should be composed of 50% matter and 50% antimatter. But if the
containment systems have to be made so light and fragile as a result
that it can only be moved at microgee accelerations, well, perhaps the
more _usable_ solution has less antimatter and more robust containment.


Sort of agree. Whatever the containment is, it will not be matter or
antimatter. A clever way of doing it is to make the missile antimatter
and use the matter of the target.


Indeed. And we are limited to pulses of several femptoseconds or more
because we use lasers that emit in the near infrared, with a
wavelength of around 1 micron. So long as our best chirped pulse
amplification lasers operate in the near infrared, we will never get
pulses shorter than several femptoseconds.

Advanced society, I expect will do better.

Magic isn't a good basis for an objective comparison.

I think we can agree that an advanced society will be able to do better
then we can. The question is how much better.


But it would be so much easier and amazingly more efficient to use a
much longer pulse (say a picosecond or so) that was made up of visible
or near UV photons, so all the energy would be absorbed by the surface
and could be used to blast through the missile's skin to the
vulnerable components underneath.

If possible you will want to by pass the skin and hit a component
underneath.

Could be prevented by making the skin out of the same material as the
internal components, if nothing else.


You would on the skin use reflective materials and spin it to spread the
heat.

The higher the frequency of the laser, the thicker the shielding
required.


Getting a single photon with
megajoules of energy is so far gone beyond anything we can currently
do it is silly to think about it in this context of realistic missile
engagements.

A single I would agree, but a lot is different.

But the big difficulty is not in the number of the photons, it's in
getting any photons _at all_ up to that energy level.

Gamma rays of sufficiently high energy have a tendency to spontaneously
decay into electron/positron pairs, for example. I imagine this makes
them rather hard to work with. I'm not an expert in the field, but I
imagine pushing the energy higher just opens up a bigger zoo of
fundamental particle/antimatter particles for things to fall apart into.

We are talking lasers, so this effect is not important. But are you sure
about this? I would expect the reverse. The higher energy of the Gamma
ray, the more stable it will be.


.

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