Re: Detection by IR

Brian Quirt wrote:
>	  a) Laser Drive: Big problem: efficiency. Yes, light has
energy. No, 
> it doesn't have very much. The kind of laser that will give you
multiple-g
> accelerations will a) consume an INCREDIBLE amount of fuel and b) be
> VERY bad news for anyone in its path. I recall a discussion on light
> propulsion (inspired by Niven and Pournelle's _The Mote in God's Eye_)
> (on another list) where it was calculated that, even for a
> non-collimated (spreading) light drive, the intensity required to
> produce the necessary thrust would make the drive a better weapon than
> ANYTHING else shown in the stories.

	Agreed, "better weapon" as in "could slice the Moon in two
parts".

	According to the knowlegeable Erik Max Francis:

The mometum of a photon is given by 
    p = E/c, 
where E is the energy of the photon, and so the thrust delivered by a
stream 
of them is
    dp/dt = dE/dt/c
or
    F = P/c
where F is the thrust and P is the power.  To get a thrust of 1 N, you
need a 
power of 300 MW.  Yes, three hundred megawatts!

	As a comparison, one of those toy cardboard Estes model rockets
	has a thrust of several Newtons.
	The Space Shuttle on the other hand has a thrust of
	2.944e7 Newtons. 
	So multiply 300 megawatts by 29,440,000 to see what kind of
	power plant you'd need for a mere Space Shuttle level of thrust.

	As a supplementary problem, how do you cloak the waste heat
	from a power plant of that size?