Re: Detection by IR

Roger Books wrote:
> 
> You know, that does bring up the question of a laser drive.  Point the
> laser to thrust.  If the laser happens to be pointing the right
> directions you could pick it up, otherwise you would see nothing,
> rec.sf notwithstanding.  As a matter of fact if I throw little steel
> pellets out (accelerating them with an linac type device) you would
> never pick them out from earth with passive systems.	(heck, I could
> cool them to 1K before I accelerate them)

	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. If your ships are laser propelled,
treat their drive as a Beam-500 or so to anything directly behind them
(or who happens to get in the way when you turn with the drive on). The
third problem is efficiency. Lasers (currently, although that may be
changing slowly) are less than 50% efficient, meaning that for every
joule you pump into movng yourself, you have to absorb a joule of heat.
This can get BAD quickly.
	As for seeing nothing, sure, if you don't count anything behind
the
drive suddenly heating up and melting....

	b) Rock drives. Fairly efficient. Require a LOT of reaction
mass. NOT
very high thrust. If you cool the rocks to 1K, you have to absorb the
resultant heat yourself. Sure, your rocks will be undetectable, but
you'll make up for it. Also, ISTR that drives based on said principles
tend to heat the mass in the launching process AND put out em radiation.
I may be wrong, of course.

-Brian Quirt