Re: Detection by IR

Roger Books wrote:
> 
> On 20-Apr-00 at 12:01, Brian Quirt (baqrt@mta.ca) 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_)
> 
> The Moties drive doesn't count, the laser stayed on the planet.  It
> was used to heat the reaction mass (ice I believe) on the acceleration
> end of the ship.  You waste lots of power but the power is coming
> from the planet where you can  afford the waste.

	No, sorry, that isn't what he was talking about. <grin>
	THE MOTE IN GOD'S EYE, page 42:

"Of course light pressure could be used for propulsion.  In fact,
the MacArthur did exactly that, using hydrogen fusion to generate
photons and emitting them in an enormous spreading cone of light."

	It goes on to describe the MacArthur landing on a moon
	to re-fuel, with the base using a Langston field on
	the landing pad to prevent the drive from burning 
	craters in the moon.

	On the other list, they calculated that the drive actually
	could punch a hole in the entire moon.

	You are also incorrect with regards to the Motie drive.
	It is a standard lightsail, moved by the light pressure
	of the laser batteries back in the home system.
	No reaction mass or ice is involved.

	You are thinking of Pournelle's laser launch system,
	which is featured in some of his other stories.
	Some have solid blocks of reaction mass on the bottom of
	the launch vehicle, others just use the atmosphere in
	the exhaust chamber as reaction mass.