Re: Engineering Newsletter

[Steve VanDevender <stevev@efn.org>]

KellySt@aol.com writes:
 > to:  rddesign@wolfenet.com
 > To: KellySt@aol.com
 > 
 > >>> Heat load on the asimov:
 > >
 > >> Kelly
 > >> This is way outside of my knowledge but couldn't this heat 
 > >> be expelled like exhaust and added to the thrust? Heat is 
 > >> just hot particles, isn't it?
 > 
 > No such luck.  Heat is eiather the thermal vibration of the molecules in an
 > object, or infared radiation (life in a radiative heater).  Can't think of
 > how we'ld pump all the heat out of the ship fast enough to keep it cool.

Heat is purely statistically random molecular motion.  Infrared
radiation is just a form of radiation that is good at inducing
heat in common materials.

Regarding this whole momentum-transfer issue, in some far-distant
posting to the newsletter I pointed out that a reflective sail is
the most efficient option for accelerating a spacecraft with
beamed power; it changes photons with momentum +p into photons
with momentum -p, and thereby increases the spacecraft momentum
by 2p.  It is unlikely that you could absorb the photons and use
them to power a mass driver with greater efficiency than the
reflectivity of a mirror.

Using beamed power to decelerate a ship that's going in the same
direction as the photons is more problematic.  At best the
efficiency is going to be bad.