RE: starship-design: doable drives

["L. Parker" <lparker@cacaphony.net>]

Adam,

Kelly is correct, there are pulse fusion systems around that don't produce
lots of neutrons, you even named one - Orion.

Current concepts for pulsed fusion are somewhat more refined than Orion,
which no one is seriously considering anymore. Try
http://antimatter.phys.psu.edu/Index.html for an in-depth look at one of the
newest concepts which is currently being tested by PSU, JPL and the USAF.
The current incarnation is neutron intensive but the technology scales to
Lithium or Boron fairly well. I wouldn't think it would be unreasonable to
see second or even third generation engines in use by 2050, which would
allow access to most of the Solar system within only a few months time, and
given sufficient fuel, could propel a probe to the stars at up to .99 c.

Your guess at the fuel ratio was, however, a little optimistic. It is more
like 10,000 or even 100,000 to 1.

Lee