@S1-A.ARPA,@MIT-MC.ARPA:FIRTH@TL-20B.ARPA (06/13/85)
From: FIRTH@TL-20B.ARPA
Here is a short list of ideas for space propulsion systems
that don't rely on taking stuff along and throwing it out
the back. They range from the serious to the silly, and they
are all based on recollections of other people's work.
(1) Dean drive. The assumption is that Newton's Third Law is
wrong, and some combination of cams, levers, balls, cogwheels
and electric drills will exhibit spontaneous motion. The
problem is that people seem to have studied Dean drives quite
extensively and they really don't work. This represents in
my view the "silly" end of the spectrum
All other systems rely on using something already out there. We
have four choices
(2) Bussard ramjet. That is, we use the mass found in space as fuel
or reaction mass. The main problems are that the mass so dilute
that we need fairly large scoops to collect it. But that is an
engineering problem, not one of principle. This is I think the
system most likely to work.
(3) Light sail. The trouble is, there isn't enough light. We need
either an enormous sail or some space-based lasers. I don't like
the idea of space-based lasers - too dangerous and too much a
"brute force" solution.
(4) Magnetic propulsion. Useful only for the inner system, ie within
the solar magnetosphere. The energy is there, it's just a question
of harnessing it somehow.
(5) Gravitic propulsion. This one is really way out. Currently, we have
absolutely no idea how to interact with a gravity field in any
controlled manner. The interaction must be possible - inded, Hawking
radiation is created by the breakdown of the vacuum under intense
gravitic stress - but we lack an adequate theory. Also, it's not
clear what the energy flux would be. If you believe Mach's principle,
then a ship could use the entire mass of the universe to power a
gravity drive.
Frankly, I'd like to see work on all four of the above. Or do we wait
for an outsider ship to sell us one in exchange for Jupiter?
Robert Firth
-------ems@amdahl.UUCP (ems) (06/18/85)
> From: FIRTH@TL-20B.ARPA > > Here is a short list of ideas for space propulsion systems > that don't rely on taking stuff along and throwing it out > the back. They range from the serious to the silly, and they > are all based on recollections of other people's work. > Sigh, this must be my day for being dense. > > (5) Gravitic propulsion. This one is really way out. Currently, we have > absolutely no idea how to interact with a gravity field in any > controlled manner. The interaction must be possible - inded, Hawking > radiation is created by the breakdown of the vacuum under intense > gravitic stress - but we lack an adequate theory. Also, it's not Who was Hawkin and what is this radiation? How can a vacuum breakdown? It is a trace of something in the vacuum, or do you really mean that the empty space itself breaks down? > clear what the energy flux would be. If you believe Mach's principle, > then a ship could use the entire mass of the universe to power a > gravity drive. > Who is Mach, and what is his principle? Did I sleep through the wrong physics lecture or something? None of these names is familiar to me (unless Mach also is the guy who gave us mach numbers ... ) -- E. Michael Smith ...!{hplabs,ihnp4,amd,nsc}!amdahl!ems This is the obligatory disclaimer of everything. (Including but not limited to: typos, spelling, diction, logic, and nuclear war)