🚀 go-pugleaf

In article <1992Nov17.023854.5180@bnr.ca> davev@bnr.ca writes:
>a)  What are people's opinions on unmanned planetary exploration
>    through the use of solar sails...

For some applications it would make sense.  A solar sail was one of the
final design concepts for the proposed US Halley-rendezvous mission,
which never got funded.  Comet rendezvous is one of the applications
where advanced-propulsion concepts really shine, because so many comets
are in such awful orbits.

It's almost unbelievable that Western space programs have stagnated to
the point where people design propulsion-critical missions using 1950s
propulsion technology, when far superior systems worked quite well in
1960s lab tests.  (The problem is that they never got flown, and hence
people planning once-in-a-lifetime missions often don't feel brave enough
to risk being the first real user.)

>b)  Why is or why is not faster than light travel possible?  ...

The most fundamental problem is that it appears to make hash out of
causality:  given any form of FTL communication (including FTL travel),
you can set up situations where a suitably-chosen observer would see
the cause-and-effect relationship reversed, with effect preceding cause.
This does Bad Things to physics.  It's sufficiently troublesome to be
a strong reason for believing FTL impossible.

Other problems, like the need for infinite amounts of energy, are
secondary.

>    ...I'd be interested in the non-conventional [means].

FTL travel conflicts so badly with modern physics that nobody is going
to take the possibility very seriously unless/until it is demonstrated.
The biggest objection to FTL travel is simply that we have no idea how
it could be done.  At the moment, FTL is fantasy, not serious speculation.
-- 
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  henry@zoo.toronto.edu  utzoo!henry