Re: Fate of SF as World Slides Down Back Side of Hubbert's Curve?

On Mar 25, 1:05=A0am, Girish <girishbhat6...@[EMAIL PROTECTED]
> wrote:
> On Mar 25, 10:52=A0am, Gene Ward Smith <g...@[EMAIL PROTECTED]
> wrote:
> > Girish <girishbhat6...@[EMAIL PROTECTED]
> wrote in
news:368e1add-6ac8-4960-86d3-=

> > f853f6286...@[EMAIL PROTECTED]
> > > Kevin Cherkauer wrote:
> > >> -- Humanity will never go to the stars (probably not even one human
> > >> will go to the stars)

> > > Not in mine or your lifetime - maybe. But eventually, yes.

> > How?

> If we knew how, we would already be working on going there, no?

We know several ways to do it using near to mid term technology.
But not using near to mid term economy.  It's just too outrageously
expensive to start on it yet.  We have difficulty scraping together
the money for a simple manned mission to Mars.  A mission to
Alpha Centauri?  Out of the question, for now.  We (almost) have
the technology.  We're very very far away from having the resources.

My favorite star****p concept for a manned return mission to Alpha
Centauri uses a relativistic kinetic impact powered rocket.  The
star****p is essentially a torus space station with a superconducting
loop magnet and is dominated by propellant tanks.

Back home in the solar system, a solar powered X-ray free electron
laser is focused by a ~1km diameter zone plate to accelerate
swarms of small sail****ps up to near-c speeds.  The X-ray laser
has sufficient range to keep on powering the small sail****ps out
to 4.3 light years.  These self-guided sail****ps form up into a long
line to encounter the star****p one by one.

The star****p puffs inert propellant in front of the ****p; the
propellant
is converted into a series of explosions of plasma by impacts with
the small sail****ps (each sail****p must first pass through the
donut-hole of the star****p before impacting the propellant puff on
the other side).

The potential exhaust velocity is near-c, and can be optimized
for any desired cruise speed.  For example, a desired cruise
speed of .3c involves a total delta-v of .9c (the final braking at the
end of the return journey can be accomplished without much
propellant or energy expenditure).  The best energy efficiency
would be acheived by starting off with a low relativistic exhaust
velocity and then gradually increasing up to .9c.  These extreme
exhaust velocities are only possible because the energy is
provided from an external stream of near-c kinetic energy
projectiles.  Not even an anti-matter rocket offers this sort of
performance, due to the energy lost to neutrinos.

Of course, an anti-matter rocket involves anti-matter generation
and handling technology far beyond our state-of-the-art, and
with plausible anti-matter generation efficiencies the costs seem
to be complete non-starters.  The relativistic kinetic impact
powered rocket involves technologies which are not too far
beyond modern capabilities, and plausible efficiencies aren't
too bad.

Isaac Kuo