Spike Jones wrote:
>
> > >Spike Jones wrote: So that puts an upper bound
> > >of about 200 nanograms of interstellarlopers per cubic
> > >kilometer. Right? Amara? spike
> >
> > Amara Graps wrote: My dear Spike, you are the third person who has asked
> > me that question in the last several months (the other two being Eric
> > Drexler and
> > Robert Bradbury).
>
> WOW cooool, Drexler, Bradbury, spike. There are three names I
> like to see mentioned in the same sentence.
>
> > You all have the same goal in mind, I know. Your
> > approach makes perfect sense to me ... but ..
>
> Today I was doing some back of the envelope calcs and I think
> I know why the other two wanted to know. If interstellar matter
> is as dense as 200 nanograms per cubic kilometer, then crossing any
> interstellar distance in one human lifetime will be extremely difficult
> if not impossible.
I don't know if you are up on the uranium salt water fission rocket that
Zubrin came up with in the early 90's. It uses water doped with 90%
weapons grade uranium salts for fuel, stored in Beryllium tubes, and
released into the combustion chamber fast enough so that the
supercritical stage of the fission chain reaction occurs just outside
the mixing chamber. Minimum 3 million pounds thrust at 10,000 sec
impulse.
Now, imagine we've got some sort of collection scoop in front of the
engine and behind the mutha hunka ice you're using as a shield, such
that the evaporating gasses are further heated by the exhaust plume of
the rocket.
Zubrin was claiming that his rocket could attain 3.9% of light speed on
a mission to Alpha Centauri for a 150 year mission.
>
> Heres how I figure: an astronaut is usually at least 30 and human
> life expectancy is about 75, so 45 years to cover... lets see, the
> nearest star is about 4 light years and some change I think, so
> about 0.1c to get there in a lifetime, neglecting acceleration and
> deceleration phases.
Alpha C is 4.4, Proxima C is 4.2 ly. The Alpha C binary of two sunlike
stars are allegedly far apart enough to allow terrestrial planets to
orbit both stars. Beta orbits out around the distance of Saturn from
Alpha. Eps Eridani has a recognisable gap in its dust disk, and Marcy et
al have evidence of jovians orbiting. Eps E is around 10 ly away.
I assume you are stating an average velocity of .1c. I think the
saltwater fission rocket could do that easy.
This archive was generated by hypermail 2b30 : Mon May 28 2001 - 09:50:35 MDT