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RE: starship-design: Interstellar mission within fifty years

> From: "L. Parker" <lparker@cacaphony.net>
> > As far as I know, still only on paper.
> > Did they produced some rocket exhaust generated by
> > actual fusion reaction?
> No, this is an engineering study. JPL has tested the reactions 
> and verified the energy output. 
Actually maintaining a sustained fusion reaction with positive energy
balance? It would be quite a media event, such an experiment!

> In other words, the technology has been proven - the
> actual engine has not been built. But it is far from being only on paper.
> > Ditto.
> > And what about the antimatter factory?
> > Current annual production is able to deliver a kilogram of antimatter
> > in several million years, counting optimistically...
> > And what about reliable containers capable to hold tons of antimatter
> > for years on?
> The production of antimatter is currently very low, however, ICAN and
> AIMSTAR do not need much, the amounts are well within what we expect to be
> able to produce within the next twenty years.
But we are discussing needs of an interstellar flight,
not a single ICAN spacecraft.

> Storage technology is hard science, already built, and tested 
The current containers can store only picograms or even less
of antiprotons, have an astronomical mass ratio (container/antimatter),
and can store the antiprotons only for few days
(they slowly annihilate inside...).

Scaling it up to tons of antimatter stored for tens of years 
without loss will need quite a breaktrough in storage methods
and technology.

> (they drove around the U.S. with the
> storage container loaded with antimatter in the back, we're still here so I
> guess it worked.)
That's news. As far as I know, they said that some time 
it will be possible... 
Did they already get proper permits to haul antimatter 
on U.S. highways? I doubt that.

> > > VASIMR is scheduled to FLY in 2005. While not exactly a fusion rocket,
> > > it is close in terms of performance...
> > >
> > We will see... I am rather skeptical, especially concerning
> > the performance.
> VASIMR's performance isn't in question, the engine is fired on a regular
> schedule and its performance is a known quantity. It hasn't been FLOWN yet
> however.
You say it has performance good enough to put it into 
a starship?

> > First, actual complex mines and factories cannot yet be fully
> > automated without human supervision, and will not without
> > real breakthroughs in AI and nanotechnology.
> > Teleoperation is also infeasible for interplanetary distances
> > (remember Sojourner...), even on the Moon
> > (ask Russian drivers of Lunokhods...).
> > Second, our starship should be a viable "permanent human
> > habitat in space", and rather large for that.
> > How to build one without any prior experience?
> > Do you think that the very first human space habitat will be
> > that going to another star?
> For the first part, these are relatively minor problems involving no new
> technology, just development and refinement of known ones. Yes, this will
> take time, but I would hardly characterize this as a major road block.
Possibly, but I would not bet too much for that...

> For the second part I would just reiterate the argument I already gave, the
> only way to get the experience we need is to start doing it. It is a self
> reinforcing process, the more we work and live in space, the better we get
> at it. 
Seems to be a misunderstanding here. 
I agree about start & self reinforcing, I even said explicitly
that prior experience is necessary. It was YOU who wrote
that building permanent habitats in space before building a starship
is "not necessarily" needed...

> > I doubt seriously if we discover a habitable planet
> > around another star. Kelly seems right here - it will
> > be either inhabitable, or deadly.
> The only way to find out is to go. 
Exactly. Almost.
I questioned that we may discover "a habitable planet" from Earth.
I am in no way against going to find out.

> Besides, I am not a fan of settling other planets, 
> I think we should start by settling the system, planets are for
> sheep...and sheep herders.
Yes and no. I think it will be easier to settle a planet 
(in the sense of building a permanent, self-sutained habitat 
for a significant number of people), that building equivalent 
artificial colony in space, at least in a foreseable future.

> > Moreover, so what? I do not think the public will care much,
> > unless general attitudes toward space exploration change significantly.
> > Hence I also consider SETI to be currently more of a distraction
> > than help.
> Perhaps not, I was merely paraphrasing someone else. It was either Marc
> Millis or Carl Sagan, either way, they certainly know more than I.
I do not question your knowledge (nor theirs).
However, I doubt if public will be so excited by finding
a "habitable" planet around another star.
At least not in these times - the presence of such a planet 
will change nothing in our life and our abilities to go there
within the life of this generation.
It will be another thing if the possibility of living outside
Earth by a significant number of people for all (or most)
of their lives becomes a common fact. Then finding a similarly
habitable planet around another star may stir some public
interest, not earlier.

I see that I must add a proper disclaimer:
I am not such a die-hard pessimist, as some of you seem to think.
My point is that quite a lot of hard problems still remains unsolved
and needs much work to solve. Hence I think that easy optimism that 
all is already essentially in place (as expressed in some posts lately) 
may be quite unreasonable, generating too much self-confidence
where a call to arms seems more appropriate.

-- Zenon