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RE: starship-design: Interstellar mission within fifty years

> From: "L. Parker" <lparker@cacaphony.net>
> > > 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!
> ANY fusion explosion produces a positive energy balance. Perhaps you should
> check out the site for AIMSTAR I posted last week, ALL of the data is there.
OK, I will. 
But did they test an actual micro-explosions in hardware?

> > But we are discussing needs of an interstellar flight,
> > not a single ICAN spacecraft.
> True, but we have to start somewhere. You will note however that the AIMSTAR
> paper uses some of the results of the ICAN testing at JPL and includes a
> rather startling observation. ICAN assumed that the antimatter would be
> consumed each time by the reaction, actually, it was not. It took three or
> four cycles before it had to be replenished. It is only a catalyst remember.
Yes, and that supports my point - as it is not an antimatter engine,
it means the true antimatter engines still need substantial technological 
(& scientific) breakthroughs.

> > 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.
> Slowly, annihilate? Not according to the paper I read. 
But they slowly annihilate. This is the reason they can 
contain antiprotons only for several days. It is posted on the web. 

> ICAN and AIMSTAR don't need tons. 
Interstellar ships will.

> An interstellar drive based on an outgrowth of AIMSTAR
> would only need a few grams, I don't see a problem.
No outgrowth of AIMSTAR will have enough performance
for our starship mission purposes.
The necessary performance will require tons of antimatter 
and efficient antimatter (not antimatter-catalysed) engine.

> > > (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.
> Well, it isn't really all that dangerous, even if the Penning Trap had
> failed, it would only have gotten a little hot, its not like it would have
> exploded or anything. Since it isn't an explosive, poison or hazardous
> waste, no permits are required.
Only because of the very small amount of antimatter contained.
Do you thing you may propel the starship with the amount
of antimatter that when annihilated will make the engine
"only a little hot"?

> > You say it has performance good enough to put it into
> > a starship?
> VASIMR? Heck no. Its strictly interplanetary. Unlike the ACMF proposals it
> will never scale to interstellar. However, it uses several technologies
> which are crucial to enhancing the performance of later generation of ACMF
> or even true antimatter drives. 
Ahh, but it is a long way to actual antimatter drives.
There even is not a viable design concept for a true antimatter engine...

> The fact that it is ready for flight 
> testing was the only thing that was significant. Someone wanted 
> an example of a real working space drive, I provided one.
But it is still not "real working". 
And it is at most interplanetary when it eventually will. 
Scaling it up to interstellar is certainly impossible.
So we are back to square one, despite your example.

> > 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...
> Nope, I said it wasn't necessary to build a manned habitat to mine
> asteroids. Then promptly intimated that WE would prefer that they were
> manned because we need the experience working in space precisely because 
> it was necessary in order to build a starship.
OK, with that I agree. Then, why you added the <G> tag to
that your sentence?

> > Exactly. Almost.
> > I questioned that we may discover "a habitable planet" from Earth.
> > I am in no way against going to find out.
> Oh I think given a few more years we will be able to tell from here whether
> it has an Earthlike atmosphere or not - which doesn't necessarily mean that
> it is "habitable". Which is why I said the only way to find out is to go.

> > 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.
> Well, I think most people, including the general public would agree with 
> you there. I am just saying that it makes more sense to settle the system's
> asteroids, moons and other ore rich bodies first, but that is a whole
> different argument.
It would be very interesting to actually compare realistic
costs and technology needs to build both kinds of habitats.
You may have more ores handy in asteroids, but much larger
demand for them and for high-technology machinery if you
want to build the habitat on or near an asteroid
instead of on a planet (with atmosphere, gravity,
appropriate temperature & possibly oceans...).
I still think the balance is towards a planet,
at least with current technology.
It may change when the space/asteroid habitats
will be a common thing, with appropriate construction
and maintenace technology evolved into something familiar 
and efficient (and possibly with gentic-engineered species 
of humans to live in this environment).

> > 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.
> I agree.
I think it is a basis for effective progress in any area - 
not too much of an easy optimism.
Just enough to feel the thing is worth the effort...

-- Zenon