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RE: starship-design: Interstellar mission within fifty years

> From: "L. Parker" <lparker@cacaphony.net>
> > > 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?
> The team working on the original ACMF concept using ion drivers actually
> performed some hardware experiments to provide enough data to confirm the
> theoretical predictions. The AIMSTAR concept however, although based on the
> data provided by the ACMF experiments, has not been tested in hardware as
> far as I am aware. The predicted performance was obtained by study of the
> original ACMF experiments.
Thank you, it means it is still only on paper, as I claimed.

> > 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.
> But it is scalable, the current generation uses hydrogen, this technology
> can be used with Lithium or Boron to achieve substantially higher ISPs.
> Improvements in magnetic confinement technology may allow it to be boosted
> even farther. As it stands right now, either of these drives turns the solar
> system into our backyard and although not suitable for manned interstellar
> travel, 
Again, exactly my point.
So I do not understand why we seem to quarrel on these issues?  ;-)

> they could put a scientific package through Alpha Centauri in only a
> few hundred years.

> > > 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.
> Are we both talking about Penning traps?
It seems so...

> > 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"?
> If you take common "flash powder" and put some in your hand and touch a
> match to it, it will flash burn, you will not be seriously injured although
> your hand may be scorched. If you take the same powder compress it into a
> tight package and light it with a suitable spark, it will quite neatly blow
> your hand off...
> To say that a few picograms of antimatter are not dangerous in a rather
> loose concentration in a Penning trap does not mean that they cannot be
> quite deadly when properly utilized.
You are right, of course, with flash powder. 
But consider the question of scale -
the difference between flash burn and blowing the hand off
is very tiny as compared with the difference 
between blowing the hand off and propelling a starship...

> > > 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.
> Here we go again, if I build a widget in my garage and test it in my garage,
> but don't actually put it in a widget machine, you mean to tell me it isn't
> real? Come on, get a life. VASIMR is fired almost daily, if you don't think
> it is a real working engine, let them test it in you living room next time!
I would rather not. 
Since it is not tested enough, it may easily blow off!  ;-)

> I understand a little skepticism now and then, there are certainly enough
> perpetual motion machines and cold fusion devices running around, but to
> call a functioning rocket engine sitting in a laboratory in a college in
> Texas not real is really pushing it!
Sorry, I stated it probably in too shortened a form.
I meant "not real working space drive".
For me, it can be called "real working space drive" 
only after being tested in space.

> I never claimed VASIMR was interstellar capable, quite the opposite, I
> specifically stated that it wasn't. 
I admit that. But then it is not good as an example of technology
ready to be used for starships - and my discussion from the very
beginning was specifically about starhip technology.

> It IS every bit as powerful as a fusion
> engine, a lot easier to do, and working now. That is all I ever claimed it
> was. This was all in response to your assertion that the technology was a
> long way off. Maybe, maybe not. VASIMR is simply an example that the
> technology may be closer than you think.
OK, OK, don't become too hot ;-))
I am not so die-hard pessimist (see my discalimer in some other letter),
I only want to have the FACTS right, not mixed with wishful thinking.
My doubts were about starship propulsion technology -
hence your examples, impressive as they may be, are simply off-topic...

> > OK, with that I agree. Then, why you added the <G> tag to
> > that your sentence?
> The grin was to emphasize the point that even though I disagreed with the
> statement about automation, I (and we) would personally rather they were
> manned because we have our own agenda, it was not meant to make you think I
> was speaking tongue in cheek! I believe that a lot more automation will be
> possible than we are allowing for, but I personally don't believe in sending
> robot probes to the stars. The whole point is that WE want to go, not our
> electronic henchmen.
OK, I agree. The grin disoriented me somewhat.

> > 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 maintenance technology evolved into something familiar
> > and efficient (and possibly with genetic-engineered species
> > of humans to live in this environment).
> I don't know. This is another of those areas where we can't tell because we
> haven't done it yet and therefore have no comparison. At a guess, I would
> speculate that it will be a net wash - it will not be a great deal more
> profitable nor a great deal more expensive for either case. Mostly because
> in order for the space portion to become possible, the rules have to change
> enough that it mandates that the costs will be equal and any technological
> improvements that make this possible will probably have off-setting benefits
> to life on Earth that we haven't even thought of yet, so again, the costs
> balance out.
Possibly they do. 
But an attempt to do a more precise comparison
would be useful anyway. I think it can be done more
precisely than our gueses and speculations here.

-- Zenon