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Re: Engineering Newsletter
> Timothy re: Kelly
> Subject : Plasma mirror
> >> Is it really that hard to keep the mirror straight? And still, if the
> >> deviates, the Asimov can still follow it (too a certain amount) by
> >> redirecting its own mirror.
> >Its kind of like balencing a meter square sheet of aluminum foil on the
> >from a fire extiquisher, and expect it to never wrinkle or twist.
> You should compare each of the 2 parts of the retro-mirror with a bridge
> over a valley. The mirror itself would be the road, behind the mirror
> would be strenghtening structure, that would be curved just like the
> The mirror would stay reasonable flat just like the road that connects
> sides of the valley.
Reasonably flat, and optically flat are very different! Optically focused
over light-years is even more different.
Again, you can't use a 2 part retro mirror since the drag mirror on the ship
has to be much smaller.
> >The ring sail is anchored to the ship. Sort of like a parachute. I.E. a
> >parachute attached to a weight forms a nice shape. Cut the corts and it
> >turns into a lose sheet flutering and twisting down.
> This assumes the wind is constant and comes always from the same side
> without small deviations. As soon as the wind comes a bit from aside, the
> parachute will turn a bit so that its movement is parallel with the
Not a big problem with a point source beam (effectivly point source). Even
given unevenness in the beam it should be handelable.
> >>If it reflects straight back, then it enters the plasma pipe, that must
> >>trouble. Please tell me what happens after the (first) reflection on the
> >Ideally, the beam reflects straight back toward a flat drag sail behind
> >ship (and straglers bounce of the inside of the ship tpward the drag
> > The beam is then directed forward toward the plasma again, and bounces
> >again. The plasma gets an extra boost forward. Then the ship gets an
> >push backward. (repeat until beam is lost, absorbed, or canceled out by
> >of phase other parts of beam.)
> I assume that the plasma is replenished all the time. So at the same time
> that the plasma is replenished inside the plasma-pipe, there are also
> reflected photons from the TC side. Doesn't that create a problem?
Can't think of any. It actually should help.
> >Because you can't build a craft thats engines and structure are so light,
> >strong, and powerfull; that they could carry a weight a thousand times
> >greater than their own and accelerate it at about 1 G. As a mater of
> >I'm concerned that a fusion driven ship capable of carrying 40 or 60
> >its weight is overly optimistic. (But I haven't gotten aroiund to
> >the numbers in the Bussard papers.)
> I don't see why you can build a craft of 1E8 kg that can propell itself
> not a craft of 1E11 kg. Just scale up the engines. If that isn't possible,
> the initial acceleration should be less, after a while the ship gets
> and the acceleration can be increased.
Its not the weight, its the mass fraction. You could scale up the craft, but
not increase the fraction of its total that is fuel or cargo (well not by
much). Given the speeds and time we're talking about, you can't go with a
ship with lower accell.
> >Also of course if the energy to accelerate the fuel doesn't need to be
> >carried in the ship, the ship can get by on less fuel.
> Yes, but that would involve a beaming technique.
No, I was talking about my fuel launcher idea, not a beamed power system.
> >Fusion could be developed in a decade or so if their was any push for it.
> > Possibly power for intersystem space craft might entice someone to
> >the R&D money for it. Though your right. Their are no current plans to
> >so. Nor for that matter to build enough of a space infastructure to
> >a project like this.
> How much push did you have in mind? There is already much research going
> Already a few seconds of "controlled" fusion are possible. Development
> possible yet, because not enough is known about the plasma flows that are
Actually there is very little research going on. Several areas considered
more promising than magnetic confinment have no funding due to competition
with established programs. In the U.S. each new model car turned out
receaves more R&D funding than all of fusion. Given the abundant conventional
fuel sources, alternate energy suplies get little interest.
> >But, if we had usable space launchers. There is a big
> >pent up demand for public and comercial access to space. When that
> >starts, building up to the space infastructure we'ld need. Think of how
> >aviation and its infastructure developed between 1915 and 1965.
> You yourself told me that you can't compare past developments so easely
> future developments. ---
I beleave I said you should consider dissimilar past developments.
> --- But I don't want to hold this against you, I also see
> that space will become a bigger and bigger part of the economy. I know
> certain commercial firms (General Motors) are developing small easy to
> produce and relative cheap launchers.
I don't beleave G.M. has any launcher program?
> >Actually NASA played around with the idea on a satellite. A couple public
> >groups were trying tyo build and launch a solar sailer in the '80's, but
> >never finished them.
> Wasn't there an experiment with a solarsail last month?
Not that I know of.
> >If your planing to send yourself to somewhere you can't really live at,
> >can't come back from, its suicide. If you propose sending others there
> >murder; and no western government or major group would be allowed to
> >such a mission.
> It's just how you want to see it. Confing the crew to 15 years living in a
> spaceship is bad enough. Giving them another 15 years may be even worse.
> Probably most people would fail the psychological test only for this
> Imagine 15 years in the same environment, always busy with the same kind
> job, then finally you find a 10 whole planets to build new things. Would
> they really like to go back? Would it really be such a crime to let those
> people stay there and try to make a living? Even if it are all rotten
> planets (which is doubtful) it probably would be better to be there than
> be in that stinking old spaceship for another 15 years
10 whole planets to build what in? They would have no place to live in other
than their ship. No resources to suvive in the ship for more than a few
decades (and we have no ability to do better than that). How are they going
to survive? What do you mean by having them "stay there and try to make a
living"? What is there for them to do that would pay for their keep and
> If we aren't planning on staying there, why go there? If it's just to
> investigate it may be better to send unmanned probes. (That would be
> a task for AI)
Your expecting a lot out of A.I.s. Humans will probably be more adaptable
for some time. Also no one would fund a A.I. exploration flight. Tax payers
want to see humans explorer, and lose all interest in programs without human
> >>Lower power levels mean not going to TC! Lower levels mean a much longer
> >>trip, and we agreed that wasn't our goal.
> So TC is out?
> >>Maybe unrepairable, but there will be many of them, so one or two less
> >>doesn't matter. The strength of nano is not only their tinyness, but
> >>their vastness (for small price? and weight). The goal will be that they
> >>become selfreproducive in a (hopefully) controlled way.
> >Hopefully. Otherwise we launched a gray goo plague to T.C. ;-)
> >Eiather way its pretty iffy tech, and doesn't solve the fundemental
> Safety is a fundamental problem.
Which they don't help particularly. Thou in our case, unless you can get
there at all, mission safty is a moot point.
> > Their is a reasonable chance of finding worlds with ecologies as
> >complex as Earth and with life forms similar to ours in size, complexity,
> >etc... And if you could survive a couple secounds on them outside of a
> >biosuit I'ld be stunned! The history of explorers here on this world,
> >our present problems with plagues like Ebola, AIDs, Etc, don't speak well
> >the odds of a carless interstellar explorer. Your microbes, and the
> >microbes would rapibly try to digest the alien life forms it sees.
> I heard that our genes would probably be so different from independant
> developped species that they would mean no harm at all. But if they
> we certainly would be able to immunize ourselves. The humane genome
> would be completed by then and we would be able to detect and probably
> every virus-disease (including AIDS).
> The reason for the history of Earth-based explorers is that their genes
> so identical to those of the species in the newly dicovered areas.
No, most deseases don't interact with our genetic structure (only viruses do)
the rest (molds, bacteria, fungus, etc..) just use us as chemical food or
fertalizer. Here we evelved defenses against those deseases, but on an alien
ecosphere the counterparts could be radically invulnerable to our defence
techneques, and we'ld have no time to evolve new ones.
Then again alergies, even to things we've been exposed to for centuries, can
kill sometimes us in minuttes.
> >True, though I think big platforms harvesting near earth asteroids and
> >cores would go first. Moon and Mars lack a human healty gravity, and its
> >much easier to ship the mined cargo from near earth objects around and
> >richer pickings!! (One estimate places the value of the oil on one
> >near earth comet core at several hundred billion dollars US!) Which is
> >of the reasons I expect space development to progress much faster than
> >expected. Free-for-the-taker valuble materials tend to encourage that.
> Comets are probably not very handy, there are few of them and they have a
> peculiar orbit. Asteroids would be easier but probably less rich of
> material. Do you know why comets have that much oil? Oil means organic
> leftovers. And if there is that much of it, that means there is a big
> of life out in the galaxy.
I ment near earth comet cores. Their are a few thousand of them charted, and
are easyier to get to than Mars.
Technically they don't hold oil, so much as a hydrocarbon sludge. But an oil
refinery would process it just the same.
> As indeed many suggested once you start living on Mars or Moon, you can't
> back to Earth easely.
More precisely the low G would deteriorate your system. Short term you
couldn't handel 1 G. Long term you die from cardiovascular, bone, and immune
> P.S. Why does your mailer add 2 >'s and a space for replied pieces of
> It looks a bit messy...
Sorry, I thought it was clearer. Is this preferable?
A, I the only one who remembers to CC Dave Levin on the address list?