Re: Engineering Newsletter

[KellySt@aol.com]

Kelly Re Timothy
 >> Timothy re : Kelly
 >>Subject    : Plasma mirror
 >>
 >>>Reasonably flat, and optically flat are very different!  Optically
focused
 >>>over light-years is even more different.
 >>
 >>OK, I give up... I hoped that this this unflatness would not be too big.
 >>But If you can't make a mirror that is flat enough than you can't make a
 >>curved mirror that is curved enough. So a curved mirror would spread 
 >>the light just as much as a flat mirror. So this means that ANY mirror 
 >>that works over a larger distance is out of the question!

Seems unavoidable.

>>>>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
coming
 >>>>reflected photons from the TC side. Doesn't that create a problem?
 >>>
 >>>Can't think of any.  It actually should help.
 >>
 >>After rethinking it, I see what you mean.
 >>The only thing I'm not sure about is what the physics of plasma reflection
 >>are. We may reflect radio-waves to the ionosphere everyday but how does it
 >>work? And does it work in the Asimov also?

It would certainly involve a much larger scale, and I don't know what the
reflection efficency is.  Or how much mass would need to be ionized to keep
up the reflection. One thing for certain, the stuff will be HOT!


 >>>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.
 >>
 >>Yes, I understood that. But do the engines take the most of the weight? Or
 >>in other words, what percentage of the ship (without fuel) is reserved for
 >>the engine? If that percentage is small it may be possible to scale up the
 >>engines a bit. But indeed there is a limit, only where is that limit?
 >>Ideally the weight of the engine grows slower than its power: Make an
engine
 >>twice as big doubles the power, but the weight increases with the
squareroot
 >>of 2.

Hard to say.  The best engines Iever heard of were liquid fueld rocket
engines.  The engines can produce thrust over a hundred times their own
weight.  The Bussard fusion/electrics produce about 6 times their weight.
 But scaled up and eliminatring the weight of the vacume chamber might make
it up to the 10's to 1 ration?  (I hope.)

 >>>>How much push did you have in mind? There is already much research   
 >>>>going on.  Already a few seconds of "controlled" fusion are possible.
 >>>>Development isn't possible yet, because not enough is known about the
 >>>>plasma flows that are used.
 >>>
 >>>Actually there is very little research going on.  Several areas
 >>>considered more promising than magnetic confinment have no funding 
 >>>due to competitionwith 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.
 >>
 >>Here in the Europe (also in the Netherlands) there are several institutes
 >>busy. Most of the research is in a very early stage. Spending more money 
 >>may help a bit but not that much as you would hope. Some things just 
 >>can't go any faster.  Besides that, it is not fair to assume that money 
 >>alone can change research that fast, otherwise antimatter may become 
 >>a possibility too.

That would be true if all major areas of research were being investigated and
resonably well funded.  But most areas of fusion research that I know of have
no funding.  Magnetic plasma fusion is geting funded, but at least in the US
the systems are dead ends.  Even if they worked they'ld be useless (to large
to be intergrated into the power grid.).  Where as more inovative designs
that are considered more promising (like Bussards among others) are geting no
funding.

 >>>I don't beleave G.M. has any launcher program?
 >>
 >>You're right, after some research and your forwarded letter, I figured it
 >>was the X-33 that I had in mind, and GM should be Lockheed Martin Skunk
 >>Works, McDonnell Douglas Aerospace and Rockwell International Corp.

Oh yeah, the single stage to orbit program (SSTO).  My excorperation, and the
NASA department I used to work at in NASA headquarters were working on that
program.  Increadable potential. It could cut costs to orbit by a factor of
100!  Fed Ex is even rumored to be seriously interested in using them for
suborbital intercontenental mail carriers.

 >>>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 supply flights?
 >>
 >>My guess was that they would construct a pre-fab habitat and from 
 >>there they would expand. Being on a planet gives you much more 
 >>resources and savety than a spaceship. Not all planets will be equal 
 >>favourable, but a solid planet the size of Earth will be better than a 
 >>spaceship after the main habitats are equipped.

I'ld debate that.  Since your stuck in an artificial habitat anyway, one in
space has easy access to all the floating ores and raw materials in the solar
system.  Much of which would be hard to get at on a planet (ever see a strip
mine) and much harder to transport.  I'm a firm beleaver that heavy industry
will largely move off earth in a century or two.  If your already off planet
and in a starship, trying to set up on a planet would be hellish.

 >>> > 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 involvement.
 >>
 >>To see? There won't be a live television show with interactive
 >>conversations. By the time Earth gets the first message of landing, the 
 >>crew is already on their way back. Also would you pay money now to see 
 >>a spectacular show that happens in 30 years?

People won't see it right away, but they will know people are out there.  I
think that would be enough to get public interest.  I know public interest in
robot probes is near nill.  As NASA constantly found.  Robots were thought of
as scout craft for maned expiditions.  If no manned folowups were planed (and
frequently mentioned) public interest in funding the robots droped way off.
 Generally a so what atitude.  Drove the Robot probe teams CRAZY!

 >>>> So TC is out?
 >>>
 >>>Seems like.
 >>
 >>So where to and when is our new goal? Until now only fusion may bring 
 >>us out of the solar system within reasonable time. Even if you use a 
 >>beam, the fusion is necessary to maintain the beam.

Well you could power the beam with big solar electric power platforms in
space.  (The kind of stuff the L-5 socyety kept proposing to power earth.)


 >>>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.
 >>
 >>Is there any hope for us? Our best hope was to find a living planet, full 
 >>of life and oxigen. Now it seems that it is better to find a barren planet

 >>with no life at all.

I would definatly prefer a dead world as a possible colony site over a lush
one like earth.  Wouldn't be as interesting to study, but much more
survivable.  The problem is any world that could support us, probably has
life.

 >>Do we indeed have not enough time to develop a anti-bodies against 
 >> these diseases? We indeed should be very careful, but that doesn't 
 >> mean that after we have found most anti-bodies we can live there.

Hell, we're still trying to find cures for all the plagues on earth.  So far
our best luck seem to be in destroying the worst sections of the ecology
(draining wetlands, fogging everything with pestasides, etc..) and building
urban semi-ecologies.  Most of the habited areas of the developed world
(europe, North America, etc..)  do this so routinely we don't even notice
anymore.  But then living in a coutry thats largly under sea level I hardly
have to tell you.  ;)

 >>>I ment near earth comet cores.  Their are a few thousand of them 
 >>>charted, and are easyier to get to than Mars.
 >>
 >>Comet cores? I'm not sure anymore what you mean, what kind of orbit 
 >>do they have? Elliptical or (near) circular? And do they turn around the 
 >>Sun or the Earth? How big are they?

Near earth in that the inner part of their orbit come in near to earths
orbit, or farther in than it.  The outer orbits are generally farther in then
jupiter.  Somethimes closer in than Mars.  After bein in that close for a
while.  Most of the light volitals melt away, and the outer surface gets
covered over by rock.  That crust helps shield the reset from sunlight.
 Compasition is estimated (by weight) at 1/3rd water ice, 1/3rd rock and
metalic ores, 1/3rd hydrocarbon sludge (thick cride oil).  Size varies.  5
kilometer across ones are fairly common.  (Weight 50 billion metric tons.)
 Estimates are about that there are a few thousand about that size in near
earth space.  Possibly more asteroids.  (It surprising we don't get more
impacts!)


 >>>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 system deterioration.
 >>
 >>Oh, I didn't know that it was that serious. But I assume we can adapt to 
 >>a thirth of Earth's gravity or is that still to little?

No one really knows.  Its assumed you'ld have the same problems, just slower
acting.


 >>>P.S.
 >>>A, I the only one who remembers to CC Dave Levin on the address list?
 >>
 >>I've never received a (personal) notice from Dave, he just left me (us?) 
 >>in the dark and I always had to hear from some others that they had 
 >>made contact with him. The least he could have done was send a 
 >>(general) note telling he had no time for the SD-project anymore.
 >>In fact the only message I got from him was the one of December 17th.
 >>So in short, I'm a disappointed by Dave's performance.


You have a point. Certainly droping the Newsletter functions off line for ..
what is it 2-3 months now?  Doesn't speak well for his enthusiasm.  Then
again the participation has been kind of slight in general lately.

Kelly RE Kevin

 >>To: All
 >>Re: various.
 >>
 >>Bio interaction between earth and E.T. organisms.  
 >>
 >>first, I believe that any viral infection is not possible, due to the 
 >>totally arbitrary rna to protien coding system that earth biology uses.
 >>
 >>Of course all this assumes that the ET biology uses DNA/RNA Glucose  
 >>ATP systems, but i do have sound Therodynamic/chemical reasons for  
 >>thinking this is the -=--- Big snip -----
 >>
 >>In short, A totally barren 1 G planent would be ideal for colonization, 
 >>but totally boring for study.  

I agree.  Its a topic that doesn't get talked about much, but the idea of
steping out of a ship on an alien world taking a breath is really shallow.  I
guess we're all just used to decontaminated parks, or advanced medicines, or
something.

On the other hand a real alien ecology could be fantastically interesting!  

 >>To: all
 >>Re: mission
 >>
 >>Ok, I think we all have come slam up against a brick wall.  Sending
 >>1 E+09 Kg _any_ distance and coming back to rest WRT the target 
 >>system is turning into a Herculean task.
 >>
 >>The charter says that we have remote sensing clues of a biosphere.  we 
 >>also have a public mandate for sending some people there to study it.
 >>
 >>I think perhaps it's time to either put the "Asimov" on a diet, or 
 >>approach the problem from the other end.  To put the "Asimov" on a diet, 
 >>I'd suggest at least a thousand fold reduction in payload down to 
 >> 1E+05 Kg

I think we're more stuck than that.  We haven't figured out any idea for
slowing down a sail or MARS driven ship from relativistic speeds.  NOt just
not doing it on that scale.  We haven't a handel on how to do it at all!


 >>I think this rules out self sustained mission, and requires a return.  I 
 >>still think we can go at 1 G, and use a MARS for the engine, but in order 
 >>to over come the photon thrust, we're going to have to bring more 
 >>reaction mass ( and use a slower exhaust velocity).  for the return trip, 
 >>I'd suggest scrapping the lineac entirely, and relying on photonic thrust 
 >>for both portions of the trip.  this means that some payload capacity 
 >>will have to be devoted to maser transmitter control packages, but i 
 >>don't see this as a real problem.  the crew should be pared down to no 
 >>more than 100 people, and the return module can totaly scrap the hab ring 
 >>which can then be left in the target system as a stepping stone for a 
 >>follow up crew if one is deemed desirable
 >>I'll follow this up with some hard numbers later,But, one thing that 
 >>strikes me off hand is this, for reflection, p= 2E/C  this is great for 
 >>acelerating.  for absorbtion, p=E/C this is a smaller amount of photonic 
 >>thrust to overcome. so for example, a energy beam that provides 10 m/s^2 
 >>acceleration via light pressure only needs a 15 m/s^s deceleration from 
 >>the engines to equal 10 m/s^2 total. and if it takes a 1000 to 1 RM to 
 >>payload ratio, then that is the cost. and we just have to live with it.  
 >>but once you get 100 people and a number of maser arrays in orbit around 
 >>another star system, then sending a follow up mission is relatively easy 

How do you get a 1000 - 1 mass ration ship to move?  Can we scale down the
ship that much?  We need the hab centrafuge to keep the crew alive and
healthy, and that dictates about a 200 meter diameter ring.  Fiting that and
the systems and sypplies all in 1E+5 kg seems unlikely.  (Thats the weight of
the shutle orbiter.  Or did you mean 1E+5 tons?)  Adding in the construction
equipment fort big maser arrays makes it even harder.


 >>the second option is to design this mission as if we had _no_ long range 
 >>information on nearby systems, and design a small ~ 5000 Kg robot. to 
 >>explore nearby systems, and return pictures and other information about 
 >>every system in a 20 ly. radius.  we might not have to slow down entirely,
 >>a .5 C flyby might work here.  and perhaps a magnetic turning might 
 >>work for some long range steering.  The robots should be small and 
 >>low-cost, so that is we lose a few, it's no biggie.  then to luanch, we 
 >>could use a particle luancher, (just like a solar sail, but you use 
 >>charged particles and a heavier acceleration factor) and once the probes 
 >>are up to speed, we don't bother with them again.  

It would seem you could get about as much info from a large teklescope array
in Sol orbit, and get results now!