Re: Engineering Newsletter

[KellySt@aol.com]

Oh, any idea why the LIT site droped off the SUNSITE server again?

>> Timothy re: Kelly
>> Subject   : Plasma mirror
>> 
>> >>What I meant with no turning, was that it just had to reflect the beam
>> >>STRAIGHT back. To do that is has a very precise orientation: the
>> >>incoming beam. The mirror does not have to track a moving object, that
>> >>is the task of the Earth beaming station. If Earth beams it to the
>> >>Asimov, then it also aims to the mirror. because the Asimov and the
>> >>retro-mirror are always lined up.
>> >
>> >That wouldn't work, but eiather way.  Straight back is still a direction
>> >to aim at, and it couldn't do it.
>> 
>> Is it really that hard to keep the mirror straight? And still, if the beam
>> 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 blast
from a fire extiquisher, and expect it to never wrinkle or twist.

>> Doesn't this problem arise also on the Asimov itself, it too uses a big
>> mirror to accelerate, if its mirror is a bit offside, it is out of the
beam
>> in seconds. If you move 1E8 metres in one second, only minute angles are
>> needed to be off the "road" 1E4 metres or so.

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.

Unevenness in the beam will tend to cause the ship to difft back and forth,
but aslong as the beam is far larger than the sail, and the transmitions
failly even (also helped by an oversized beam).  It should be managable.

>> >We have no real idea whats in interstellar space, but is fair to expect a
>> >few comets, asteroids ect; and I don't think we can plan on everything in
>> >our way getting neatly blown out of the way.
>> 
>> If there are indeed so many rocks that we have to worry, then we certainly
>> should make use of them. How big do you think the chances are that any of
>> these lumps comes even near the Asimov?

How could you make use of them?  Your runing past them at a relativistic
speed.

Hopefully the odds are low, but prudent designers assume they will have the
worst possible luck.

>> >NO!  A retro reflecter mirror wil not work unless the retro-mirror is
much
>> >bigger.
>> >-If its the same size and the retro mirror is straight in frount of the
>> > ship.
>> > It will be in the shaddow of the ships drag mirror.  So it won't 'see'
>> > any of the beam to reflect.
>> >-Even if its not in the line of sight.  Being the same size as the drag
>> > mirror on the ship.  It can't reflect anymore energy back to the drag
>> > mirror,
>> > than the mirror gets directly from earth.  So It wouldn't be able to
>> > decelerate the ship.
>> 
>> These two remarks mean that you haven't understood how I planned to make
>> that retro-mirror!
>> It was constructed of two mirrors at a right angle to each other... (See
>> previous letters)
>> 
>>              A|----\ 
>>        O-----------/   

Sorry thought that idea was droped.  With this you have two mirrors flaping
in the breze trying to aim at something.  Your odds of aiming accuratly have
droped accordingly.  Also you still have to focus back toward a smaller sail
on the ship.

>> >>             )
>> >> -------------)
>> >>            //)
>> >>          (--------| Plasma
>> >>          (--------| Plasma
>> >>            \\)
>> >> ------------)
>> >>            )
>> >> 
>> >> ( are the small mirror at the Earth side of the Asimov
>> >> ) are the big mirror at TC side of the Asimov
>> >> -- / \ Light rays
>> >
>> >Pretty much it.  Imagine the ship as a hollow pipe with a plasma in the
>> >inside of the pipe and in frount of it.  (The ship surrounds the plasma,
>> >not the other way round.)  The microwaves are reflected back and inward
by 
>> >the forward main ring sial, toward the rear ring sail (drag sail) which
>> >reflects it forward inside the open area of the ship toward the plasma.
>> >It heats and is reflected off the plasma backward.
>> 
>> And then after it has reflected backward? The ship needs to absorb or
better
>> to reflect the photons in the direction of TC. 

Yes.  If you could work out the angles and put a flat drag sail straight
behind the ship (inside the rear ring sail that reflected the energy to the
plasma) that would be ideal.  Assuming the plasma isn't perfectly flat
(highly likely) some energy will be reflected outward and it should be
accounted for in the design of the ship.  

>> If it reflects straight back, then it enters the plasma pipe, that must
mean trouble.
>> Please tell me what happens after the (first) reflection on the plasma.

Ideally, the beam reflects straight back toward a flat drag sail behind the
ship (and straglers bounce of the inside of the ship tpward the drag sail).
 The beam is then directed forward toward the plasma again, and bounces back
again.  The plasma gets an extra boost forward.  Then the ship gets an extra
push backward.  (repeat until beam is lost, absorbed, or canceled out by out
of phase other parts of beam.)


>> >> Indeed, that's what I'm saying. If a system is only 10% or even 0.1%
>> >> efficient, then for example a fusion system that uses a 1:1000
ship:fuel
>> >> ratio as well.
>> >
>> >As well what?  Efficency is not nessisary for a system to be usable, but
a
>> >ship that needs to carry a thousand times its weight in fuel simply can't
>> >be built.
>> 
>> I really don't see why, please explain. (See also the last paragraph of
this
>> letter.)

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 fact
I'm concerned that a fusion driven ship capable of carrying 40 or 60 times
its weight is overly optimistic.  (But I haven't gotten aroiund to looking up
the numbers in the Bussard papers.)

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.

>> >You've never suggested how you think such amounts of anti-matter could be
>> >made.  Or how we could build such engines.  Or store such amounts of
>> >antimater.  2050 is to close for us to overcome all those problems on
that
>> >scale.
>> 
>> That means fusion is also out of the question! I've heard that the first
>> commercial fusion power plant would be there at 2050. From there it is
still
>> a big step to scaling up such a power plant about 1E8 times.
>> And if fusion isn't our source for the beaming station what is? 

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 invest in
the R&D money for it.  Though your right.  Their are no current plans to do
so.  Nor for that matter to build enough of a space infastructure to support
a project like this.  But, if we had usable space launchers.  There is a big
pent up demand for public and comercial access to space.  When that demand
starts, building up to the space infastructure we'ld need.  Think of how fast
aviation and its infastructure developed between 1915 and 1965.

>> >>How to store the anti-matter? Just like normal matter, create anti-atoms
>> >>and anti-solids. Finally charge it and suspend it in electro/magnetic
>> >>bottles. OK, it sounds easy, but it seems to be possible.
>> >
>> >In theory, but its a big jump from theoretically possible to usable.
>> 
>> You are right. But the only experiment done with moving an object by laser
>> light involved a mass of about a milligram.  So that would mean that any
>> lightsailing technique is not much more than theory too.

Actually NASA played around with the idea on a satelight.  A couple public
groups were trying tyo build and launch a solar sailer in the '80's, but they
 never finished them.


>> What I mean is that probably none of the existing and almost-ready-to-use
>> techniques could bring us to TC.

To T.C.?  Definatly.  Thats why we spent so much time on the maser mirrors
and such.

>> >We went around on that question a lot a few months ago.  Yes you have to
>> >bring the crews back.  No one would fund a suicide run without a desparte
>> >need, and we don't have one.
>> 
>> Staying there isn't necessary suicide! Going back may be a bigger risk.

If your planing to send yourself to somewhere you can't really live at, and
can't come back from, its suicide.  If you propose sending others there its
murder; and no western government or major group would be allowed to launch
such a mission.

>>  (On that question I didn't vote for a 2-way trip)
>> 
>> >> I think that we have to assume that this minimum is possible, otherwise
>> >> no system is possible unless we "invent" anti-gravity, or if we use a
>> >> ship that has much less mass (which is almost impossible).
>> >> So it would be better if one the rules of the SD "discussion" was that
a
>> >> minimum (unknown?) power source of 1E18 watt is available in 2040.
>> >
>> >Or limit the discussion to systems and power levels that seem likely.
>> 
>> Lower power levels mean not going to TC! Lower levels mean a much longer
>> trip, and we agreed that wasn't our goal.

Agreed.

>> >> Increasing efficiency or affordability make any design more probable
and
>> >> feasable. If for example the space shuttle had AI and nanotech. it
would
>> >> probably much more saver, reliable and cheaper.
>> >
>> >True, but since we havn't figured out a near lightspeed ship thats more
>> >than marginaly plausible, trying to cut costs on it doesn't mater.  All
>> >that would do would be to make a nonfunctional system cheaper.
>> 
>> It makes a lot of difference if one needs 1000 Watt or 1000*1000 Watt. For
>> the first a simple petrol-generator will do, but for de latter you need
>> almost a complete power-plant.

If you can build one petrol (gasoline) generator, at worst you can build a
thousand others and string them together for a special project.  Maybe well
start mass producing O'Neil type solar power sattelites.

>> >> If one makes such a big ship, a lot of things may go wrong and endanger
>> >> the trip. The more complex the ship, the more probable that the trip
>> >> isn't completed. NanoAI will decrease that probability significantly.
>> >
>> >But of course, Nano are about the most complex and unrepairable systems
>> >we've even theorized making.
>> 
>> 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 also
>> 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 problems.

>> >The odds of finding lifeforms and planets are hard to judge. Certainly
>> >we're only taking about a handful of stars within search range.  But it
>> >seems likely all of them could have planets, and we have no idea how
picky 
>> >life is about where it can form.  In Sol, earths a yes, Mars is a maybe
>> >(please send unbroken lab gear) Venus I'd bet strongly against.  As for
>> >the rest and their moons... ??
>> >
>> >One thing we can be sure of, none of the planets out there will be
>> >habitable. Earth wouldn't be habitable to us if we hadn't evolved here.
>> 
>> Why wouldn't they be habitable? It would be possible that there are
already
>> other forms of life there. (Not necessary intelligent)

Agreed.  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, and
our present problems with plagues like Ebola, AIDs, Etc, don't speak well for
the odds of a carless interstellar explorer.  Your microbes, and the planets
microbes would rapibly try to digest the alien life forms it sees.


>> >> In any event a handfull of starsystems should keep us busy for a
>> >> couple decades.  Obviously past 2100 all the systems were 
>> >> discussing will seem archaic, and our physics quite naive.
>> 
>> Probably the next century would keep us busy only by "colonizing" moon and
>> mars. And maybe some nice asteroids for their low gravity.

True, though I think big platforms harvesting near earth asteroids and comet
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 much
richer pickings!!  (One estimate places the value of the oil on one average
near earth comet core at several hundred billion dollars US!)  Which is one
of the reasons I expect space development to progress much faster than
expected.  Free-for-the-taker valuble materials tend to encourage that.  ;-)

Kelly