Re: Engineering Newsletter

[Kevin C Houston <hous0042@maroon.tc.umn.edu>]

Kevin replies to Timothy
> Reading the kind of English that you guys write is not too difficult so I
> can almost always manage without any help.

I'm not sure if that is a compliment or a put-down   ;)

> 
> >and a lot smaller if you could put in orbit at mercury's distance.
> 
> Yes a radius of 580 kilometre, but would it not become too hot? (the
> radiation level is about 10000 Watt/m^2)

I think the heat could be kept below the melting point of silicon.  As 
the Temperature goes up, so does the blackbody radiation.


> 
> >> That would always be anti-matter or a beam that is very tight.
> >
> >i don't agree, that's true only if you want to do it in a man's 
> >lifetime.  if you are willing to accept a lower speed, then you can do 
> >the trip with a _lot_ less energy.
> 
> The the answer is also easy, with one Joule you could come everywhere. (live
> support not included ;) )


That reminds me of a great new travel method making use of Hiesenberg 
Uncertainty principle:  as Temperature approaches Abs Zero, Momentum 
becomes zero to the last decimal, and the position becomes _infinite_.  
the recent cooling of some atoms down to nanokelvins of Abs Zero, makes 
me hopeful that this might someday work.  although how you go from room 
temp to even a "balmy" -40 (celsius, Farenhiet, what's the diff. ;) )
is another question, but if you could make to that emp and survive, then 
perhaps you could make it to Abs Zero.
> >> You could see anti-matter just as ordinary matter. All physic laws that are
> >> valid for matter do hold for anti-matter. Thus fusion would work.
> >> In fact Hydrogen is also a metal, it just has a very low melting point, I
> >
> >only if you put it under a hellish pressure.
> 
> No, the tables I use say that it gets solid at 14K for normal pressure (1 Atm.)


Solid yes.  Metal, no.  at one atm, hydrogen becomes an ice-like solid, 
which does not have any free electrons.  only at great pressures 
(ie Jovian core) does the hydrogen take on any metallic properties.

> 
> >Actually, if we could get any respectable solid at all, like Li maybe, 
> >then we could give it an electricall charge and keep it suspended that way
> 
> Yes, I proposed that idea some weeks ago.
> 

Oops, musta missed that one.


> >assuming that your 1000 Km radius solar array is correct,  I get
> >(1000 * 1000)^2 *PI() = 3.14 E+12 m^2 of solar cells
> 
> I rounded it to 1E12...
> 
> >i think your estimate of solar cell production is way too liberal,
> >I say 1 m^2/day is more likely.
> >so now we need 8.6 E08 robots to do the job in ten years
> >I think your three day replication estimate is good.
> >using exponential growth, I get 2^T=8.6 E08  T=29 days 3 * T =89 days
> >thats if we start with one robot.  I think we would probably start with a 
> >1000.
> 
> That would save 30 days, is it worth carrying that much extra load to gain
> 30 days?

one robot may not be able to replicate in three days, with out some 
minimum number of "support" units,  to mine ore, cart raw materials to 
easy places etc etc


> 
> >   if we let reproduction continue for 100 days ( nice round number)
> >we'd have 8.59 E09 robots
> 
> 1E13 Robots, or did you start with one instead of 1000 robots?
> 

Yes I did, sorry about that


> (Note: Probably all robots will be worn out after a few years, so you may
> need 3 or 4 times more than you originally would think, that would only cost
> a few days extra)

Any robot could probably repaired far cheaper than it could be re-built 
from scratch, and this could be done at any time, not just at the outset

> 
> >, and at the lesuirely rate of 1 m^2/day, we 
> >could build the entire solar array in 365 days.  100 robots could work on 
> >each maser transmitter, and all of them could be built in a month.  we'd 
> >still have plenty of robots left over to build habitats, mine fusion 
> >fuel, or whatever other job we needed done.  with that many pentium level 
> >processers, the resultant computer power would be staggering!
> 
> Yeah, not to mention the memory they would have 10 PentaBytes (1E16 bytes),
> but only if they can communicate well enough...
> 

i think TCP/IP would be much better suited to robotic units than to humans

> >Now, as Kelly says, when you get this many "Grunts", the job of the top 
> >boss becomes more and more difficult.  but with several layers of "middle 
> >managment" computers, I think it would be doable ( although, maybe not at 
> >the speed I was reffering to
> 
> For 3E4 robots I thought it could be controlled, but 1E10 may become a
> serious problem. If they use radio communication to check each other, they
> need a quite broad bandwith. Also the chance for collisions may increase
> significantly.

This is where you have some robots dedicated to the task of routing.  if 
each robot has a long-range low-bandwidth transmitter (to call for help, 
or report on distant conditions) and a high-bandwidth short-range (10m?) 
transmitter, then there should not be too much radio interferance.  As 
for physically bumping into each other, one robot in 1024 could be 
dedicated (aside from it's router duties) the task of "traffic control", 
telling two robots when they get too close to each other (say within two 
meters) 

> 
> Another problem by building the array may be the amount of materials that
> have to be transported. Say a solar cell weighs 2 kg/m^2, so the total
> weight of the array is about 2 * 3.14E12 kg. That makes about 1.7E9 kg per
> day, that's not nothing...

in thinking about this, i was struck by the comment you made about the 
radius of the solar collector being about the same as the face of the 
moon, and i thought, what if instead of putting it (the collector) in 
orbit around the sun at Mercury's distance, why not just cover the 
surface of mercury with solar panels? (not too difficult if you have 
self-replicating robots) They could exist underground safely, and the 
maser array could be placed on the south pole of mercury (TC is below the 
ecliptic)  Mercury would provide more than enough counter-weight for the 
beam, and the low gravity would assist the robots in maintaining the arrays

> 
> >yeah, I think we are going to need that technology in many areas.  
> >Computer circuitry, accelerator coils, fusion containment coils  anywhere 
> >you have a lot of energy, and no way to remove the heat.
> 
> Computer circuits mostly need semi-conductors, so I think super-conductors

Ever hear of a Josephson <sp?> junction?

> may not work there. But the other applications may be useful. Oh by the way,
> super conductors can't conduct infinite currents... I don't know what their
> maximum is though, I asked someone who worked with them but he didn't know
> either, they used only small currents and small pieces.

yes, i knew that, but that may be a limitation of technology, or is it 
fundamental?

Keivn