# Re: Engineering Newsletter

```Timothy replies to Kevin:

>Oh, you two can go on argueing if you want to, don't let me stop you.  I
>just thought that the ground had been covered many times before in finest
>detail.  I did not realize that you were still confused as to what Kelly
>meant.  i suppose that's my own fault for thinking that all members of
>this group speak english with perfect understanding (typical american
>attitude i know, but at least I can admit my mistake)  I'm just glad this
>dicussion isn't taking place in Dutch or Polish

I understand what Kelly means, but not why he thinks it. I'm also glad the
discussion is not in Polish :) For me it doesn't matter much if I have to
write English or Dutch, most words I know, the ones I don't I can quickly
look up in my computerized dictionary which I use about 4 times per letter.
Reading the kind of English that you guys write is not too difficult so I
can almost always manage without any help.

>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

>> 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 ;) )

>I meant by eff. Question, "what will the eff. of energy to antimatter
>conversion be?"  or How many kilowatts does it take to make a gram of
>anti-matter?

Theoretically I'd say m=0.5 E/c^2 because if you create anti-matter, you
create have to create an equal amount of matter. So that means a maximum
efficiency of 50%. When creating the anti-matter the amount of lost energy
could be kept small (10%) by reusing the wrong anti-matter and by
"recycling" the lost heat. So anti-matter efficiency in total may indeed not
so big as hoped. Maybe 30% after having used it in the spacevessel.

>> 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.)

>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.

>> How much work can one robot unit do? Say 1m^2/second.
>> So that means about 3E4 robots are needed.
>> How long would one robot need to replicate itself? Say 3 days.
>> Using exponetial growth: 2^T=3E4 --> T=173 --> 3*T=519 days needed to make
>> 3E4 robots.
>
>Tim, i think you have a little problem here. 2^173= 1.19 E+52 robots

Yes, I did 173^2=3E4, really stupid...

>In fact, I'm having trouble following where some of your numbers come from.
>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?

>   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?

(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)

>, 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...

>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.

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...

>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
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.

Timothy

```