[ExI] [wta-talk] MIT boffins crack fusion plasma snag

hkhenson hkhenson at rogers.com
Sat Dec 13 18:27:06 UTC 2008

At 12:55 AM 12/13/2008, John Clark wrote:

>That boat has sailed, the world is already awash in hundreds of tons of
>poorly guarded Plutonium, and you only need a few pounds for a bomb.

Reactor grade plutonium is nasty stuff, typically 20% Pu 240.  If 
they *really* know what they are doing, people can make bombs out of 
this stuff.  But the high neutron flux out of the Pu 240 makes 
premature detonation almost a sure thing unless the design is very 
sophisticated.  Thus what should be a Nagasaki yield (21,000 tons of 
TNT equivalent) became 400 tons in the North Korean bomb test, the 
difference largely being the Nagasaki bomb was made of weapons grade plutonium.

>only a matter of time till you will wake up one fine morning and open your
>favorite newspaper and find that a major city has simply disappeared
>overnight. Bummer.

Bummer anyway, but a 10kt terrorist device set off at ground level 
doesn't knock a very big hole in a city.  See the map of DC and the 
area affected by such a 
If you ever see a big flash, move at right angles to the wind.


>And the trouble with power satellites is that you have to invest about a
>trillion dollars before you get your first watt of usable energy, before you
>can really know if the idea will work. And don't tell me you have it all
>worked out, in a project that large, that astronomically huge, something out
>of left field that neither you or anybody else imagined could easily turn
>out to be a total show stopper. And then you kiss your trillion dollars

It isn't going to cost anywhere close to a trillion bucks to see if 
the idea works.  The engineering risk is so low that I don't think 
there is any point in going through testing it in stages.  For 
example, if you were to ask a thousand microwave engineers it they 
thought there would be any problem in transmitting 5 GW of power to 
the ground from GEO, at least 990 of them would say it's a not a 
problem.  Maybe all 1000 of them.  We have been transmitting 
microwave energy down from GEO for decades from communications satellites.

The current best estimates are in the $350 billion range.  Of course 
that assumes the project were done in a more permissive legal 
environment, say China.  The big ticket items are either a partial 
space elevator (rockets up to the end about one earth diameter out) 
or a 4 GW laser for the pop up and push transport system.  Both need 
to be sized to about a million tons per year if power sats are going 
to replace fossil fuels over a 30 year span.  I don't have a figure 
on the partial elevator, but the laser transport system (under 
$100/kg to GEO) looks like $40 billion for the lasers (at $10/watt) 
$20 billion for the mirrors in GEO and $20 billion for the pop up 
rockets that loft 50 ton laser stages to 260 miles.  A 4 MW test 
(0.1%) Jordin Kare says can be done for a billion.  That's worth 
building for either method because you really want to clean up the 
space junk for an elevator.  A 4MW laser will deorbit at least 100kg/hr.

>I really really hope my skepticism about power satellites proves to be

Well, if you or anyone else who groks high school physics and can 
follow the math wants to help reduced the skepticism, try going over 
the figures in the web sites I have posted here.  If you can find 
holes, point them out.  If you can't, say so on the discussion pages.

>I hope my skepticism about a Polywell producing a boron hydrogen
>fusion reaction that produces more energy than it consumes is wrong too.
>It could happen, I know it's incredible and stretches credulity to the
>breaking point but believe it or not I've been proven wrong before.

I don't care how power sats are implemented.  I don't even care if 
they *are* implemented as long as we find a way (or ways) to replace 
the energy we now get from fossil fuels.  People who have tried find 
current "renewables" to fall short. http://www.withouthotair.com/ 
Make a case with physics and math for Polywell boron fusion.  Send it 
to David MacKay.   If you can make a convincing case, I will drop 
mucking with power sats and join that bandwagon.


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