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

[hkhenson]

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.

>It's
>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 
blast. 
http://www.unitedstatesaction.com/nuclear-low-yield-weapons-impact.htm 
If you ever see a big flash, move at right angles to the wind.

snip

>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
>away.

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
>wrong,

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.

Keith