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

[hkhenson]

At 10:40 AM 12/15/2008, John K Clark wrote:
>"hkhenson" <hkhenson at rogers.com> Wrote:
>
>>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.
>
>The trouble is that we live in a era where a simple attack helicopter or
>even a Tom Cruise movie can end up costing two or three times what was
>predicted, and you're talking about Space Elevators (made of who knows what)
>and continuous duty 4GW Lasers. Is it any wonder that few can take your
>financial estimates seriously?

If you end a space elevator an earth diameter out, current materials 
will do the job.  "g" is down to .25 and that makes a huge difference.

CW solid state welding lasers you can buy *today* at $10/watt.  I 
can't see any reason that buying a million 4 kW units should be more 
expensive than buying one.

>Everybody thought the Space Shuttle would make it cheap to get into space,
>it's reusable after, but those estimates were off by at least an order of
>magnitude. We'd have been better off sticking with the 40 year old Saturn 5.

Most people who knew how the program had been compromised for 
political reasons knew it was going to be bad from the point they 
picked solid rockets.  They could have built a fly back stage with F1 
engines but they didn't.

>I don't think anybody will be convinced by paper and pencil stuff, you need
>actual hardware that produces usable energy where the path to scaling up the
>pilot plant is clear, and that will take many many billions of dollars.

Waste of money to try it out.  If you build *ONE* pilot GW power sat 
using current rockets it will cost as much as building the entire 
transport and production line.  There are times, and this is one of 
them, that just building the whole thing is less expensive than 
trying it small.  The physics of power sats just does not work trying 
to do it small.  (At least not for microwave transmission.)

>>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.
>
>The problem is not physics, the problem is economics.

You have to start with the physics.  How else can you do the economics?

What assumptions do you want to use?

Keith