[ExI] Power satellites

[hkhenson]

At 01:14 PM 5/1/2009, Stefano wrote:
>On Tue, Apr 28, 2009 at 4:33 AM, hkhenson <hkhenson at rogers.com> wrote:
> > It would have to be structured carefully so at the end the customers were
> > getting cheap power (and synthetic oil).
>
>In fact, natural fossil and other chemical fuels and the possible
>scarcity thereof are really not an issue when you have abundant, cheap
>energy from another source. Not only because the latter can replace
>the former for most purposes, but also because they can easily -
>albeit obviously with energy-negative processes - synthesised in
>arbitrary quantities.

Details including capital cost here:  http://htyp.org/Dollar_a_gallon_gasoline

>The point on which I have increasing doubts is whether they are really
>suited to carry a significant mass of matter out of deep gravity
>wells.

For almost a year I have been talking about how to do 
this:  http://htyp.org/Hundred_dollars_a_kg  Compared to using 
chemical rockets for the same traffic, using lasers ablation 
propulsion for the second stage reduced the lift off mass (per hour) 
by a fact of 5, from one 6000 ton rocket to four 300 ton 
rockets.  This provides at least a five to one reduction in transport 
cost to GEO.

>In fact, were the earth more massive, it might even be impossible, if
>I am not mistaken, to achieve escape velocity with chemical-reaction
>rockets, given that any such fuel would not contain enough energy to
>lift itself, let alone any useful payload and the necessary vehicle.

The key word you use here is "useful."  But you can put number on 
it.  If you want to say anything about space you really have to 
understand the rocket equation.  Even a graphical understanding of it 
is good enough.  Look 
here: 
<http://en.wikipedia.org/wiki/File:Deltavs.svg>http://en.wikipedia.org/wiki/File:Deltavs.svg 
and check out what mass ratio you need for a delta V of just 3 times 
the exhaust velocity.

>And even from planets of earth mass, the margin available for the
>latter with which we have to work is very limited indeed, so that no
>engineering magic can do more than working on decimals...

The problem is not getting off *our* rock.  It is getting off cheaply.

Keith