Low cost power sats

Your assumptions on launch costs don't make sense. Just building that many launch vehicles would lower their cost substantially through mass production. And launching to LEO, then using cheaper methods to tug the satellite to GEO would also bring the costs down a lot. But I certainly agree that launch costs have to come down. The problem is somewhat a chicken and egg situation: to get the costs down you need the demand that would permit mass production; to get the demand, you need more practical launch costs. Committing to a large scale SSP program would break the logjam. By the way, the problem isn't "just" replacing existing dirty energy sources, but addressing increasing planetary demand. And finding "10,000-20,000" neighborhoods willing to invite in a nuclear power plant would be quite a trick.

>I disagree that the cost has to be less than other energy sources.
>First, the society is already starting to charge the actual cost of
>energy, not just the market price, by imposing carbon taxes in one
>form or another. Second, a societal decision that non-carbon fuels
>are required to fight climate change seems likely.

Neither apply when costing against nuclear power which is where this
discussion came from.

>Third, increases in demand for energy beyond what existing sources
>can produce will make cost comparisons less than useful.

Again, 10-20,000 1GW reactors will supply most of the fall off in
existing fossil sources. We can even make synthetic oil using off
peak power for a couple of hundred dollars a barrel.

>Finally, many special purposes already require energy that costs
>multiples of so-called current rates, e.g. supplying forward
>military bases or research stations in Antarctica.

Sorry, neither of these make a lick of sense from an
engineering/ economic standpoint. Military base loads are too small,
Antarctica would take a large number of power sats in weird orbits to
power it, and again, the load is too small to make sense.

>All of these are rapidly making space solar power currently needed
>and useful, even without the much-needed decreases in launch costs.

I am sorry to say I disagree. Consider the cost of building one
20,000 ton 5 GW test power sat with the current rockets. At
$20,000/kg and 20 million kg, that's $400 billion for just the lift
cost. On a per kW bases that $80,000/kW, at least ten times higher
than nuclear reactors.

For some number in the $100 billion range we could build a transport
system that would drop the price to $100/kg to GEO. It's less
expensive to put a hundred billion dollars into transport
infrastructure and then build the first power sat than it is to build
one with the current transport costs.

And in addition, you get this nifty ablation propulsion laser that
you can use to clean up all the space junk in a few years.

Keith

>
>----------
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>snip
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> >I'm actually very much in favor of solar power satellites and other
> >developments that will motivate us to move into space in a big way,
> >but I also try to keep a clear head where other promising sources of
> >energy are concerned -- and nuclear power is eminently available,
> >and the technology therefor more than ready.
>
>This is a cogent statement.
>
>If we are proposing space based solar power as a player--and it has
>to be a huge player if it is to be used at all--then we have to make
>a case that it is less expensive. Not equal or a little more
>expensive, but less expensive by 5 to 10 ten times.
>
>Now in the long run, we *know* this is doable--mining the moon or
>asteroids for power sat materials. But the most optimistic of us
>know it will take decades to build up a space industry and the need
>comes far sooner.
>
>So the only way for power sats to make sense is to lower the cost of
>lifting them to GEO to the point where transport isn't a really big
>factor. This means reducing $20,000/kg to $100/kg or less. The most
>optimistic people I know of think they might get it down to this
>level to LEO, but that's not where we want it, and there is a cost
>factor of about 3 to get to GEO with rockets.
>
>I accidentally stumbled on a way that might do it. Unfortunately
>rocket people who have been focused on going into LEO have a very
>hard time with it. Kind of like you are used to picking up lead
>weights and someone slips in a painted chunk of wood.
>
>It involves a suborbital boost up to about 200 miles and about a
>mile/sec forward velocity. The delta V for this is far less than
>going into LEO, in English units it is about 12,000
>feet/sec. Orbital is close to twice that speed, but because Ke = 1/2
>mv^2, it is only about 1/4 of the energy, so it is easy to do with a
>highly reusable booster. The actual speed at separation is around
>Mach 5 so it's possible winged vehicles could do it as well as
>vertical takeoff.
>
>The second stage is powered from the ground with a huge laser. The
>exhaust velocity is much higher than you can get with chemical fuels
>so the mass ratio is low. That means that 1/3 to 1/2 of it gets to
>GEO as useful payload.
>
>People, particularly Jordin Kare, worked for years on laser
>propulsion to go directly into space. The result has been small
>payloads or really huge lasers. Rockets are not bad if you are not
>trying for a high multiple of their exhaust velocity. This rocket
>and laser kludge lets you take a lot longer to accelerate the laser
>stage (only about a g) so you can push much larger payloads with a
>relatively small laser.
>
>The method makes no sense for traffic models smaller than a good
>fraction of a million tons per year. But if you are serious about
>power sats replacing fossil fuels, that's just what is needed.
>
>Keith Henson
>

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