gmalivuk wrote:but it just seems a bit funny that you'd quote a number completely contradicting the point you're trying to make.
25 Billion is the high
estimate produced by the UN. They also estimated as low
as 3 Billion. I think if you actually took that snippet in context you would have seen that it supports my argument, which is that population growth is unlikely to be that dramatic.
idobox wrote:Solt, are you suggesting the use of space-based solar power for off grid applications? It is going to be very complicated to beam energy to a foot soldier with enough accuracy, and without burning him. Ships could use it, but why bother solar when you have nuclear already working?
Well, the "without burning him" part is simply wrong. These systems work on resonance and so only a correctly sized antenna will pick up a significant amount of energy. The soldier could be bathed in the beamed energy and only the receiver on his back will actually pick up any of it.
As for being accurate enough to only hit your guys but not give the enemy power, that's certainly a problem but it doesn't sound intractable. I'm not an EE but you could probably use some kind of transmitting array on the satellite (with multiple transmitters, each with a very narrow area of effect, as opposed to a point source) that would have the ability to shut down power to some areas of the battlefield. Maybe you could periodically tell all your guys to shut off their receivers and then try to overload any bad guys' receiver. Maybe if there's a way to change antenna geometry a little bit you can change the transmission frequency and antenna geometry continuously so anyone who doesn't know the pattern ahead of time will be able to pick up much less power.
I can think of more methods but the point is, the system is feasible and the need is justifiable. Nuclear is great for ships but not really feasible for foot soldiers (even wearing power suits). Fuel cells have the same problems as fossil fuels, and batteries just don't have the capacity. As for fossil fuel, every gram of fuel used by your soldiers has to be shipped to the battlefield, and these battlefields are usually really shitty terrain such as the mountains of Afghanistan. Not even dirt roads are guaranteed. Convoys are open to attack (as has been happening to NATO supply lines going to Afghanistan), fuel is expensive as hell by the time it reaches the destination, and even when it is near
your soldiers and vehicles, it still must be protected, and your units have to stop their activity periodically to return to the forward operating base and resupply. Plus they have to carry that extra fuel around with them in preparation to use it, adding tons of weight and driving power requirements up even further. In contrast, all you have to do is figure out how to defend a satellite from ground based lasers and you can avoid all of these problems. And in the process you subsidize commercial space power production and launch, just like the military subsidized the development of transistors and satellites for the initial wave of commercial applications.
Incidentally, I do think nano-scale nuclear power plants will play a big role in the future, but this thread is about space.
idobox wrote:We have land on Earth that is practically free (deserts), with much easier maintenance and access to the grid. If solar power ever becomes an economically sound alternative to nuclear power, it will still be more cost efficient to do it on the ground.
Not exactly. You still have to build underground superconducting conduits to major population centers, including under oceans, which will be expensive as all hell. Space based solar power needs almost no transmission infrastructure, just receivers at key points in the already existing distribution grid.
idobox wrote:I don't know if there are orbits with more than 12h of exposure a day
There are plenty. You can craft a sun-synchronous orbit such that it is continuously in sunlight, day round and year round. A Molniya-type orbit could be created that spends the vast majority of its time (8 hours) on one side of the planet, and flings itself around the night side in less than 4 hours. A Molniya orbit can also be tuned to be constantly in view at a single point on earth for those 8 hours, meaning 3 satellites can completely cover a point (in fact, a whole country) with transmissions, while in sunlight the whole time, and without having to be in geosynchronous orbit. This is the orbit Russia uses for satellite TV, given that geosynchronous orbit, which must be over the equator, is practically below the horizon for a large part of their country.
BirdMav wrote: Is there technology that is currently available that can store solar energy?
The reason hydrogen is probably the way of the future is that, unlike gasoline, it can be made from electricity. No one can make gasoline economically from electricity, it has to be mined. So, hydrogen can be made from (or, can act as a battery for) solar power.