Thursday, July 19, 2012
A Little Moon Dust
The world needs cheap, clean energy. We don't need to put more frakking poisons into the ground, we don't need heavy shale oil, brought to us by incompetents who keep having spills in our water-sheds, from Wyoming to Michigan and coming soon to the Mississippi. What we really need is point-of-use power generation, which is wind-turbines in our glass and steel canyons, solar roofs on our homes and garbage turned into energy. This wouldn't solve our energy problem; we're addicted to cheap hydrocarbons, our economy is based on them (I build food service equipment, some of which is fueled by natural gas or LP, and some of it uses electricity by the half kilowatt and on up; the 36" Electric Griddle has 3 240 Volt, 4,000 Watt elements, for 12 KW!). But it would help, a lot, with our switch over to some other way of powering our vehicles, and providing electricity for the grid. How do we do that? Drop rocks from the Moon, of course! 8-P
11 km/s skimming atmo less 2 km/s to get it off the Moon in the first place, is 121 Megajoules, less 4 MJ, or 117 MJ per kg, some 32.5 KW-hr/kg, about $3.25 worth of electricity. If a million people need 30 KW-hr/day (Wild-Ass-Guess, one kilo of moon dust), that's 10^6 kg/day and 30 GW-hr. Three hundred million Americans need 300,000 tonnes of Moon dust a day; 7 billion people need 7 million tonnes/day, about 80 tonnes/second. 210 billion KW-hr is $21 Billion per day, 210 TW-hrs/day. 7 billion people need 11 MW-hr/year, $1100 worth of electricity (which is more than most of the world can afford), 77 Petawatt-hours worth $7.7 Trillion.
Real demand is probably closer to 30 Billion KW-hr a day, $3 Billion, 30 million tonnes of Moon dust per day, and 35 tonnes per second. If peak demand was 400 tonnes per second, we need a launch capacity on the Moon of 400 tonnes/s, call it 4 million kg worth of mass-driver @ $1100/kg, $4.4 Billion worth, which could only happen if it gets built out of lunar materials.
We need a catcher in low Earth orbit to grab that moon dust and harvest that energy, about 33 times what we need on the Moon, over 132 million kilograms; again, it'll mostly have to come form the Moon, and still cost in the neighborhood of $150 Billion. That supplies 11 trillion KW-hr of electricity, worth about a Trillion dollars at 10 cents a KW-hr. A couple of pennies on the KW-hr would pay for the system in a year... so my numbers must be so much moon dust.
BTW, if we want to stockpile building material in LEO, just slow the moon dust down by 3 km/s, and still get nearly half of the energy... and since we're designing an order of magnitude of extra capacity into the system, we could do it, make money, provide energy for a world thirsty for clean power and maybe build Vinnies' private space program at the same time? 8-P