The Space Reviewin association with SpaceNews

Orion spacecraft illustration
An offshoot of Project Orion, an initiative to develop a spacecraft propelled by nuclear explosions, could generate a large share of the power needed for Earth. (credit: NASA)

Fire and brim stone

Fusion drives and terraforming are two exciting ideas worked on by NASA that have some applications here on Earth. By utilizing inertial containment fusion while we wait for magnetic containment fusion, energy independence can be achieved. Another prospect is to terraform Earth to allow it to produce more energy.

Fire it up

Project Orion is familiar to most readers as the NASA project that postulated using external combustion nuclear bombs for propulsion. Since magnetic containment fusion is taking too long to implement, how about pulsed fusion using bombs in an internal combustion engine for electric power production? In the 1970s, project PACER envisioned a molten salt coolant shower over a small (10 terajoules, or 2.5 kilotons of TNT) explosion once every 45 minutes.

If it is too scary for the Earth, how about putting the reactor on the Moon and running it on helium-3?

Perhaps it could be scaled up to a large (50 petajoule) explosion. The average energy per warhead over the life of the US nuclear program was about 3 PJ (0.6 megatons) and the average cost $5 million. To be conservative, we would need some mass production advantage which we would get producing 10,000 warheads a year ($50 billion). That would be 27 explosions a day. Since the warheads would be blown up the same week or day they were built, the stewardship costs would go way down. Security costs would go up, but the security cost per warhead would probably be low. That would burn about a million kilograms of deuterium a year. A tiny bit of tritium could be thrown in as an accelerant. We would be on a budget, so we would be trying to minimize the price of the bombs even if radioactivity would be a little higher with more plutonium and bomb design a little trickier with less tritium. World consumption of electricity is now 50 exajoules (14 trillion kilowatt-hours) a year, so reactor efficiency would only need to be about 10 percent or so to supply the entire world electricity demand.

If it is too scary for the Earth, how about putting the reactor on the Moon and running it on helium-3? Power could be beamed back by microwave or sent back as platinum group metals, as suggested by Dennis Wingo (see “Review: Moonrush”, The Space Review, August 16, 2004), which could make terrestrial combustion more efficient. Heavy industry could be moved off Earth so that carbon production could be lessened. The electricity could power a mass driver to send the good stuff back to Earth if water was too dear to crack for rocket fuel. The electricity could drive a lunar space elevator.

Space nukes are not too popular politically. If fusion in space has turned your sunshine to rain, perhaps you would prefer hydro and solar.

Dam it

Another opportunity for spinoffs is the terraforming concept. What better to terraform than Terra itself? What if we could get 2.5 million square kilometers of solar electricity generation online overnight and trillions of cubic meters of hydro flow? The way to do it is dam the Mediterranean Sea. There is about half a meter per year more evaporation than rainfall in the Mediterranean. That can be converted to hydro power if the Straits of Gibraltar are dammed. Since the Mediterranean is an average of 1500 meters deep, if it dried up the height difference to the Atlantic (called the head) would be 1500 m. Half a meter of net evaporation on 2.5 million square kilometers allows us to flow 1.25 trillion cubic meters of sea water and not fill the Mediterranean back up. If you throw in the Black Sea and the Caspian Sea, that would be about 3.3 million square kilometers dry seabed now available for solar power. This would not raise the ocean level in the rest of the world by much. The Mediterranean, Caspian, and Black Sea together contain only 0.3% of the Earth’s water.

What better to terraform than Terra itself?

The efficiency would be quite low: 1500 meters of head for a kilo of water is only 15 kilojoules while evaporation is 2.3 megajoules (less than one percent efficiency on the solar). But we make it up in volume. We would get 500 gigawatts on average or 15 exajoules a year, which is about 30% of annual world consumption.

One challenge is that we would have to wait 3,000 years in order for the water to dry up. Investing in pumping on its face is a good deal because you pay an average of 750 m of head in exchange for 1500 m of head back in the other direction. The interest payments kill you though—breakeven is 1500 years later at a half-a-meter per year evaporation rate.

Perhaps we can make money on real estate instead. Living below sea level is not such a big risk if the buildings can float. Gibraltar would be even better protected than during the 19th century. If we sell 500,000 square kilometers of prime oceanfront real estate like Gallagher proposed for the Gulf of California and keep two million for power production, that probably would not pay for 1500 years of electricity and would not leave any money over to compensate the formerly coastal communities. Even if we had the money, we still would need to build planet-wide power capacity to do the pumping.

A cheaper slower investment would be to just not flow any rivers into the basin and divert them elsewhere. That would only get us an extra 10 centimeters a year—not much but not terrible. We would save 500 years that way. 2500 years is a long time to wait for payback, though.

The pay as you go approach would have us flow the rivers in and collect a small head of hydro on that. We would get to the bottom of the sea in 3,750 years, but we would be flowing 250 billion cubic meters of water at 50 m of head after 100 years (plus 0.5 a year). If we use plastic or something to keep the hot water on top, we might be able to increase the evaporation rate. Pulsing the inflow might get some waves going further increasing evaporation.

Damming and draining the Mediterranean is not just idle fantasy: the Earth did this trick on its own about five million years ago. The Mediterranean was enclosed when Europe and Africa collided. The Mediterranean emptied, then subsequently filled via the biggest waterfall ever.

Perhaps the fast way to empty the Mediterranean is geothermal heating, which sounds like Martian-style terraforming. The deepest point in the Mediterranean is 5,000 meters in the Ionian Sea. Perhaps that would be a good spot for a core tap. Maybe Mount Etna is the logical spot for a core tap. Isn’t it about time we start building energy capacity instead of mining it? Since we are in a hurry, perhaps we would want to put the fusion plant in the Mediterranean and use the waste heat to boil your French roast.