Uranium and thorium are lithophile elements, so they shouldn't be too difficult to find on rocky, oxygen-heavy asteroids. The only elements that may be difficult to find would be those that form volatile molecules, because they typically get gradually blown away by solar wind, or stripped away all at once by a catastrophic cosmic event. To find those elements in space, you look for a metals-dominant asteroid.Ĭhalcophile elements like sulfur, and on Earth their rarity (in terms of the amount we can dig up) is between lithophiles and siderophiles, because they tend to stratify above the iron-lovers and below the oxygen-lovers. The mass near the surface is only there due to quirks of geology. Elements like gold and platinum are considered rare on Earth not because the planet does not have a great quantity of them, but because the vast majority of that mass is way down in the iron core, where we cannot yet reach it. Siderophile elements like to form solid solutions with iron, and may not oxidize to lighter minerals readily. To find those elements in space, you look for a rock-dominant (oxidized) asteroid. For instance, the dominant aluminum ore bauxite is frequently found close to the surface of the earth. Lithophile elements like to oxidize into minerals and float on top of any dense metal core. The Goldschmidt classification of an element defines sort of chemical cliques for the elements. There is uranium on Earth, the Moon, and Mars, so we can reasonably expect it to be present on other less massive objects in the solar system.īut you also have to consider that materials stratify based on their density and chemical affinity. Įverything in the solar system is pretty much made out of the same stuff. The scaremonger's goto example of chernobyl lacked such safety measures because the Soviets didn't care about human life.Īlso worth reading is The Health Hazards of NOT Going Nuclear. The only concern with nuclear plants is a large release of radiation, which is unlikely due to the layers of shielding and containment. Nuclear is safer than every other form of large scale energy generation ever devised. The more we embrace nuclear power, the greater its benefits to human well being. Radiation is everywhere in the real world, it is a natural part of life, yet we treat it like any amount is a lethal danger, when in low doses it is not a meaningful threat.įukushima was a non-event, and yet it caused a movement to shut down all nuclear power. None of the plant's neighbors got sick, and no discernible increase in the rate of cancer deaths is expected. Everything at Fukushima went wrong, and yet only 8 out of 2400 workers were exposed to out-of-tolerate levels of radiation. What was the death toll from Fukushima? Zero. You'd need some very expensive/elaborate test facility that can capture the hot, radioactive exhaust, or you'd need to do all the actual testing in space (also expensive/elaborate).ĭangerous compared to what? What is your standard of measure for danger? What are the alternatives to provide vital energy for human flourishing? It's very expensive to test them on Earth, since the exhaust carries away some small amount of fission products and people don't just tolerate such radioactive pollution like back in the 1960s. That said, I agree that it would be expensive to develop nuclear thermal rockets. But you can have nuclear power in space with extremely low risks to the terrestrial environment if you use it only for missions that leave Earth orbit, and turn on the reactor only after the risky initial ascent on chemical boosters. The fission products from a live reactor of course include very-short-lived, very-high-radioactivity nuclides. Uranium 235 has a 700 million year half life, hence very low radioactivity. Regarding the many comments in this discussion about accidents during initial launch: if nuclear thermal rockets are fueled with uranium 235, and don't reach criticality until after the risky chemical-booster ascent out of atmosphere, they should be quite safe. I don't think that they are in the sweet spot for uncrewed probe missions, but the combination of higher-than-chemical ISP and higher-than-electrical thrust seems like a good match for crewed missions to Mars or beyond. They also provide orders of magnitude more thrust than electrical propulsion does. Nuclear thermal rockets have low specific impulse compared to electrical propulsion, but better ISP than any chemical rockets.
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