Editing 2115: Plutonium
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This comic pokes fun at the properties of {{w|plutonium}}, claiming that it is so unrealistically powerful that it may as well be random science fiction jargon. Indeed, the ability for a metal to radiate energy sounds impossible (this comic leaves out the inherent dangers of highly radioactive material). This is reflected by Megan and Hairy treating Cueball's idea as a joke. | This comic pokes fun at the properties of {{w|plutonium}}, claiming that it is so unrealistically powerful that it may as well be random science fiction jargon. Indeed, the ability for a metal to radiate energy sounds impossible (this comic leaves out the inherent dangers of highly radioactive material). This is reflected by Megan and Hairy treating Cueball's idea as a joke. | ||
| − | There are devices that need substantial electrical power over long time – | + | There are devices that need substantial electrical power over long time – in the order of decades – but local sources of energy are insufficient or unavailable, yet constructing a power line or resupplying them with some power source (like fuel, fresh chemical batteries etc.) is either impossible or overly costly. Such devices include maritime beacons and buoys, automatic weather and science stations located in remote areas, and – most importantly – deep space probes and some planetary probes or science packs. Probes sent beyond Jupiter cannot effectively rely on photovoltaic panels for energy, because the great distance to the Sun means that the amount of solar radiation per unit of area is very low, requiring impractically large (and thus heavy) panels to provide enough energy. Carrying a lot of fuel adds mass to the probe, making them more expensive to launch. |
| − | Instead, such devices usually use {{W|radioisotope thermoelectric generator}}s (RTGs). In an RTG the natural radioactive decay of some unstable isotope (such as {{w|plutonium-238}} or {{w|strontium-90}}) produces a lot of heat, which is then used to generate energy using {{W|thermopile}}s, which generate electricity directly from temperature differences using the {{W|thermoelectric effect}}. The key element of an RTG, a pellet of radioactive material such as plutonium dioxide, could be facetiously described as a "power orb" – a lump of a substance that gives out heat apparently out of nothing | + | Instead, such devices usually use {{W|radioisotope thermoelectric generator}}s (RTGs). In an RTG the natural radioactive decay of some unstable isotope (such as {{w|plutonium-238}} or {{w|strontium-90}}) produces a lot of heat, which is then used to generate energy using {{W|thermopile}}s, which generate electricity directly from temperature differences using the {{W|thermoelectric effect}}. The key element of an RTG, a pellet of radioactive material such as plutonium dioxide, could be facetiously described as a "power orb" – a lump of a substance that gives out heat apparently out of nothing. |
Plutonium-238 must be produced from uranium in a nuclear reactor. Unlike plutonium-239, the {{W|Alpha decay|alpha radiation}} emitted by plutonium-238 is relatively harmless, as it is quickly absorbed by surrounding material and turned to heat – but plutonium is still incredibly dangerous if it gets inside a human body unprotected. In pure form it produces a little more than half a watt of heat per gram, which slowly drops as the material decays to lead, emitting a quarter watt per gram after 100 years. Other disadvantages of RTGs include the risk of contamination in the event of a launch failure, and the relatively limited supply of plutonium. | Plutonium-238 must be produced from uranium in a nuclear reactor. Unlike plutonium-239, the {{W|Alpha decay|alpha radiation}} emitted by plutonium-238 is relatively harmless, as it is quickly absorbed by surrounding material and turned to heat – but plutonium is still incredibly dangerous if it gets inside a human body unprotected. In pure form it produces a little more than half a watt of heat per gram, which slowly drops as the material decays to lead, emitting a quarter watt per gram after 100 years. Other disadvantages of RTGs include the risk of contamination in the event of a launch failure, and the relatively limited supply of plutonium. | ||
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==Trivia== | ==Trivia== | ||
| − | *{{w|Kerbal Space Program}}, a space simulator game which has been featured in xkcd several times | + | *{{w|Kerbal Space Program}}, a space simulator game which has been featured in xkcd several times has its own version of the RTG, running on Bluetonium-239 - but due to the lack of a half-life mechanic, the RTG is simply an infinite source power - an actual videogame power orb. Randall has made [[:Category:Kerbal Space Program|several references]] to the game |
{{comic discussion}} | {{comic discussion}} | ||
