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NASA Running Low On Fuel For Space Exploration
smooth wombat writes "With the end of the Cold War came warmer relations with old adversaries, increased trade and a world less worried about nuclear war. It also brought with it an unexpected downside: lack of nuclear fuel to power deep space probes. Without this fuel, probes beyond Jupiter won't work because there isn't enough sunlight to use solar panels, which probes closer to the sun use. The fuel NASA relies on to power deep space probes is plutonium-238. This isotope is the result of nuclear weaponry, and since the United States has not made a nuclear device in 20 years, the supply has run out. For now, NASA is using Soviet supplies, but they too are almost exhausted. It is estimated it will cost at least $150 million to resume making the 11 pounds per year that is needed for space probes."
To all the smart alecks, no they can't use weapons grade plutonium, which is 239, they need 238, which has a much shorter half-life (88 y compared to 24100 y) and therefore gives off much more energy. They don't need an isoptope that is fissile, they need one with a short half-life.
Sr-90 is not a good as Pu-238 for 3 reasons.
1. Shorter half life (28.8 years vs. 87.7), thus the power drops off faster.
2. Lower energy density, thus less power to start with, or more weight.
3. It produces beta radiation (Pu-238 produces alpha radiation) and requires much more shielding (and thus more weight) so it doesn't mess with the electronics.
upon the advice of my lawyer, i have no sig at this time
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"Just decommission a few nuclear warheads each year."
Except that nuclear warheads use Plutonium-239, and the power plants NASA uses are based on Plutonium-238.
And converting Pu-239 into Pu-238 is much more difficult than converting rad-waste into Pu-238.
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This about Pu-238 for use in thermoelectric generators. Pu-239 does not produce enough heat.
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