NASA’s Plutonium Problem Could End Deep-Space Exploration

[MicaelS]

http://www.wired.com/wiredscience/2013/09/plutonium-238-problem/

I know there are people who are anti-nuclear, but to lose deep-space exploration over a lack of plutonium-238 is simply unacceptable to me. Period.

But, once again Congressional stupidity is at fault here, not anti-nuclear activism.

In 1977, the Voyager 1 spacecraft left Earth on a five-year mission to explore Jupiter and Saturn. Thirty-six years later, the car-size probe is still exploring, still sending its findings home. It has now put more than 19 billion kilometers between itself and the sun. Last week NASA announced that Voyager 1 had become the first man-made object to reach interstellar space.

None of this would be possible without the spacecraft’s three batteries filled with plutonium-238. In fact, Most of what humanity knows about the outer planets came back to Earth on plutonium power. Cassini’s ongoing exploration of Saturn, Galileo’s trip to Jupiter, Curiosity’s exploration of the surface of Mars, and the 2015 flyby of Pluto by the New Horizons spacecraft are all fueled by the stuff. The characteristics of this metal’s radioactive decay make it a super-fuel. More importantly, there is no other viable option. Solar power is too weak, chemical batteries don’t last, nuclear fission systems are too heavy. So, we depend on plutonium-238, a fuel largely acquired as by-product of making nuclear weapons.

But there’s a problem: We’ve almost run out.

Many of the eight deep-space robotic missions that NASA had envisioned over the next 15 years have already been delayed or canceled. Even more missions — some not yet even formally proposed — are silent casualties of NASA’s plutonium poverty. Since 1994, scientists have pleaded with lawmakers for the money to restart production. The DOE believes a relatively modest $10 to 20 million in funding each year through 2020 could yield an operation capable of making between 3.3 and 11 pounds of plutonium-238 annually — plenty to keep a steady stream of spacecraft in business.

[DetlefK]

1. How a plutonium-battery works:

It's the thermoelectric effect.

You need two wires, made from different metals, e.g. iron and copper.
Connect them on one end.
Heat that point, e.g. with a piece of plutonium that's lukewarm from radioactive decay, but make sure that the other ends of the wires are unaffected.
The temperature-difference leads to a shift in electron-density, which is visible as an electric voltage between the untampered ends of the wires.
Connect an electronic device, e.g. a lamp, to the loose ends of the wires and it will run as long as the temperature-difference is upheld.

[madrchsod]

2. thanks for the explanation...

[RC]

3. I'm waiting for the wind power people to come along and ask why we can't use the solar wind to power

our space probes.

[eppur_se_muova]

4. Other isotopes work, but Pu-238 is the best for several reasons.

https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator#Selection_of_isotopes

Considering the number of engineers in Congress, lots of luck explaining this one ...