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Nuclear vs. solar power for deep space probes

Aug. 05, 2014, under history, opinions, space t/e/d

While checking to see if Space Power Now has started appearing in search engines, I came across an article in which the author implied that nuclear power supplies for satellites are inherently evil and dangerous. I have to disagree.

The ESA’s Rosetta comet explorer is scheduled to arrive at its target (comet 67P/Churyumov-Gerasimenko) Wednesday, 6 August, 10:45-11:45 CEST – about 27-28 hours from now as I’m writing this. (See the rosetta blog for current information.) Among other things, Rosetta has two solar panels, with a combined area of 64 m², each 14 m in length. The total span from tip to tip is 32 m. The solar panels power a suite of 11 science instrument packages, guidance computers, and the radio system for transmitting data back to Earth. They were only generating about 395 W when Rosetta was 5.25 AU (Astronomical Unit, roughly the distance from Earth to the Sun) from the Sun. Power output is now up to 850 W at 3.4 AU as the probe is encountering the comet and comet operations begin. According to the ESA, “The solar cells in Rosetta’s solar panels are based on a completely new technology, so-called Low-intensity Low Temperature Cells. Thanks to them, Rosetta is the first space mission to journey beyond the main asteroid belt relying solely on solar cells for power generation. Previous deep-space missions used nuclear RTGs, radioisotope thermal generators. The new solar cells allow Rosetta to operate over 800 million kilometres from the Sun, where levels of sunlight are only 4% those on Earth.”

Rosetta is a fine example of using advanced technology solar cells to operate at a greater distance from the Sun than was previously possible. However, somewhere beyond the orbit of Jupiter, collecting enough solar energy to run a reasonable set of instruments and a radio transmitter will become “difficult” in addition to using an inordinate percentage of the weight of a probe.

Nuclear power has been invented, the only way it could be “disinvented” would be to destroy civilization and any memory of it being used. Personally, I’d rather keep the nuclear power, and use it like a hammer, screwdriver, or other tool for productive purposes: I enjoy civilized life, which is why I’m as anxious as I am to make Space Power Now work.

Since Henri Becquerel discovered uranium salts emitted rays that resembled X-rays in their penetrating power in 1896, our understanding – and fear – of radioactive materials and radiation has grown. Radioactive materials, and equipment that utilize the radiation they produce, are potentially very dangerous if they are not properly handled. With due caution, they can be utilized to achieve objectives that would otherwise be impossible – like sending probes to the outer planets with enough instrumentation and radio power to return useful scientific data.

Tools are not evil, and should not be condemned as such: It is only when they are wielded by evil-minded people that tools cause evil results.

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