Fifty Years of Space Nuclear Power - with a comment by James Oberg

[bananas]

http://www.fas.org/blog/secrecy/2011/06/space_nuclear_power.html

Fifty Years of Space Nuclear Power
June 28th, 2011 by Steven Aftergood

Fifty years ago this week, on June 29, 1961, an electrical generator driven by nuclear energy was launched into space for the first time.

<snip>

“The men and women involved in Voyager did something that is absolutely the equal of Magellan or Columbus or any of the great explorers of terrestrial discovery,” said project contributor (and FAS sponsor) Ann Druyan. She and Voyager project scientist Ed Stone offered “Perspectives on More Than 3 Decades of the Voyager Mission” (pdf) in an article by Randy Showstack in the May 10 issue of Eos, the weekly newspaper of the American Geophysical Union (scroll down to the middle of the first page).

<snip>

Unfortunately, the plutonium 238 power sources that are used to power these missions are not only expensive, they are dirty and dangerous to produce and to launch. The first launch accident (pdf) involving an RTG occurred as early as 1964 and distributed 17,000 curies of plutonium-238 around the globe, a 4% increase in the total environmental burden (measured in curies) from all plutonium isotopes (mostly fallout from atmospheric nuclear weapons testing).

<snip>

A good deal of effort has been invested to make today’s RTGs more or less impervious to the most likely launch accident scenarios. But they will be never be perfectly safe. In order to minimize the health and safety risks involved in space nuclear power while still taking advantage of the benefits it can offer for space exploration, the Federation of American Scientists years ago proposed (pdf) that nuclear power — both plutonium-fueled RTGs and uranium-fueled reactors — be used only for deep space missions and not in Earth orbit.

Although this proposal was never officially adopted, it represents the de facto policy of spacefaring nations today.

<snip>

James Oberg posted a comment there:

1. Jim Oberg Says:
June 29th, 2011 at 5:42 pm

One of the other controversial space nuclear power accidents was the loss of the Russian ‘Mars-95′ probe, as described in my 1999 article in ‘New Scientist’ linked here:
http://www.jamesoberg.com/plutonium.html

The saddest part was how the Russian government and the Clinton administration promoted the false notion — at first a mistake, and later a convenient camouflage — that the craft’s nuclear batteries had safely sunk in the deep Pacific Ocean. Much more likely was that they fell over the Atacama Desert near the Chile-Bolivia border, where local residents were never alerted to watch out for them. Political pretense may have taken a human toll, because nobody seems to have ever even looked for the hazardous objects.

Jim O

[Confusious]

1. I don't support putting RTGs in earth orbit

In deep space, or even to mars, there is nothing else that can do the job.

Solar arrays would be to large and expensive.

Unless people just want to cut any deep space missions, there's no other practical choice.

[Drale]

2. 100% agree

until we figure out fusion and are able to scale it to a semi portal size nuclear is the only option for deep space travel at this point.

[Lionel Mandrake]

3. There are actually three practical sources of electrical power in space

1. Solar arrays work well close to the Sun, fairly well on Mars, but are impractical for missions beyond Mars.

2. RTGs are the topic of this thread and should not be confused with

3. Nuclear reactors, which have also been used in space, but are far more dangerous than RTGs.

A Soviet spy satellite powered by a reactor fell to Earth in 1978, spreading radioactive waste in parts of Canada.
Read more: http://archives.cbc.ca/science_technology/space/clips/12848/

[bananas]

4. Solar works as far as Jupiter, and the technology improves exponentially with time

This August the solar-powered Juno spacecraft will be launched for Jupiter.
Nuclear isn't needed at all for manned Mars expeditions.
Zubrin's Mars Direct can use solar or nuclear.
Ad Astra's VASIMR can use solar or nuclear to get to Mars in a few weeks.
When NASA evaluated solar for Cassini it was only 1% overweight, and there were several ways around that.

[Lionel Mandrake]

6. Sort of, and no, respectively.

Yes, probes of Jupiter and beyond can be designed to use solar power, but you end up with a spacecraft dominated by huge solar arrays, and the possible science payloads are restricted to those requiring only modest amounts of electrical power. Juno is a good example of this.

http://www.nasa.gov/mission_pages/juno/spacecraft/index.html

It's also true that solar cells are more efficient than they used to be, but the improvement is hardly exponential with time. The laws of physics dictate that the electrical power produced by a solar array will never exceed the power of the sunlight striking that array, which is proportional to area and inversely proportional to the square of the distance from the sun.

[bananas]

5. There's also fuel cells. nt

[Lionel Mandrake]

7. Oh yeah, I forgot about fuel cells.

Fuel cells have been used primarily for missions that last days, not years.