Curiosity is powered by a Uranium-238 radioisotope thermoelectric generator. Yes, that means Curiosity is powered by nuclear power but is relatively safe as long as the radioactive material is handled safely at the end of its lifetime of power generation.
RTGs were developed in the late 1950s in the United States by Mound Laboratories in Ohio jointly with the Atomic energy Commission. They are designated as Systems for Nuclear Auxiliary Power or SNAP, we like acronyms, and the first one used was SNAP-3 on the US Navy Transit 4A spacecraft in 1961. This was the sat navigation system used to provide accurate positioning for our Polaris Missile Submarines.
The Russians have used RTG for lighthouse power in remote areas although the US was the first to use one on land at uninhabited Fairway Rock in Alaska in1966.
Currently RTGs sit on the moon as the result of their use on Apollo 12, 14, 15, 16, and 17. They were part of the power pack necessary for ALSEP, Apollo Lunar Surface experiment Packages, and were designated as SNAP-27 and powered the long lived part of the Lunar Lander package. These stations transmitted information about moonquakes and meteor impacts, lunar magnetic and gravitational fields, the Moon's internal temperature, and the Moon's atmosphere for several years after the missions. After ten years, a SNAP-27 still produces more than 90% of its initial output of 70 Watts. 70 Watts doesn't sound like a lot but it was back then. There are currently two Viking missions with RTGs sitting on Mars.
The fuel capsule, containing 3.8 kilograms (8.36 pounds) of fuel, was carried to the Moon in a separate Fuel Cask attached to the side of the Lunar Lander. The fuel cask provided thermal insulation and added structural support to the fuel capsule. On the Moon, the Lunar Lander pilot removed the fuel capsule from the cask and inserted it in the RTG. Yes the Astronaut loaded the RTG which was inactive until landing.
Because an RTG is used in a spacecraft not intended for return to earth normally storage of the spent plutonium-238, it is non explosive by the way, is not an issue but there was one incident that is rarely talked about. When Apollo 13 returned to the earth they used the Lunar Lander as a life raft until just before reentry when the Lander was discarded and the Command Module was used for reentry. The Lunar vehicle mostly burned up on reentry but the plutonium-238 went to the bottom of the South Pacific Ocean near the Tonga Trench and has never been recovered. By the way NASA referred to it as the Lunar Module (LM) but the flyboys called it a Lander for obvious reasons.
Spirit and Opportunity, 2004 Mars Rovers, were powered by solar energy because they were small. All long range unmanned missions are usually powered by an RTG for a reliable source of power. It has been a long running issue with the anti-nuke people over the years but thankfully other than 13s LM SNAP-27 no real issues have resulted although it is unknown if RTGs were on any failed missions out of Vandenberg in California which is a military launch site for covert and private launches of military equipment.
The RTG on Curiosity is a new design from Boeing and generates 125 watts of power from 2000 watts of thermal energy at the start of the mission. it has a life of 14 years but Curiosity is unlikely to make it that long. The Multi-Mission Radioisotope Thermoelectric Generator or MMRTG is 4 times more powerful than the solar powered Rovers from 2004 and also provides warmth for sensitive equipment and actually pumps fluids to some.
A manned mission to Mars will require something different the the current MMRTG technology and solar will not cut it either. The spacecraft in transit to Mars will require a separate and more powerful source of power that will have to be nuclear in nature with a backup in case of problems. The Mars Lander will also require special power depending on duration of the mission on the surface.
On Apollo the Service Module provided electrical power with three fuel cells built into the North American Aviation designed Command and Service Module combo but they had limited lifetime sufficient for Lunar missions. The fuel cells provide power for heat, electricity and potable water. This system would not be capable of handling any long duration manned mission like Mars.
Our dipshit politicians, in both parties, along with NASA incompetence have allowed us to lose our way in the space program. The Shuttle was not a bad idea but even a decent idea badly managed is not good and add to that the needless deaths of 14 Astronauts and two lost Shuttles and even I have to admit NASA got what it deserved in so many ways.
Challenger was launched below 48 degrees which was the minimum requirements for a warm launch site like Kennedy (I hate calling it Canaveral). They launched at 42 degrees F with icicles hanging off the Shuttle despite knowing that previous launches below 48 resulted in solid booster leaks. Rubber O-rings have several key properties one of which is a known expansion rate given a starting temperature of the compound. They played Russian Roulette with the lives of 7 Astronauts and the Astronauts lost.
Columbia was even worse. They knew the wing was hit by foam from the Martin Marietta external tank yet they never sent any of crew out for a check and ALL Shuttle command crew are EVA qualified and have equipment available to perform an inspection. They then played Russian Roulette with these 7 Astronauts and Columbia disintegrated because on reentry to plasma generated by compression and heating of even a thin
atmosphere found its way into the wing and weakened the structure and killed 7. One NASA dipshit even claimed they never worry about reentry on NASA television but was quickly shut up because the simple truth is if anything goes wrong on reentry the spacecraft is severely compromised and unlikely to survive plus their is the communication blackout cause by ionization caused by the compression and heating of the atmosphere.
This is what happens when mediocrity, which is government hack, meets engineering requirements and the hacks win. First rule of manned spaceflight is the book is it. You follow the book and never violate the procedures and I mean never unless something untoward happens and then you check the book for a process that might work and improvise if necessary.
Even on Apollo NASA violated the book and killed 3 Astronauts in the Apollo 1 pad fire. I look at NASA sometimes and wonder where we went wrong but I deeply believe in the manned space program but sometimes it is hard to justify even if the NASA budget is less than 1% of the total federal budget. Somehow I think the Defense budget could have spared a few billion here and there. NASA has been a bureaucratic mess since just before Apollo 10 when the hacks realized we were going to pull it off and they weaseled their way in with the help of your local elected officials and the hammer of budget cuts.
Obama was quick to jump on the early success of Curiosity but he, along with Congress, destroyed the careers of many of our best engineers in Florida because the men and women that get the vehicles into orbit and prepare them and repaired the Shuttle were among the best and the brightest and Obama lied to them like every politician lies to them. Men and women with 20-30 plus years experience in missile and space exploration vehicles were just laid off. That is like Apple firing everybody in the company that knows who to put the product together so it will work and can be delivered to the consumer.
Maybe we will wake up when the Chinese and their lead painted spacecraft returns humans to the moon. I should stop now because it infuriates me. How the hell did we go from putting a man on the moon to outsourcing to Russia the sending of our people to the International Space Station? The answer is stupidly simple. Political correctness, political expediency, and political cowardliness and a NASA where the bog pieces always seemed to float to the top the quickest. (think cesspool)
The end of my rant.