On February 18, Perseverance landed spectacularly on Mars. We have already received the first photos and the first audio recordings from the bottom of the Red Planet. NASA’s fifth rover to date is built very similarly to Curiosity, which has been on Mars since 2012. Perseverance also has a radioisotope generator on board (MMRTG for short for multi-mission radioisotope thermoelectric generator). Around five kilograms of plutonium 238 decay slowly and regularly. The heat generated is converted into electricity. The generator can generate 110 watts of electrical power over an operating period of at least 14 years. One of the predecessor rovers, Opportunity, had lasted as long after landing in 2003 – albeit with solar cells.
60,000 km range for Tesla Model S?
Projected, the MMRTG in Perseverance, which loses a little bit of power every year, provides over 10,000 kilowatt hours of energy. To put it into perspective: The latest versions of the Tesla Model S have around 100 kilowatt hours of battery capacity and can travel around 600 kilometers on one charge according to the standard. If the Tesla had the radioisotope generator of the NASA rover on board, it could theoretically drive more than 60,000 kilometers at a time with its capacity.
So would such a generator be a possible solution for powering electric cars? No, because of course the Mars rover needs very little power for its very low speed, a maximum of 0.15 kilometers per hour, unlike a fast Tesla. A radioisotope generator would be too big and far too expensive for the power a car needs. Because the production of radioactive fuel alone is immensely expensive. Despite the many millions of dollars spent on this, the US can currently only produce a few hundred grams of plutonium 238 per year.
Nevertheless, radioisotope generators have also been used on Earth. In the sixties and seventies, some pacemakers carried such atomic batteries in miniature format. From 1971 to 1976, 284 plutonium pacemakers were used in patients in the Federal Republic of Germany alone. The Soviet Union even built large generators of this type to meet the electricity needs of remote lighthouses and military stations. In the last few decades they have been laboriously dismantled and disposed of in Russia.
Why Perseverance didn’t fly SpaceX
Today, their use in space probes is only considered responsible if solar cells are not enough for them. For example, missions to the outer solar system, such as those from Voyager 1 and 2, but also recently from the Pluto probe New Horizons, were carried out atomically.
Perseverance is expected to travel many kilometers on Mars over the next few years, test a small aerial drone for the first time and take samples that a new American-European joint mission will later bring to Earth. The rover was launched on July 30, 2020 with an Atlas V rocket. NASA announced the selection of the launcher back in 2016. At this point the Atlas V had already had dozens of successful launches behind it. SpaceX’s Falcon-9 couldn’t quite keep up at the time. In the meantime, valuable scientific satellites have also been transported by Tesla’s sister company, for example the exoplanet scout TESS in April 2018. At the end of 2021, the asteroid probe DART will fly on a Falcon. And of course people are now also flying the SpaceX rocket – the next time on April 20 with four astronauts to the ISS.