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NASA and Nuclear Power

marssoilviewNASA’s history with nuclear power dates all the way back to the early 1960s when the U.S. Navy launched a navigation satellite powered by nuclear energy.

Nuclear energy’s ability to withstand the most extreme conditions has made it an important part of space missions, including the Mars 2020 mission. The next journey to the Red Planet will focus on bringing back soil samples and exploring the atmosphere of Mars to determine its habitability for human life.

NASA recently highlighted the significance of nuclear energy stating, “Mars, Venus, Jupiter, Europa, Saturn, Titan, Uranus, Neptune, the moon, asteroids and comets.  A number of these missions could be enabled or significantly enhanced by the use of radioisotope power systems (RPS).”

A RPS works like this: Through the natural decaying process, isotopes produce a tremendous amount of heat. In the case of an RPS, as the isotope plutonium-238 decomposes the heat is converted into electricity which in turn is used to power travel through space. Plutonium-238 is an artificial element with a half-life of 88 years. The longevity of nuclear energy makes the RPS an ideal and reliable source of power generation even under the harshest of circumstances.

The challenging environment includes temperature extremes not known to earth. Take the moon for example. Temperatures on the surface of the moon can fluctuate between highs of 125 degrees Celsius and lows of -175 degrees. Another challenge with travelling to the outer reaches of the solar system, such as with the New Horizons missions, is being able to conduct research in the dark, requiring a power source that can still operate without the energy of the sun.

For the Mars missions, a big factor in power selection is dust. During its infamous dust storms, the red planet can kick up dust to last for weeks at a time, coating “continent-sized areas,” according to NASA.

Nuclear power has the added benefit of being compact.

“Solar would be too big and we’ve that learned dust in the Martian atmosphere accumulates on the solar cells, so unless you have wind storms to clear them off, you will kill the missions off by running down the batteries,” according to Dr. Ralph McNutt, principal investigator for the New Horizons Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI), from the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland. “If you want to run rovers on Mars and do it accurately and if you want to go to the moon and really investigate in permanent shadows you need nuclear power.”

Compact size isn’t just beneficial, it’s required when working in outer space. Einstein’s theory of relativity (E=Mc2), essentially states that the further the distance you want to travel, the more speed is required, therefore the mass of the object travelling must decrease.

The Rover for Mars 2020 will be about the size of a car and will measure approximately 7 feet in height. The nuclear powered MARS 2020 mission will launch in the summer of 2020 and could provide new clues to past life on the not so distant planet.

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Exploring Mars: Nuclear Power Makes it Possible

Three years after landing on Mars, the Curiosity rover is still going strong. The size of an SUV, rovers have been leading the way in scientific discoveries on the Red Planet by collecting pictures and data. Since 2012 the rover mission has been powered by nuclear energy.mars rover

“Previous rovers were solar powered and the life span wasn’t long, but the switch to nuclear allowed it to live longer,” according to Dr. Ashwin Vasavada, a lead scientist on a team of 500 experts who are the eyes and ears on Earth for rover’s missions.

“Dust would accumulate on the solar panels over time and there is no way to clean the panels,” says Vasavada. “You can’t bring water with you. So in order to remove that risk we went to a longer, more reliable power supply.”

Curiosity carries about five kilograms of on-board nuclear power. Heat and electricity are generated by the decay of plutonium-238. As it erodes, it transforms itself into uranium-234. This change gives off a tremendous amount of heat, some of which circulates through Curiosity to keep the instruments warm, and some which converts into electricity to keep the rover working 24/7.

That’s where Ryan Bechtel comes in, along with his team at the Office of Space and Defense Power Systems at the U.S. Department of Energy. As a power systems safety manager for NASA, he and his fellow engineers are responsible for powering Curiosity.

The rover’s power system uses a design based on similar technology used for the Viking landers in the 1970s.It’s called a Multi Mission Radioisotopic Thermoelectric Generator (MMRTG). Approximately two feet high and two feet in diameter, the MMRTG keeps the rover going around the clock. That’s an accomplishment, in a world where nighttime temperatures usually drop well below -70C – and sometimes reach -100C.

“It makes operations significantly easier because you don’t have to worry about the weather conditions and where the sun is pointed in the sky depending on season or time of day,” says Bechtel. “So it allows for continuous charging for the battery, which ultimately results in more science being collected.”

Innovation—some of it Canadian—turns up in other Curiosity systems, including the Alpha Particle X-Ray Spectrometer (APXS). This instrument, funded by the Canadian Space Agency, sits on the rover’s arm, looking down at the surface. It detects and analyzes the chemical elements within the rocks and soil. This helps scientists to determine more precisely the history of Mars, and to assess whether the Red Planet could ever have supported life.

While the science teams are sifting through Curiosity’s data, they’re also preparing for the next big step in Martian exploration – the Mars 2020 probe. It’s scheduled to land in February 2021.

The Mars 2020 rover will test new technology to benefit future robotic and human exploration of Mars. And, just like Curiosity, it will run on nuclear power.