How does Curiosity get around Mars? Now, that is the question of the day. Mars is no different than the Earth in the fact that the rover needs power to do stuff. Curiosity must have a source of power for its 23 month trek over Martian terrain, as it drags around its 2,000 pound structure and operates its multitude of instruments. Enter the Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) by Hamilton Sundstrand Rocketdyne engineers in Canoga Park and the DOE. Nuclear power is alive, well, and crucial to this $2.5 billion Mars mission and the future of space travel.
Multi-Mission Radioisotope Thermoelectric Generator (MMRTG)
For 50 years, radioisotope sources have been used to power missions to explore seven planets in our solar system. Approximately 26 missions have been powered, as well as many other space craft such as the New Horizons now half-way between Earth and Pluto, on its way to the stars. The principle of the nuclear battery is simple: to operate in harsh environments, over a long period of time, in the vacuum of space. The MMRTG is a ‘space battery’ which provides an uninterrupted, reliable source of heat and electricity to operate Curiosity day and night. How does it do this? Through the natural decay of plutonium-238. Solar, once used for power, became unreliable – and at times the panels became covered with silt. Another power source needed development, and the atomic battery fit the requirements.
Space Battery: The Design
The MMRTG generates small increments of power, slightly above 100 watts, with a minimum lifetime of 14 years. The battery uses plutonium-238 as the radioisotope with decay by alpha particles, easily shielded, with a high release of energy. The half-life is 87.7 years, long enough to release energy at a continuous rate over a long period of time. Pu-238 energy output is .5 kilowatts per kilogram, so approximately 4.8 KG (10.6 lb) of plutonium dioxide provides 2,000 watts of thermal power and 120 watts of electrical power. Nuclear batteries have two parts: a heat source (Pu-238) in a sturdy container, and thermoconductors placed in the walls of the container to convert the heat energy to electricity. Conversion of heat directly to electricity was first developed 150 years ago and has continued on its path for safe, reliable energy in harsh environments.
Nuclear Power in the Future
The future of nuclear power is expanding in new and inventive ways. Some might think it is relegated to the power generation on Earth, for human consumption, but it is space-bound. Safely powering satellites, spacecraft and even unmanned lighthouses on earth, the future of the MMRTG is bright.
NASA. Mars Science Lab. (2012). Accessed August 14, 2012.
Gold, S. Mars rover Curiosity safely lands on Mars. (2012). Los Angeles Times. Accessed August 14, 2012.
US Department of Energy. Powering Curiosity; Exploring New Horizons-DOE’s MMRTG. OSTI blog. Accessed August 14, 2012.
U. S. Department of Energy. Multi-Mission Radioisotope Thermoelectric Generator. (2008). Accessed August 14, 2012.