Editor's note: With the successful landing of the Mars Curiosity probe, we are reprising and updating from last November this feature on ORNL's role in the U.S. space exploration mission.
August 6, 2012 — The Curiosity rover that was launched toward Mars over the Thanksgiving holiday includes a significant contribution from ORNL and DOE. ORNL developed and fabricated the protective iridium alloy cladding that's central to the generator that powers the rover.
The rover's mobile instrument platform is too large to rely on solar-powered batteries and uses a plutonium oxide-powered generator, as do all of NASA's deep-space probes such as Voyager and Cassini. ORNL's iridium alloy cladding encapsulates the fuel. Radioisotope Power Systems program manager James King explained this chapter in ORNL's longstanding role in NASA's deep-space exploration:
"We did have a role in the Mars Science Lab," King said. "We produced the iridium alloys, clad vent sets for the Pu-238 fuel containment, and the Carbon Bonded Carbon Fiber insulator sets used in the generator. This is the first launch using a new radioisotope thermoelectric generator, the Multi-Mission Radioisotope Thermoelectric Generator."
ORNL's iridium alloy "clad vent sets" are resistant to heat and impact and are designed and tested to remain intact even during an unplanned reentry during the spacecraft's launch or subsequent gravitational-assist flybys. The iridium alloy-clad vent sets have been used in other deep-space missions (such as Voyager, Galileo and Ulysses) and are present on the Pluto New Horizons mission to explore Pluto and the Kuiper Belt.
"ORNL has been involved with the development of this generator for several years," King said. "In addition to the component production, we conducted several materials characterization and testing studies to support the design and safety analyses activities. The iridium alloy was tested in temperature ranges applicable to this system to insure adequate ductility was available for the safe containment of the fuel during accident conditions. Also, an extensive generator insulation material testing program was performed to insure adequate performance during operation. Materials and fabrication support consultation was provided to program participants as the generator was developed."
DOE's Idaho National Laboratory assembled and extensively tested the power system.
King noted in November that the real payoff would come later this year when the probe reaches Mars.
"We put a lot of effort into this generator and are very excited about the successful launch of the Mars Science Lab," he says. "The next difficult part of the mission is the actual landing of Curiosity on Mars next August. This will be followed by the actual operation of the rover conducting scientific experiments over the next two Earth years which is one Mars year."