On Monday, NASA announced that its advanced ion propulsion engine operated for 48,000 hours, or five and a half years – and that’s without stops for fuel or coffee. Developed under NASA's Evolutionary Xenon Thruster (NEXT) project, the engine now holds the record for the longest test duration of any type of space propulsion system.
NEXT is a solar electric propulsion system where electricity from the spacecraft’s solar panels is used to power a a 7-kW class ion thruster. In this, particles of xenon gas are electrically charged and then accelerated to speeds up to 90,000 mph (145,000 km/h). Such thrusters have already been used on spacecraft, such as NASA’s Dawn probe, and engineers are very interested in them because of their much higher performance compared to conventional chemical rocket engines.
The test was carried out in a vacuum chamber at NASA’s Glenn Research Center in Cleveland, Ohio, where the NEXT thruster continually fired day and night. In December, it had already passed 43,000 hours of operation and when it passed 48,00 hours it had consumed 1,918 lb (870 kg) of xenon propellant and generated a total impulse that would take over 22,000 lb (10,000 kg) of conventional rocket propellant for comparable applications.
NASA hopes to use NEXT or some version of it in a wide range of deep space missions. The thrust made by an ion engine is tiny compared to a chemical rocket, but its very high efficiency combined with its ability to fire for years on end means that it can build up astonishing speeds over time. As for the test model, it is on its way to a well-deserved retirement as it is switched off.
"The NEXT thruster operated for more than 48,000 hours," says Michael J. Patterson, principal investigator for NEXT at Glenn. "We will voluntarily terminate this test at the end of this month, with the thruster fully operational. Life and performance have exceeded the requirements for any anticipated science mission."