Following its October 2023 launch, the mission used its electric propulsion system intermittently to position itself to harness Mars’ gravity for a propellant-saving speed boost and a slight trajectory change. With that flyby now behind it, the spacecraft shifted on September 28 to running its thrusters nearly continuously, pausing just once each week to check in with mission controllers on Earth.<\/p>\n
The spacecraft’s solar-powered propulsion system uses electromagnetic fields to steadily deliver up to 250 millinewtons of force, about the weight of holding one AA battery. The system relies on the Hall effect, in which ions of the inert gas xenon are expelled to create thrust and a bright blue glow. Each of the four thrusters operates one at a time. Though the thrust is tiny, it builds over the journey, and at maximum cruise speed the spacecraft will travel more than 100,000 mph relative to an observer on Earth.<\/p>\n
“It’s now ‘pedal to the metal’ to the asteroid Psyche,” said Don Han, the mission’s navigation lead at NASA’s Jet Propulsion Laboratory. “The thrusters will be operating nearly 90% of the time from now until we reach the asteroid.” The spacecraft uses two five-panel, cross-shaped solar arrays with a collecting area of 800 square feet to generate electricity. It launched with nearly 2,400 pounds of xenon in seven tanks and has used about one third of that supply in three years, leaving enough to reach its target and orbit the asteroid during a two-year prime science mission.<\/p>\n
Steve Snyder, lead engineer for propulsion operations at JPL, said the sun-powered system requires unique planning. “For the next three months, we’ll be thrusting at full power before we begin slowly throttling down to approximately half power as the spacecraft moves farther away and its solar arrays receive less sunlight.” As the thrusters expel xenon ions, the magnetic field causes the ions to swirl, creating a slight torque that could interfere with pointing. The spacecraft uses reaction wheels to absorb that momentum, periodically turning off a thruster, rotating, and running a different thruster at low power to remove the buildup.<\/p>\n
Snyder noted the mission is also producing new science about the thrusters themselves. “This is the first time anyone has been able to measure this effect on a Hall thruster as a function of power level and of operating time, and for such a long duration in space,” he said. When the spacecraft arrives in 2029, it will insert into orbit around the asteroid, which is about 173 miles across and thought to be the partial core of a planetesimal. If it proves to be an ancient metallic core, it could offer a window into the interior of rocky planets like Earth.<\/p>\n
“The Mars flyby was an incredible opportunity for the team to calibrate instruments and practice procedures for a planetary encounter,” said Lindy Elkins-Tanton, principal investigator at the University of California, Berkeley. “Now we are cruising with confidence deeper into the solar system.”<\/p>\n
The spacecraft will thrust at full power for roughly three months before throttling down to about half power, then insert into orbit around Psyche in summer 2029 for a series of mapping orbits.<\/p>\n","protected":false},"excerpt":{"rendered":"
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