NASA's Psyche Spacecraft Shifts Into Nearly Nonstop Thrust on Its Long Haul to the Asteroid Belt

NASA's Psyche spacecraft has begun the longest sustained thrusting period of its three-year journey, running its ion engines almost without interruption as it climbs toward the main asteroid belt between Mars and Jupiter, according to a mission update NASA published on Oct. 22. The probe is headed for 16 Psyche, a metal-rich body that scientists believe may be the exposed core of an early, shattered planet.

Since Sept. 28, the spacecraft has fired its propulsion system almost continuously, pausing only briefly each week to check in with controllers on Earth. "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, in the agency's update. The team expects the thrusters to run roughly 90 percent of the time between now and arrival at the asteroid.

A Gentle but Relentless Push

Psyche's propulsion is not a dramatic rocket burn but a slow accumulation of speed. The spacecraft carries four Hall-effect thrusters that ionize xenon gas, firing one at a time to produce up to 250 millinewtons of thrust — a force roughly equal to the weight of a single AA battery, NASA said. Over the course of its cruise, that steady push will carry Psyche to more than 100,000 mph (160,900 kph) relative to an observer on Earth.

• Thrusters running almost continuously since Sept. 28, 2026, pausing only briefly each week
• Cruise speed: more than 100,000 mph (160,900 km/h) relative to Earth
• Fuel: nearly 2,400 pounds (1,090 kg) of xenon loaded at launch in seven tanks; about a third used in three years
• Journey: roughly 2.2 billion miles (3.6 billion km) from Earth to the asteroid, per NASA's Jet Propulsion Laboratory mission overview

Power for the thrusters comes from two cross-shaped solar arrays, each with five panels, as the spacecraft moves farther from the sun. NASA says the engines will run at full power for about three months before gradually tapering off as sunlight grows weaker with distance. Because the ionized exhaust also imparts a slight twisting force on the spacecraft, engineers periodically shut down the main thruster and briefly fire a different one at low power to unload the resulting momentum from Psyche's reaction wheels.

A Planet's Missing Core

Psyche launched on Oct. 13, 2023, aboard a SpaceX Falcon Heavy rocket from Kennedy Space Center, and used a gravity-assist flyby of Mars on May 15, 2026, to bend its trajectory and conserve propellant, according to the University of California, Berkeley's Space Sciences Laboratory, which built one of the mission's science instruments. That flyby also doubled as a rehearsal, letting the team calibrate cameras and sensors before the real encounter.

The destination asteroid is about 173 miles (280 km) across at its widest point, according to the JPL mission overview, and is composed largely of metal rather than rock or ice — unusual among the hundreds of thousands of known asteroids. The leading hypothesis is that Psyche is the leftover metallic core of a planetesimal, one of the building blocks of rocky planets, that lost its rocky outer layers to ancient collisions. Because no spacecraft can descend into Earth's own core, studying an exposed one up close is otherwise impossible, which is part of why NASA selected the mission for its Discovery program in 2017.

A Multi-Institution Effort Nearing Its Target

The mission is led by Arizona State University, where principal investigator Lindy Elkins-Tanton is a professor in the School of Earth and Space Exploration, according to ASU's news office. Day-to-day operations and navigation are handled by JPL, which is managed for NASA by Caltech and which built and operates the spacecraft's solar-electric propulsion system; the spacecraft chassis was built by Maxar.

"Now we are cruising with confidence deeper into the solar system, powered by sunlight," said Lindy Elkins-Tanton, the mission's principal investigator.

The propulsion system itself has drawn attention beyond the mission team. Independent coverage of Psyche's thrusters, described by Phys.org as "sci-fi worthy" for their faint blue ion glow, noted that the mission relies on electric propulsion precisely because it allows a relatively small spacecraft to reach deep-space velocities without carrying the heavy chemical fuel loads that conventional rockets require.

What Comes Next

Psyche is not expected to reach its target for years. NASA's mission overview puts gravity capture at the asteroid around late July 2029, with orbital science operations beginning that August and continuing for at least 26 months, during which the spacecraft is meant to map at least 80 percent of the asteroid's surface, measure its magnetic field and gravity, and characterize its composition at varying altitudes. The agency currently expects the prime mission to run through Nov. 1, 2031. Riding along separately is the Deep Space Optical Communications experiment, a laser-communications technology demonstration that has already set distance records for optical data transmission from deep space.

For now, the spacecraft's task is simpler: keep its engines lit, conserve its remaining xenon, and close the long gap to the asteroid belt one steady, low-thrust push at a time.