Thrusters supplied by Aerojet Rocketdyne, an L3Harris Technologies company, placed NASA’s Lucy spacecraft right on target for its successful November 1 flyby of Dinkinesh, a main-belt asteroid. This flyby was a critical dress rehearsal for Lucy’s primary mission of making the first-ever close-up observations of Trojan-belt asteroids starting in 2027.

Lucy passed within 265 miles of Dinkinesh while zipping along at about 10,000 miles per hour relative to the tiny asteroid. To make continuous observations during such a close pass, the spacecraft had to perform an about-face as it came and went, a maneuver that Bill Cahill, Aerojet Rocketdyne's senior manager of program management, likened to driving a car past something scenic and “whipping your head around” to keep it in view.

“Our precision thrusters enabled such tight, reliable targeting that the spacecraft was able to fly within 300 miles of a tiny, half-mile wide asteroid that is 300 million miles away on the other side of the sun,” Cahill said. “The more precise the approach, the better the data. And this is only a dress rehearsal for the primary targets out in Jupiter’s orbit.”

Launched in October 2021 aboard an Atlas V rocket whose Centaur upper stage was powered by Aerojet Rocketdyne’s RL10 engine, Lucy is on a 12-year journey that will take it to a record 10 asteroids, including eight Trojan bodies that share the same orbit as Jupiter. Named after the fossilized skeleton of a human ancestor, the mission is expected to provide clues about the early formation of the outer planets.

“Aerojet Rocketdyne’s propulsion complement aboard Lucy includes eight MR-103J attitude control engines, each generating 0.2 pounds of thrust, and six MR-106L engines that generate five pounds of thrust each,” Cahill said. “The 106s are used for trajectory and delta-v (change-of-velocity) maneuvers,” he explained.

Weighing 3,300 pounds fully fueled and measuring nearly 52 feet across from the outermost arcs of its twin circular solar panels, Lucy is taking a circuitous route to the Trojan belt that includes two gravity-assist Earth flybys. Dinkinesh is the first of two main-belt asteroids that Lucy will encounter along the way. Between the close encounters, Lucy will make multiple trajectory correction maneuvers aided by the MR-106L engines.

“The performance of our engines during these maneuvers will directly contribute to how long the mission ends up being,” Cahill added. “The goal here is to use as little propellant as possible and make maneuvers as precise as can be so we can open up new opportunities to extend the mission and expand on the science they’re getting out of this primary mission.” 

Aerojet Rocketdyne’s Redmond, Washington, facility designed and built all of the spacecraft’s thrusters.

“Aerojet Rocketdyne has been a part of almost all of NASA’s Discovery missions to date, and our hardware has had the privilege of visiting every planet, as well as numerous small bodies like this one, throughout the solar system as part of NASA missions,” said Ken Young, Redmond site director. “It is fun to see something we built enabling science that was not possible in the past.”

Click here to learn more about Aerojet Rocketdyne's Solid Rocket Motors.

Click here to learn about Spacecraft Thrusters on SATNow.