The reaction wheel is seen in the center of this image, shown as a black circulate object two feet wide in width. It’s shown at a slight angle as it is being installed on the spacecraft. Two engineers are seen facing the camera from behind the reaction wheel, and they hold the reaction wheel while it is being installed. The reaction wheel is resting slightly on a small cart with wheels. Above the reaction wheel and the engineers is the body of the spacecraft, which is barely visible.
Source: NASA/JPL-Caltech
Published: November 21, 2022

Engineers install a 2-foot-wide reaction wheel onto the main body of NASA’s Europa Clipper spacecraft at the agency’s Jet Propulsion Laboratory in Southern California. In all, four wheels were integrated onto the spacecraft, which is being assembled for its launch to Jupiter’s moon Europa in October 2024.

When the spacecraft heads through deep space, slips into orbit around Jupiter, and collects science observations while flying dozens of times by Europa, the wheels rotate the orbiter so that its antennas can communicate with Earth and so its science instruments, including cameras, can stay oriented. Two feet wide and made of steel, aluminum, and titanium, the wheels spin rapidly to create a force that causes the orbiter to rotate in the opposite direction. The wheels will run on electricity provided by the spacecraft’s vast solar arrays.

Scientists believe the icy moon Europa has a vast internal ocean that may have conditions suitable for supporting life. Europa Clipper will fly by the moon about 50 times while its suite of science instruments gathers data on the moon’s atmosphere, surface, and interior – information that will help scientists learn more about the ocean, the ice crust, and potential plumes that may be venting subsurface water into space.