Engineers at NASA's Kennedy Space Center in Florida completed stacking the twin SLS (Space Launch System) solid rocket boosters - seen in this Feb. 19, 2025, photo - inside the Vehicle Assembly Building for the agency's Artemis II crewed test flight around the Moon.

During stacking operations, which began Nov. 20, 2024, technicians used a massive overhead crane to lift each booster segment into place on mobile launcher 1, the 380-foot-tall structure used to process, assemble, and launch the SLS rocket and Orion spacecraft.