Shown here is the Vernier rocket motor used on the Surveyor unmanned lunar landing probe, the first U.S. spacecraft to soft-land on the Moon on June 1, 1966. Developed and built by the Reaction Motors Division of the Thiokol Chemical Corporation, the regeneratively cooled Vernier produced between 30 and 104 pounds of thrust for 4.8 minutes, though the engine could be throttled and typically fired for short bursts. It provided propulsion for mid-course trajectory correction maneuvers and attitude and velocity control before and during landing. The Surveyor's main solid-fuel retro rocket provided the primary propulsion during descent to the lunar surface. Given the mission requirements, the Surveyor had to be reliable and also have a restart capability. Protection from the harsh environment of space, especially solar radiation, required that exposed surfaces be coated with gold plate 0.001 inches thick and polished to a high luster.

Of the seven Surveyor probes launched between 1966 and 1968, five landed successfully on the moon. Photographs and other data gathered by the spacecraft provided important information subsequently used in the Apollo program.