The LR-101 is a fixed thrust, single start vernier thruster developed by Rocketdyne in the mid-to-late fifties and used in the Atlas, Thor and Delta launch vehicles until 1990.

After sustainer burnout, this pair of thrusters would switch to feed off the remaining propellant, effectively becoming a Pressure-fed engine.

[6] Additionally, the Atlas, Thor and Delta Rockets each possessed unique aerodynamically shielded gimbal mounts in the vicinity of their primary engines to provide large arcs for the vernier thrusters.

[7] The LR-101 is one of the most common vernier thrusters utilized in American rocketry and has become a sought-after object for item collectors and builders of amateur rockets.

[8] On the 'Galactic Aztec', the engine used RP-2 (Kerosene) as a propellant instead of RP-1, which was utilized in the SM-65 Atlas and PGM-17 Thor ballistic missiles as well as the later commercial Delta rockets.