Little Joe II - Launch Vehicle Development

Launch Vehicle Development

Man-rating of the launch escape system was planned to be accomplished at minimum cost early in the Apollo program. Since there were no reasonably priced launch vehicles with the payload capability and thrust versatility that could meet the requirements of the planned tests, a contract was awarded for the development and construction of a specialized launch vehicle. Fabrication of the detail parts for the first vehicle started in August 1962, and the final factory systems checkout was completed in July 1963. There was an original fixed-fin configuration and a later version using flight controls.

The vehicle was sized to match the diameter of the Apollo spacecraft service module and to suit the length of the Algol rocket motors. Aerodynamic fins were sized to assure that the vehicle was inherently stable. The structural design was based on a gross weight of 220,000 pounds (100,000 kg), of which 80,000 pounds (36,000 kg) was payload. The structure was also designed for sequential firing with a possible 10-second overlap of four first-stage and three second-stage sustainer motors. Sustainer thrust was provided by Algol solid-propellant motors. Versatility of performance was achieved by varying the number and firing sequence of the primary motors (capability of up to seven) required to perform the mission. Recruit rocket motors were used for booster motors as required to supplement lift-off thrust.

A simplified design, tooling, and manufacturing concept was used to limit the number of vehicle components, reduce construction time, and hold vehicle cost to a minimum. Because overall weight was not a limiting factor in the design, over designing of primary structural members greatly reduced the number and complexity of structural proof tests. Whenever possible, vehicle systems were designed to use readily available off-the-shelf components that had proven reliability from use in other aerospace programs, and this further reduced overall costs by minimizing the amount of qualification testing required.

The Little Joe II launch vehicle proved to be very acceptable for use in this program. Two difficulties were experienced. The qualification test vehicle (QTV) did not destruct when commanded to do so because improperly installed primacord did not propagate the initial detonation to the shaped charges on the Algol engine case. The fourth mission (A-003) launch vehicle became uncontrolled about 2.5 seconds after lift-off when an aerodynamic fin moved to a hard over position as the result of an electronic failure. These problems were corrected and the abort test program was completed.

Minor spacecraft design deficiencies in the parachute reefing cutters, the drogue and main parachute deployment mortar mountings, and the command module/service module umbilical cutters were found and corrected before the manned Apollo flights began. However, all command modules flown achieved satisfactory landing conditions and confirmed that, had they been manned spacecraft, the crew would have survived the abort conditions.