From Chariots for Apollo: A History of Manned Lunar Spacecraft, NASA SP-4205:
Early in the contract, North American and Houston engineers had agreed on a flight-test program, putting boilerplate command and service modules through structural tests and checking out the abort escape system. In mid1961, while he was still with NASA before joining North American in 1962, Alan Kehlet had suggested using a fin-stabilized, clustered-rocket, solid-propellant booster for these tests. The "Little Joe II" (named after the Project Mercury test vehicle) would be able to propel a full-sized Apollo reentry spacecraft to velocities as great as those in the critical portions of the Saturn trajectory and to altitudes of 60,900 meters. The tests would be a simple and fairly inexpensive way of determining - in flight - the full-scale spacecraft configuration concepts, systems performance, and structural integrity. Tests of the launch escape system at maximum dynamic pressure would be most important. In May 1962 the Convair Division of General Dynamics was selected to develop the vehicle and named Jack Hurt as its program manager.
Although launch sites at Wallops Island, Virginia; Eglin Air Force Base, Florida; and the Cape were considered, the New Mexico desert north of El Paso, Texas, was picked early in the spring of 1962 as the Little Joe II test area. The Army's White Sands Missile Range (WSMR) seemed the most suitable for Little Joe II ballistic flights.
NASA engineers expected to conduct three kinds of tests at White Sands: (1) pad aborts, in which a solid-fueled rocket mounted on a tower attached to the top of the command module would pull the spacecraft away as it would have to do if the Saturn threatened to blow up on the launch pad; (2) maximum-dynamic-pressure ("max q") tests, in which the rocket would pull the spacecraft away from the launch vehicle if the booster veered off course shortly after launch; and (3) high-altitude tests, in which the rocket would haul the spacecraft away from the launch vehicle if the Saturn were unable to boost its payload to orbital flight.
Apollo leaders also expected to flight-test the lunar module in New Mexico, using the Little Joe II booster.
The first Little Joe II, a qualification test vehicle without a payload, was launched successfully on 28 August 1963.
At White Sands, New Mexico, on the morning of 13 May 1964, a Little Joe II launch vehicle rammed Boilerplate (BP) 12 to an altitude of 4,700 meters, to see if the launch escape system could propel the spacecraft away from the booster after it had reached transonic speed. Only one incident marred an otherwise successful flight. A parachute riser broke during descent, collapsing one of the three main parachutes. The boilerplate landed safely on the two remaining parachutes, in what one engineer later called "a welcome unplanned result of the test."
As 1964 drew to a close, the Little Joe II abort test program at White Sands was nearing its third and, in many ways, most crucial launch. Because of their fixed fins, the first two solid-fueled rockets had been somewhat erratic in flight. Jack B. Hurt's people at the Convair plant of General Dynamics in San Diego then built a relatively simple attitude control and autopilot system for the rest of their vehicles to allow hydropneumatic operation of "elevons," like ailerons, in each of the four fins while in flight. In addition, for the "max q" (maximum dynamic pressure) and high-altitude abort tests coming up, small reaction control motors were installed in the fin fairings to increase the precision of aiming control to the test points desired.
Vehicle No. 12-51-1, as it was called, with four Recruit and two Algol motors, was the most powerful Little Joe II yet flown, intended to develop 1,500 kilonewtons (340,000 pounds of thrust to lift itself and its cargo - BP-23 and the launch escape tower - more than 9 kilometers high. The whole assemblage, weighing 41,500 kilograms, was pointed toward the north at a point in space where the launch escape system, fitted with canards, would pull the capsule and boost protective cover away from the Little Joe II while traveling at a speed of mach 1.5. This area was in the middle of the region where a Saturn V ought to experience max q.
At precisely 8:00 on the morning of 8 December, Little Joe II roared upward, straight and true. Thirty-six seconds later - almost out of sight and two seconds, or 900 meters, early - the planned abort took place. After an 11-second coast period, the canards deployed, and the capsule tumbled four times in its turnaround before stabilizing blunt-end forward and jettisoning the escape system. The boost protective cover shattered slightly more than expected, but the two drogue parachutes deployed. Its three main parachutes opened, and BP-23 drifted gently to rest, 11,000 meters uprange from the launch site, after 7.5 minutes of flight. Max q had been higher than predicted, but all else had worked well; at the end of 1964, Little Joe II, with its payload, was ready for more stringent flight tests.
Meanwhile, flight testing of the lunar module within the earth's atmosphere was finally ruled out when Langley discovered in wind tunnel investigations that the Little Joe II-lander combination would be aerodynamically unstable.
Several dozen newsmen gathered at White Sands Missile Range, New Mexico, on 19 May to watch Mission A-003, an abort test of a boilerplate spacecraft at an altitude of 35,000 meters. At 6 that morning, the Little Joe II ignited and rammed its payload skyward. A few seconds after liftoff, a fin-vane at the base of the booster stuck and started the 13-meter-tall spacecraft-booster combination spinning like a bullet. Twenty-six seconds into the flight and still on a true course, the vehicle started coming apart. The abort-sensing system signaled the launch escape tower rocket to fire and pull the spacecraft away at an altitude of 4,000 meters.
While newsmen watched the fluttering remains of the Little Joe II, BP-22's parachutes lowered it gently to the desert floor. Apollo had another answer: the launch escape system worked in a real abort situation.
Little more than a month later, on 29 June, the launch team in New Mexico prepared to test an abort off the pad. The year before, a similar test had proved the escape tower rocket could jerk the spacecraft safely away from an exploding launch vehicle. But both the spacecraft and its escape system had since gained weight. In the second test, the rocket pulled the spacecraft higher in the air and farther downrange than expected.
Before starting Apollo-Saturn IB launches, however, the operations people had to clean up one outstanding matter in New Mexico. NASA had hoped to finish the Little Joe II abort qualification program by the end of 1965, but on 17 December the Flight Readiness Board refused to accept the booster and canceled a launch set for the next day. A month later, at 8:15 on the morning of 20 January 1966, the last Little Joe II headed toward an altitude of 24 kilometers and a downrange distance of 14 kilometers. Then, as designed, the launch vehicle started to tumble; the launch escape system sensed trouble and fired its abort rocket, carrying the command module away from impending disaster. All went well on Mission A-004-the launch, the test conditions, the telemetry, the spacecraft (Block I production model 002), and the postflight analysis. The spacecraft windows picked up too much soot from the tower jettison motor, but the structure remained intact. Little Joe II was honorably-retired, its basic purpose - making sure the launch escape and earth landing systems could protect the astronauts in either emergency or normal operations - accomplished.
In addition, the Apollo Project Office, which had been part of the MSC Flight Systems Division, would now report directly to the MSC Director and would be responsible for planning and directing all activities associated with the completion of the Apollo spacecraft project. Primary functions to be performed by the Office would include:
Letter contract No. NAS 9-150, authorizing work on the Apollo development program to begin on January 1, 1962, was signed by NASA and NAA on December 21. Under this contract, NAA was assigned the design and development of the command and service modules, the spacecraft adapter, associated ground support equipment, and spacecraft integration. Formal signing of the contract followed on December 31.
Pad aborts: PA-1, PA-2, etc.
Missions using Little Joe II launch vehicles: A-001, A-002, etc. Missions using Saturn C-1 launch vehicles: A-101, A-102, etc. Missions using Saturn C-1B launch vehicles: A-201, A-202, etc. Missions using Saturn C-5 launch vehicles: A-501, A-502, etc.
The 'A' denoted Apollo, the first digit stood for launch vehicle type or series, and the last two digits designated the order of Apollo spacecraft flights within a vehicle series.