In the Apollo Program, the Saturn V carried men to the moon. The Saturn IB brought men into earth orbit, and the Saturn I brought payload into orbit. There was a fourth booster, essential to the program, that not as many people talk about - Little Joe II. This rocket was designed to test the Launch Escape System.
The Launch Escape System consisted of an escape tower fixed to the top of the command module during launch. If the launch vehicle started to malfunction, e.g. blow up, the launch tower would fire a solid rocket motor, which pulled the command module away from the failing rocket. There were three wires that ran the entire length of the Saturn V booster. If two of the three wires were broken, it told the computer that the launch vehicle was breaking up, and the escape tower would fire.
To test this system, NASA performed a series of “Apollo Abort Tests” at White Sands Missile Range in New Mexico, because at the time, the launch schedule at Cape Canaveral was too busy. They tested in two ways; by firing the escape tower from the ground, or firing it from an airborne Little Joe II rocket. The command modules used in these tests were boilerplate test articles, which simulated the shape and weight of a flightworthy command module.
On the third, of four total, test flight of the escape system, Little Joe II started rolling uncontrollably during launch. In the documentary film, “Moon Machines”, Dale Myers, North American Aviation Command & Service Module Program Manager remarked, "This time, they made a little mistake in how they hooked up the roll gyros, and the vehicle started to roll." The rolling accelerated to 335 degrees per second, which caused Little Joe II to break up in flight. Myers said, "When it broke, it broke the link on the escape rocket. The escape rocket fired, and pulled the command module right off the top." After the escape tower did its job, the parachutes deployed successfully, and the command module made a safe landing. "It was a perfectly successful flight; a very well-instrumented flight. It gave us all the data we needed about the launch escape system, but the (launch) vehicle had failed in the process."
This Little Joe II stands on display next to a beautiful Mercury-Redstone booster in Rocket Park at NASA Johnson Space Center in Houston, Texas.