Chimpanzee Ham's space mission in 1961

In 1961, the chimpanzee Ham was launched aboard the Mercury-Redstone 2 mission from Launch Complex 5 at Cape Canaveral as part of NASA's efforts to test spacecraft systems before human spaceflight.

Mission exceeded expectations

The mission exceeded its planned parameters, reaching an altitude of 253 kilometers instead of the intended 185 kilometers, and achieving a speed of 9,400 kilometers per hour, much higher than the target of 7,000 kilometers per hour. The flight also lasted longer than expected.

Technical issues caused overperformance

The overperformance was due to a launcher overperformance and excessive thrust from the ejection rocket. A thrust regulator operated above its nominal level, and a fuel mixture ratio servo valve remained stuck in the open position, leading to early depletion of liquid oxygen.

Cabin pressure drop during flight

At two minutes and eighteen seconds into the flight, the pressure inside the capsule dropped dramatically due to a loose pin on an air intake valve. However, Ham was protected by a pressurized seat, which prevented any harm from the depressurization.

Capsule recovered with seawater

The capsule splashed down 679 kilometers from the launchpad, far from the planned recovery area. When recovered by the USS Donner, it contained about 45 centimeters of seawater, which had entered through damaged openings but did not reach Ham’s sealed chamber.

Legacy of the mission

The mission exposed critical engineering flaws, prompting revisions to the thrust regulator and speed integrator. Ham, who died in 1983, was honored with a historical plaque in 2026. The mission contributed to the success of later crewed flights, including Alan Shepard's historic flight.