Mercury Atlas 5 (MA-5) was the second and final orbital qualification flight of the Mercury systems prior to manned orbital flight. On-board was a 17 kg, five-year-old chimpanzee named Enos. Enos performed various psychomotor activities during the flight and was found to be in excellent physical condition following splashdown.
A metal chip in a fuel supply line caused a problem with the attitude control system, leading to the failure of a roll reaction jet. This resulted in the spacecraft drifting 30 degrees from nominal attitude at which point the automatic controls would bring the spacecraft back to nominal attitude. This entire process caused an extra pound of fuel to be consumed each orbit. In addition to this, a problem developed in an inverter to the electrical system, resulting in an temperature problem in the capsule. Both of these difficulties could have been corrected with a human pilot on-board, but ground control decided to shorten the mission and bring it down after the second orbit. (Three orbits had been planned.)
The spacecraft was recovered 410 km southeast of Bermuda by the USS Stormes one hour and fifteen minutes following splashdown. The spacecraft was hauled aboard the ship with its lanyard, cracking the window.
Enos died at Holloman Air Force Base, New Mexico, one year (November 4, 1962) following his historic flight. He had been under observation, day and night, for two months prior to his death with a case of shigella dysentary, a type resistant to antibiotics. His illness and death were unrelated to his orbital flight.