Mercury-Atlas 5 - Launch and Orbit

Launch and Orbit

The flight used Mercury spacecraft # 9 and Atlas # 93-D. On February 24, 1961 spacecraft # 9 arrived at Cape Canaveral. It took forty weeks of preflight preparation. This was the longest preparation time in the Mercury program. The mission of spacecraft # 9 kept changing. It had been first been configured for a suborbital instrumented flight, then for a suborbital chimpanzee flight, then a three-orbit instrumented mission, and finally for the orbital flight that Enos flew.

MA-5 was planned as a close approximation of the upcoming MA-6 manned orbital mission. Mercury-Atlas 5 would be launched from Complex 14 at Cape Canaveral on a heading 72.51 degrees east of north. Orbital insertion of the Mercury spacecraft would occur 480 miles (770 km) from Cape Canaveral. The altitude would be 100 miles (160 km) and the speed would be 25,695 feet per second (7,832 m/s). Retrofire was planned to take place at 4 hours, 32 minutes, and 26 seconds after launch. The spacecraft would land 21 minutes and 49 seconds after retrofire. Reentry temperatures were expected to reach 3,000 °F (1,650 °C) on the heatshield, 2,000 °F (1,090 °C) on the antenna housing, 1,080 °F (582 °C) on the cylindrical section, and 1,260 °F (682 °C) on the conical section. The spent Atlas sustainer engine was expected to reenter the atmosphere after 9⅓ orbits.

On October 29, 1961, three chimps and 12 medical specialists moved into quarters at the Cape to prepare for the flight. The name given to "Enos," the chimp selected to fly the MA-5 mission, in Hebrew means "man". Enos's backups were (in order possible call-up) Duane, Jim, Rocky and Ham (the MR-2 veteran). Enos was from Cameroon, Africa, (originally called Chimp # 81), and was purchased by the USAF on April 3, 1960.

On November 29, 1961, about five hours before launch, Enos and his spacesuit-couch were inserted in the spacecraft. During the countdown, various holds took 2 hours and 38 minutes. Liftoff came at 15:08 UTC. The Atlas launched the MA-5 spacecraft into an orbit of 99 by 147 miles (159 by 237 km).

The turnaround and damping maneuver consumed 6 pounds (2.7 kg) of the 61.5 pounds (27.9 kg) of control fuel aboard. The spacecraft used less fuel than the MA-4 did during the same maneuver. MA-5 assumed its planned 34 degree orbital attitude and after that, through the first orbit the thrusters used only 1.5 pounds (0.68 kg) of fuel to maintain a correct position.

At the end of the first orbit, ground controllers noticed the capsule clock was 18 seconds too fast. As it passed over Cape Canaveral a command was sent to update the clock to the correct time. The Mercury Control Center at Cape Canaveral received information that all spacecraft systems were in good condition.

Then as the MA-5 passed over the Atlantic tracking ship at the beginning of the second orbit, indications were received that inverter temperatures were rising. The environmental control system malfunction was also confirmed by Canary Island trackers. Abnormal heating had occurred on earlier flights; in such cases, inverters had continued working or had been switched to standby. There was no alarm at Mercury Control. When the spacecraft reached Muchea, Australia, high thruster signals and capsule motion excursions were detected. Other data indicated that the 34 degree orbit mode was being maintained. When the MA-5 crossed the tracking station at Woomera, Australia, attitude control problems were not detected, so earlier reports were discounted.