Mercury-Atlas 8 (MA-8) was the fifth United States crewed space mission, part of NASA's Mercury program. Astronaut Walter M. Schirra Jr., orbited the Earth six times in the Sigma 7 spacecraft on October 3, 1962, in a nine-hour flight focused mainly on technical evaluation rather than on scientific experimentation. This was the longest U.S. crewed orbital flight yet achieved in the Space Race, though well behind the several-day record set by the Soviet Vostok 3 earlier in the year. It confirmed the Mercury spacecraft's durability ahead of the one-day Mercury-Atlas 9 mission that followed in 1963.
Planning began for the third U.S. orbital mission in February 1962, aiming for a six-or-seven-orbit flight to build on the previous three-orbit missions. NASA officially announced the mission on June 27, and the flight plan was finalized in late July. The mission focused on engineering tests rather than on scientific experimentation. The mission finally launched on the morning of October 3, having been delayed two weeks because of problems with the Atlas booster. A series of minor booster problems during launch and a faulty temperature controller in Schirra's pressure suit were the only technical problems noted during the flight. The spacecraft orbited in both automated and passive flight modes for prolonged periods while the pilot monitored it and carried out some minor scientific experiments. After six orbits, the capsule landed in the Pacific Ocean half a mile from the recovery carrier, and was hoisted aboard for Schirra to disembark.
The scientific results of the mission were mixed. The astronaut returned healthy after nine hours of confinement in a low-gravity environment. Observation of the Earth's surface proved unproductive, however, because of heavy cloud cover and bad photographic exposures. The public and political reaction was muted compared with that of earlier missions, as the Cuban Missile Crisis soon eclipsed the Space Race in the news. The mission was a technical success: all the engineering objectives were completed without significant malfunctions, and the spacecraft used even less fuel than expected. This confirmed the capabilities of the Mercury spacecraft and allowed NASA to plan with confidence for a day-long flight, MA-9, which had been an early goal of the Mercury program.
Mission parameters
- Mass:
- Perigee: 156 km
- Apogee: 285 km
- Inclination: 32.5°
- Period: 88.91 min
Background
By 1962, both the United States and the Soviet Union had flown two solo spaceflights in the Space Race. There was a widespread perception, however, that the United States was falling behind; its two missions had been suborbital and had lasted only a few minutes. The Soviet missions had both orbited the Earth, and the second, Vostok 2, had remained in orbit for a full day. Using the new high-powered Atlas booster, the coming orbital Mercury missions were expected to reduce the gap between the two countries.
NASA announced the first two orbital missions at the end of November 1961, shortly after the Mercury-Atlas 5 (MA-5) test flight, which had carried a chimpanzee and twice orbited the Earth. MA-6 was planned as the first orbital flight, with John Glenn as the primary crew and Scott Carpenter as his backup. The follow-up mission, MA-7, was to be crewed by Deke Slayton, with Wally Schirra as his backup. The flight control experiments included manually turning the spacecraft around, yaw and pitch manoeuvres to determine how easy it was to control the spacecraft attitude, realignment of the onboard gyroscopes in flight, and leaving the spacecraft to drift on-orbit.
Spacecraft modifications
The spacecraft and booster were almost identical to those used on the two preceding Mercury orbital flights. The spacecraft had heating blankets removed from the retrorocket motors, to save weight, and a SOFAR bomb was added. This would be ejected at the time the main parachute was deployed, and would help recovery crews find the spacecraft after it landed. The Atlas LV-3B booster assigned to the mission, No. 113-D, was accepted by NASA at the Convair plant on July 27 and delivered on August 8.
Because the Atlas was flying on a slightly lofted trajectory, the booster engines cut off 2 seconds earlier than planned, but the sustainer engine burned for about 10 seconds longer than intended, giving an extra of velocity and putting the spacecraft in a slightly higher orbit than planned.
Post-flight
The post-flight analysis reported no major malfunctions—the only troublesome anomaly being the suit temperature controls— and all the engineering objectives of the mission were deemed successfully completed.
The success of MA-8 made the preparation for MA-9 "considerably easier", Since the recent relocation of the Astronaut Hall of Fame to the Kennedy Space Center Visitor Complex, Sigma 7 has most recently been placed on display at the complex's new Heroes and Legends Hall.