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. In February 1962, the first draft planning began for MA-8, the third orbital mission, with a goal of "six or seven" orbits, as an intermediate step towards a day-long 18-orbit flight. The decision to move to six orbits rather than seven was driven by the mission rules on contingency recovery operations; a seventh orbit would have required significant additional recovery forces to be able to reach the capsule anywhere on its trajectory within eighteen hours. The six-orbit profile had other effects on the recovery plans; the optimum recovery point was moved to the Pacific Ocean, rather than the Atlantic.
On March 15, 1962, NASA announced that Slayton was medically unfit and would be replaced by Scott Carpenter as the prime crew for the MA-7 mission. The decision to replace him with Carpenter, rather than his official backup Schirra, was justified by the large amount of training Carpenter had managed while preparing for the long-delayed MA-6 mission. After the success of the MA-6 and MA-7 missions, both of three orbits, pressure began to mount to fly an extended mission. On June 27, 1962, NASA first announced its plan for the upcoming MA-8 mission, which would last for "as many as six" orbits. Schirra was named as the prime crew for MA-8, with Gordon Cooper as his backup, repeating the backup-one fly-one pattern set by the previous two missions. The pattern would be repeated for MA-9, flown by Cooper, and the planned but cancelled MA-10, which would have been flown by Cooper's backup, Alan Shepard.
The Soviet Union had not flown any further flights by the time MA-7 landed, putting both sides of the Space Race even at two orbital flights each. While the Soviets had flown for longer, the Mercury program was gaining momentum, with a six-orbit mission currently planned and press speculation about a one-day mission. However, in mid-August, the Soviet Union launched two orbital missions, Vostok 3 and Vostok 4, within a day of each other. The two craft were in intersecting orbits, but despite much speculation did not attempt to rendezvous; they completed missions of 64 and 48 orbits respectively, just under four and three days, landing within a few minutes of each other on August 15. This was far ahead of anything currently planned for Mercury, and NASA quickly considered the prospect of modifying a capsule to have an active manoeuvring and rendezvous capability, using technology being developed for the Gemini program. However, after examining the time and safety implications of this proposal, it was decided to abandon the idea and continue with the planned six-orbit mission.
Mission objectives
The original MA-8 flight plan was issued on July 27; although it was revised slightly in August and September, it remained broadly unchanged until launch. This was an improvement on the situation with MA-7, which had had frequent and extensive alterations, making it difficult for the pilot to train efficiently. The aim was for the flight to be an engineering-oriented mission, focusing on the operation of the spacecraft rather than on scientific experimentation, to help pave the way for a future long-duration mission.
The mission objectives involved evaluating the performance of the spacecraft over six orbits, as well as the effect of prolonged microgravity on the pilot. The specific spacecraft systems would also be evaluated and tested, and the worldwide tracking and communications network would be tested to see how well it would stand up in an extended mission. 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.
Four non-engineering scientific experiments were planned, two requiring the active involvement of the astronaut and two completely passive. The first involved the astronaut watching for four high-powered flares while passing over Woomera, Australia, and for a xenon arc lamp while passing over Durban, South Africa. The second involved two sets of photographs to be taken using a 70mm Hasselblad camera as well as conventional color photographs of the Earth from orbit. Focusing on geological features and cloud patterns, photographs were to be taken through a set of colored filters provided by the U. S. Weather Bureau. The latter were intended to help calibrate the spectral reflectivity of clouds and surface features, which in turn would help improve the cameras on future weather satellites. The passive experimentation packages were two sets of radiation-sensitive photographic films, from the Goddard Space Flight Center and the U. S. Navy School of Aviation Medicine, and a set of eight different experimental ablative materials attached to the outside of the spacecraft to test their performance during re-entry.
Naming
For his spacecraft, Schirra originally favored the name Phoenix, while his wife championed Pioneer. He ultimately dubbed the vessel Sigma 7 because, as the mathematical symbol for the summation of elements, the name reflected that "the flight was the sum of the efforts and energies of a lot of people."
The seven appended to the end was in honor of the seven original astronauts selected for Mercury, a tradition inadvertently started by prior Mercury pilot, Alan Shepard, who incorporated the seven in "Freedom 7" as his spacecraft was factory model no. 7. The other astronauts liked the symbolism, and so each added 7 to their spacecraft names as well.. The nose art with the sigma logo was painted by Cece Bibby.
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. A number of modifications were made to the reaction control system, and the communications equipment was upgraded.
The Atlas booster (Vehicle 113D) had been modified since the previous flight, and now included baffled fuel injectors and a new hypergolic fuel igniter instead of the original pyrotechnic igniter. This would eliminate problems with combustion instability and allow the booster to be released immediately upon attaining full thrust instead of being held on the pad for a few moments. There were considerable delays getting the vehicle ready for flight. It was supposed to be shipped to Cape Canaveral in July, but after failing the factory composite test at Convair, the planned delivery of the Atlas was delayed a month.
Mission preparation
The capsule built for the mission, Mercury Spacecraft No. 16, had been delivered to Cape Canaveral on January 16, 1962. 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. After the delayed arrival of the booster at the Cape, the Air Force then revealed that two recent static firings of MA-3 engines had suffered turbopump failures, and that the explosion of Atlas 11F one second after liftoff in April had been traced to a malfunction of the sustainer turbopump. All of these failures had occurred while the sustainer HS valve was moving to the open position and while running untested hardware modifications. The Air Force recommended that NASA conduct a static firing test of 113D just to be on the safe side. On September 6, the tests were scheduled to continue until September 24, which allowed for a probable launch on October 3. A static firing test on the pad would expose the sustainer turbopump to the failure mode in question. In the meantime, a fuel leak caused by a faulty weld in a piece of plumbing caused further delays. The static firing test was carried out on September 8 and the booster reported as ready for assembly on September 18. The Flight Safety Review Board met on September 24 to go over the fifteen Atlas launches since Carpenter's flight, which included three failures. Atlas 67E malfunctioned due to a random quality control fault that would be avoided with the tightly managed Mercury program, and Atlas 145D had sent Mariner 1 into the Atlantic Ocean thanks to a guidance system problem, which was of no concern to Mercury as its boosters used a different model of guidance system. Atlas 57F went off-course and was destroyed by RSO action, but more than a month later, the Air Force had not yet announced any cause of the failure.