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.

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.

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.

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.

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.

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."

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.

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.

[28] Concerns had been raised that the radiation belt produced in orbit by the recent Operation Dominic nuclear tests would be dangerous to crewed space missions, but an extensive study announced in early September declared that it was safe to fly.

[37] The "turtle club" was a recurrent joke among the astronaut corps; on being challenged with this question, the correct response was "you bet your sweet ass I am", with a failure to give the password being punishable by buying a round of drinks.

[40] Crossing over the eastern coast of Africa, he began to feel overheated; this problem was also apparent to the ground controllers, who were having a debate with the flight surgeon over whether it was safe to continue or if the mission should be ended after the first orbit.

[41] Schirra eventually stabilized the problem over time, slowly dialing the suit's control knob to a high cooling setting;[42] he compared the heat to that of "mowing a lawn in Texas".

[42] On the second orbit, he confirmed the existence of Glenn's "fireflies", the shower of small bright particles first reported on MA-6, and during the night section practiced yaw manoeuvres using first the Moon and then known stars as reference points.

The second proved difficult to work with, as the small windows of the Mercury capsule gave a very limited field of view, making it hard to identify constellations.

Travelling across the Pacific, he again fell back into automatic flight, chatting with Gus Grissom at the Hawaiian tracking station about the qualities of the manual control system.

He took advantage of this quiet period to test his spatial awareness and motor control, which he found was broadly unaffected by weightlessness, and to eat a light meal.

At Hawaii, he was given clearance for a full six-orbit mission, and as he crossed over towards California shut down the electrical power for a second period of drifting flight, during which he occupied himself taking photographs with the onboard camera.

[45] On the fourth orbit, drifting in an inverted spacecraft with the Earth 'above' him, Schirra continued his photography and attempted—unsuccessfully—to spot the Echo 1 satellite while passing over East Africa.

He used a small bungee cord exercise device for "a little bit of stretching", before dropping into manual attitude control, where he reported a sudden burst of oversteering and high fuel use.

Over the Atlantic he returned to observation and photography; he failed to spot the planned high-power light near Durban, in South Africa, due to cloud cover, but did make out the brightly lit city of Port Elizabeth.

[50] As the spacecraft continued towards re-entry after the de-orbit burn, Schirra used the high-power thrusters to put the capsule in the correct orientation, noting that the attitude control felt "sloppy".

[54] After doing this, examinations showed clear bruising on his hand from operating the heavy ejector switch, which he felt provided an important vindication for fellow pilot Gus Grissom's hatch expulsion accident during the Liberty Bell 7 mission.

Schirra remained aboard for three days of medical tests and debriefing before disembarking, while the spacecraft was offloaded at Midway Island and transferred to an aircraft for further transport.

[57] 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.

[14] The fuel-conservation measures were found to have worked particularly well, with even less fuel than anticipated being consumed; despite the technical changes, the official report gave full credit for this to the pilot.

[59] Analysis of the radiation-sensitive plates confirmed that there had been a very low radioactive flux inside the spacecraft,[60] and the six ablative materials tested were all deemed broadly satisfactory despite some difficulty comparing them to each other.

[63] Schirra noted that the sheer amount of cloud coverage, worldwide, could provide problems for future activity of this kind; however, Africa, and the south-western United States, were perfectly clear.

Postflight medical examination of Schirra disclosed nothing significant other than a degree of orthostatic hypotension caused by sitting inside the cramped capsule for hours.

[64] Schirra's post-flight report noted the "fireflies" seen on the previous two missions, and emphasized the remarkable visual effect of the thick band of the atmosphere visible around the horizon.

[75] The spacecraft was to be equipped with several cameras, building on Schirra's photographic work, though weight and power limitations did restrict the amount of scientific experiments that could be scheduled.