Sigma 7

The words

1. Coolant Valve

   Schirra’s suit became too warm early in the flight. He brought the temperature under control; postflight investigators found that dried lubricant had restricted flow through a coolant valve.

   pp. 476, 484 · NASA history: Schirra’s suit and hatch (opens a new tab)

2. Dosimeter

   An instrument that measures accumulated exposure to radiation.

   Sigma 7 carried several dosimeters to record Schirra’s radiation exposure. Some could be read during flight, while others were placed in his helmet liner and clothing.

   pp. 83–84, Special Studies · NASA report: tests and Schirra’s account (opens a new tab)

3. Free Drift

   Flight without active control of a spacecraft’s orientation.

   Schirra used free drift for part of Sigma 7’s flight to conserve steering fuel. It also gave him time to observe Earth and take photographs.

   NASA: Sigma 7’s flight and recovery (opens a new tab)

4. Fuel Economy

   Schirra’s smooth maneuvers and careful use of the steering controls kept fuel consumption below the flight plan’s prediction. The results helped NASA assess Mercury’s ability to make longer flights.

   pp. 95–96 · NASA report: tests and Schirra’s account (opens a new tab)

5. Greek Letter

   The capital Greek letter sigma, Σ, is used for summation in mathematics. Schirra chose it as an engineering symbol for his Mercury flight.

   NASA: Sigma 7’s flight and recovery (opens a new tab)

6. Hackensack

   Hackensack, New Jersey, was Schirra’s birthplace. After Sigma 7, welcome-home celebrations took him through Hackensack and his hometown of Oradell.

   NASA: Sigma 7’s flight and recovery (opens a new tab)

7. Hasselblad

   Schirra carried a modified Hasselblad 500C camera aboard Sigma 7. The photographs he brought back began a long association between Hasselblad cameras and American spaceflight.

   Did you know?

   The camera began as a standard consumer model. Its black finish helped reduce reflections when Schirra photographed the view from orbit.

   NASA Spinoff: Schirra’s Hasselblad (opens a new tab)

8. Pacific Ocean

   Sigma 7 became the first crewed Mercury mission to splash down in the Pacific Ocean, where Kearsarge waited northeast of Midway Island.

   NASA: Sigma 7’s flight and recovery (opens a new tab)

9. Plunger

   Once Sigma 7 was aboard Kearsarge, Schirra used the plunger that released its explosive side hatch. The action left a superficial injury on his hand.

   p. 484 · NASA history: Schirra’s suit and hatch (opens a new tab)

10. Sigma

    Sigma 7 was the capsule flown by Schirra on Mercury-Atlas 8. The number honored the seven astronauts selected for Project Mercury.

    Did you know?

    During launch preparations, Schirra found a dummy ignition key in his capsule. He recalled it as one of the small gestures from people preparing his flight.

    NASA report: tests and Schirra’s account (opens a new tab) · NASA: Sigma 7 mission record (opens a new tab)

11. Six Orbits

    Schirra completed six Earth orbits on October 3, 1962. The mission tested Mercury’s spacecraft, tracking network and support teams over a longer flight than the earlier three-orbit missions.

    NASA: Sigma 7 mission record (opens a new tab)

12. Summation

    Schirra said Sigma represented the combined efforts of the Mercury team. The name acknowledged the many people whose work went into the spacecraft and mission.

    p. 96, Pilot’s Flight Report · NASA report: tests and Schirra’s account (opens a new tab)

13. USS Kearsarge

    USS Kearsarge recovered Sigma 7 with Schirra still inside. The carrier then provided a place for his medical examinations and technical debriefings as it sailed toward Hawaii.

    NASA: Sigma 7’s flight and recovery (opens a new tab)

14. Wally Schirra

    Schirra piloted Sigma 7 and later commanded Gemini 6A and Apollo 7, flying in all three of the early American human-spaceflight programs.

    NASA: Schirra’s three spaceflights (opens a new tab)

15. Whale Boat

    A motor whaleboat from Kearsarge carried a line to Sigma 7. Schirra remained inside the capsule while sailors prepared to hoist it onto the carrier.

    NASA: Sigma 7’s flight and recovery (opens a new tab)