Mercury-Atlas 7

For the group of astronauts, see Mercury Seven.
Mercury-Atlas 7
Mission type Test flight
Operator NASA
Harvard designation 1962 Tau 1
SATCAT № 295
Mission duration 4 hours, 56 minutes, 5 seconds
Distance travelled 122,344 kilometers (76,021 mi)
Orbits completed 3
Spacecraft properties
Spacecraft Mercury No.18
Manufacturer McDonnell Aircraft
Launch mass 1,350.0 kilograms (2,976.2 lb)
Crew
Crew size 1
Members M. Scott Carpenter
Callsign Aurora 7
Start of mission
Launch date May 24, 1962, 12:45:16 (1962-05-24UTC12:45:16Z) UTC
Rocket Atlas LV-3B 107-D
Launch site Cape Canaveral LC-14
End of mission
Recovered by USS Intrepid (CV-11)[1]
Landing date May 24, 1962, 17:41:21 (1962-05-24UTC17:41:22Z) UTC
Orbital parameters
Reference system Geocentric
Regime Low Earth orbit
Perigee 154 kilometers (83 nmi)
Apogee 259 kilometers (140 nmi)
Inclination 32.5 degrees
Period 88.63 minutes
Epoch May 24, 1962[2]


Malcolm Scott Carpenter

Project Mercury
Manned missions
← Mercury-Atlas 6 Mercury-Atlas 8 →

Mercury-Atlas 7, launched May 24, 1962, was the fourth flight of Project Mercury, the first manned space program of the United States. The Mercury spacecraft, named Aurora 7, made three Earth orbits, piloted by astronaut Scott Carpenter. He was the sixth human and the fourth American in space.

A targeting error during reentry took the spacecraft 250 miles (about 400 km) off-course, delaying recovery of Carpenter and the spacecraft. The mission used Mercury spacecraft No. 18 and Atlas launch vehicle No. 107-D.

Crew

Position Astronaut
Pilot M. Scott Carpenter
Only spaceflight

Backup crew

Position Astronaut
Pilot Walter M. Schirra

Crew notes

The original prime crew for Mercury Atlas-7 was to have been Deke Slayton, with Schirra as his back-up. However Slayton was removed from all flight crew availability after the discovery of cardiac arrhythmia during a training run in the g-loading centrifuge. If Slayton had flown MA-7, his spacecraft would have been named Delta 7, as this would have been the fourth manned flight and Delta (Δ) is the fourth letter in the Greek alphabet.[3]

Mission parameters

Mission highlights

Mercury spacecraft No. 18 was delivered to Cape Canaveral, Florida on November 15, 1961. Atlas vehicle 107D was rolled out of the Convair factory in San Diego, California on February 25, 1962. It was delivered to Cape Canaveral on March 6, 1962.

During late 1961-early 1962, Convair developed a new, improved Atlas propulsion system which would use a hypergolic igniter instead of a pyrotechnic cartridge and baffled fuel injectors, removing the need for hold-down time on the pad to guard against combustion instability (the launch vehicle could be released as soon as full thrust was built up). NASA were not willing to jeopardize the flights of John Glenn or Scott Carpenter with an untested booster modification, so their launch vehicles retained the old-style propulsion system, the new one being flown on Wally Schirra's flight later in the year.

Atlas 107D incorporated two small changes from 109D (Glenn's booster), specifically removal of an insulation blanket from the common propellant tank bulkhead that was deemed unnecessary and booster jettison changed to one second earlier (T+130 seconds instead of 131 seconds). Launch vehicle performance was overall excellent with one small anomaly in that one of the sustainer hydraulic switches moved to the abort position at T+265 seconds because a faulty pressure transducer produced an erroneous reading indicating loss of sustainer engine hydraulic pressure. However, since another transducer indicated correct pressure levels until after SECO, the launch proceeded normally (both switches had to be tripped for the ASIS system to generate an abort signal). The Atlas's flight path was so accurate that Aurora 7 reached almost the exact orbital parameters planned for the mission. SECO occurred at T+309 seconds and capsule separation at T+312 seconds.

Carpenter was awakened at 1:15 AM on the morning of the flight and ate a breakfast of orange juice, filet mignon, eggs, toast, and coffee. Prior to insertion in the capsule, he was administered a hydration regimen of water, juice, coffee, and sweet tea.

MA-7 launch

The focus of Carpenter's five-hour mission was on science. The full flight plan included the first study of liquids in weightlessness, Earth photography, and an unsuccessful attempt to observe a flare fired from the ground. At dawn of the third and final orbit, Carpenter inadvertently bumped his hand against the inside wall of the cabin and solved a mystery from the previous flight. The resulting bright shower of particles outside the spacecraft - what John Glenn had called "fireflies" - turned out to be ice particles shaken loose from the spacecraft's exterior. Near the end of the flight, Carpenter found that by banging his hand against the wall of the capsule, he could shake more "fireflies" loose. At first, it was thought that the particles could be marker dye or shark repellant, both green-colored, however testing confirmed that neither of those were likely to escape from their packages in zero gravity.

Carpenter had solid food items for the first time (in the form of freeze-dried cubes in a plastic bag) instead of paste squeezed out of a tube, which produced problems with loose crumbs floating inside the cabin. The food cubes had been coated with an anti-crumbling agent, however they may have accidentally been crushed prior to launch, breaking the coating. Carpenter expressed concern about crumbs being sucked into ventilation intakes in the capsule, in addition a candy bar included in the food supply melted from high cabin temperatures (up to 102°F). By the end of the second orbit, he informed Mercury Control that most of the food was a mess and he would avoid touching it for the rest of the flight aside from taking a xylose capsule.

It was then suspected that the fireflies were either steam from the life support system turning into snow when exposed to open space or debris on the exterior of the spacecraft being shaken loose, however the former was considered the more probable explanation. Steam generated by the life support system formed condensation between the spacecraft bulkhead and the heat shield which then escaped into space and froze.

Like Glenn, Carpenter circled the Earth three times. Total time weightless 4 h 39 min 32 s. The performance of the Mercury spacecraft and Atlas launch vehicle was excellent in nearly every respect. All primary mission objectives were achieved. The single mission-critical malfunction which occurred involved a failure in the spacecraft pitch horizon scanner, a component of the automatic control system. This anomaly was adequately compensated for by the pilot in subsequent in-flight operations so that the success of the mission was not compromised. A modification of the spacecraft control-system thrust units was effective. Cabin and pressure-suit temperatures were high but not intolerable. Some uncertainties in the data telemetered from the bioinstrumentation prevailed at times during the flight; however, associated information was available which indicated continued well-being of the astronaut.

Equipment was included in the spacecraft which provided valuable scientific information; notably that regarding liquid behavior in a weightless state, identification of the airglow layer observed by Astronaut Glenn, and photography of terrestrial features and meteorological phenomena. An experiment which was to provide atmospheric drag and color visibility data in space through deployment of an inflatable sphere was partially successful. The flight further qualified the Mercury spacecraft systems for manned orbital operations and provided evidence for progressing into missions of extended duration and consequently more demanding systems requirements.

Partly because he had been distracted watching the fireflies and partly because of his busy schedule, and a malfunction of the automatic alignment system, Carpenter overshot his planned reentry mark and splashed down 250 miles (400 km) from target.

After several hours of frantic searching, Carpenter was located in an area northeast of Puerto Rico and taken aboard the aircraft carrier USS Intrepid. Other than slight exhaustion, he was in good health and spirits and postflight medical exams did not find any significant physical changes or anomalies.

NASA however were unhappy with the astronaut's performance due to his needlessly high expenditure of attitude control gas which resulted in reentry and landing taking place well off-course and so Carpenter was sidelined for future missions. He left the space program in 1964 to participate in the Navy's Sealab program.

Aurora 7 is displayed at the Museum of Science and Industry in Chicago, Illinois.[4]

Mercury-Atlas three-orbit flight events

T+ Time Event Description
T+00:00:00 Liftoff Mercury-Atlas lifts off, onboard clock starts.
T+00:00:02 Roll Program Mercury-Atlas rotates along its axis 2.5 deg/s from 30° to 0°.
T+00:00:16 Pitch Program Mercury-Atlas begins a 0.5 deg/s pitch from 90° to 0°.
T+00:00:30 Radio Guidance Lock General Electric-Burroughs guidance system locks onto radio transponder in Atlas booster to guide the vehicle until orbit insertion.
T+00:01:24 Max Q Maximum dynamic pressure ~980 lbf/ft² (47 kPa)
T+00:02:10 BECO Atlas Booster Engine Cutoff. Booster engines drop away.
T+00:02:33 Tower Jettison Escape Tower Jettison, no longer needed.
T+00:02:25 Atlas Pitchover After tower separation, vehicle pitches over further.
T+00:05:20 SECO Atlas Sustainer Engine Cutoff, spacecraft reaches orbit, velocity 17,547 mph (7,844 m/s).
T+00:05:24 Spacecraft Separation Posigrade rockets fire for 1 second giving 15 ft/s (5 m/s) separation.
T+00:05:25 5-Second Rate Damping ASCS damps spacecraft rates for 5 seconds in preparation for turnaround maneuver.
T+00:05:25 Turnaround Maneuver Spacecraft (ASCS) system rotates spacecraft 180 degrees, to heat shield forward attitude. Nose is pitched down 34 degrees to retro fire position.
T+00:05:30
T+04:30:00		 Orbital Operations Orbital operations and experiments for 3 orbits.
T+04:30:00 Retro Sequence Start Retrofire in 30 s; (ASCS) checks for proper retro attitude −34° pitch, 0° yaw, 0° roll.
T+04:30:30 Retrofire Three retro rockets fire for 10 seconds each. They are started at 5 second intervals, firing overlaps for a total of 20 seconds. Delta V of 550 ft/s (168 m/s) is taken off forward velocity.
T+04:31:00 Retract Periscope Periscope is automatically retracted in preparation for reentry.
T+04:31:50 Retro Pack Jettison One minute after retrofire retro pack is jettisoned, leaving heatshield clear.
T+04:33:00 Retro Attitude Maneuver (ASCS) orients spacecraft in 34° nose down pitch, 0° roll, 0° yaw.
T+04:40:30 0.05 G Maneuver (ASCS) detects beginning of reentry and rolls spacecraft at 10 degrees per second to stabilize spacecraft during reentry.
T+04:50:20 Drogue Parachute Deploy Drogue parachute deployed at 22,000 ft (6.7 km) slowing descent to 365 ft/s (111 m/s) and stabilizing spacecraft.
T+04:50:25 Snorkel Deploy Fresh air snorkel deploys at 20,000 ft (6 km) ECS switches to emergency oxygen rate to cool cabin.
T+04:51:55 Main Parachute Deploy Main parachute deploys at 10,000 ft (3 km). Descent rate slows to 30 ft/s (9 m/s).
T+04:52:00 Landing Bag Deploy Landing Bag Deploys, dropping heat shield down four feet (1.2 m).
T+04:52:30 Fuel Dump Remaining hydrogen peroxide fuel automatically dumped.
T+04:57:10 Splashdown Spacecraft lands in water.
T+04:57:10 Rescue Aids Deploy Rescue aid package deployed. The package includes green dye marker, recovery radio beacon, and whip antenna.

See also

References

 This article incorporates public domain material from websites or documents of the National Aeronautics and Space Administration.

  1. ↑ "This New Ocean - Ch13-9".
  2. ↑ McDowell, Jonathan. "SATCAT". Jonathan's Space Pages. Retrieved March 23, 2014.
  3. ↑ Evans, Ben. ""Change in Velocity": The Misfortune of Deke Slayton – Part 1". americaspace.com. AmericaSpace. Retrieved 23 June 2014.
  4. ↑ "Mercury MA-7". Encyclopedia Astronautica. Retrieved 2008-03-13.
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