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Mercury program
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Mercury program

The Mercury program\ was the United States's first successful manned spaceflight program. At the time, it was also called Project Mercury. It ran from 1959 through 1963 with the goal of putting a man in orbit around the Earth. Early planning and research was carried out by NACA, while the program was officially carried out by the newly created NASA. The name Mercury comes from the Roman god (it is also the name of the innermost planet of the solar system).

The Mercury program cost $1.5 billion in 1994 dollars. See NASA Budget.


Mercury spacecraft (also called a capsule or space capsule) were very small one-man vehicles; it was said that the Mercury spacecraft were not ridden, they were worn. Only 12.13 cubic meters of volume, the Mercury capsule was barely big enough to include its pilot. Inside were 120 controls, 55 electrical switches, 30 fuses and 35 mechanical levers.

During the launch phase of the mission, the Mercury spacecraft and astronaut, were protected from launch vehicle failures by the Launch Escape System. The LES consisted of a solid fuel, 52,000 lbf (231 kN) thrust rocket mounted on a tower above the spacecraft. In the event of a launch abort, the LES fired for 1 second, pulling the Mercury spacecraft away from a defective launch vehicle. The spacecraft would then descend on its parachute recovery system. After booster engine cutoff (BECO), the LES was no longer needed and was separated from the spacecraft by a solid fuel, 800 lbf (3.6 kN) thrust jettison rocket, that fired for 1.5 seconds.

To separate the Mercury spacecraft from the launch vehicle, the spacecraft fired three small solid fuel, 400 lbf (1.8 kN) thrust rockets for 1 second. These rockets are called the Posigrade rockets.

The spacecraft had only attitude control thrusters. After orbit insertion and before retrofire they could not change their orbit. The spacecraft had three sets of control jets for each axis (yaw, pitch and roll), supplied from two separate fuel tanks. An automatic set of high and low powered jets and a set of manual jets, fueled from either the automatic tank or the manual tank. The pilot could use any one of the three thruster systems and fuel them from either of the two fuel tanks to provide spacecraft attitude control.

The Mercury spacecraft were designed to be totally controllable from the ground in the event that the space environment impaired the pilot's ability to function.

The spacecraft had three solid fuel, 1000 lbf (4.5 kN) thrust retrorockets that fired for 10 seconds each. One was sufficient to return the spacecraft to earth if the other two failed. The first retro was fired, five seconds later the second was fired (while the first was still firing). Five seconds after that, the third retro fires (while the second retro is still firing). This is called ripple firing.

There was a small metal flap at the nose of the spacecraft called the "spoiler". If the spacecraft started to reenter nose first (another stable reentry attitude for the capsule), airflow over the "spoiler" would flip the spacecraft around to the proper, heatshield first reentry attitude.

Suborbital Mercury capsules encountered lower reentry temperatures and used a beryllium heat-sink heat shields. Orbital missions encountered much higher atmospheric friction and temperatures during reentry and used ablative shields.

NASA ordered 20 production spacecraft, numbered 1 through 20, from McDonnell Aircraft Company, St. Louis, Missouri. Five of the twenty spacecraft were not flown. They were, Spacecraft # 10, 12, 15, 17, 19. Two unmanned spacecraft were destroyed during flights. They were Spacecraft # 3 and # 4. Spacecraft # 11 sank and was recovered from the bottom of the Atlantic Ocean after 38 years. Some spacecraft were modified after initial production (refurbished after launch abort, modified for longer missions, etc) and received a letter designation after their number, examples 2B, 15B.

A number of boilerplate spacecraft (prototype/replica spacecraft, made from non-flight materials or lacking production spacecraft systems and / or hardware) were also made by NASA and McDonnell Aircraft and used in numerous tests, including launches.


The Mercury program used three boosters: Little Joe, Redstone, and Atlas. Little Joe and Redstone were used for suborbital flights, Atlas for orbital ones. Starting in October, 1958, Jupiter missiles were also considered as suborbital launch vehicles for the Mercury program, but were cut from the program in July, 1959 due to budget constraints. The Atlas boosters required extra strengthening in order to handle the increased weight of the Mercury capsules beyond that of the nuclear warheads they were designed to carry. Little Joe was a solid-propellant booster designed specially for the Mercury program.


The first Americans to venture into space were drawn from a group of 110 military pilots chosen for their flight test experience and because they met certain physical requirements. Seven of those 110 became astronauts in April 1959. Six of the seven flew Mercury missions (Deke Slayton was removed from flight status due to a heart condition). Beginning with Alan Shepard's Freedom 7 flight, the astronauts named their own spacecraft, and all added 7 to the name to acknowledge the teamwork of their fellow astronauts

Mercury had seven prime astronauts, all former military test pilots, known as the Mercury 7. NASA announced the selection of these astronauts on April 9, 1959.


The program included 20 unmanned launches. Not all of these were intended to reach space and not all were successful in completing their objectives. The fifth flight in 1959 launched a monkey named Sam into space. Other non-human space-farers were Miss Sam and Ham and Enos, both chimpanzees.

The Mercury program used the following rockets:


Primate Flights




(Mercury 5 was an orbital flight "manned" by Enos the chimp. See "Mercury-Atlas 5" above.)

Manned Mercury launches

Mercury Flight insignias

Flight patches are available to the public that purport to be patches from various Mercury missions. In reality, these patches were designed long after the Mercury program ended by private entrepreneurs. When genuine flight patches were created by crews in the Gemini program, this caused a public demand for Mercury flight patches, which was filled by these private entrepreneurs. The only patches the Mercury astronauts wore were the NASA logo and a name tag. Each manned Mercury spacecraft, however, was decorated with a flight insignia. These are the genuine Mercury flight insignias. They were approved by the Mercury astronauts and painted on their spacecraft. Each flight insignia is illustrated in the photo above.

Follow on programs

Gemini program Apollo program Space Shuttle program


The Mercury astronauts trained, in part, at Langley Air Force Base in Hampton, Virginia. In Hampton, several bridges throughout the city bear the name of the Mercury astronauts, and the main route in the city is named Mercury Boulevard, honoring the Mercury program.

Further reading

See also

External links