Imagine: The United States is technologically behind in a race with its adversary, the Soviet Union, to explore the new territory of outer space. You have been chosen from a pool of 110 qualified pilots to be one of seven men to go into outer space. You have trained long hours, both physically and mentally, for this mission. You have watched the explosions of many of the same kind of rockets that will be carrying you into space. Now you sit atop one of those rockets filled with explosive rocket fuel. Mission Control is counting down. The world is watching you on television. In minutes, you will be either in outer space or dead from a massive explosion. There is no turning back. The fate of the fledgling space program is riding on you and the success of your mission.


Photo courtesy NASA

This was the situation on May 5, 1961, when astronaut Alan B. Shepard, Jr. stepped into his Freedom 7 capsule and became the first American to go into outer space. Freedom 7 was the first flight of Project Mercury, America's premiere space program.

If you did not live through this time, it may be difficult to understand the significance of this program and these men. America was in the midst of the Cold War with the Soviet Union (Russians), and the two countries were racing for dominance of outer space. The Soviets were the first to launch a satellite into outer space, Sputnik. Although America was behind in the race, the accomplishments of Project Mercury set the stage for America's later moon landings and eventual domination of space exploration.

In this edition of How Stuff Works, we will relive history as we look at Project Mercury -- the spacecraft, the missions and the people who made it all possible.

The Right Stuff
In 1958, the early days of Project Mercury, it was not clear what type of person could be an astronaut. Several types were considered, including stunt men, circus performers, swimmers and race-car drivers. President Eisenhower decided that the astronauts should be military pilots, particularly test pilots. Furthermore, they should be college-educated, family-oriented, of average height and build, in excellent health and dedicated to flying advanced aircraft.

Astronaut Selection
For a good depiction of the rigors of astronaut selection and training, read or watch "The Right Stuff."
NASA officials began screening the service records of military flyers. They narrowed the field of 508 down to 110 pilots from the Marines, Navy and Air Force (no Army pilots were invited because none had graduated from a test-pilot school). Of these 110 men, 69 reported to Washington, D.C. in February 1959 for the screening tests, which included interviews (technical and psychological), written tests and medical examinations. Of these 69 men, 32 were selected and agreed to undergo further testing in Ohio and New Mexico. These tests included extensive medical and psychological evaluations, as well as stress tests in conditions such as high G-forces, vibration and isolation.


Photo courtesy NASA
America's Mercury astronauts
Top row (L-R): Shepard, Grissom, Cooper
Bottom row (L-R): Schirra, Slayton, Glenn, Carpenter

On April 9, 1959, at a press conference in Washington, D.C., NASA introduced the Project Mercury astronauts:

  • Lieutenant Malcolm S. (Scott) Carpenter (U.S. Navy)
  • Captain Leroy G. (Gordon) Cooper (U.S. Air Force)
  • Lieutenant Colonel John H. Glenn (U.S. Marine Corps)
  • Captain Virgil I. (Gus) Grissom (U.S. Air Force)
  • Lieutenant Commander Walter M. Schirra (U.S. Navy)
  • Lieutenant Commander Alan Shepard (U.S. Navy)
  • Captain Donald K. (Deke) Slayton (U.S. Air Force)
Most of the Mercury astronauts were veterans of World War II and/or the Korean War. They had extensive flight experience and were in excellent health.


Photo courtesy NASA
Mercury astronauts during desert survival training
After selection, the crew underwent several years of training in the Mercury-spacecraft systems, as well as flight training, continuous medical evaluations and survival training in many environments (such as desert, jungle and ocean). They worked hard, played hard and endured many hours of separation from their families, each crew member vying to become the first American in outer space.

The astronauts became celebrities as the press and public focused on them. They made public appearances for NASA to promote the fledgling space program, and they used the public attention to increase their influence in the program.

In addition to training and public relations, they consulted on the development of the Mercury spacecraft. Despite objections from the engineers who designed the spacecraft, the astronauts insisted on having a window, manual re-entry thruster controls and an escape hatch with explosive bolts -- they wanted the ability to actively fly the spacecraft and, if necessary, escape from it. They were pilots, and the thought of merely riding in a totally automated spacecraft went against their nature.

After years of preparation, the initial flight assignments were made: Shepard would be the first American in space, followed by Grissom and then Glenn.

The Spacecraft
The Mercury spacecraft was designed to carry one man alone into outer space and return him safely. It was cone-shaped -- 6.8 feet (2 m) long, 6.2 feet (1.9 m) in diameter at the base -- with a small cylinder on top. The spacecraft weighed between 2,300 and 3,000 pounds (1,043 to 1,360 kg), depending on the mission, and sat on top of a booster rocket. Atop the spacecraft, there was an emergency escape tower that could lift the capsule off the booster, raising it to an altitude where the parachutes could open and return the capsule and astronaut to the ground at a safe distance from the launch pad. On the blunt end of the spacecraft there was a heat shield, which protected the capsule from the heat of re-entry, and a retro-pack, which were small rocket thrusters that slowed the spacecraft down for re-entry.



Photo courtesy NASA
Mercury spacecraft: exterior view (top), cutaway view (bottom)


Photo courtesy NASA
Spacecraft interior (looking forward)
Like any spacecraft, Mercury had to provide the following systems:

  • Life support - Three, spherical oxygen bottles provided a pure oxygen atmosphere in the capsule. Lithium-hydroxide canisters removed the exhaled carbon dioxide. Blowers and fans were used to circulate the air and cool the astronaut. Insulation and double walls helped keep the cabin at a liveable temperature. Drinking water was supplied on-board. A urine-collection system was integrated into the capsule. The astronaut wore a pressure suit and helmet for insulation and protection against cabin-depressurization.

  • Power - Electrical power was supplied by various combinations of 1,500-watt and 3,000-watt batteries. Water was used to cool the various electrical systems.

  • Radio/tracking communications - High-frequency (HF) and ultra-high-frequency (UHF) transmitters and receivers were used to relay voices, telemetry data and navigational data to and from the ground. Antennae and recovery beacons were located in the cone of the spacecraft. A television camera was located in the cabin to monitor the astronaut.

  • Maneuvering - Maneuvering in the pitch, roll and yaw directions (x, y, z axes) was accomplished by reaction-control thrusters that used pressurized hydrogen-peroxide fuel. The reaction-control thrusters could be controlled either automatically or manually. Three solid rocket engines (posigrade motors) were used to separate the spacecraft from the booster, and three more solid rocket engines (retrograde motors) were used to slow the spacecraft for re-entry into Earth's atmosphere.


    Photo courtesy NASA
    Landing-bag deployment

  • Re-entry - The spacecraft had an ablative heat shield to protect it from the temperature during re-entry -- about 2,000 degrees Fahrenheit (1,093 degrees Celsius). The structure of the shield was honeycombed aluminum with many layers of glass-fiber material. As the spacecraft descended, the material of the heat shield boiled away, taking the heat away with it. Double walls and insulating material kept the cabin temperature liveable (but still hot).

  • Landing - After re-entry, a small, drogue parachute was deployed at 21,000 ft (6,405 m) to begin to slow the spacecraft for landing. The main parachute was deployed at 10,000 ft (3,050 m), further slowing the spacecraft in preparation for its water landing. Just prior to hitting the water, a landing bag inflated from behind the heat shield to reduce the force of impact. Upon landing, additional bags inflated around the nose of the craft to keep the capsule upright in the water, and the parachutes were released. Once the recovery helicopter hooked onto the spacecraft, the astronaut blew the escape hatch to exit the capsule. It was also possible to exit the capsule through the nose by crawling behind the instrument panel and out through the nose cone.

The Mercury spacecraft had two boosters, the Redstone and Atlas rockets. Both rockets were ballistic missiles that were modified to carry spacecraft payloads instead of warheads.


Photo courtesy NASA
Mercury boosters: Redstone (left) and Atlas (right)

NASA encountered several failures of the early Redstone and Atlas launches, with the launch vehicles exploding at various stages. When the problems were fixed, unmanned and animal launch tests were conducted. The Redstone was used on the first two manned suborbital flights, but it was not as powerful as the Atlas. The Atlas was used to place men into orbit on the remaining Mercury flights.

Shepard's Freedom 7 Mission

Photo courtesy NASA
Alan Shepard, the first American in outer space
The goals of the Mercury space program were to orbit a manned spacecraft around the Earth, investigate man's ability to function in space and recover the man and spacecraft safely. By 1961, the race to accomplish these goals was in high gear because of the Cold War. The astronauts had been selected and trained, and the spacecraft built and tested. NASA officials, particularly the lead rocket scientist Wernher Von Braun, insisted that the booster/spacecraft be tested by flying chimpanzees into outer space. Two such flights occurred before it was certified as ready for a manned mission. While these tests were being conducted, the Soviets launched Cosmonaut Yuri Gagarin into Earth orbit. In April 1961, Gagarin became the first man to reach outer space. NASA was criticized by the press and public, who felt that the United States could have put a man in outer space before the Soviets. The Soviet achievement placed the United States far behind in the space race. NASA relied on astronaut Alan Shepard to put America back in the game.

On May 5, 1961, Alan Shepard climbed aboard his Mercury spacecraft, called Freedom 7. His mission was to fly into outer space and return safely in a sub-orbital flight that would last about 15 minutes. There were numerous delays in the countdown, and Shepard was on the pad for hours. Finally, at 9:43 AM, Alan Shepard was launched into outer space. Shepard reached an altitude of 116 miles (187 km) and landed 303 miles (488 km) down-range from Cape Canaveral, where he was recovered by the aircraft carrier Lake Champlain. He reached a peak velocity of 5,134 miles per hour (8,260 kph) and experienced a force as high as 11 Gs (11 times the acceleration due to gravity) upon re-entry. The flight lasted 15 minutes and 28 seconds. Unlike Gagarin, Shepard was able to maneuver the craft during flight. Shepard's historic flight launched the U.S. space program, ultimately, to the moon.



Photo courtesy NASA
Alan Shepard during recovery (top) and on-board the carrier after his flight

Alan Shepard was later grounded due to an inner-ear disorder. He worked in the Astronaut Office for many years before having surgery to correct his ear problem. He moved on to command the Apollo-14 mission and walk on the moon. He was the only Mercury astronaut to go to the moon, as well as the only man (to this day) to golf on the moon. Alan Shepard died in 1998.

Shepard's groundbreaking flight was followed by another sub-orbital flight by Gus Grissom and four orbital flights by Glenn, Carpenter, Schirra and Cooper (to learn about these subsequent Mercury missions, see How Project Mercury Missions Worked). The men and missions of Project Mercury established that America could place a person in orbit, that he could survive in space and that he could return successfully. Project Mercury established a foothold for America in the space race and paved the way for Projects Gemini and Apollo. As of 2001, Mercury astronauts Glenn, Carpenter, Schirra, and Cooper are still alive, although retired from space endeavors. The pioneering contributions of these men to aviation and space exploration will always be remembered.

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