|Goal||Manned Orbital flight|
US flight firsts:
|Rockets||Atlas D, Redstone and Little Joe|
|Contractor||McDonnell Aircraft (spacecraft)|
|Cost||$1.73 billion (current prices)|
|Followers||Gemini and Apollo|
|Rival||Vostok program (Soviet)|
Project Mercury was the first human spaceflight program of the United States, running from 1959 through 1963. An early highlight of the Space Race, its goal was to put a solo human into Earth orbit and return the person safely, ideally before the Soviet Union. Taken over from the US Air Force by the newly created civilian space agency NASA, it spanned twenty unmanned developmental missions involving test animals, and successful missions completed by six of the seven Mercury astronauts.
The Space Race had begun with the 1957 launch of the Soviet satellite Sputnik 1. This came as a shock to the American public, and led to the creation of NASA to expedite existing U.S. space exploration efforts, and place most of them under civilian control. After the successful launch of the Explorer 1 satellite in 1958, manned spaceflight became the next goal.
The Soviet Union put the first human, cosmonaut Yuri Gagarin, into a single orbit aboard Vostok 1 in April 1961. Shortly after this, on May 5, the US launched its first astronaut, Alan Shepard, on a suborbital flight. Soviet Gherman Titov followed with a day-long orbital flight in August, 1961. The U.S. reached its orbital goal on February 20, 1962, when John Glenn made three orbits around the Earth. When Mercury ended in May 1963, both nations had sent six people into space, but the US was still behind the Soviets in terms of total time spent in space.
The cone-shaped Mercury capsule was produced by McDonnell Aircraft, and carried supplies of water, food and oxygen for about one day in a pressurized cabin. Mercury flights were launched from Cape Canaveral, Florida, on modified Redstone and Atlas D missiles. The capsule was fitted with an escape rocket to carry it safely away from the launch rocket in case of a failure of the latter. The flight was designed to be controlled from the ground via the Manned Space Flight Network, a system of tracking and communications stations; back-up controls were outfitted on board. Small retrorockets were used to bring the spacecraft out of its orbit, after which an ablative heat shield protected the spacecraft from the heat of atmospheric reentry. Finally, a parachute slowed the craft for a water landing. Both astronaut and capsule were recovered by helicopters deployed from the nearest suitable U.S. Navy ship.
The program took its name from the wing-footed, fleet god of travel in Roman mythology, and is estimated to have cost $1.73 billion (current prices) and to have involved the work of 2 million people. The astronauts were collectively known as the "Mercury Seven", and each spacecraft was given a name ending with a "7" by its pilot.
After a slow start riddled with humiliating mistakes, the Mercury Project gained popularity, its missions followed by millions on radio and TV around the world. Its success laid the groundwork for Project Gemini, which carried two astronauts in each capsule and perfected space docking maneuvers essential for lunar travel, and the subsequent Apollo Moon-landing program announced a few weeks after the first manned Mercury flight.
- 1 Creation
- 2 Spacecraft
- 3 Launch vehicles
- 4 Astronauts
- 5 Mission profile
- 6 Flights
- 7 Impact and legacy
- 8 Graphics
- 9 Notes
- 10 References
- 11 Bibliography
- 12 External links
Project Mercury was officially approved on October 7, 1958 and publicly announced on December 17. Originally called Project Astronaut, President Dwight Eisenhower felt that gave too much attention to the pilot. Instead, the name Mercury was chosen from classical mythology, which had already lent names to rockets like the Greek Atlas and Roman Jupiter for the SM-65 and PGM-19 missiles. It absorbed military projects with the same aim, such as the Air Force Man In Space Soonest.[n 1]
Following the end of World War II, a nuclear arms race evolved between the US and the Soviet Union to develop long-range missiles. At the same time both sides also developed satellites for gathering weather data, communications, and intelligence, mostly in secret. As a result, Americans were shocked when the Soviet Union placed the first satellite into orbit in October 1957, followed by a growing fear that the US was falling into a Missile gap. A month later, the Soviets launched Sputnik 2, carrying a dog into orbit. Though the animal was not recovered alive, it was obvious their goal was manned spaceflight. Unable to disclose details of military space projects, President Eisenhower ordered the creation of a civilian space agency in charge of civilian and scientific space exploration. Based on the federal research agency National Advisory Committee for Aeronautics (NACA), it was renamed the National Aeronautics and Space Administration. It achieved its first goal, an American satellite in space, in 1958. The next goal was to put a man there.
The limit of space was defined at the time as a minimum altitude of 62 mi (100 km), and the only way to reach it was by using rocket powered boosters. This created risks for the pilot, including explosion, high g-forces and vibrations during lift off through a dense atmosphere, and temperatures of more than 10,000 °F (5,540 °C) from air compression during reentry.
In space, pilots would require pressurized chambers or space suits to supply fresh air. While there, they would experience weightlessness, which could potentially cause disorientation. Further potential risks included radiation and micrometeoroid strikes, both of which would normally be absorbed in the atmosphere. All seemed possible to overcome: experience from satellites suggested micrometeoroid risk was negligible, and experiments in the early 1950s with simulated weightlessness, high g-forces on humans, and sending animals to the limit of space, all suggested potential problems could be overcome by known technologies. Finally, reentry was studied using the nuclear warheads of ballistic missiles, which demonstrated a blunt, forward-facing heat shield would create a shock wave that would force most of the heat generated to flow around the spacecraft while slowing it.
Organization and facilities
T. Keith Glennan had been appointed the first Administrator of NASA, with Hugh L. Dryden (last Director of NACA) as his Deputy, at the creation of the agency on October 1, 1958. Glennan would report to the president through the National Aeronautics and Space Council. The group responsible for Project Mercury was NASA's Space Task Group, and the goals of the program were to orbit a manned spacecraft around Earth, investigate the pilot's ability to function in space, and to recover both pilot and spacecraft safely. Existing technology and off-the-shelf equipment would be used wherever practical, the simplest and most reliable approach to system design would be followed, and an existing launch vehicle would be employed, together with a progressive test program. Spacecraft requirements included: a launch escape system to separate the spacecraft and its occupant from the launch vehicle in case of impending failure; attitude control for orientation of the spacecraft in orbit; a retrorocket system to bring the spacecraft out of orbit; drag braking blunt body for atmospheric reentry; and landing on water. To communicate with the spacecraft during an orbital mission, an extensive communications network had to be built. In keeping with his desire to keep from giving the US space program an overly military flavor, President Eisenhower at first hesitated to give the project top national priority (DX rating under the Defense Production Act), which meant that Mercury had to wait in line behind military projects for materials; however, this rating was granted in May 1959.
Twelve companies bid to build the Mercury spacecraft on a $20 million ($162 million) contract. In January 1959, McDonnell Aircraft Corporation was chosen to be prime contractor for the spacecraft. Two weeks earlier, North American Aviation, based in Los Angeles, was awarded a contract for Little Joe, a small rocket to be used for development of the launch escape system.[n 2] The World Wide Tracking Network for communication between the ground and spacecraft during a flight was awarded to the Western Electric Company. Redstone rockets for suborbital launches were manufactured in Huntsville, Alabama by the Chrysler Corporation and Atlas rockets by Convair in San Diego, California. For manned launches, the Atlantic Missile Range at Cape Canaveral Air Force Station in Florida was made available by the USAF. This was also the site of the Mercury Control Center while the computing center of the communication network was in Goddard Space Center, Maryland. Little Joe rockets were launched from Wallops Island, Virginia. Astronaut training took place at Langley Research Center in Virginia, Lewis Flight Propulsion Laboratory in Cleveland, Ohio, and Naval Air Development Center Johnsville in Warminster, PA. Langley wind tunnels together with a rocket sled track at Holloman Air Force Base at Alamogordo, New Mexico were used for aerodynamic studies. Both Navy and Air Force aircraft were made available for the development of the spacecraft's landing system, and Navy ships and Navy and Marine Corps helicopters were made available for recovery.[n 3] South of Cape Canaveral the town of Cocoa Beach boomed. From here, 75,000 people watched the first American orbital flight being launched in 1962.
Robert R. Gilruth, head of Space Task Group, 1969
The Mercury spacecraft's principal designer was Maxime Faget, who started research for manned spaceflight during the time of the NACA. It was 10.8 feet (3.3 m) long and 6.0 feet (1.8 m) wide; with the launch escape system added overall length was 25.9 feet (7.9 m). With 100 cubic feet (2.8 m3) of habitable volume, the capsule was just large enough for the single crew member. Inside were 120 controls: 55 electrical switches, 30 fuses and 35 mechanical levers. The heaviest spacecraft, Mercury-Atlas 9, weighed fully loaded 3,000 pounds (1,400 kg). Its outer skin was made of René 41, a nickel alloy able to withstand high temperatures.
The spacecraft was-cone shaped, with a neck at the narrow end. It had a convex base, which carried a heat shield (Item 2 in the diagram below). consisting of an aluminum honeycomb covered with multiple layers of fiberglass. Strapped to it was a retropack (1) consisting of three rockets deployed to brake the spacecraft during reentry. Between these were three minor rockets for separating the spacecraft from the launch vehicle at orbital insertion. The straps that held the package could be severed when it was no longer needed. Next to the heat shield was the pressurized crew compartment (3). Inside an astronaut would be strapped to a form-fitting seat, with instruments in front and his back to the heat shield. Underneath the seat was the environmental control system supplying oxygen and heat., scrubbing the air of CO2, vapor and odors, and (on orbital flights) collecting urine.[n 4] The recovery compartment (4) at the narrow end of the spacecraft contained three parachutes: a drogue to stabilize free fall and two main chutes, a primary and reserve. Between the heat shield and inner wall of the crew compartment was a landing skirt, deployed by letting down the heat shield before landing. On top of the recovery compartment was the antenna section (5) containing both antennas for communication and scanners for guiding spacecraft orientation. Attached was a flap used to ensure the spacecraft was faced heat shield first during reentry. A launch escape system (6) was mounted to the narrow end of the spacecraft containing three small solid-fueled rockets which could be fired briefly in a launch failure to separate the capsule safely from its booster. It would deploy the capsule's parachute for a landing nearby at sea.
The astronaut lay in a sitting position with his back to the heat shield, which was found to be the position which best enabled a human to withstand the high g-forces of launch and re-entry. A form-fitted fiberglass seat was custom-molded from each astronaut's space-suited body, for maximum support. Near his left hand was a manual abort handle to activate the launch escape system if necessary prior to or during liftoff, in case the automatic trigger failed.
To supplement the onboard environmental control system, he wore a pressure suit with its own oxygen supply, which would also cool him. A cabin atmosphere of pure oxygen at a low pressure of 5.5 psi (equivalent to an altitude of 24,800 feet (7,600 m)) was chosen, rather than one with the same composition as air (nitrogen/oxygen) at sea level. This was easier to control, avoided the risk of decompression sickness (known as "the bends"),[n 5] and also saved on spacecraft weight. Fires (which never occurred) would have to be extinguished by emptying the cabin of oxygen. In such case, or failure of the cabin pressure for any reason, the astronaut could make an emergency return to Earth, relying on his suit for survival. The astronauts normally flew with their visor up, which meant that the suit was not inflated. With the visor down and the suit inflated, the astronaut could only reach the side and bottom panels, where vital buttons and handles were placed.
The astronaut also wore electrodes on his chest to record his heart rhythm, a cuff that could take his blood pressure, and a rectal thermometer to record his temperature (this was replaced by an oral thermometer on the last flight). Data from these was sent to the ground during the flight. The astronaut normally drank water and ate food pellets.[n 6]
Once in orbit, the spacecraft could be rotated in three directions: along its longitudinal axis (roll), left to right from the astronaut's point of view (yaw), and up or down (pitch). Movement was created by rocket-propelled thrusters which used hydrogen peroxide as a fuel.  For orientation, the pilot could look through the window in front of him or from a screen connected to a periscope which could be turned 360°.
The Mercury astronauts had taken part in the development of their spacecraft, and insisted that manual control, and a window, be elements of its design. As a result, spacecraft movement and other functions could be controlled three ways: remotely from the ground when passing over a ground station, automatically guided by onboard instruments, or manually by the astronaut, who could replace or override the two other methods. Experience validated the astronauts' insistence on manual controls. Without them, Gordon Cooper's manual reentry during the last flight would not have been possible.
Development and production
The Mercury spacecraft design was modified three times by NASA between 1958 and 1959. After bidding by potential contractors had been completed, NASA selected the design submitted as "C" in November 1958. After it failed a test flight in July 1959, a final configuration, "D", emerged. The heat shield shape had been developed earlier in the 1950s through experiments with ballistic missiles, which had shown a blunt profile would create a shock wave that would lead most of the heat around the spacecraft. To further protect against heat, either a heat sink, or an ablative material, could be added to the shield. The heat sink would remove heat by the flow of the air inside the shock wave, whereas the ablative heat shield would remove heat by a controlled evaporation of the ablative material. After unmanned tests, the latter was chosen for manned flights. Apart from the capsule design, a rocket plane similar to the existing X-15 was considered. This approach was still too far from being able to make a spaceflight, and was consequently dropped.[n 7] The heat shield and the stability of the spacecraft were tested in wind tunnels, and later in flight. The launch escape system was developed through unmanned flights. During a period of problems with development of the landing parachutes, alternative landing systems such as the Rogallo glider wing were considered, but ultimately scrapped.
The spacecraft were produced at McDonnell Aircraft, St. Louis, Missouri in clean rooms and tested in vacuum chambers at the McDonnell plant. The spacecraft had close to 600 subcontractors, such as Garrett AiResearch which built the spacecraft's environmental control system. Final quality control and preparations of the spacecraft were made at Hangar S at Cape Canaveral.[n 8] NASA ordered 20 production spacecraft, numbered 1 through 20. Five of the 20, Nos. 10, 12, 15, 17, and 19, were not flown. Spacecraft No. 3 and No. 4 were destroyed during unmanned test flights. Spacecraft No. 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.)[n 9] A number of Mercury boilerplate spacecraft (made from non-flight materials or lacking production spacecraft systems) were also made by NASA and McDonnell. They were designed and used to test spacecraft recovery systems and the escape tower. McDonnell also built the spacecraft simulators used by the astronauts during training.
The Mercury program used two launch vehicles for manned missions.[n 10] The most important was the Atlas LV-3B or Atlas D, a two-stage liquid fueled rocket used for orbital flight. It was developed by Convair for the Air Force during the mid-1950s and was fueled with liquid oxygen (LOX) and kerosene. It was 67 feet (20 m) by itself and with the spacecraft and the launch escape system (including the adapter that held both to the launch vehicle), its total height was 95 feet (29 m). The first stage was a booster skirt with two engines using liquid fuel from the sustainer stage. This together with the larger sustainer stage gave it sufficient power to launch a Mercury spacecraft into orbit. Both stages fired from lift-off until staging of the booster; the sustainer through an opening in the booster. After staging, the sustainer stage continued alone. The sustainer also steered the rocket by thrusters guided by gyroscopes. Smaller vernier rockets were added on its sides for precise control of maneuvers. The Atlas was made of paper-thin stainless steel and had to be kept under constant internal pressure by fuel or helium in order to prevent the rocket from collapsing. This meant that the airframe of the launch vehicle could be reduced to 2% of the weight of the fuel. The Atlas D rocket also required extra strengthening in order to handle the increased weight of the Mercury spacecraft beyond that of the nuclear warheads it was designed for. Its internal guidance system also had to be moved accordingly to its greater length. The Titan missile was also considered for later Mercury missions but was not ready in time.[n 11] The Atlas was flown to Cape Canaveral and transported to the launch pad on a dolly. At the launch pad, the rocket and dolly were lifted to a vertical position by the service tower and the Atlas was then held by clamps to the launch pad.
The other manned launch vehicle was the Mercury-Redstone Launch Vehicle which was an 83 feet (25 m) (spacecraft and escape system included) tall single-stage launch vehicle used for suborbital (ballistic) flights. It had a liquid-fueled engine that burned alcohol and liquid oxygen producing about 75,000 pounds of thrust, which was not enough for orbital missions. It was a descendant of the German V-2, and developed for the U.S. Army during the early 1950s. It was modified for Project Mercury by removing the warhead and adding a collar for supporting the spacecraft together with material for damping vibrations during launch. Its rocket motor was produced by North American Aviation and its direction could be altered during flight by its fins. They worked in two ways: by directing the air around them or by directing the thrust by their inner parts (or both at the same time). Both the Atlas-D and Redstone launch vehicles contained an automatic abort sensing system which allowed them to abort a launch by firing the launch escape system if something went wrong. The Jupiter rocket, a relative of the Redstone, was originally considered for the suborbital launch vehicle, but was replaced by the Redstone in July 1959 due to budget constraints.
A smaller launch vehicle (55 feet (17 m) long) called Little Joe which carried a Mercury spacecraft with an escape tower mounted on it, was used for unmanned tests of the launch escape system. Its main purpose was to test the system at a point called max-q, at which air pressure against the spacecraft peaked, making separation of the launch vehicle and spacecraft most difficult. It was also the point at which the astronaut was subjected to the heaviest vibrations. The Little Joe rocket used solid-fuel propellant and was originally designed in 1958 by the NACA for suborbital manned flights, but was redesigned for Project Mercury to simulate an Atlas-D launch. It was produced by North American Aviation. It was not able to change direction, instead its flight depended on the angle from which it was launched. Its maximum altitude was 100 mi (160 km) fully loaded. A Scout launch vehicle was used for a single flight intended to evaluate the tracking network; however, it failed and was destroyed from the ground shortly after launch.
Erection of Redstone at Launch Complex 5
- Malcolm Scott Carpenter (1925–2013), USN
- Leroy Gordon "Gordo" Cooper, Jr. (1927–2004), USAF
- John Herschel Glenn, Jr. (1921–), USMC
- Virgil Ivan "Gus" Grissom (1926–1967), USAF
- Walter Marty "Wally" Schirra, Jr. (1923–2007), USN
- Alan Bartlett Shepard, Jr. (1923–1998), USN
- Donald Kent "Deke" Slayton (1924–1993), USAF
Shepard became the first American in space by making a suborbital flight in May 1961. He went on to fly in the Apollo program and became the only Mercury astronaut to walk on the Moon. Gus Grissom, who became the second American in space, also participated in the Gemini and Apollo programs, but died in January 1967 during a pre-launch test for Apollo 1. Glenn became the first American to orbit the Earth in February 1962, then quit NASA and went into politics, but returned to space aboard STS-95. Deke Slayton was grounded in 1962, but remained with NASA and flew on the Apollo-Soyuz Test Project in 1975. Gordon Cooper became the last to fly in Mercury and made its longest flight, and also flew a Gemini mission.  Carpenter's Mercury flight was his only trip into space. Schirra flew the third orbital Mercury mission, and then flew a Gemini mission. Three years later, he commanded the first manned Apollo mission, becoming the only person to fly in all three of those programs.
One of the astronauts' tasks was publicity; they gave interviews to the press and visited project manufacturing facilities to speak with those who worked on Project Mercury. To make their travels easier, they requested and got jet fighters for personal use. The press was especially fond of John Glenn, who was considered the best speaker of the seven. They sold their personal stories to Life magazine which portrayed them as patriotic, God-fearing family men. Life was also allowed to be at home with the families while the astronauts were in space. During the project, Grissom, Carpenter, Cooper, Schirra and Slayton stayed with their families at or near Langley Air Force Base; Glenn lived at the base and visited his family in Washington DC on weekends. Shepard lived with his family at Naval Air Station Oceana in Virginia.
Selection and training
It was envisaged that the pilot could be any man or woman willing to take a personal risk. On President Eisenhower's insistence, however, the first Americans to venture into space were drawn from a group of 508 military test pilots. This excluded women, since there were no female military test pilots. It also excluded the NACA's X-15 pilot and later astronaut Neil Armstrong, since he was a civilian.[n 12] It was further stipulated that candidates should be between 25 and 40 years old, no taller than 5 ft 11 in (1.80 m), and hold a college degree in science or engineering. The college degree requirement excluded the X-1 pilot Chuck Yeager, the first person to exceed the speed of sound. He later became a critic of the project, ridiculing especially the use of monkeys.[n 13] Joseph Kittinger, a stratosphere balloonist, met all the requirements but preferred to stay in his contemporary project. Some other potential candidates declined because they did not believe that manned spaceflight had a future beyond Project Mercury.[n 14] From the original 508, 110 candidates were selected for an interview, and from the interviews, 32 were selected for further physical and mental testing. Their health, vision, and hearing were examined, together with their tolerance to noise, vibrations, g-forces, personal isolation, and heat. In a special chamber, they were tested to see if they could perform their tasks under confusing conditions. The candidates had to answer more than 500 questions about themselves and describe what they saw in different images. Jim Lovell, later astronaut in Gemini and Apollo, did not pass the physical tests. After these tests it was intended to narrow the group down to six astronauts but in the end it was decided to keep seven.
The astronauts went through a training program covering some of the same exercises that were used in their selection. They simulated the g-force profiles of launch and reentry in a centrifuge at the Naval Air Development Center, and were taught special breathing techniques necessary when subjected to more than 6 g. Weightlessness training took place in aircraft, first on the rear seat of a two-seater fighter and later inside converted and padded cargo aircraft. They practiced gaining control of a spinning spacecraft in a machine at the Lewis Flight Propulsion Laboratory called the Multi-Axis Spin-Test Inertia Facility (MASTIF), by using an attitude controller handle simulating the one in the spacecraft. A further measure for finding the right attitude in orbit was star and Earth recognition training in planetaria and simulators. Communication and flight procedures were practiced in flight simulators, first together with a single person assisting them and later with the Mission Control Center. Recovery was practiced in pools at Langley, and later at sea with frogmen and helicopter crews.
G-force training, Johnsville, 1960
Weightlessness simulation in a C-131
MASTIF at Lewis Research Center
Egress training at Langley
Project Mercury had two kinds of missions: suborbital, and orbital. In the suborbital mission, a Redstone rocket lifted the spacecraft for 2 minutes and 30 seconds to an altitude of 32 nautical miles (59 km), separated from it and let it continue on a ballistic curve. Though not necessary for re-entry because orbital speed had not been attained, the spacecraft's retrorockets were fired, and the spacecraft landed in the Atlantic Ocean. Orbital missions also landed in the Atlantic, and a flotation collar, not ready for suborbital missions, was fastened around the spacecraft after landing. The suborbital mission took 15 minutes, had an apogee altitude of 102–103 nautical miles (189–191 km), and a downrange distance of 262 nautical miles (485 km).
Preparations for a mission started a month in advance with the selection of the primary and back-up astronaut; they would practice together for the mission. For three days prior to launch, the astronaut went through a special diet to minimize his need for defecating during the flight. On the morning of the trip he typically ate a steak breakfast. After having sensors applied to his body and being dressed in the pressure suit, he started breathing pure oxygen to prepare him for the atmosphere of the spacecraft. He arrived at the launch pad, took the elevator up the launch tower and entered the spacecraft two hours before launch.[n 15] Once the astronaut was secured inside, the hatch was bolted, the launch area evacuated and the mobile tower rolled back. After this, the launch vehicle was filled with liquid oxygen. The entire procedure of preparing for launch and launching the spacecraft followed a time table called the countdown. It started a day in advance with a pre-count, in which all systems of the launch vehicle and spacecraft were checked. After that followed a 15 hour hold, during which pyrotechnics were installed. Then came the main countdown which for orbital flights started 6½ hours before launch (T – 390 min), counted backwards to launch (T = 0) and then forward until orbital insertion (T + 5 min).[n 16]
On an orbital mission, the Atlas' rocket engines were ignited 4 seconds before lift-off. The launch vehicle was held to the ground by clamps and then released when sufficient thrust was built up at lift-off (A). After 30 seconds of flight, the point of maximum dynamic pressure against the vehicle was reached, at which the astronaut felt heavy vibrations. The booster engines were cut off and released after 2 minutes and 10 seconds (B). At this point, the launch escape system was no longer needed, and was separated from the spacecraft by its jettison rocket (C).[n 17] The launch vehicle moved gradually to a horizontal attitude during launch until, at an altitude of 87 nautical miles (161 km), the spacecraft was inserted into orbit (D). This happened after 5 minutes and 10 seconds in a direction pointing east, whereby the spacecraft would gain speed from the rotation of the Earth.[n 18] Here the spacecraft fired the three posigrade rockets for a second to separate it from the launch vehicle.[n 19] Just before orbital insertion and sustainer engine cutoff, g-loads peaked at 8 g (6 g for a suborbital flight). In orbit, the spacecraft automatically turned 180°, pointed the retropackage forward and its nose 14.5° downward and kept this attitude for the rest of the orbital phase of the mission, as it was necessary for communication with the ground.[n 20] Once in orbit, it was not possible for the spacecraft to change its trajectory except by initiating reentry. Each orbit would typically take 88 minutes to complete. The lowest point of the orbit called perigee was at the point where the spacecraft entered orbit and was about 87 nautical miles (161 km), the highest called apogee was on the opposite side of Earth and was about 150 nautical miles (280 km). When leaving orbit (E) the angle downward was increased to 34°, which was the angle of retrofire. Retrorockets fired for 10 seconds each (F) in a sequence where one started 5 seconds after the other. During reentry (G), the astronaut would experience about 8 g (11–12 g on a suborbital mission). The temperature around the heat shield rose to 3,000 °F (1,650 °C) and at the same time, there was a two minute radio blackout due to ionization of the air around the spacecraft. After re-entry, a small, drogue parachute (H) was deployed at 21,000 ft (6,400 m) for stabilizing the spacecraft's descent. The main parachute (I) was deployed at 10,000 ft (3,000 m) starting with a narrow opening that opened fully in a few seconds to lessen the strain on the lines. Just before hitting the water, the landing bag inflated from behind the heat shield to reduce the force of impact (J). Upon landing the parachutes were released. An antenna (K) was raised and sent out signals that could be traced by ships and helicopters. Further, a green marker dye was spread around the spacecraft to make its location more visible from the air.[n 21] Frogmen brought in by helicopters inflated a collar around the craft to keep it upright in the water. The recovery helicopter hooked onto the spacecraft and the astronaut blew the escape hatch to exit the capsule. He was then hoisted aboard the helicopter that finally brought both him and the spacecraft to the ship.[n 22]
The number of personnel supporting a Mercury mission was typically around 18,000, with about 15,000 people associated with recovery.[n 23] Most of the others followed the spacecraft from the World Wide Tracking Network, a chain of 18 stations placed around the equator, which was based on a network used for satellites and made ready in 1960. It collected data from the spacecraft and provided two-way communication between the astronaut and the ground. Each station had a range of 700 nautical miles (1,300 km) and a pass typically lasted 7 minutes. Mercury astronauts on the ground would take part of the Capsule Communicator or CAPCOM who communicated with the astronaut in orbit.[n 24] Data from the spacecraft was sent to the ground, processed at the Goddard Space Center and relayed to the Mercury Control Center at Cape Canaveral. In the Control Center, the data was displayed on boards on each side of a world map, which showed the position of the spacecraft, its ground track and the place it could land in an emergency within the next 30 minutes.[n 25]
On April 12, 1961 the Soviet cosmonaut Yuri Gagarin became the first person in space on an orbital flight. Alan Shepard became the first American in space on a suborbital flight three weeks later, on May 5, 1961. John Glenn, the third Mercury astronaut to fly, became the first American to reach orbit on February 20, 1962, but only after the Soviets had launched a second cosmonaut, Gherman Titov, into a day-long flight in August 1961. Three more Mercury orbital flights were made, ending on May 16, 1963 with a day-long, 22 orbit flight. However, the Soviet Union ended its Vostok program the next month, with the human spaceflight endurance record set by the 82-orbit, almost 5-day Vostok 5 flight.
All of the manned Mercury flights were successful. The main medical problems encountered were simple personal hygiene, and post-flight symptoms of low blood pressure. The launch vehicles had been tested through unmanned flights, therefore the numbering of manned missions did not start with 1. Also, since two different launch vehicles were used, there were two separate numbered series: MR for "Mercury-Redstone" (suborbital flights), and MA for "Mercury-Atlas" (orbital flights). These names were not popularly used, since the astronauts followed a pilot tradition, each giving their spacecraft a name. They selected names ending with a "7" to commemorate the seven astronauts. Mercury-Redstone flights were launched from Launch Complex-5 while the Mercury-Atlas flights were launched from Launch Complex-14. Times given are Universal Coordinated Time, local time + 5 hours.
|Mercury-Redstone 3||Freedom 7||Shepard||14:34 on May 5, 1961||15 m 22 s||0||117 (188)||—||5,134 (8,262)||3.5 (5.6)|
|Mercury-Redstone 4||Liberty Bell 7||Grissom||12:20 on July 21, 1961||15 m 37 s||0||118 (190)||—||5,168 (8,317)||5.8 (9.3)|
|Mercury-Atlas 6||Friendship 7||Glenn||14:47 on February 20, 1962||4 h 55 m 23 s||3||162 (261)||100 (161)||17,544 (28,234)||46 (74)|
|Mercury-Atlas 7||Aurora 7||Carpenter||12:45 on May 24, 1962||4 h 56 m 5 s||3||167 (269)||100 (161)||17,549 (28,242)||248 (400)|
|Mercury-Atlas 8||Sigma 7||Schirra||12:15 on October 3, 1962||9 h 13 m 15 s||6||176 (283)||100 (161)||17,558 (28,257)||4.6 (7.4)|
|Mercury-Atlas 9||Faith 7||Cooper||13:04 on May 15, 1963||1 d 10 h 19 m 49 s||22||166 (267)||100 (161)||17,547 (28,239)||5.0 (8.1)|
|Mercury-Redstone 3||First American in space. Recovered by carrier USS Lake Champlain.|
|Mercury-Redstone 4||Spacecraft sank during recovery when hatch unexpectedly blew off.[n 26] Recovered by carrier USS Randolph.|
|Mercury-Atlas 6||First American in orbit. Retropack retained during re-entry.[n 27] Recovered by frigate USS Noa.|
|Mercury-Atlas 7||Carpenter replaced Deke Slayton.[n 28] Recovered by destroyer USS Farragut.|
|Mercury-Atlas 8||The flight closest to plan. Carried out maneuvering tests. Recovered by carrier USS Kearsarge.|
|Mercury-Atlas 9||First American in space for over a day. Last American solo mission.[n 29] Recovered by USS Kearsarge.|
|Recovery variations||MA6) spacecraft and astronaut hoist onboard directly; MA8) spacecraft and astronaut towed by boat to ship; MA9) spacecraft with astronaut inside flown to ship.|
The unmanned flights used Little Joe, Redstone, and Atlas launch vehicles. They were used to develop the launch vehicles, launch escape system, spacecraft and tracking network. One flight of a Scout rocket attempted to launch an unmanned satellite for testing the ground tracking network, but failed to reach orbit. The Little Joe program used seven airframes for eight flights, of which three were successful. The second Little Joe flight was named Little Joe 6, because it was inserted into the program after the first 5 airframes had been allocated.
|Little Joe 1||August 21, 1959||20 s||Failed test of launch escape system during flight. Due to an electrical malfunction, the escape tower ignited ½ hour before launch and took the spacecraft with it, leaving the rocket on the ground.|
|Big Joe 1||September 9, 1959||13 m 00 s||Partly successful test of heat shield and Atlas/spacecraft interface. Actually the first Mercury-Atlas flight. Recovered by USS Strong (DD-758) 2,407 km SE of Cape Canaveral. Altitude: 65 mi (105 km) Qualified ablative heatshield.|
|Little Joe 6||October 4, 1959||5 m 10 s||Test of spacecraft aerodynamics and integrity. Partial success. No additional tests|
|Little Joe 1A||November 4, 1959||8 m 11 s||Partially successful test of launch escape system during flight with boiler plate capsule. The rescue tower rocket ignited 10 seconds too late. Recovered by USS Opportune 11.5 mi (18.5 km) SE of Wallops Island.|
|Little Joe 2||December 4, 1959||11 m 6 s||Successful escape test with primate at high altitude. Carried Sam, a rhesus macaque. Recovered by USS Borie (DD-704) 194 mi (312 km) SE of Wallops Island, Virginia; altitude: 53 mi (85 km).|
|Little Joe 1B||January 21, 1960||8 m 35 s||Successful maximum-q abort and escape test with primate with boiler plate capsule. Carried Miss Sam. Altitude: 9 mi (15 km)|
|Beach Abort||May 9, 1960||1 m 31 s||Test of the off-the-pad abort system. Success.|
|Mercury-Atlas 1||July 29, 1960||3 m 18 s||Failed test of spacecraft / Atlas combination. Exploded while passing through max-q To save weight, the airframe had been made thinner since Big Joe, which led to a collapse. The next Atlas was strengthened by a temporary solution while the rest were made from the same specifications as Big Joe.|
|Little Joe 5||November 8, 1960||2 m 22 s||Failed first test of escape system with a production spacecraft. The clamp holding the spacecraft was deflected by air pressure; due to this and an incorrect wiring, the escape tower ignited too early and further failed to separate spacecraft from launch vehicle. The clamp was subsequently tested by a rocket sled. Altitude: 10 mi (16 km)|
|Mercury-Redstone 1||November 21, 1960||2 s||Failed test of production spacecraft at max-q. Engine shutdown caused by improper separation of electrical cables; vehicle rose 4 in (10 cm) and settled back on the pad.[n 30]|
|Mercury-Redstone 1A||December 19, 1960||15 m 45 s||Successful qualification of spacecraft / Redstone combination. First flight of Mercury / Redstone. Recovered by USS Valley Forge Altitude: 130 mi (210 km)|
|Mercury-Redstone 2||January 31, 1961||16 m 39 s||Carried the chimpanzee Ham on suborbital flight. Recovered by USS Donner (LSD-20) 422 mi (679 km) SE of Cape Canaveral; altitude: 157 mi (253 km)|
|Mercury-Atlas 2||February 21, 1961||17 m 56 s||Qualified Mercury/Atlas interface. Recovered by USS Donner 1,432 mi (2,305 km) SE of Cape Canaveral.|
|Little Joe 5A||March 18, 1961||23 m 48 s||Second test of escape system with a production Mercury spacecraft. Partially successful. Tower fired 14 seconds too soon; it failed to separate the spacecraft from the rocket.|
|Mercury-Redstone BD||March 24, 1961||8 m 23 s||Last Redstone test flight. (BD: Booster Development)|
|Mercury-Atlas 3||April 25, 1961||7 m 19 s||Orbital (upgraded from suborbital) flight with robot astronaut.[n 31] Failed: was aborted when it did not go into orbit; boiler plate capsule recovered and reused in Mercury-Atlas 4.|
|Little Joe 5B||April 28, 1961||5 m 25 s||Successful third test of escape system with a production spacecraft. Concluded Little Joe program.|
|(May–July, 1961: manned suborbital flights)|
|Mercury-Atlas 4||September 13, 1961||1 h 49 m 20 s||Successful test of environmental control system with robot astronaut in orbit. Completed one orbit and sent data to the ground; first orbital flight of the project. Recovery by USS Decatur (DD-936) 176 mi (283 km) east of Bermuda.|
|Mercury-Scout 1||November 1, 1961||44 s||Failed test of Mercury tracking network. Was aborted after malfunction of guidance system; results of Mercury-Atlas 4 and Mercury-Atlas 5 were used instead.|
|Mercury-Atlas 5||November 29, 1961||3 h 20 m 59 s||Successful test of environmental control system in orbit with Chimpanzee Enos that completed a two-orbit flight, performing tasks to prove it possible for a person to function during a flight.[n 32] Last Mercury-Atlas test flight. Recovery by USS Stormes (DD-780) 255 mi (410 km) SE of Bermuda.|
|(February 1962 – May 1963: manned orbital flights)|
|Mercury-Jupiter 1||July 1, 1959|
|Mercury-Jupiter 2||Chimpanzee||First Quarter, 1960||July 1, 1959||Proposed maximum dynamic pressure test for capsule.|
|Mercury-Redstone 5||Glenn (likely)||March 1960||August 1961||Suborbital flights were planned for four other astronauts.|
|Mercury-Redstone 6||April 1960||July 1961|
|Mercury-Redstone 7||May 1960|
|Mercury-Redstone 8||June 1960|
|Mercury-Atlas 10||Freedom 7-II||Shepard||October 1963||June 13, 1963||Intended to be a three-day mission[n 33]|
|Mercury-Atlas 11||Grissom||Fourth Quarter, 1963||October 1962||Intended to be a one-day mission|
|Mercury-Atlas 12||Schirra||Fourth Quarter, 1963||October 1962||Intended to be a one-day mission|
Impact and legacy
The project was delayed by 22 months, counting from the beginning until the first orbital mission. It had a dozen prime contractors, 75 major subcontractors, and about 7200 third-tier subcontractors, who together employed two million persons. An estimate of its cost made by NASA in 1969 gave $392.6 million ($1.73 billion adjusted for inflation), broken down as follows: Spacecraft: $135.3 million, launch vehicles: $82.9 million, operations: $49.3 million, tracking operations and equipment: $71.9 million and facilities: $53.2 million.
Today the Mercury program is commemorated as the first manned American space program. It did not win the race against the Soviet Union, but gave back national prestige and was scientifically a successful precursor of later programs such as Gemini, Apollo and Skylab.[n 34] During the 1950s, some experts doubted that manned spaceflight was possible.[n 35] Still when John F. Kennedy was elected president, many including he had doubts about the project. As president he chose to support the programs a few months before the launch of Freedom 7, which became a great public success.[n 36] Afterwards, a majority of the American public supported manned spaceflight, and within a few weeks, Kennedy announced a plan for a manned mission to land on the Moon and return safely to Earth before the end of the 1960s. The six astronauts who flew were awarded medals, driven in parades and two of them were invited to address a joint session of the US Congress. As a response to the selection criteria, which ruled out women, a private project was founded in which 13 women pilots successfully underwent the same tests as the men in Project Mercury. It was named Mercury 13 by the media[n 37] Despite this effort, NASA did not select female astronauts until 1978 for the Space Shuttle.
In 1964, a monument commemorating Project Mercury was unveiled near Launch Complex 14 at Cape Canaveral, featuring a metal logo combining the symbol of Mercury with the number 7. In 1962, the United States Postal Service honored the Mercury-Atlas 6 flight with a Project Mercury commemorative stamp, the first US postal issue to depict a manned spacecraft. The stamp first went on sale in Cape Canaveral, Florida on February 20, 1962, the same day as the first manned orbital flight. On May 4, 2011, the Postal Service released a stamp commemorating the 50th anniversary of Freedom 7, the first manned flight of the project. On film, the program was portrayed in The Right Stuff a 1983 adaptation of Tom Wolfe's 1979 book of the same name. On February 25, 2011, the Institute of Electrical and Electronic Engineers, the world's largest technical professional society, awarded Boeing (the successor company to McDonnell Aircraft) a Milestone Award for important inventions which debuted on the Mercury spacecraft.[n 38]
Freedom 7 at the United States Naval Academy, 2010
Liberty Bell 7 at the Kansas Cosmosphere and Space Center, 2010
Friendship 7 at the National Air and Space Museum, 2009
Aurora 7 at the Museum of Science and Industry (Chicago), 2009
Sigma 7 at the United States Astronaut Hall of Fame, 2011
Faith 7 at Space Center Houston, 2011
Ground track and tracking stations for Mercury-Atlas 8. Spacecraft starts from Cape Canaveral in Florida and moves east; each new orbit-track is displaced to the left due to the rotation of the Earth. It moves between latitudes 32.5° north and 32.5° south. Key: 1–6: orbit number. Yellow: launch. Black dot: tracking station. Red: range of station; Blue: landing.
Control panels and handle
The control panels of Friendship 7. The panels changed between flights, among others the periscope screen that dominates the center of these panels was dropped for the final flight.
Earth landing system tests
Drop of boilerplate spacecraft in training of landing and recovery. 56 such qualification tests were made together with tests of individual steps of the system. An alternative landing system using a paraglider was proposed but did not get beyond model tests.
- Man in Space Soonest was the first part of a four-phase Moon landing program estimated to finish in 1965, cost a total of $1.5 billion ($12.1 billion), and be launched by a "Super Titan" rocket.
- The name Little Joe was adopted by its designers from the throw of a double deuce in a craps game since this resembled the four-rocket arrangement in the blueprints for the vehicle.
- NASA's planning for recovery operations in the summer of 1960 was, according to the Navy, asking for the deployment of the whole Atlantic Fleet and might have cost more than the entire Mercury program.
- On the first suborbital flight there was no urine collection whereas on the other, the astronaut had a reservoir added to the space suit
- The decision to eliminate the use of any gas but oxygen was crystalized when a serious accident occurred on April 21, 1960, in which McDonnell Aircraft test pilot G.B. North passed out and was seriously injured when testing a Mercury cabin/spacesuit atmosphere system in a vacuum chamber. The problem was found to be nitrogen-rich (oxygen-poor) air leaking from the cabin into his spacesuit feed.
- Moisture and urine was reclycled into drinking water.
- The rocket plane approach to manned space flight was pursued by the Air Force with their Dyna-Soar project, which was cancelled in 1963 Toward the end of the 1960s, NASA began the development of a reusable space plane, which was ultimately developed into the Space Shuttle program.
- Test and rework of Mercury-Redstone 2 at the Hangar required 110 days.
- They received a letter designation after their number, examples 2B, 15B. Some were modified twice; for example, spacecraft 15 became 15A and then 15B.
- The word booster is sometimes used for launch vehicle like in Mercury-Redstone Booster Development. With the latter as an exception, the word booster is only used for the first stage of the Mercury-Atlas in this article.
- Instead, it was used for the Gemini program which followed.
- Armstrong left the Navy in 1952, and became a Lieutenant, Junior Grade, in the US Naval Reserve. He remained in the reserve for eight years until he resigned his commission in 1960.
- John Glenn did not have a college degree either, but used influential friends to make the selection committee accept him.
- At the beginning of the project both President Eisenhower and NASA's first administrator T. K. Glennan believed that USA would put the first man in space, and that this would be the end of the Space Race.
- Inside the spacecraft the other astronauts had usually prepared a practical joke, such as a sign saying "No handball playing".
- Countdown was controlled from the blockhouse at the Launch Complex until 2 min. before launch then it was transferred to Mission Control Center. The countdown of the last 10 sec. before launch would be given to the astronaut by one of the others and included on TV transmissions which had already started.
- In the event of a launch abort before this point, the launch escape system would fire its main rocket for one second, pulling the spacecraft and astronaut away from the launch vehicle and a possible explosion. At this point, the spacecraft could be separated from the launch vehicle and land using its parachute.
- The direction of insertion was east and slightly to the north, this meant that on at three orbit flight the tracking network was utilized best possible and a landing could take place in the North Atlantic Ocean.
- The sustainer would disintegrate and fall down; after the launch of Friendship 7 a part of the sustainer was found in South Africa.
- In orbit the spacecraft would be drifting meaning changing its attitude by it self. This was countered automatically by the attitude control system (ASCS) which released oxygen produced from peroxide through small thrusters. To save fuel, however, the spacecraft would be let adrift from time to time especially on longer missions.
- Radar chaff and a SOFAR bomb which could be detected by the recovery ship's hydrophone were eliminated as unnecessary measures after the first orbital flight.
- It was also possible to exit the capsule through the nose cylinder; only Carpenter did this. In the two last missions the spacecraft with the astronaut inside was dragged by a boat to the ship, hoisted aboard and where upon the astronauts left through the hatch. During Carpenter's mission a seaplane from the US Air Force got to the landing site about 1½ hour ahead of the Navy ships and offered to pick him up. This, however, was declined by the admiral in charge of Mercury recovery operations, which led to controversy and a Senate hearing about the incident.
- T. J. O'Malley pushed the button to launch Glenn while site Manager and Launch Conductor at Complex 14, Calvin D. Fowler, pushed the button to launch Carpenter, Schirra and Cooper.[full citation needed]
- Occasionally this communication was broadcast on live TV while the spacecraft was passing over the United States.
- The World Wide Tracking Network went on to serve subsequent space programs, until it was replaced by a satellite relay system in the 1980s Mission Control Center was moved from Cape Canaveral to Houston in 1965.
- It was recovered in 1999.
- Launch of Friendship 7 was postponed repeatedly during two months; a frustrated politician compared the spacecraft-Atlas combination to "a Rube Goldberg device on top of a plumber's nightmare".
- Carpenter's overshoot of the landing site was caused by a malfunction in the automatic stabilization, which meant that retrofire was out of line with the movement of the spacecraft
- Likely to be so according to Alexander & al.
- Immediately after the Redstone's engine shut down, the capsule's escape rocket jettisoned itself, leaving the capsule attached to the booster. The escape rocket rose to an altitude of 4,000 ft (1,200 m) and landed about 400 yd (370 m) away. Three seconds after the escape rocket fired, the capsule deployed its drogue parachute; it then deployed the main and reserve parachutes.
- A machine that produced the same heat, vapor and CO2 as an astronaut.
- Was given a reward in the form a banana pellet or a punishment in the form of mild electrical shocks depending on whether or not he gave the right response to a given signal; by mistake he was sometimes given shocks on right answers.
- In November 1962 it was intended to be a three-day mission with extra supplies attached to the heat shield. By January 1963, it was changed to a one-day back up mission for Mercury-Atlas 9. Was cancelled after the success of the latter.
- International rules required that a pilot must land safely with the spacecraft; in reality, Gagarin landed separately by parachute; however, the Soviet Union did not admit this until 1971 when their claim was no longer in danger of being challenged.
- In May 1957, five months before Sputnik I, the president of McDonnell, the later prime contractor, predicted that manned spaceflight would not take place before 1990.
- Along the roads in USA, drivers stopped to follow Freedom 7 on the radio. Later, 100 millions saw or listened to Friendship 7, the first orbital flight, on TV or radio. The launch of Sigma 7 and Faith 7 were relayed live via communication satellite to television audiences in Western Europe. Two of the three major US networks covered Sigma 7 minute-by-minute, the rest were showing the opening of the World Series.
- It gave Soviet leader Khrushchev the idea of launching the first women cosmonaut Valentina Tereshkova on 16 June 1963.
- Boeing received the award in recognition of Project Mercury's pioneering "navigation and control instruments, autopilot, rate stabilization and control, and fly-by-wire systems."
- The stamp was issued February 20, 1962, the day of John Glenn's flight in Friendship 7. This one has a First Day of Issue postmark from Cape Canaveral post office.
- The only patches the Mercury astronauts wore, were the NASA logo and a name tag. Each manned Mercury spacecraft was painted black and decorated with a flight insignia, its call-sign, an American flag and the words United States.
- Grimwood 1063, p. 12.
- Alexander & al. 1966, p. 132.
- Catchpole 2001, p. 92.
- Alexander & al. 1966, p. 102.
- Catchpole 2001, pp. 12-14.
- Catchpole 2001, p. 81.
- Alexander & al. 1966, pp. 28, 52.
- Catchpole 2001, p. 55.
- Alexander & al. 1966, p. 113.
- Catchpole 2001, pp. 57, 82.
- Catchpole 2001, p. 70.
- Alexander & al. 1966, p. 13.
- Alexander & al. 1966, p. 44.
- Alexander & al. 1966, p. 59.
- Catchpole 2001, p. 466.
- Alexander & al. 1966, p. 357.
- Alexander & al. 1966, pp. 35, 39–40.
- Alexander & al. 1966, p. 49.
- Alexander & al. 1966, pp. 37-38.
- Alexander & al. 1966, p. 61.
- Alexander & al. 1966, pp. 98–99.
- Catchpole 2001, p. 82.
- Alexander & al. 1966, pp. xiii, 134.
- Alexander & al. 1966, p. 134.
- Alexander & al. 1966, p. 143.
- Catchpole 2001, p. 157.
- Alexander & al. 1966, pp. 121, 191.
- Alexander & al. 1966, p. 137.
- Alexander & al. 1966, p. 124.
- Alexander & al. 1966, p. 216.
- Alexander & al. 1966, p. 21.
- Catchpole 2001, p. 158.
- Catchpole 2001, p. 89–90.
- Catchpole 2001, p. 86.
- Alexander & al. 1966, p. 141.
- Catchpole 2001, pp. 103-110.
- Alexander & al. 1966, p. 88.
- Catchpole 2001, p. 248.
- Catchpole 2001, pp. 172-173.
- "History-At-A-Glance". City of Cocoa Beach. Retrieved 24 June 2013.
- Catchpole 2001, p. 150.
- Catchpole 2001, p. 131.
- Alexander & al. 1966, p. 47.
- Alexander & al. 1966, p. 245.
- Alexander & al. 1966, p. 490.
- Catchpole 2001, p. 136.
- Catchpole 2001, pp. 134–136.
- Alexander & al. 1966, pp. 140, 143.
- Catchpole 2001, pp. 132–134.
- Catchpole 2001, p. 132.
- Alexander & al. 1966, p. 188.
- Catchpole 2001, p. 134.
- Catchpole 2001, pp. 136–144.
- Catchpole 2001, pp. 136-137.
- Catchpole 2001, p. 138.
- Catchpole 2001, p. 139.
- Catchpole 2001, pp. 144–145.
- Catchpole 2001, p. 144.
- Catchpole 2001, p. 135.
- Catchpole 2001, pp. 145–148.
- Catchpole 2001, p. 147.
- Alexander & al. 1966, p. 199.
- Catchpole 2001, pp. 179–181.
- Catchpole 2001, p. 179.
- Catchpole 2001, p. 142.
- Catchpole 2001, p. 191.
- Gatland 1976, p. 264.
- Catchpole 2001, p. 410.
- Giblin 1998.
- Alexander & al. 1966, pp. 48–49.
- Alexander & al. 1966, p. 246.
- Catchpole 2001, pp. 191, 194.
- Catchpole 2001, pp. 343-344.
- Catchpole 2001, pp. 142–143.
- Alexander & al. 1966, p. 499.
- Catchpole 2001, p. 143.
- Catchpole 2001, p. 141.
- Catchpole 2001, pp. 98–99.
- Alexander & al. 1966, p. 501.
- Catchpole 2001, p. 152.
- Catchpole 2001, p. 153.
- Catchpole 2001, p. 159.
- Catchpole 2001, p. 149.
- Alexander & al. 1966, p. 63.
- Alexander & al. 1966, p. 64.
- Alexander & al. 1966, p. 206.
- Alexander & al. 1966, pp. 78-80.
- Alexander & al. 1966, p. 72.
- Catchpole 2001, p. 229.
- Catchpole 2001, p. 196.
- Alexander & al. 1966, p. 198.
- Catchpole 2001, pp. 132, 159.
- Catchpole 2001, pp. 184-188.
- Grimwood 1963, pp. 235–238.
- Catchpole 2001, pp. 402–405.
- Alexander & al. 1966, pp. 126 & 138.
- Alexander & al. 1966, pp. 96, 105.
- Catchpole 2001, p. 107.
- Catchpole 2001, pp. 225, 250.
- Catchpole 2001, p. 211.
- Alexander & al. 1966, p. 22.
- Catchpole 2001, p. 212.
- Catchpole 2001, pp. 458-459.
- Alexander & al. 1966, p. 25.
- Alexander & al. 1966, p. 305.
- Catchpole 2001, p. 216.
- Unknown 1962, p. 50.
- Catchpole 2001, p. 206.
- Catchpole 2001, p. 207.
- Catchpole 2001, pp. 209, 214.
- Alexander & al. 1966, p. 151.
- Grimwood 1963, p. 69.
- Catchpole 2001, p. 197.
- Alexander & al. 1966, p. 638.
- Catchpole 2001, p. 223.
- Catchpole 2001, p. 284.
- Catchpole 2001, p. 198.
- Alexander & al. 1966, p. 125.
- Alexander & al. 1966, pp. 392–397.
- Alexander & al. 1966, p. 164.
- Alexander & al. 1966, p. 640.
- Alexander & al. 1966, p. 341.
- Catchpole 2001, p. 445.
- Catchpole 2001, p. 442.
- Catchpole 2001, pp. 440,441.
- Catchpole 2001, pp. 446-447.
- Alexander & al. 1966, pp. 640–641.
- Catchpole 2001, p. 99.
- Catchpole 2001, p. 104.
- Catchpole 2001, p. 96.
- Catchpole 2001, p. 100.
- Catchpole 2001, p. 97.
- Catchpole 2001, p. 91.
- Alexander & al. 1966, pp. 160–161.
- Catchpole 2001, pp. 92–93.
- Catchpole 2001, p. 93.
- Catchpole 2001, p. 98.
- Catchpole 2001, p. 94.
- Catchpole 2001, p. 105.
- "Gimbal Rig Mercury Astronaut Trainer". NASA. 9 June 2008. Retrieved 13 December 2014.
- "Gimbal Rig" on YouTube
- Catchpole 2001, pp. 105, 109.
- Catchpole 2001, p. 111.
- Alexander & al. 1966, p. 346.
- Alexander & al. 1966, pp. xiii, 99.
- Unknown 1961a, p. 7.
- Catchpole 2001, pp. 208, 250.
- Catchpole 2001, pp. 250, 308.
- Catchpole 2001, p. 166.
- Catchpole 2001, p. 475.
- Catchpole 2001, p. 110.
- Catchpole 2001, p. 278.
- Catchpole 2001, p. 280.
- Catchpole 2001, p. 188.
- Catchpole 2001, p. 281.
- Catchpole 2001, pp. 188, 242.
- Catchpole 2001, p. 340.
- Unknown 1962, p. 46.
- Catchpole 2001, pp. 188, 460.
- Catchpole 2001, p. 133.
- Unknown 1961, p. 10.
- Alexander & al. 1966, p. 333.
- Catchpole 2001, p. 120.
- Catchpole 2001, p. 462.
- Catchpole 2001, p. 324.
- Unknown 1961, p. 9.
- Alexander & al. 1966, p. 574.
- Unknown 1962, p. 9.
- Alexander & al. 1966, p. 356.
- Alexander & al. 1966, p. 508.
- Unknown 1962, p. 3.
- Catchpole 2001, pp. 124, 461–462.
- Catchpole 2001, p. 117.
- Catchpole 2001, pp. 121, 126.
- Alexander & al. 1966, p. 360.
- Alexander & al. 1966, p. 479.
- Catchpole 2001, p. 118.
- Alexander & al. 1966, p. 332.
- Alexander & al. 1966, pp. 377, 422.
- Catchpole 2001, p. 476.
- Alexander & al. 1966, pp. 640-641.
- Alexander & al. 1966, p. 638-641.
- Alexander & al. 1966, pp. 640–641 when nothing else is mentioned in table.
- Alexander & al. 1966, p. 373.
- Alexander & al. 1966, p. 375.
- Alexander & al. 1966, p. 422.
- Alexander & al. 1966, p. 432.
- Alexander & al. 1966, p. 433.
- Alexander & al. 1966, p. 440.
- Alexander & al. 1966, p. 456.
- Alexander & al. 1966, p. 484.
- Alexander & al. 1966, p. 476.
- Alexander & al. 1966, p. 483.
- Alexander & al. 1966, p. 487.
- Alexander & al. 1966, pp. 353,375,433,457,483-484,501.
- Catchpole 2001, p. 231.
- Alexander & al. 1966, pp. 638–641 when nothing else is mentioned in table.
- Alexander & al. 1966, p. 208.
- Alexander & al. 1966, pp. 203–204.
- Alexander & al. 1966, p. 209.
- Alexander & al. 1966, p. 210.
- Catchpole 2001, p. 232.
- Catchpole 2001, pp. 234, 474.
- Alexander & al. 1966, p. 212.
- Alexander & al. 1966, p. 276.
- Catchpole 2001, p. 243.
- Alexander & al. 1966, p. 291.
- Alexander & al. 1966, p. 298.
- Alexander & al. 1966, p. 294.
- Alexander & al. 1966, p. 297.
- Alexander & al. 1966, p. 310.
- Alexander & al. 1966, p. 316.
- Alexander & al. 1966, pp. 638-639.
- Alexander & al. 1966, pp. 321–322.
- Alexander & al. 1966, p. 327.
- Alexander & al. 1966, p. 330.
- Alexander & al. 1966, p. 335.
- Catchpole 2001, p. 275.
- Alexander & al. 1966, p. 337.
- Alexander & al. 1966, p. 386-387.
- Alexander & al. 1966, p. 389.
- Alexander & al. 1966, p. 397.
- Catchpole 2001, p. 312.
- Alexander & al. 1966, p. 404.
- Alexander & al. 1966, p. 406.
- Grimwood 1963, p. 169.
- Grimwood 1963, p. 81.
- "Mercury-Jupiter 2 (MJ-2)". Astronautix.com. Retrieved 2012-05-24.
- Catchpole 2001, p. 474.
- Cassutt & Slayton 1994, p. 104.
- Cassutt & Slayton 1994, p. 101.
- "Mercury MA-11". Encyclopedia Astronauticax. Retrieved 22 June 2013.
- "Mercury MA-12". Encyclopedia Astronautica. Retrieved 22 June 2013.
- Lafleur, Claude (2010-03-08). "Costs of US piloted programs". The Space Review. Retrieved February 18, 2012.
- Wilford 1969, p. 67.
- Alexander & al. 1966, p. 643.
- Catchpole 2001, p. cover.
- Catchpole 2001, p. 417.
- Alexander & al. 1966, p. 272.
- Alexader & al. 1966, p. 306.
- Alexander & al. 1966, p. 434.
- Alexander & al. 1966, p. 363.
- Alexander & al. 1966, pp. 362, 435, 459, 486, 502, 584.
- Alexander & al. 1966, pp. 435, 501.
- Catchpole 2001, p. 447.
- Catchpole 2001, pp. 447–448.
- Catchpole 2001, p. 448.
- "Mercury Monument Dedication at Launch Complex 14". Kennedy Space Center. Retrieved June 29, 2013.
- "Mystic stamp company". Retrieved 1 April 2012.
- "Stamps Mark Shepard's 1961 Flight". US Postal Service. Retrieved 5 May 2011.
- "The Right Stuff". IMdB. Retrieved 2011-10-04.
- "Boeing Press Release". Retrieved 25 February 2011.
- Dorr, Eugene. "History of Patches". Retrieved 20 June 2013.
- Australian Broadcasting Corporation (February 15, 2008). "Moment in Time – Episode 1". Retrieved June 25, 2013.
- Catchpole 2001, p. 128.
- Unknown 1962, p. 8.
- Alexander & al. 1966, p. 91.
- Alexander & al. 1966, p. 265.
- Alexander & al. 1966, p. 368.
- Catchpole 2001, pp. 425, 428.
- "Introduction to future launch vehicle plans [1963-2001]. 3.The Space Shuttle (1968-72)". Retrieved 3 February 2014.
- Grimwood 1963, pp. 216-218.
- Grimwood 1963, p. 149.
- Alexander & al. 1966, p. 503.
- Hansen 2005, p. 118.
- Catchpole 2001, p. 440.
- Catchpole 2001, p. 407.
- Catchpole 2001, p. 282.
- Catchpole 2001, p. 180.
- Alexander & al. 1966, p. 215.
- Grimwood 1963, p. 164.
- Alexander & al. 1966, pp. 195, 450.
- Alexander& al. 1966, p. 445.
- Catchpole 2001, pp. 363, 382.
- Alexander & al. 1966, p. 457.
- Press release for Gordon Cooper's Mercury Atlas launch on May 15, 1963
- Catchpole 2001, p. 409.
- Catchpole 2001, p. 88.
- Alexander & al. 1966, p. 409, 411.
- Alexander & al. 1966, p. 453-454.
- Alexander & al. 1966, p. 506.
- Catchpole 2001, p. 309.
- Alexander & al. 1966, p. 405.
- Catchpole 2001, pp. 385-386.
- Siddiqi 2000, p. 283.
- Alexander & al. 1966, p. 119.
- Alexander & al. 1966, p. 423.
- "Mercury Atlas 8". NASA. Retrieved 22 June 2013.
- Alexander & al. 1966, p. 472.
|Wikimedia Commons has media related to Mercury program.|
- Alexander, C. C.; Grimwood, J. M.; Swenson, L. S. (1966). This New Ocean: a History of Project Mercury (PDF). USA: NASA. ISBN 1934941875.
- Cassutt, Michael; Slayton, Donald K. "Deke" (1994). Deke! U.S. Manned Space: From Mercury to the Shuttle (1st ed.). New York, USA: Forge (St. Martin's Press). ISBN 0-312-85503-6.
- Catchpole, John (2001). Project Mercury - NASA's First Manned Space Programme. Chichester, UK: Springer Praxis. ISBN 1-85233-406-1.
- Gatland, Kenneth (1976). Manned Spacecraft (Second ed.). New York: Macmillan. p. 304.
- Giblin, Kelly A. (Spring 1998). "'Fire in the Cockpit!'". American Heritage of Invention & Technology (American Heritage Publishing) 13 (4). Archived from the original on November 20, 2008. Retrieved March 23, 2011.
- Grimwood, James M. (1963). [
http://spacemedicineassociation.org/timeline/1958/Project%20Mercury-A%20Chronology-NASA%20SP-4001.pdfProject Mercury. A Chronology - NASA SP-4001] (PDF). Washington DC, USA: NASA.
- Hansen, James R. (2005). First Man: The Life of Neil A. Armstrong. Simon & Schuster. ISBN 0-7432-5631-X.
- Kranz, Gene (2000). Failure is not an option. New York, USA: Berkley Books. ISBN 0-425-17987-7.
- Siddiqi, Asif A. (2000). Challenge To Apollo: The Soviet Union and the Space Race, 1945-1974 (PDF). USA: NASA. ISBN 1780393016. Archived from the original (PDF) on 2008-09-16.
- Unknown (1961). Results of the first U.S. manned suborbital space flight (PDF). USA: NASA.
- Unknown (1961a). Results of the second U.S. manned suborbital space flight (PDF). USA: NASA.
- Unknown (1962). Results of the first United States manned orbital space flight, 20 February 1962 (PDF). USA: NASA.
- Wilford, John Noble (July 1969). We Reach the Moon. New York, USA: Bantam Books.
- The Mercury Project (Kennedy Space Center)
- Space Medicine In Project Mercury By Mae Mills Link
- Project Mercury Simulator for Mac and PC
- PDFs of historical Mercury documents including familiarization manuals.
- Project Mercury Drawings and Technical Diagrams
- Project Mercury - 1963 NASA Space Program Documentary (Video)