Project Mercury was the first human spaceflight program of the United States, running from 1958 through 1963. An early highlight of the Space Race, its goal was to put a man into Earth orbit and return him safely, ideally before the Soviet Union. Taken over from the US Air Force by the newly created civilian space agency NASA, it conducted 20 uncrewed developmental flights (some using animals), and six successful flights by astronauts. The program, which took its name from Roman mythology, cost $2.83 billion (adjusted for inflation). The astronauts were collectively known as the "Mercury Seven", and each spacecraft was given a name ending with a "7" by its pilot.
The Space Race began 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 US space exploration efforts, and place most of them under civilian control. After the successful launch of the Explorer 1 satellite in 1958, crewed spaceflight became the next goal. The Soviet Union put the first human, cosmonaut Yuri Gagarin, into a single orbit aboard Vostok 1 on April 12, 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 US 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 Soviets led the US in total time spent in space.
The Mercury space 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 Air Force Station in Florida, on launch vehicles modified from the Redstone and Atlas D missiles. The capsule was fitted with a launch escape rocket to carry it safely away from the launch vehicle in case of a failure. 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 it 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 a US Navy ship.
The Mercury project gained popularity, and its missions were 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 crewed lunar landings in the subsequent Apollo program announced a few weeks after the first crewed Mercury flight.
Creation
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.
Background
Following the end of World War II, a nuclear arms race evolved between the US and the Soviet Union (USSR). Since the USSR did not have bases in the western hemisphere from which to deploy bomber planes, Joseph Stalin decided to develop intercontinental ballistic missiles, which drove a missile race. The rocket technology in turn enabled both sides to develop Earth-orbiting satellites for communications, and gathering weather data and intelligence.
Americans were shocked when the Soviet Union placed the first satellite into orbit in October 1957, leading to 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 human 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 named the National Aeronautics and Space Administration (NASA). The agency achieved its first goal of launching a satellite into space, the Pioneer 1, in 1958. The next goal was to put a man there.
The limit of space (also known as the Kármán line) 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 (5,500 °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 could solve the problem of heating.
Organization
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 crewed 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 overtly 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, a little more than a year and a half after Sputnik was launched.
Contractors and facilities
Twelve companies bid to build the Mercury spacecraft on a $20 million ($221 million adjusted for inflation) 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. 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 crewed 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. 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.
Spacecraft
The Mercury spacecraft's principal designer was Maxime Faget, who started research for human 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, the 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 a single crew member. Inside were 120 controls: 55 electrical switches, 30 fuses and 35 mechanical levers. The heaviest spacecraft, Mercury-Atlas 9, weighed 3,000 pounds (1,400 kg) fully loaded. 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 posigrade rockets: 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 of him and with 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. 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. (See also Mission profile for details.)
The Mercury spacecraft did not have an on-board computer, instead relying on all computation for reentry to be calculated by computers on the ground, with their results (retrofire times and firing attitude) then transmitted to the spacecraft by radio while in flight. All computer systems used in the Mercury space program were housed in NASA facilities on Earth. (See ground control for details.)
Pilot accommodations
The astronaut lay in a sitting position with his back to the heat shield, which was found to be the position that best enabled a human to withstand the high g-forces of launch and reentry. A 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 or 38 kPa (equivalent to the partial pressure of oxygen at sea level or the pressure of atmospheric air at an altitude of 24,800 feet or 7,600 metres) was chosen, rather than the atmosphere at sea level. This was easier to control, avoided the risk of decompression sickness ("the bends"), and also saved on spacecraft weight. Fires (which never occurred during the course of Project Mercury) 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.
Despite the lessons learnt from the U2 program, which also utilized a pressure suit, initially no urine collection device was included for the Mercury astronauts. An inquiry on the subject was made in February 1961 by a student, but NASA responded by stating that "the first space man is not expected to have 'to go". The expected short flight times meant that this was overlooked, although after Alan Shepard had a launch delay of four hours, he was forced to urinate in his suit, short-circuiting some of the electrodes monitoring his vital signs. Gus Grissom wore two rubber pants on the second Mercury flight as a crude workaround. It would take until the third flight in February 1962 before a dedicated urine collection device was installed.