As NASA started its first full calendar year of existence on January 1, 1959, groups of engineers and managers were busy starting up the various programs the newborn space agency was assigned. Perhaps the busiest of these groups was the Space Task Group (STG) under the direction of Robert R. Gilruth. Based at NASA’s Langley Research Center in Virginia, STG was charged with developing the country’s first manned spacecraft for Project Mercury (see “The Origins of NASA Mercury Program”). The project’s goal was to send a man into orbit using a modified version of the USAF Atlas D ICBM and safely return him to Earth. While Project Mercury would build on years of research conducted by the USAF, various aerospace contractors, as well as NASA’s predecessor, the NACA (National Advisory Committee on Aeronautics), there was still an incredible amount of work to be done before the first flight. The fact that the Soviet Union was also likely developing a manned spacecraft in secret only added to the sense of urgency that pervaded NASA.

The Contractor

All during late December of 1958, selected members of NASA management and STG were busy evaluating the bids they had received from 11 potential contractors to build the Mercury spacecraft. But even before NASA officially selected Mercury’s prime contractor, it was already taken for granted by many that the McDonnell Aircraft Corporation (which merged with Douglas Aircraft in 1967 and is today is part of Boeing) would win. Starting in October of 1957 McDonnell had assigned 20 people to study manned spaceflight concepts as part of the USAF-sponsored Manned Ballistic Rocket Research System or MIS (Man In Space) program. This number swelled to 40 when work on the USAF Dyna-Soar aerospace glider project was added (see “The Future That Never Came: The X-20 Dyna Soar Aerospace Plane”).

By June of 1958 the company had 70 people on their team. Many of these engineers worked closely with the NACA Langley group that was already laying the groundwork for what would become Project Mercury. Throughout the summer of 1958 McDonnell were involved directly with NACA helping to define their manned ballistic capsule concept. This close relationship continued until the official call for proposals was released by NASA in November. Since the McDonnell proposal incorporated the vast majority of the elements STG desired in their manned spacecraft design, the company had a clear edge in the competition from the start.

After a lengthy evaluation process, the Source Selection Board officially recommended McDonnell as Mercury’s contractor on January 9, 1959. NASA Administrator T. Keith Glennan accepted the board’s recommendation and telephoned James S. McDonnell himself later that day with the good news. On February 6, 1959, a contract to procure a dozen capsules at an estimated cost of $18.3 million (plus a company fee of $1.5 million) was signed. While the actual costs would almost immediately start to spiral upwards, the focus moved to finalizing the new spaceship’s design so that construction could begin.

The Spacecraft

By the time McDonnell was officially on the project, STG engineers had already decided on all the important design elements of the Mercury spacecraft based on exhaustive research. It was the task of McDonnell’s engineers to produce a working design from this research and start cutting metal to build it. But with the low Earth orbit payload capability of the modified Atlas D ICBM launch vehicle estimated to be about 1,300 kilograms, the final capsule design would have to be the ultimate in efficient compact engineering.

The Mercury capsule was a truncated cone topped with a cylinder with a total height of 2.92 meters. The small pressurized cockpit would occupy the largest portion of the capsule with most other systems packed throughout the cramped interior. Recovery systems and horizon sensors would be housed in the small cylindrical section at the top. At the base, where the heatshield was located, Mercury was 1.88 meters across. At this time a metal heatsink like those successfully used in the first ICBM reentry vehicles was in the lead for the heatshield design. A lighter weight but still experimental ablative heatshield where a ceramic coating would absorb heat, char, and break away in small pieces (thus carrying the heat of reentry away from the capsule) was also being actively developed. The structure of the capsule was primarily composed of titanium which was lighter than steel and remained strong even at high temperatures.

Mounted underneath the heatshield was a retrograde package consisting of three solid rocket motors. Each motor produced 4.45 kilonewtons of thrust for about ten seconds. The three motors were ignited sequentially at the end of the orbital mission and would start the capsule’s descent from orbit. Also mounted in this housing was a trio of smaller posigrade rockets producing only 1.78 kilonewtons of thrust each for a second. The purpose of these smaller motors was to separate and move the capsule safely away from its spent Atlas booster once orbit had been achieved. After the retrograde package had completed its task at the end of orbital flight, it was discarded prior to reentry.

Mounted on top of the Mercury capsule was the launch escape tower. Standing 4.57 meters tall, the tower consisted of a light structural truss topped by a cylinder housing a pair of solid rocket motors. Conceived by Maxime A. Faget (who later became STG’s Flight Systems Chief) and his team at Langley in July of 1958, this structure was designed to pull the capsule safely away from the Atlas rocket in case of a catastrophic failure either on the pad or early during the ascent. To accomplish this, the larger motor produced 230 kilonewtons of thrust for a second. The capsule would then execute a normal water landing by parachute some distance downrange. The second motor was designed to pull the escape tower away from the ascending spacecraft 150 seconds after launch with a 1.5 second burst of 3.6 kilonewtons of thrust. For the rest of the powered ascent, the retrograde rockets could safely push the capsule away from the booster in case of an emergency.

McDonnell (as well as the USAF in the MIS program) originally preferred a pusher-rocket configuration for a launch escape system with large motors attached at the base of the capsule. Faget’s tractor design had the benefit of being easily jettisoned during flight when the hardware was no longer needed. This increased the amount of usable hardware that could be orbited as well as exposing the astronaut to the hazards of pyrotechnic devices for as short a period as possible.

The choice of the Atlas D ICBM as Mercury’s launch vehicle required that other special accommodations be made for the pilot. One of the reasons the USAF did not want to use the Atlas for MIS was because of the punishing G loads. While an astronaut could easily withstand the peak 6 Gs acceleration during a normal ascent, the rocket’s flight profile was such that peak loads could reach as high as 20 Gs during a ballistic reentry after an abort. The USAF felt that anything higher than 12 Gs should not be allowed but Faget and his team came up with a solution. They designed a contoured couch fitted to each pilot. This couch design had been tested in July 1958 at the Navy Acceleration Laboratory in Johnsville, Pennsylvania and allowed test subjects to withstand loads in excess of 20 Gs without ill effects.

One of the important engineering decisions that had to be made early in the Mercury program dealt with the capsule’s life support system. Ideally one would want to reproduce the Earth’s atmosphere inside the capsule for its occupant – a two gas oxygen-nitrogen system operating at 1013 millibars. Unknown to American engineers at the time, Soviet engineers chose this route with their manned spacecraft design. But American research also suggested that a single-gas atmosphere of pure oxygen in the 200 to 460 millibar pressure range was also a viable option – an approach which was initially championed by STG engineer, Stanley C. White. A single-gas environmental system would be much simpler, lighter, and more reliable than a two-gas system. The lower pressure also allowed the capsule’s pressurized cabin to be of lighter construction and would be less prone to leaking.

White, who was working with the subcontractor of Mercury’s environmental control system AiResearch Manufacturing, convinced their engineers that a one-gas system should be used. In the end, a pure oxygen atmosphere at a pressure of 345 millibars was approved as being sufficient for astronaut life support and heat transfer requirements (to remove excess heat from the cabin). This atmosphere would become the standard for American crewed spacecraft until the introduction of the Space Shuttle in 1981. The one major drawback of this standard, however, was the extreme fire hazard of a pure oxygen atmosphere especially at pressures approaching that at sea level – a fact that would be painfully demonstrated eight years later with the Apollo 1 tragedy (see “The Future that Never Came: The Unflown Mission of Apollo 1“).

NASA’s First Astronauts

One of the most important components of the Mercury spacecraft (and the point behind the whole project) was its pilot. But with the significant number of unknowns associated with spaceflight, it was difficult to agree on a standard for selecting astronauts. In November of 1958, STG took on this formidable task and developed NASA’s first astronaut selection criteria. Reflecting the chauvinism of the time, the candidate had to be a male between 25 and 40 years of age. In addition to being in excellent physical health, each sponsored candidate had to be shorter than 180 centimeters in order to fit into the cramped Mercury cockpit.

Initially it was felt that a strong background in the sciences would be of prime importance for an astronaut. STG required that candidates hold a degree in science or engineering and have at least three years of experience in the science, engineering or with aircraft, balloons or submarines. Alternatively, the candidates could hold a Ph.D. or have six months of medical experience. The original STG plan called for gathering 150 candidates from open applications. From these applications, 36 would be called in for initial evaluations and, of these, a dozen would proceed to nine months of intense training. At the end of the process, six would be formally invited to become astronauts.

But by the end of 1958 this plan had been abandoned at the request of President Eisenhower who wanted the first astronauts to be jet pilots selected from the armed services’ test pilot schools. While arguments could be made that “flying” a ballistic capsule hardly required the skill of a top notch test pilot, their training and abilities could significantly increase the chances for a successful mission (or successfully surviving an unforeseen emergency). In January 1959, NASA management set down a new set of criteria for astronauts. The physical and educational requirements stayed the same as did the desire to limit the final selection to six men. Now applicants would be required to have a minimum of 1,500 hours flying time in high performance jet aircraft.

The Department of Defense provided NASA with the records of 508 military pilots. White, Robert B. Voas and William S. Augerson selected five US Marine, 47 US Navy and 58 USAF pilots from the list. These 110 men were divided into three groups and brought to Washington for interviews and further screening starting on February 2, 1959. With 69 men from the first two groups passing the initial screening, the third group was excused to relieve the burden on the remainder of the selection process. Further evaluation narrowed the field to 36 pilots. Of these men, 32 volunteered to continue the process and undergo a series of exhaustive medical tests at the Lovelace Clinic in Albuquerque, New Mexico starting on February 7.

Tests at the clinic were followed by stress tests at the Wright Air Development Center starting on February 15. Additional psychological testing and high-G rides in a centrifuge followed. In the end a list of 18 candidates was delivered to Langley for final consideration. It was found to be impossible to select only six finalists from the candidates so a list of seven names was ultimately submitted to NASA’s upper management. NASA Administrator Glennan approved the list on April 2, 1959 and on April 9 America’s first seven astronauts, dubbed the “Mercury Seven” by the press, were presented at a Washington press conference.

US Navy Lieutenant M. Scott Carpenter, who was about to turn 34 years old when selected by NASA, became a naval aviator in 1949 after leaving school one course shy of meeting the graduation requirements for a BS Aeronautical Engineering at the University of Colorado at Boulder. Initially, Carpenter flew reconnaissance and anti-submarine warfare missions along the coasts of Russia and China during the early years of the Cold War. He subsequently attended the US Naval Test Pilot School in 1954 and became a test pilot. Before being chosen for NASA’s initial group of astronauts, he served as the Air Intelligence Officer of the USS Hornet.

USAF Captain L. Gordon Cooper, Jr., 32 years old, was commissioned as an officer in the newly formed USAF in 1949 after briefly serving as a US Marine at the end of World War II. After completing flight training in 1950, he served as a fighter pilot in West Germany for four years while taking college extension courses. After returning to the US, he finished work on his BS in Aerospace Engineering in 1956 at the US Air Force Institute of Technology and subsequently attended the USAF Experimental Flight Test School. Afterwards, Cooper served at the Flight Test Engineering Division at Edwards Air Force Base as a test pilot and project manager before becoming an astronaut.

US Marine Corps Lt. Colonel John H. Glenn, Jr., 37 years old, left school before completing his degree requirements for a BS in Chemistry and enlisted in the service in March of 1942. After completing his flight training one year later as a US Marine, Glenn went on to a distinguished career as a combat pilot in the Pacific theater during World War II and later in Korea. After Korea, he attended the US Naval Test Pilot School in 1954 and served in various capacities testing new naval fighter systems. He entered the national spotlight after completing the first supersonic transcontinental flight on July 16, 1957 flying an F8U Crusader 3,935 km from Los Alamitos, California to New York City in 3 hours, 23 minutes and 8.3 seconds, including the time to perform three low-speed aerial refuelings. He had been working in various capacities supporting the development of manned spacecraft technology when he was selected to become an astronaut.

USAF Captain Virgil I. “Gus” Grissom, 33 years old, was inducted into the US Army Air Forces (the predecessor of the USAF) in 1944. After being discharged from the service following the end of World War II, Grissom attended Purdue University earning a BS in Mechanical Engineering in 1950. Afterwards, he reenlisted in the military, earned his USAF pilot wings and subsequently flew 100 combat missions in Korea. After the war, he attended the US Air Force Institute of Technology and earned a BS in Aeromechanics in 1956 before receiving test pilot training. Grissom was assigned as a test pilot in the fighter branch at Wright-Patterson Air Force Base when he was chosen to become part of NASA first group of astronauts.

US Navy Lt. Commander Walter M. Schirra, Jr., 36 years old, graduated from the US Naval Academy in 1945 and earned his pilot wings three years later. He subsequently served as a fighter pilot first aboard the USS Midway in the Mediterranean and later in Asia where he flew 90 combat missions over Korea. Afterwards, Schirra became a test pilot at Naval Ordnance Test Station China Lake, California (NOTS) testing new weapon systems and was later deployed in Asia aboard the aircraft carrier USS Lexington. After his tour of duty in Asia, he attended the Naval Test Pilot School in 1958 and was a test pilot at Naval Air Station Patuxent River before being selected as an astronaut.

US Navy Lt. Commander. Alan B. Shepard, Jr., 35 years old, graduated from the US Naval Academy in 1944 and served on various vessels in the Pacific theater during the closing months of World War II. He earned his naval aviator wings in 1947 and entered the US Naval Test Pilot School in 1950. Following various combat-related assignments, he returned to being a test pilot in 1954. After serving as a test pilot instructor, Shepard entered the Naval War College and upon graduation in 1957, he became the Aircraft Readiness Officer on the staff of the Commander-in-Chief – Atlantic Fleet before being selected by NASA as part of the “Mercury 7”.

USAF Capatain Donald K. “Deke” Slayton, 35 years old, enlisted in the US Army Air Corps after graduating from high school in 1942 and flew 65 combat sorties in B-25 Mitchell bombers while stationed in Italy and another seven combat missions in the A-26 Invader over Japan. After the war, he enrolled in the University of Minnesota in Minneapolis and graduated with a BS in Aeronautical Engineering in 1949. In 1952, Slayton transferred to active duty in the USAF and later served as an F-86 Sabre pilot and maintenance officer while stationed in West Germany. He entered the Air Force Test Pilot School in 1955 and became a test pilot at the Flight Test Center at Edwards Air Force Base where he had been assigned when he was selected as part of NASA’s first group of astronauts.

Only a half a year after being founded, NASA seemed to be making progress in the undeclared manned space race. But much more work still remained to be done before any of the Mercury 7 would make their first spaceflight.

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Related Video

Here is footage of the press conference on April 9, 1959 where the Mercury 7 astronauts were first introduced to the public.

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Related Reading

“The Origins of NASA’s Mercury Program”, Drew Ex Machina, December 17, 2018 [Post]

“The Future That Never Came: The X-20 Dyna Soar Aerospace Plane”, Drew Ex Machina, April 10, 2016 [Post]

“A History of Suborbital Crewed Spaceflights”, Drew Ex Machina, May 5, 2016 [Post]

General References

David Baker, The History of Manned Spaceflight, Crown Publishers, 1981

William M. Bland, Jr., “Project Mercury”, in The History of Rocket Technology, Eugene M. Emme (editor), Wayne State University Press, pp. 212-240, 1964

Loyd S. Swenson Jr., James M. Grimwood, and Charles C. Alexander, This New Ocean: A History of Project Mercury, NASA, SP-4201, 1966