Project Mercury

John Florens | Jan 29, 2023

Table of Content


The Mercury programme was the first human space programme in the United States. The programme was carried out by NASA between 1959 and 1963 and included twenty automatic test flights with or without humans and six flights with astronauts in space. The main aim of the programme was to put a man into space for the first time in the world, and to overtake the Soviet Union in the space race. The goals were later changed when the Soviets took the lead with the Vostok programme and President John F. Kennedy announced the Apollo programme, from then on the Mercury programme was designed to maximise the space experience.

The programme began in October 1958, with the first informal announcement of the start of work (still only within NASA) on 7 October 1958 by T. Keith Glennan, Director of the newly formed Space Agency, and the formal announcement to the US public on 17 December 1958.

Immediately after the internal announcement of the programme, the requirements for the equipment, infrastructure and future astronauts were drawn up, and the suppliers for the programme were selected (in the US model, the equipment was designed and manufactured by private companies on a contract basis). The schedule for the test flights was also set. Two main types of flight were planned: suborbital and orbital. The hardware for the two types of space flight was also selected. For both flight profiles, the newly developed McDonnell Mercury spacecraft was chosen, the Redstone rocket for suborbital flights and the Atlas rocket for orbital space flights.

The main goal of the programme was not achieved, as the world's first astronaut was Yuri Gagarin, aboard Vostok-1 on 12 April 1961 - so NASA did not put the first man into space - so Alan Shepard, launched on 5 May on Mercury-Redstone-3, did not become the first man, only the first American to go into space. Later, John Glenn's Mercury-Atlas-6 made the first orbital flight (the first "real space flight" in the public mind) on 20 February 1962. Three more flights were made, culminating in Gordon Cooper's Mercury-Atlas-9 on 15 May 1963.

Already after the first manned flight, the Mercury programme was transformed into a space experience programme in preparation for the moon landing, which, having fulfilled its tasks, continued in the Gemini programme.

Space race and the Cold War

After the Second World War, the former allied powers and the countries around them were united in two political blocs, and a political and military confrontation, the so-called Cold War, emerged. This confrontation, however, could not be settled by direct military action, partly because of the memory of the devastation of war and partly because of the threat of nuclear weapons, and so, in addition to the background armament and the deterrence based on it, and the intervention in smaller-scale local wars, each side seized every opportunity to emphasise the leadership and superiority of its country or political bloc. Such areas included sporting and scientific achievements. When technical science had reached the stage of development where the achievement of outer space was no longer a fiction (or science fiction), the United States and the Soviet Union announced that they would be the first to attempt to reach outer space. With this step, space exploration had already become part of the Cold War before it was born, a tool of the Cold War.

On 29 July 1955, US President Dwight D. Eisenhower announced through his spokesman that his country would launch a satellite as part of the International Geophysical Year. In the Soviet Union, in response, on 8 August 1955 the Presidium of the Central Committee of the USSR issued a secret decision to start developing satellites. Thus began the space race.

"Sputnik crisis"

The International Geophysical Year ran from 1 July 1957 to 31 December 1958, and the United States was preparing to fulfil the President's proclamation to launch the world's first satellite with the Vanguard programme. However, the Soviet Union unexpectedly launched Sputnik-1, the world's first space instrument, on 4 October 1957, without any prior official announcement, ahead of the American attempts. In the US, this was interpreted almost as a declaration of war (the Soviets' real message in putting the satellite into orbit was that if we could get an object around the Earth, we could reach any point on the Earth, we could bomb any point on the Earth).

The American public saw the Soviet satellite flight as a defeat similar to the Pearl Harbor attack, and the press demanded an immediate retaliation from the government. To add to the US government's woes, the launch of the Vanguard probe, intended to be the world's first satellite, ended in spectacular failure (the rocket exploded on the launch pad) during a public television broadcast. President Eisenhower (who had previously shown no interest in space exploration, either as a scientific achievement or as a political propaganda tool), made the achievement of space a national priority in the wake of the failure.

The creation of NASA

On 1 October 1958, President Dwight Eisenhower established the National Aeronautics and Space Administration by decree, with the aim of concentrating the previously fragmented and sometimes parallel space developments, and enabling the US to respond as quickly as possible to Soviet advances. The goal set for NASA from the moment it was founded was to overtake the Soviet Union by being the first to launch more advanced space assets from the Soviet Union and also to overtake its rival by putting a man into space.

Previously, the US had had a government agency for aeronautical development, including high-speed flight and rocketry, and from November 1957 space flight research, NACA, which had been the backbone of NASA when it was founded, but the new organisation also incorporated the research results, personnel and equipment, as well as the budget resources, of experiments carried out by the army, navy and university workshops. The NACA's space flight section was the Special Committee on Space Technology, also known as the Stever Committee, after its chairman, with names such as Wernher von Braun, later the designer of the moon rocket, Robert Gilruth, later the director of NASA's manned space flight section, and Abe Silverstein, the creator of the hydrogen-oxygen propulsion system. This group of experts is considered the core of the new agency's space section.

A new organisation was needed because the technology needed to reach outer space was a top secret military technology that could not be openly disclosed to the public, and therefore a civilian state organisation was needed that could demonstrate the military capability without revealing its military nature. The creation of the Space Agency, with NACA and other military programmes as precursors, can be seen as a process rather than a new beginning, since the main tasks and the allocation of human and material resources had already been defined between the entry into force of the National Aeronautical and Space Act in July 1958 and the official start of operations on 1 October 1958.

By the time NASA was founded, Explorer-1 (and a little later Vanguard-1) had succeeded in answering the challenge posed by Sputnik-1 and Sputnik-2, and the next logical step was to put a man in space. Work was already underway within the NACA and other military organisations on the theoretical basis for this, and by pooling and integrating the expertise and the work materials and financial resources, these separate work materials were very quickly forged into a single concept.

One of the most significant of the projects merged into the new space agency was the Air Force's Man in Space Soonest project, which aimed to put a man in space, but until its merger into NASA, in most areas (e.g. the concept of a possible spacecraft, or possible flight profiles) only hypotheses were reached by Air Force and NACA engineers. The most progress was made in outlining the requirements for the astronaut, to the point where eight candidates for future flights were selected:

Later, the selection of these candidates was cancelled and new astronaut candidates were recruited according to a new criteria and selection system, but the Man in Space Soonest initiative provided a good basis for the Mercury programme. (Interestingly, only two of the eight candidates selected ended up going into space: Neil Armstrong as commander of Gemini-8 and Apollo-11, and Joseph Walker during the suborbital flights of the X-15 programme).

While it may seem that most space-related initiatives (such as the Man-in-space-soonest, ARPA agency programs, or X-15) originated outside of NACA, this is more due to the fact that the military and its related agencies carried the budget and project organization themselves, so their programs were documented, had names, etc. At the same time, there were also major efforts within NACA, with research at Langley Space Center on extreme altitude wingless vehicles (spacecraft), but most of this was basic research, not aimed at a specific space flight, but rather at laying the foundations for technical possibilities. Later, therefore, Langley became the starting point for the concrete realisation of human spaceflight on this knowledge base.

Basic concept

The start of the Mercury programme - like the start of NASA itself - was not a project, but an existing process was taken forward in the new organisation, and then became a specific programme, given a name and an organisation. The core of the programme dates back to August 1958, when NACA Director Hugh Dryden and Robert Gilruth, deputy director of the Langley Flight Research Laboratory (later Langley Space Center), briefed Congress on the plan for a one-man space capsule to be launched into space, with a request for a $30 million grant. During September, another defence government agency, ARPA, joined the plan, contributing additional development capacity. This collaboration laid the foundations for the programme:

The project launch itself was spontaneous rather than planned, project-like: On 7 October 1958, Keith Glennan, the newly appointed head of NASA, authorised the design of manned flight at a meeting of some of his engineering colleagues. The handful of engineers gathered together the initiatives that had already been taken, in a fragmented way, by NASA's predecessor organisations and projects. Most activities were then initiated by management formalising and formalising previously informal processes and channeling them into a single stream. Shortly afterwards, on 5 November 1958, the Space Task Group was formed, now within NASA, and took the idea forward in an organised way (by setting out detailed requirements).

Detailed information

The first step in the design was to answer the question "where to fly?", and to define the part of space where the 24-hour stable orbit around the Earth, as defined in the baseline requirements, could be achieved. The lower theoretical limit (100 kilometres altitude) was already known from Tódor Kármán's calculations before the first satellites were launched, but it did not meet the requirements for a 24-hour flight, the restraining effect of the atmosphere being too great, but NASA had concrete experimental data from the evaluation of the data of the half-dozen satellites launched by the end of 1958 to determine the orbit. The Space Task Group concluded that an orbit with an average altitude of 160 kilometres (100 miles) would be adequate (with both proximity and longitude within ±40 kilometres (25 miles). The calculations were based on a 1 tonne space capsule, and were done because the Atlas intercontinental ballistic missile, outlined in the baseline, was 'the most reliable launch vehicle available to meet the objective' and was still just about capable of achieving these flight parameters.

As regards the launch vehicle and spacecraft requirements in the baseline requirements ("the most reliable launch vehicle available" and "a ballistic capsule designed for high aerodynamic drag"), Max Faget's ready-made concept of a "bare Atlas" was adopted. Faget had been working on rocket propulsion issues within the NACA since 1946 and was involved in the development of the X-15 rocket plane. The X-15 experiments were later continued in the X-20 Dyna-Soar project (an initial space shuttle concept), with Faget's participation. In November 1957, the designer presented his vision of a possible manned space flight, in which he envisioned existing military ballistic missiles as the means of propulsion, proposed solid-propellant booster rockets for re-entry from Earth orbit, and sketched the spacecraft as a wingless capsule shaped for ballistic flight. At a joint NACA - Air Force engineering meeting in January 1958, Faget's idea was taken further. At this meeting, it was taken as an obvious fact that rocket propulsion was needed to reach space, and the X-20 being a military programme, the choice of ICBMs, a recent development, was made. Of the possible missiles, the Atlas ICBM was the most capable, but as even this was considered by the engineers to be weak, a 'stripped down' missile with an additional upper stage and of course stripped of its warhead and its launch adaptor was accepted by consensus as being suitable for the task. (As a side-track, in McDonnell Project 7969, a spacecraft development project launched at the end of 1957 at the McDonnell aircraft factory at the factory's own risk, development of a possible space capsule to fit the concept was also started with the help of Faget's advisers.)

The Space Task Group got the idea, which was already well advanced in its development (and had been proposed for implementation in several technical discussions), and in early November 1958 the Faget "stripped-down Atlas" plan was officially adopted. A procurement briefing for prospective manufacturers was called for 7 November 1958.

Although it was not included in the basic requirements, the Space Task Group was also responsible for formulating a set of requirements for the spacecraft occupant. To this end, the Task Group first planned to convene a conference of industrial and military leaders, with the participation of some aero-physicians, to identify a group of 150 astronaut candidates (based on their personal recommendations). The method and criteria for selecting the candidates were also developed at this time. It would have involved first asking for a proposal for a larger group of 150 people, which would have been narrowed down to 36, taking into account aero-medical criteria, and then, after nine months of training, 12 candidates would have been selected from these 36, of whom the best six would have become astronaut candidates. Those selected would have to be men aged between 25 and 40, with pilot training, under 180 cm tall, in excellent physical condition, with a university degree in a science subject. An additional requirement was that the candidate should be willing to take the risks involved in experimental flying, be able to tolerate difficult physical conditions and be able to make quick and correct decisions under high stress or in emergency situations. A draft of the notice specifying this was completed on 22 December 1958, but it was not green-lighted, and after the Christmas holidays, on 28 December 1958, President Eisenhower decided that the pool of military pilots was sufficient for the pool of candidates and that, for reasons of national security, only those selected should be chosen. In the first week of January 1959, the Space Task Group submitted the criteria to the Pentagon and the selection of candidates began.


One of the many tasks of the Space Task Group was to name the programme. In the US, it is customary to distinguish government programmes by some easy-to-remember, catchy name for the public, the contracting manufacturers and the press. By the end of autumn 1958, the Space Task Group had come up with the not-so-sounding name "Project Astronaut" for the programme. Some managers saw the name as a risk of overemphasising the astronaut role, while others wanted to see a return to the previous naming system. Abe Silverstein (head of rocket development) suggested Mercury, a god of Roman mythology, as a name. The Roman god (also known as Hermes in Greek) was a sort of established brand name in various areas (see Ford's brand) and is one of the most familiar mythological figures to Americans, so his familiarity and popularity made him a suitable name for the programme. Moreover, it fitted in well with the American concept of using such mythological names in rocketry (Jupiter the arch-god - Jupiter launcher, Atlas, Titan carrying the Earth on his shoulders - Atlas rocket, etc.). On November 26, 1958, Keith Glennan and Hugh Dryden, two of NASA's top executives, accepted the proposal and the name "Project Astronaut" was replaced by "Project Mercury".

Press release

In the United States, all government programmes were public - in contrast to the Soviet practice of the time, where space experiments were kept completely secret until they were successfully carried out - and this was particularly the case with the Mercury programme, which was specifically designed to be public to demonstrate a payback to the Soviet Union. It was for this reason that Keith Glennan - waiting for the 55th anniversary of the Wright brothers' flight to add to the solemnity of the announcement - made an official announcement on 17 December 1958 that his country was embarking on a space programme to put a man into space, the Mercury programme.

Developing the spacecraft

The design of the spacecraft started with the "naked Atlas" concept proposed by Max Faget. From the principles formulated at NASA's Langley Space Center, the Space Task Group drew up a call for proposals for 20 October 1958, which was later issued to prospective manufacturers. A production call was sent out on 23 October 1958 to 40 manufacturing plants, to which 38 responded and sent representatives to the first design meeting on 7 November 1958. Of the 38 applicants, 19 expressed an interest in building the spacecraft and were given the design document 'S-6 Human Spacecraft Specification'. By 11 December 1958 (the deadline for bids), the field was narrowed to 11 manufacturers.

To speed up the programme, NASA itself was barely ahead of the suppliers working for it: while the prospective manufacturers were studying the requirements and preparing the first design sketches for the proposals, the space agency itself was drawing up the technical and financial evaluation criteria for the proposals received.

In the selection process, two equally ranked candidates, McDonnell Aircraft and Grumman Aircraft, were finally shortlisted. One of the two was chosen for a particular reason: Grumman was at the time the winner of several bids for Navy contracts, and the Space Task Group feared that the company would not be able to meet the demands of several challenging development projects at once and that the development of the Mercury spacecraft would be delayed. So the right to build the spacecraft was awarded to McDonnell Aircraft on 12 January 1959. The contract was signed by James McDonnell, the president of the manufacturing company, on 5 February 1959 and Keith Glennan on 12 February 1959, in which the manufacturer agreed to design, manufacture and deliver 12 Mercury space capsules to NASA for a total of $19 450 000. The pace of development was so rapid that James McDonnell, in a speech in May 1957 (before the Sputnik-1 flight), put the first man in space in 1990, i.e. he envisaged a development of several decades, which in practice took two years.

McDonnell already received a 50-page study from NASA during the tender phase, which described the basic design criteria and aspects of the spacecraft (essentially the NACA

The basic idea behind the construction of the capsule was as simple as possible: 'the only goal is to put a man into space for a short time'. In practice, this meant cramming everything into a single space, everything related to navigation, the astronaut's life support, the operation of the spacecraft. Almost all the systems were placed inside the cabin, filling every nook and cranny and leaving little room for the astronaut. (Later, during the flight phase, it became clear in practice that this was a design dead end, since the systems, spread out over several points of the cabin, in the spaces available, the wiring connecting them, the chaos, and the failure of one system meant that several others had to be dismantled and rearranged in preparation for flight. In order to solve this problem, and precisely because of the negative experience with the Mercury spacecraft, the philosophy of dividing the spacecraft into two parts, a capsule and a technical unit, was introduced from the next space programme, the Gemini programme onwards.)

It was in the fulfilment of the third chapter of the baseline requirements, set out at the start of the programme, that the most protracted dilemma in the design unfolded. As early as the mid-1950s (when nuclear warheads were fitted to missiles), it became obvious that an object falling through the atmosphere at high speed would be subjected to enormous thermal stress from air friction. Different forces have developed different solutions to the problem: the army has experimented with composite heat shields made of heat-burning, melting (but heat-dissipating) materials, and the air force with versions made of heat-absorbing materials. For a long time, the Space Task Group experts could not decide (one material's advantage was another's disadvantage and vice versa), so they left both development directions open. Tests were then under way with the two types of heat shield when the conceptual flaw in the heat-absorbing version was discovered: the heat shield made of heat-absorbing material would have had to be removed from the spacecraft during the final stages of landing, as it would have been extremely hot on landing, posing a hazard to the astronaut in the cabin, and

After the conceptual design of the cabin, detailed design and testing of the experimental spacecraft components began. The first of these tests were drop tests of the capsule. These included both free-fall and descent tests with various parachute systems, during which more than a hundred life-size concrete-filled space capsule mock-ups were dropped at sea or on land landing sites. These drop tests were used to develop the optimum parachute braking system for landing.

Another series of tests was used to develop the rescue rocket. In the event of a launch accident, the designers planned a device consisting of small rockets (and a lattice structure to attach them to the capsule) which, in the event of a problem, would 'pull' the capsule off the rocket as quickly as possible and carry the spacecraft and its occupant to a safe distance from the explosion site, which would inevitably occur. The first test on Wallops Island was so disastrous (shortly after the rockets were launched, the rocket started to tumble upwards and after two complete tumps, it hit the ocean) that the idea of rethinking the whole system from the ground up was raised. After a month's work, the designers corrected the errors and the device became capable of saving the Mercury cabin in the event of a launch problem.

The third series of tests was carried out to finalise the shape of the Mercury spacecraft in the wind tunnels of the Langley Space Centre and the Ames Space Centre. To do this, mock-ups of the spacecraft in various sizes were taken into the wind tunnel to test the properties of the spacecraft in the trans-, super- and hypersonic speed ranges of flight.

In a fourth series of tests, the technical solution for the final phase of the landing, the descent, had to be developed, and a choice had to be made between landing on water and landing on land. The engineers preferred the water landing. The landing was planned to be 9 m

The fifth series of tests was aimed at the final design of the parachute system, with the main focus on the behaviour of the deployment parachute and the main parachute at extreme speeds and

Development of the rocket

The engineers selected three different types of rocket for the flights:

The Space Task Group searched for a human space launch vehicle among medium- and long-range rockets developed for the US military, and the final candidate was found in the Atlas intercontinental ballistic missile, developed by Convair for the US Air Force, which is about to enter service. The Atlas was such a recent development that its first successful test launch (still under the military code name SM-65 Atlas) did not take place until 17 December 1957. The Atlas specification included, for the first time in the USA, the performance required to place an object of equivalent mass to a spacecraft in orbit around the Earth, the requirement to place a 1.5-2.5 tonne body into a stable orbit above 300 kilometres. However, the newness of the rocket and the uncertainty of its reliability meant that additional launch vehicles were needed to begin flight tests. The Redstone rocket met the reliability requirement, earning the prestigious nickname "Good Old Reliable" for its previous successful flights. In addition to reliability, there was another consideration - the cost of the tests. For many tests, it was not necessary to accelerate an entire space capsule to orbital velocity, just to get it to the right altitude. Orbital flights were the most expensive - the cost of producing an Atlas rocket was estimated at $2.5 million - while a Redstone launch cost $1 million. The Redstone was also identified as a possible launch vehicle because of the consideration that it would save millions of dollars per test. They also did so with the Little Joe rocket, which can be operated at even lower cost and is well suited for certain sub-tests. For those tests where it was not necessary to place the test object in orbit around the Earth - and this was the case for most of the initial tests - engineers also defined sub-orbital flight profiles (so-called space jumps).

NASA quickly realised that the Atlas rocket was immature and in need of testing, and that the cost of a launch was high at $2.5 million per launch, while the Atlas did not have the capacity for a series of tests. In addition, the Redstone rocket, which could replace the Atlas for these less demanding tests, was itself an expensive device, costing $1 million per launch. It was therefore decided to use a cheaper launch vehicle. At the time of the decision, however, the missile did not yet exist and had to be developed.

The requirements were laid down by NASA at the end of 1958, and then further refined. These required the future rocket to be capable of launching the Mercury spacecraft in such a way that the cabin forces could be tested at high altitude, the rescue system, the landing parachute system and the post-landing search and rescue procedures could be evaluated. Subsequent refinements to the specification included the ability to measure in-flight and landing (impact) parameters of the cabin, noise, heat and pressure parameters generated by the missile, in particular the effects on the on-board living organism(s), with minimum telemetry instrumentation. These parameters had to be able to be monitored at different critical altitudes (6000, 75 000 and 150 000 metres). Based on these requirements, Max Faget's team created the first rocket within NASA, named Little Joe, which made its first launch on Wallop Island on 21 August 1959.

For the first time in the history of spaceflight, the rocket design plans included the need to "bundle" the engines. Accordingly, the installation of four modified solid-fuel Sergeant (also known as Castor or Pollux) engines was included, as well as the use of four Recruit auxiliary engines. By parameterising the four engines, a maximum thrust of 1020 kilonewtons could be achieved, theoretically allowing a spacecraft of 1800 kg to be propelled in ballistic orbit to an altitude of 160 km (thus simulating the properties of the Atlas).

In November 1958, 12 companies were invited to tender for the production of the missile, based on the requirements and basic designs, and the North American Aircraft Company won the tender on 29 December 1958. Under the contract, the manufacturer was to deliver seven flying examples and a mobile launch tower. The first airworthy North American production aircraft took off on 21 January 1960.

The Redstone rocket was also included in NASA's space programme for cost-saving and reliability reasons. The basic PGM-11 Redstone was one of the oldest US military short-range ballistic missiles, developed in 1952 and in service with NATO's Western European Forces from 1958 to 1964. The missile was a direct descendant of the German V-2, designed by Wernher von Braun at the Redstone Arsenal. NASA was looking for alternatives to the Atlas rocket, both to reduce the cost of experiments and for reasons of reliability (the Redstone was considered a particularly reliable rocket, and thus fitted the safety requirements for putting man into space), and chose the Redstone, albeit an improved version of it better suited to the purpose. Redstone became the rocket of choice for suborbital flights in the Mercury programme.

The original military version of the Redstone was not capable of getting a Mercury cabin to the required altitude on a parabolic flight, but an improved derivative of the Redstone, the Jupiter-C, had an extended fuselage, larger tanks inside and, with the increased burn time, was capable of reaching higher altitudes. The Jupiter-C had just switched to the A-7 engine (the military had switched to this variant for its own missiles because of the potential component shortages of the engines used previously, a risk), which posed problems. The basic Redstone rocket still used the V-2 propellant (75% ethyl alcohol, 25% water), but the Jupiter-C rocket switched to the so-called hydyne propellant (60% asymmetric dimethylhydrazine and 40% dimethylnetriamine), which was much more efficient but also much more toxic, which was a problem in its application. In addition, hydyne had never been used on the A-7, so the engineers decided that the missile, converted for space applications, would again use the ethyl alcohol version. The extended burn time posed an additional problem: the graphite thrust vector baffles used in normal rockets could fail during the extended burn time, so NASA put out a call for better quality baffles. Another modification was also made to the design to allow for longer burn times: the rocket received an additional nitrogen cylinder to fill the tank with neutral gas in proportion to the rate of ejection, and the turbopump received an additional hydrogen peroxide tank.

Another difference between the military and space rocket was the rescue and abort system. On the one hand, the Redstone, which is suitable for spaceflight, was equipped with a so-called automatic in-flight abort detection system. This meant that the rocket could detect when the flight parameters were about to deviate from the norm, and then the system could automatically initiate the rescue process when the rescue rocket separated the capsule from the launcher (of course, the abort could be triggered by the astronaut himself or by the control centre, but there were flight profiles where there was simply no time for manual intervention). And, of course, compared to the military version, there was the escape rocket, which, in case of trouble, could disconnect the capsule from the rocket and take it to a safe distance. Changes were also made to the so-called tail section of the rocket (which, strangely enough, was not on the back of the rocket but on top of it, connecting the cabin to the launch vehicle). This section contained the rocket's electronics and guidance system, as well as the adapter that received the space capsule, and in the military Redstones, when the rocket burned out, this section split, with one half remaining with the rocket and the other half continuing to fly with the combat section, while in the space rocket version, the whole remained with the launch vehicle. Another change has been made to improve the reliability of the Redstone. The military version's ST-80 autopilot has been replaced by a much simpler, more reliable version, the LEV-3.

By the end of development, the Mercury-Redstone deviated from the military Redstone by a total of 800 points, so in the end NASA had a newly developed rocket rather than the original, reliable version. The first flight of the upgraded launcher took place on 21 November 1960, which failed, followed by three more or less successful flights before it finally carried the two-man spacecraft with Alan Shepard and Gus Grissom.

One of the central pieces of hardware in the Mercury programme was the launch vehicle. The requirements were simple: it had to be able to accelerate a 1500-800 kg object to first cosmic velocity and place it in orbit around the Earth. The only tool the US had at its disposal was the military's intercontinental ballistic missile, the SM-65D Atlas. The rocket was the latest technology available, with its first test launch taking place on 11 June 1957 (albeit unsuccessfully at the time). NASA's dilemma was whether to make the existing but unreliable rocket reliable or to wait for the Titan II ICBM development process (with possibly the same uncertain outcome), so the decision was made to test and improve the Atlas.

Convair, the rocket's manufacturer, had a dedicated production line for the Mercury programme, with trained, experienced personnel who could be used to ensure high quality. The products destined for space underwent an extensive redesign, involving the following components:

The rocket was based on two basic design principles. One of these principles was the so-called one-and-a-half stage layout: the rocket had one main engine and two side accelerators. These were started simultaneously at launch (so it was easier for the engineers to visually check the operation), then the boosters were shut down before the main engine during orbit and the boosters (or their associated tanks) were never shut down. The other principle was the so-called gas balloon design or system. To minimise weight, the rocket was designed with the thinnest possible sidewalls, so thin that the rocket would collapse under its own weight when empty. Its stability and structural strength were initially provided by the pressure of the propellant and then, as it ran out during flight, by the pressure of the neutral helium gas in the tanks. During the tests, the latter design principle proved to be the weakest link, requiring modifications and further tests.

The first Mercury launch took place on 29 July 1960, but the real proof came on 20 February 1962, when John Glenn and Friendship 7 flew.

Flight profiles

Space flight had already been decided with the flight of Sputnik-1, it was considered a real space flight if it was performed in orbit around the Earth, so naturally NASA set this as the goal for the first American astronaut flight. However, at the end of 1960, it became clear to the Americans from the Soviet experiments - several satellites in orbit with large masses (equivalent to the mass of a human flight cabin) of living beings - that their rival was ahead of them, and it was then that the idea was conceived that the programme should branch out in two alternative directions: continuing preparations for orbital flight and preparing a suborbital human flight as a separate direction. NASA thought that it would be reassuring to the public if, although America was at a visible disadvantage in orbital flight, which was seen by all as the obvious 'real' option, the path to this would be built up in stages and the first stage (the space jump) would be won. The Redstone rocket, originally intended only for testing, and the Mercury capsule have therefore been put into operation, a process in which a space jump in automatic mode, without a passenger, then with a monkey and finally with a cosmonaut, will be used in three stages to beat the Soviets.

Infrastructure improvements

The most important infrastructure issue was the choice of the launch site. Interestingly, although there is a theory for selecting a launch site to reach space - the closest possible location to the equator - no site was deliberately sought when the Mercury programme was launched, but, in order to adapt to the circumstances in which NASA was formed (the space agency was also created by concentrating the experiments of the various military forces), NASA opened a liaison office at Cape Canaveral, one of the most advanced missile ranges of the US Department of Defense and the Army and Navy, with the task of bringing the military tests that had been taking place there to NASA. Given that the military already had a base and launch site for the Redstone rockets at Cape Canaveral, this base was designated for the Mercury flights, regardless of the fact that NASA was a civilian organization and Cape Canaveral was a military base.

In preparation for manned spaceflight, NASA was given the S-hangar, built by the Air Force in 1957 (first used for aircraft maintenance and storage) and then given to the Naval Research Laboratory's Vanguard programme for further experiments. In 1959, a formal agreement was also reached between the owner of the facility, the Department of Defense, and NASA to take over the hangar and its associated infrastructure. From then on, Mercury spacecraft from the production site were received here. It was later used for the Gemini programme and continued to be used until the Space Shuttle.

The main supporting infrastructure for the flights was the launch sites. Two of these were also designated for NASA, following the logic of the take-over of previous experiments. The LC-5 (Launch Complex) became the launch pad for the Redstone rockets and the LC-14 for the Atlas rockets (and the Big Joe rockets used in the tests). The LC-5's career began in 1956 under the auspices of the Air Force (Cape Canaveral Air Force Station), when it was used to test Jupiter medium-range ballistic missiles at the Cape, before being replaced by the Juno II, an evolution of the Jupiters, which were used to launch satellites into orbit. NASA was then given the launch pad for the Redstone rockets, first in automatic mode, then with a monkey and finally with a human.

The story of LC-14 is a little more complicated. The launch pad was built in 1957 to launch military Atlas rockets, and was converted in 1959 to launch Atlas-D rockets and space launches. At the time, it was considered the only launch site designated for Atlas rockets, so the Mercury program could not have it exclusively, but had to share it with MIDAS satellites, Big Joe test launches, and other intercontinental rocket launches before it could be exclusively in the hands of NASA. Later, all Mercury-Atlas launches were launched from here, and later Atlas-Agena launches were also launched from here.

Further planning was required to design landing and subsequent rescue operations and to manage the maintenance of radio contact during the flight. The Navy was selected to handle both tasks simultaneously.

At a press conference in Washington D.C. on April 9, 1959, NASA presented to the public the seven men who, after rigorous medical and psychological testing, had been selected to become the first men to go into space. At the same time as they were unveiled, the public learned a new word: astronaut (in American terminology, astronaut, which has its roots in Greek mythology, associating with the Argonauts, and literally meaning star sailor).

But the public unveiling was preceded by a lengthy, secret selection project. The selection process was based on medical assumptions that would-be space travellers would face deadly dangers: a collapse of the orbit in zero gravity, the inability to eat or drink without gravity, psychological difficulties, and a kind of space madness that could make the lonely spacecraft unable to control it. To counteract these dangers, a selection system was devised to select candidates who were highly above average in terms of health and psychology.


The selection of astronaut candidates was carried out under President Eisenhower's instructions - and slightly modified from the requirements laid down by the Space Task Group - with the military flying corps being invited to draw up a list of potential candidates. A total of 508 potential candidates were screened in Washington, from which 110 pilots were selected as suitable candidates (the list included five Marines, 47 Navy and 58 Air Force pilots, with no one from the Army Air Forces being found suitable). In the second stage of the selection process, the candidates were divided into three main groups and the first 35 were ordered to Washington for interviews in early February 1959, under a confidentiality order. Charles Donlan, who headed the project on behalf of the Space Task Group, was pleased to note that the vast majority of the candidates were looking forward to participating in the Mercury programme. This was due to the fact that the programme required volunteers, and prospective pilots were not expected to be led to the task. A week after the interviews of the first group, the second group arrived in Washington and underwent their interviews. The proportion of volunteers among those found suitable was so high that there was no need to call in a third group (especially as the final contingent of 12 originally thought to be suitable was reduced to 6). After the interviews of the two groups, 69 people went on to the selection process.

Despite clear physical parameters, six of the 69 were rejected because their height was too great. Finally, 56 candidates were rejected because of additional withdrawals from the general, technical and psychological tests of the second round. The number of those selected was then reduced to 32, who were taken by the Space Task Group for detailed medical tests, including special elements, at the Lovelace Clinic in Albuquerque, New Mexico, and then at the Wright-Patterson Base Aeromedical Laboratory.

For one week, starting on 7 February 1959, candidates underwent a six-phase, all-encompassing, multi-day medical examination at the Lovelace Clinic. This involved first a review of the candidates' medical history, followed by detailed general medical tests such as a vision test, ECG and reflex tests, a colonoscopy and blood test, or a sperm count. This was followed by a full range of X-rays, from dental X-rays to stomach X-rays. The next step was physical performance tests, which included cardiac stress tests on a bicycle ergometer, lung capacity measurements and body density measurements. At the end of the week-long tests, the data were summarised and recorded on medical records for each candidate.

Immediately following the clinical trials, the group moved to Wright-Patterson Air Force Base for stress tests between 16 February and 27 March 1959. These tests were designed to assess the psychological and physical stress tolerance of the candidates. The physical tests included simple stair or treadmill loading exercises, or centrifuge tests requiring high endurance, or multi-axis rotary chair exercises familiar to pilots from aeromedical examinations. In the parallel psychological tests, candidates were tested with unexpected or unpleasant stimuli, such as thermal or cold water tests or dark chamber exercises. Psychological tests also included the Rorschach test, which is otherwise subject to credibility doubts.

At the end of the Wright Patterson tests, the Nominating Committee put forward 18 fully medically qualified candidates at the close of the test series at the end of March 1959. The Space Task Group Selection Committee met on 1 April 1959 and from the 18 suitable candidates, seven were finally selected for astronaut training. This group was announced by NASA on 2 April 1959, and were then introduced as the Mercury Seven (Mercury 7) on 9 April 1959 in Washington as the future US astronauts, and with these seven pilots, astronaut training began.

Original Weeks

The following group, known in the press as the Mercury Seven, started the training:

Six of them went up into space as part of the programme (Slayton was removed from the group in 1962 due to heart problems, and only flew on the Soyuz-Apollo programme in 1975 after heart surgery).

The astronaut candidates stepped into the limelight with their presentation. As well as the natural interest of the public - there was hardly a more exotic profession than "astronaut" at the time. NASA itself further boosted the popularity of its candidates by encouraging a deal between the astronauts and a major American magazine, which bought the rights to publish stories about astronauts in a $500 000 offer. As part of the deal, he published his reports on the lives of astronauts in the Life series, as well as their biographies. In this series of articles, which ran for 28 issues between 1959 and 1963, Life created a new American hero, portraying astronauts as a kind of 'everyday superhero', embellishing their backgrounds and portraying their everyday lives outside training in the American stereotype.

In addition to the Mercury Weeks, two other names - both of them posthumous - were used for NASA's first seven astronauts. One was Astronaut Group 1, which NASA used afterwards when it started recruiting additional astronaut groups for the Gemini programme and then the Apollo programme, and wanted to distinguish the groups selected at different times. But it was not only NASA, but the astronauts themselves, who distinguished themselves by naming the group themselves, and so the Original Seven became known and later the most publicly used group name, also to distinguish it from the others (such as the New Nine recruited in 1962, or the Fourteen in 1963).

Astronaut training

The training was very similar to the selection programme at Wright-Patterson Airbase: they practised their take-off and entry profiles in centrifugal acceleration simulations, trained in a suitcase, in a heat chamber or in carbon dioxide chambers, or maintained their fitness by various sports. But there were also completely new areas. They toured the plants of various suppliers, learning about the hardware being built, visited Cape Canaveral, the starting point for their future space missions, and went to Akron to see the space suit manufacturing plant. They also began a process of specialization, with Carpenter, for example, with his naval experience, becoming an expert on the spacecraft's communications and navigation systems, Grissom immersing himself in Mercury's control and electromechanical systems, and Glenn helping with the cabin instrument panel. The training included flight exercises in addition to the above tests. On the one hand, they continued their previous flights in high-performance fighters to maintain their flying skills, and on the other, they practiced for the weightlessness they would face by flying parabolic flights in NASA's C-131 aircraft, which had been designed for the purpose.

A total of twenty Mercurys were built, three failed launches, five were put into ballistic orbit, and six orbited the Earth. Six experiments were performed with humans, two of them only in ballistic orbit. The spacecraft allowed a single human to fly in space for 24 hours, up to a maximum of 36 hours. The chemical batteries were capable of 1500-3000 watt-hours (Wh), depending on the task. It was bell-shaped, 3.4 metres high including the booster rockets, with a maximum width of 1.9 metres. It was of double-walled construction, the outer casing being of nickel alloy, the inner of titanium alloy, with an insulating material of ceramic fibre between. The rescue rocket was mounted in the nose. The height of the rescue tower is 6.2 metres. The stabilizing parachute and the stabilizing infrared horizon finder were installed in the antenna housing. The cabin is 1.9 metres in diameter and 1.5 metres high. During the time in service, the astronaut performed the required tasks in a sitting position, with almost no movement.

Alan Shepard was the first American to go into space in the Freedom 7 spacecraft, making a suborbital space jump. John Glenn was the first American to orbit the Earth in the Friendship 7 spacecraft. The Soviets also surpassed the Americans in manned spaceflight with the Vostok programme.

Unmanned test flights

The Mercury programme's first attempt would have been Little Joe 1, had it not been thwarted by a glitch. The experiment did not take place at Cape Canaveral, but on Wallop Island, and the engineers wanted to see how the escape tower would behave, particularly at the time of maximum dynamic pressure (the maximum drag at take-off). For this purpose, a Little Joe rocket was sufficient, as it could simulate the desired dynamic pressure, and then a model of the Mercury spacecraft was built on this launch vehicle, and finally the only complete system, the rescue tower.

However, the planned flight was a complete failure in 1959. On 21 August 1959: 35 minutes before the planned launch, when the automatic and the self-destruct were connected to the power source of its own battery, the explosive charges separating the spacecraft units were triggered unexpectedly - the crew preparing for launch began a panic flight - and finally the rescue tower (which correctly detected the emergency) was launched with the attached spacecraft model, while the rocket remained in the launch pad. The rescue rocket then did its job in exemplary fashion, taking Mercury to the required altitude of about 600 metres, where it released it. The test report was completed in less than a month, and the cause of the failure was identified as a so-called "stray current" caused by an improper winding.

In addition to the Little Joe series of experiments on Wallop Island (which essentially had to prove the rescue rocket's functionality), NASA also started testing another important component, the heat shield. This required a more powerful launch vehicle, the so-called Big Joe rocket. The Big Joe was essentially the Atlas rocket. In the Big Joe experiment, the Atlas-10D launch vehicle was mated to a non-operational but mass and size efficient Mercury spacecraft, and a heat shield (which heats up on re-entry, burns up, burns, slowly disintegrates, but distributes heat efficiently) was fitted to the spacecraft, selected after a lengthy design debate.

The launch took place on 9 September 1959 from Cape Canaveral, launch pad 14. During the flight, everything worked perfectly until about the two-minute mark, at which point control received an error signal on the telemetry: the stage separation failed. Because the stage continued to fly as dead weight, there was no chance of the spacecraft reaching the planned altitude and speed. With the rocket stage remaining on the spacecraft (thus defeating the primary purpose of the heat shield), control had to play with the reactive control thrusters (essentially the small auxiliary thrusters that do the steering) to bring the rocket down, which was ultimately successful, although the propellant for steering was completely consumed. The Mercury spacecraft finally reached a top altitude of 140 km and after a flight of 2292 km, it reached the Atlantic Ocean, where rescue teams found it relatively intact after a few hours of searching.

On 4 October 1959, the next Mercury test took place - again on Wallop Island - which was unmarked at the time and only later given the designation Little Joe 6. The test was essentially a step backwards from the failed first attempt, the only thing in common being that the launch vehicle used was the same one that had been left on the launch pad in August. As regards the flight test objectives, the step back meant that the only tests were to verify the suitability of the rocket and the flight characteristics and robustness of the spacecraft. To this end, a space capsule of sufficient mass and size, but with no systems and therefore inoperable, and an equally inoperable escape tower were assembled with the rocket.

During the experiment, Little Joe lifted the 16.5 metre high and 20 tonne structure to an altitude of 65 kilometres, where at the end of the two-and-a-half minute flight, the controls triggered the self-destruct as planned. The pieces of the spacecraft hit the ocean 115 kilometres away. The experiment was deemed a success.

On Wallop Island, experiments were continuous, with Little Joe rockets being launched every month to the day. Thus, on 4 November 1959, Little Joe 1A was launched, an exact replica of the failed Little Joe 1 flight. The objectives were the same, the flight was intended to verify the suitability of the rescue rocket, with the addition of collecting as much data as possible on the parachute system. The capsule designated for flight was again an inoperative mock-up, with only the rescue rocket intact. The experiment was also attended by the press, after a short battle in which journalists fought to get first-hand information about the flight (NASA staff therefore gave the press a detailed "training" beforehand, so that any interruptions in the countdown would not be reported as a mistake or failure).

On 4 November, the LJ-1A finally completed a partially successful flight. The rocket lifted the space capsule into the air apparently without a hitch, but the rescue rocket did not deploy until 10 seconds after the point of maximum dynamic load. The parachute system functioned perfectly, as did the rescue operations, so the secondary and tertiary operational objectives were 100% achieved. The reason for the malfunctioning of the rescue rocket was not revealed, only speculations were made. The failure has led to a repetition of the experiment.

Little Joe 2 was launched from its usual location on Wallop Island on 4 December 1959, and was a substantial improvement on the previous attempt. Although the LJ-1A was not an unqualified success, the experimenters did add live flight to the Little Joe-Mercury experiment. They were curious to see how a simple organism like a small copper monkey would behave under the effects of spacecraft motion, weightlessness and radiation at high altitudes. Later, they planned to launch an additional biological package: oat grains, rat neurons, tissue cultures and bugs were prepared to travel with the monkey.

The launch took place in the presence of two new astronaut candidates, Alan Shepard and Virgil Grissom. Little Joe lifted Mercury to 30 000 metres, and the launching rescue rocket raised the altitude even further, taking the capsule to 84 000 metres, before it free-fell from the dead centre. Peak altitude ended up being nearly 30 000 metres lower than planned, caused by miscalculated drag. Sam the monkey ended up experiencing only 3 minutes of weightlessness instead of the planned 4. At the end of about 6 hours of tossing and turning, the rescue teams managed to pull the little monkey out of the sea safely, after a smooth landing. The experts declared all the preliminary objectives a success and were enthusiastic - especially about the perfectly functioning Little Joe launcher - although later opinions became more nuanced, with biologists in particular complaining about the less than satisfactory results of the animal experiment. The main objective was achieved, however, and the rescue rocket proved to be perfectly suited to a possible emergency rescue of the spacecraft with living beings - even humans - on board.

Sam the monkey's voyage was followed by a repeat of the not entirely successful Little Joe 1 and 1A flights, with the minor twist that the spacecraft was again carrying "someone", Miss Sam, a small female copper monkey. On 21 January 1960, another Little Joe rocket was launched from Wallop Island, and this time it finally performed as expected. The rocket was less than 15 kilometres short of its planned altitude and reached a speed of over 3,200 km

The only real novelty of the flight was a rescue exercise, with engineers simulating an emergency at Little Joe's burn-out altitude and the rescue rocket having to be launched. The operation went off without a hitch, with a further 75 m

In February 1960, at a meeting in Los Angeles, NASA decided (based somewhat on the Little Joe and Big Joe tests) on the final Mercury spacecraft, Atlas rocket, rescue rocket configuration, and planned to implement it with the final configuration. The finality - and perhaps the presence of working hardware - was also evident in the fact that the flight was not intended to be launched as Big Joe, but as the final Mercury-Atlas-1. For the flight, they therefore took McDonnell's factory-built space capsule No. 4 and installed additional equipment and instrumentation. The spacecraft was more of a measuring workshop in its final build-up than a functional space vehicle, given the missing systems (life support, pilot seat, instrument panel, steering thrusters, etc.) that had not yet been installed.

Parameters to be tested before the flight

On 24 July, the parameters to be achieved by the spacecraft (5700 m

One minute after the launch, all contact with the rocket was lost. A second before the transmission was interrupted, a signal was received via telemetry that the pressure difference between the fuel tank and the liquid oxygen tanks had suddenly ceased. As no visual control was available through the cloud, it was not possible to know whether this signal was the cause of the problems or the end result of the problems in which the tanks were destroyed, but it was clear from the signals that the rocket and spacecraft had been destroyed. The causes were difficult to uncover, although rescue teams managed to find the crashed rocket and Mercury space capsule in the sea. The cause of the failure could not be determined, but NASA decided to repeat the flight, only to load the spacecraft with instruments for the next test.

The design of the Little Joe 5 experiment began about a year before the planned launch, and the original idea was to launch the first operational Mercury space capsule or rescue rocket by incorporating a special "package" containing a medium-sized chimpanzee to test the behaviour of the spacecraft and its occupant at maximum Q. However, delays in landing the space capsule, problems with the so-called 'staple ring' connecting the spacecraft and the rocket, and the separation pyrotechnics built into it, delayed the preparations, so Robert Gilruth decided (with the agreement of the STG engineers) to take the chimpanzee out of the planning objectives, so that the crew could concentrate more on technical matters. Later, further problems arose with the installation of the helium and hydrogen peroxide tanks, causing further delays. There were also additional weight problems with the flying hardware, which raised the possibility of an unwanted landing in Africa.

The launch was finally scheduled for 8 November 1960. On that day, the experiment ended in complete failure. The rocket lifted off from Wallop Island at 10:18 local time (15:18 UTC) and was destroyed after only 16 seconds of flight. The rescue rocket was then fired ahead of time, while the launch vehicle was still accelerating the spacecraft, but all the components remained in a coupled state, veered off course and crashed into the sea. The capsule rose to an altitude of only 16.2 km and crashed into the sea 20.9 km from the launch pad, far short of the target range. Rescue teams later recovered some of the wreckage from the sea for further analysis.

In the second half of 1960, the idea was mooted within NASA - partly for fear of the Soviets getting ahead of them and partly to save costs - to split the experiments and, in addition to the orbital flight with the Atlas rocket, to perform a so-called space jump (ballistic orbit flight) with a lower-powered rocket, which would be space flight only in that it would cross the Kármán Line. The Redstone rocket was chosen and the Mercury spacecraft was built on top of it to test the space jump.

To test the new flight profile, the engineers planned to fly a full-scale Mercury space capsule (factory number 2) with a Redstone launcher (marked MR-1) and a full-scale escape tower. The plan was to use this combination of equipment to test the spacecraft's automatic guidance and landing system, as well as the ground launch, rescue and tracking infrastructure. In addition, they also wanted to test the operation of the abort detection system (the system was configured to detect and report an abort situation to the control system, but not to trigger an abort itself).

The launch was first scheduled for 7 November 1960, but a fault was detected in the helium system (the pressure unexpectedly dropped to a quarter of its normal value), so the launch had to be postponed, the spacecraft and the heat shield dismantled from Redstone, the fault rectified (by replacing the tanks and rewiring) and the assembly reassembled. The new launch was scheduled for 21 November 1960. This was the first time that Mercury's control centre was used to guide the flight.

The launch took place at 9:00 local time (14:00 UTC) from the LC-5 launch pad. The surprised controllers saw through the periscope of the new control centre that the rocket roared, then suddenly the roar stopped, the rocket jerked, then settled on its tailplane and silence settled on the launch pad. Immediately afterwards, the rescue rocket starts up and flies away, but leaves the space capsule on top of the rocket. Three seconds after the escape rocket flies away, the parachute of the capsule deploys and covers the capsule, half deploying. The situation became quite dangerous due to the malfunctioning of the system: the fully loaded rocket was standing on the launch pad without any safety, relying solely on gravity, with the parachute hanging over the side of the whole assembly, threatening to be blown over by a small gust of wind.

The failure eventually went down in reports as the "four-inch flight" (others have summarized the event as "all we fired was the rescue missile"). First, the command chose among several options to wait until the batteries needed to power the missile's systems were depleted so that the liquid oxygen could slowly boil off and the explosive missile could be approached. The troubleshooting that began soon revealed the cause of the problem: during the launch, different cable connectors were disconnected from the rocket in different sequences, and a wrong cable (a shorter cable from a different type of Redstone) was pulled out of the rocket in the wrong order, so the engine detected this as a shutdown command and stopped the launch process well before it was complete. Once the fault was identified, it was decided to repeat the test.

Less than a month after the failed attempt, NASA was ready to make another space jump. The Mercury-Redstone-1A flight was a complete repeat of the failed attempt on 19 November. The spacecraft was the same (factory number Nr.2) as the one that had been dismantled from MR-1, and the rocket used for assembly was the MRLV-3. The purpose of the flight remained the same: to verify the operability of the automatic guidance and landing system and the flight abort system using the operational space capsule, rocket and escape tower.

The launch took place on 19 December 1960, when the Redstone rocket lifted off from the Cape Canaveral LC-5 launch pad at 11:15 am (16:15 UTC), the engine operated for 143 seconds, and the spacecraft was finally carried to an altitude of 210 kilometres (210 miles), and landed in the Atlantic Ocean 378 kilometres (378 miles) from the launch site. The maximum end-of-flight speed was 7900 km

After the successful Mercury-Redstone-1A mission, NASA immediately moved on to the Redstone rocket spaceflights, as this was the quickest way for the United States to beat the Soviets to the punch. The next step was to make a fully fledged space jump with a fully equipped spacecraft, but first with a monkey on board, a kind of dress rehearsal before flying a man so that the effects on living organisms could be studied. The objectives of Mercury-Redstone-2 were defined accordingly. However, instead of the rhesus monkeys already used in the Little Joe experiments, a chimpanzee, a primate with a more human-like physique, was chosen for the flight. At Holloman Air Force Base, a colony of 40 monkeys had already been established for the experiments, and one was chosen for the flight. The monkey chosen was born in Cameroon in 1956 and was transferred to America in 1959, and for the experiment the original Chang (the "inventory number" was changed from 65 to Ham. Ham did not have the original English meaning of 'ham', but was an acronym made up of the initials of the Holloman Aerospace Medical Center, which ran the experiment. What was new for Ham, compared to the previous flight, was the need to devise tests to test not only vital functions but also the organism's response to weightlessness and the effects of spaceflight. The most important of these tests was to subject the animal to different sound and

Twenty veterinarians and caretakers, with six of the best animals selected at Holloman Base, were transferred to Cape Canaveral on 2 January 1961, where they were assigned a separate ward. The new location first began a period of acclimatisation, as the monkeys were moved from Holloman's altitude of around 1500 metres above sea level to sea level, so that the monkeys' measured health values changed for objective reasons. The animals were then divided into two separate groups, where members of the two groups were not allowed to come into contact, thus preventing a possible infectious disease from sweeping through all the candidates at the same time. During the period leading up to the launch, the chimps practised daily the tasks they had learned at Holloman base, only this time the light and sound signals and the responding arms were incorporated into a life-size Mercury cabin model to allow the animals to get used to the new 'working environment'. On the day before the launch, a member of the Space Task Group and a veterinarian from the Dutch team examined the animals and selected the most suitable candidate, Ham. The chimpanzee assigned to the flight was also assigned a backup, a female named Minnie. For the two selected specimens, the take-off process began 19 hours before the scheduled launch, when they were fitted with biosensors to measure their vital signs and fed a diet. Seven and a half hours before the start, a final medical check was carried out. Four hours before take-off, the two animals were placed in pressurised seats specially designed for the flight and taken to the launch pad.

The Mercury-Redstone-2 launch took place on 31 January 1961 at 11:55 (16:55 UTC), following a series of launch delays due to problems (the launch pad elevator jammed, too many people were unnecessarily present in the launch pad environment, one system took 20 minutes longer to settle, and the cover of one of the rocket's connectors got stuck). The chimp's journey was far from trouble-free. One minute after launch, telemetry data detected a 1 degree deviation in trajectory, and the deviation increased. The acceleration lasted for 137 seconds, at which point the rocket's automatic engine shut down as programmed. The rescue rocket detected the engine shutdown as a failure, but instead of disengaging, it fired up and continued to lift the capsule. The failure of the escape rocket over-accelerated the spacecraft, pushing the planned distance of about 7081 km

Despite the difficulties, the monkey did a great job. As with the ground training, he had to pull levers on various cues and only missed twice out of 50 times (again punished by a small electric shock). On landing, one more problem became apparent to the control. The failure occurred during the rocket separation and the false launch of the rescue rocket, the brake booster rockets used for the final trajectory setting on landing (which were bundled in a "package" and strapped to the bottom of the cabin for easy detachment at the end of the braking) were detached prematurely. Therefore, the braking manoeuvre did not take place at the top of the trajectory. The capsule then returned to atmosphere and, due to the multiple changes in trajectory, Ham was subjected to 14.7 G at maximum deceleration. The problems did not leave the spacecraft on descent. Ham splashed down in the Atlantic Ocean after a 16 minute 39 second flight, 679 kilometres from the launch site and 90 kilometres from the closest waiting ship, the destroyer USS Ellison. During the landing, the cabin was damaged, the heat shield was torn off and there was a leak, so water began to pour into the cabin, threatening to sink it. A P2V search and rescue aircraft sent to monitor the landing and to locate the cabin's location in the water discovered the Mercury cabin tossed upside down in the water 27 minutes after landing. The command then ordered the Navy to order helicopters for an early rescue, as the boat recovery would have taken at least 2 hours. The closest helicopter carrier, the USS Donner, sent a search and rescue helicopter, which eventually recovered the sinking space capsule. The pilots estimate that about 360 litres of water had accumulated inside the cabin by the time it was recovered. In addition to the damage to the cabin wall, water also entered the cabin through a valve (the same valve through which air escaped during the initial phase of the flight and remained open). Following the extraction, the helicopter transported the cabin to the USS Donner and the door was opened on board. Marines found Ham strapped into his seat, safe and sound. The animal, who was in good condition, was given an apple and an orange from the galley, which he had consumed with relish.

Ham's mission was not a clear success, so it became necessary to make changes to the rocket and test its functionality on another test flight before manned spaceflight.

Meanwhile, progress was also being made on the other branch of the experiment, orbital flight. The key was to make the Atlas rocket space-qualified for the Mercury programme, which had failed spectacularly with Mercury-Atlas-1. During the investigation of the accident, suspicion was focused on the design of the rocket as a possible source of failure. The Atlas was a so-called kerosene-oxygen rocket (i.e. using RP-1 kerosene as fuel and liquefied oxygen as oxidizer), which had its first successful launch on 17 December 1957 as a military ballistic missile. The design philosophy of the structure was quite unique, the engineers used the so-called 'gas balloon' method: the tanks of the spacecraft were made of stainless steel thinner than paper and were filled at the rate of their evacuation with helium gas at a pressure of 170-413 kPA, which provided structural strength to the entire rocket. According to the testers, the rocket blew up or fell apart due to insufficient structural strength, so the next Atlas rocket was given a steel strap (known as a bonding brake or belt in astronaut slang) as reinforcement to compensate for the structural weakness of the 'thin-walled' version. The strap was first tested in a laboratory and wind tunnel and found to be suitable, but there was a long debate between the Space Task Group, the Air Force and Convair as to whether it was a suitable solution. In the end, the majority opinion of STG and Convair recommended to James Webb, the new head of NASA, that he should authorise the flight (Webb, as a few days' leader, took the risk of going against the Air Force, which had more experience in operating the rocket and was opposed to the experiment, and of bringing all the consequences of a failure upon himself and NASA.)

Strangely enough, however, the engineers did not specify an orbital test, but only a suborbital one, as a precautionary measure, the rocket was essentially just supposed to accelerate the Mercury capsule to an automatic space jump. Webb's decision was taken and the rocket, manned rocket and rescue rocket were quickly assembled and set for launch. On 21 February 1961, at 9:28 (14:28 UTC), the spacecraft was launched without a hitch, monitored by controllers from the local control centre. Several people hardly dared to breathe at the launch, and audible sighs of relief were heard when, after 1 minute of flight, the rocket and spacecraft passed the max Q zone and continued to accelerate as planned. The telemetry sequentially indicated the launch vehicle shutdown, spacecraft separation from the rocket, separation from the escape tower, spacecraft rollover to the braking ignition, the braking maneuver, and finally the separation of the braking package. Radio contact was lost at this point due to distance, but soon the outbound USS Greene reported that it was picking up signals from the returning capsule and rocket, and that it was visually monitoring the re-entry. In the landing area (an ellipse 20×40 miles in diameter with errors), the USS Donner awaited the spacecraft's arrival. The destroyer spotted the spacecraft, and the rescue helicopters dispatched lifted Mercury aboard within 24 minutes. The attempt was a complete success.

The engineers considered it vital to test the behaviour of the spacecraft system in the maximum dynamic pressure range (max Q), and expected to make progress in this area by repeating the failed Little Joe 5 flight (even though data from the Mercury-Atlas tests were already available). That is why a repeat of LJ-5 was targeted, especially in the light of the fact that the left-ended attempt had failed to clearly identify the cause of the failure.

On 18 March 1961, at 11:49 (16:49 UTC), Little Joe 5 was launched from Wallop Island, but this time everything didn't work right. Just 20 seconds after launch and 14 seconds before the time limit, the escape rocket was activated again, the spacecraft separated from the rocket and almost hit it, and then descended into the ocean on the parachute. The capsule finally landed 28 kilometres from the designated landing point with a slightly damaged parachute. According to post-flight analysis, the dynamic pressure (drag) exerted such a structural deformation force on the structure of the spacecraft that the twisting of the fuselage and the fuselage back and forth eventually fouled the electronics, which gave a false abort command. The experiment was again unsuccessful, or at least partially successful.

Ham's trip was not a clear success, so much so that Alan Shepard's flight in Mercury-Redstone-3 was not to follow, but Wernher von Braun, Director of NASA's Marshall Space Flight Center, was forced to make changes to the rocket and test the functionality of the changes on another test flight. In the meantime, some controversy had erupted between the rocket designer and the press chief over how to present the safety issues concerning the first US astronaut to the public. NASA's communication policy was that no astronaut would be allowed into space until they could guarantee 100% that the hardware was reliable for the safe return of the passenger, while von Braun said that the risk was a risk that had to be accepted, and that it was definitely there, and that it was greater than driving a car on America's roads, but certainly not greater than that of the shuttle pilots from which the candidates came. The latest flight has not even been given a serial number, but has been given the unscheduled Mercury-Redstone-BD (or Booster Development) designation. Redstone was changed at a total of seven locations. One modification was to prevent the rocket from accelerating too fast, which was achieved by modifying a small servo valve to allow less hydrogen peroxide to enter the steam generator that drives the fuel pumps, thus reducing the pumps' power. Also modified was the so-called thrust reducer, a component that controls the amount of fuel flowing through the engine, which was also designed to prevent over-acceleration. Another source of problems was the vibration of the upper part of the rocket caused by the air forces, so four stiffeners were installed and the insulation on the rocket wall was modified (65 sensors were installed to test the effects). Five more circuit breakers were installed to allow the engine to be shut down as accurately as possible before the oxidizer ran out.

The launch also gave the ground crew the opportunity to practice in real conditions, which they would later encounter with human space launch vehicles. On the day of the launch, an M113 armoured vehicle was parked 300 metres from the launch site, in which the crew - including the "fire master" who oversaw the launch - took their seats and waited for the bone flier to do its work in the noise of the launch. Another vehicle - an empty truck coated with asbestos - was parked 20 metres from the rocket's gas jet deflector, simulating the position of the mobile escape tower. During the launch preparations, there was a minor problem with the fuel temperature rising to near boiling point and some liquid spilling from the rocket. The refuelling process was controlled by a computer, which had to be adjusted to solve the problem.

On 24 March 1961, at 12.30 local time (17:30 UTC), the rocket was launched. The rocket lifted off as planned, although the end-of-fire velocity was 26.7 m

Following the first successful Atlas missile test, preparations for the next test have begun. It is now certain that the improved D-100 production rocket will be used for this test - with the Mercury No 8 cabin. The improvement was to replace the sidewall of the rocket with a thicker material, which promised greater structural stability, to avoid the Mercury-Atlas-1 crashing for this reason. The original plan was for the Atlas to take the Mercury capsule on a long-trajectory ballistic flight over the Atlantic (2,000-2,500 kilometres instead of the 400-500 kilometres of the Mercury-Redstone space jump), but following Gagarin's flight the flight plan was completely rewritten and a single-turn orbital flight was now planned. In addition, a robotic spacecraft was fitted with a "robot" which, in addition to receiving various instruments, was able to imitate breathing by means of a special pump system to measure the loads during flight, thus testing the life-support system. According to Plan B, if the Atlas rocket had not reached the required speed, the flight could have been interrupted anywhere over the Atlantic and transformed into a mission at least as close as originally planned to suborbital flight.

Mercury-Atlas-3 was launched on 25 April 1961 at 11.15 local time (15:15 UTC) without any major delays, but due to a control system failure - the spacecraft flew straight up and did not lock on to its orbit - it had to be self-destructed at the 43rd second of the flight. The only functioning unit was the escape rocket, which automatically separated Mercury before the Atlas exploded, so that it could later descend into the ocean. Part of the wreckage of the Atlas, including its guidance system, was found two months later at the crash site, deeply embedded in the mud, allowing the cause of the failure to be identified.

On Wallop Island, preparations were underway for the seventh Little Joe launch, as it was deemed absolutely necessary to carry out the failed tests of the LJ-5 and LJ-5A. For this purpose, they used Mercury cabin number 14, which this time was loaded with even more instruments. The original plan was for the rocket to climb a steep trajectory up to 15 000 metres, where it could detach from the spacecraft, the escape tower could detach, the parachute could eject from the parachute housing and the landing could begin. The maximum Q force of about 5000 kg

On 28 April 1961, at 9:03 (14:03 UTC), the take-off took place. Observers immediately saw that one of the Castor engines had failed to start, making it obvious that the trajectory would be much lower. In the end, the rocket took the spacecraft to an altitude of only 4500 meters, while the force detected during max Q was nearly double that. The planned abort of the flight occurred at the 33rd second. The spacecraft finally landed 3.5 kilometres from the landing point, and the rescue helicopter lifted it out without any problems. Given the structure, which can carry twice the load, the experiment was declared a success despite the fact that the trajectory was completely off the mark.

The failure of Mercury-Atlas-3 has completely rewritten the plans for the next flight. The original plans included a repeat of the previous space flight with a monkey on board, but this was later changed to a robot astronaut replacing the monkey and a flight with 3 orbits of the Earth, to be carried out by NASA in April 1961. Then, due to the failure of MA-3 and then a series of delays in the production of Atlas, the experiment was postponed and the flight plan was changed. In addition, an unusual decision was made to use Mercury cabin number 9 for the flight: cabin number 8 of the MA-3, which had fallen into the sea, was fished out of the sea, the necessary repairs and replacements were made and it was built on top of the Atlas rocket. Subsequently, factory defective transistors were found in the manufacturing plant and it was suspected that they might have been used in the Atlas and even in the spacecraft, so the already assembled assembly was returned to the hangar and disassembled again. NASA then ordered as thorough an inspection as possible, as the US could hardly afford to be late in the space race - especially after the achievements of Gagarin and Tyitov - and even less to fail. The launch date was also delayed for a long time by inspections, while the hurricane season hit, and preparations had to be halted twice because of hurricanes.

The new plans called for Mercury-Atlas-4 to fly orbital, not suborbital, but orbital, with only 1 orbit around the Earth. During this time, the behaviour of the rocket and spacecraft could be observed throughout the launch process (and of the rocket for three more days until natural deceleration brought it back into the atmosphere). In essence, everything (acceleration, rocket separation, braking, re-entry) was very similar to the space jumps, but on a larger scale, with a higher load on the structure, a higher heat shield and a larger area to be covered by the search and rescue teams deployed at sea.

Finally, on 13 September 1961, the fourth Mercury-Atlas spacecraft was launched and made a successful orbit around the Earth. The biggest question after launch was whether the structural reinforcement provided by the thickened sidewall would be sufficient for the rocket. Although the instruments measured severe vibrations in the first few seconds, the rocket withstood both this load and the subsequent maximum dynamic vibration (the maximum vibration load, called max Q, which varies with air density and velocity) well. The spacecraft underperformed or overperformed on some flight parameters and eventually settled into a slightly different but satisfactory orbit around the Earth. During the orbit, the only anomaly observed was in the oxygen supply system, which then ran out of the gas needed to sustain the astronaut (apparently due to a minor leak in the absence of a user) much faster than planned. The other systems worked satisfactorily. At the end of the single orbit, in the Hawaii area, the control system slowed the spacecraft down with deceleration rockets and the capsule began its re-entry into the atmosphere. After a flight of 1 hour 49 minutes 20 seconds, it landed 176 kilometres from Bermuda, where it was taken on board by the destroyer USS Decatur. The flight was successful, with subsequent analysis judging all operations satisfactory.

Mercury-Scout-1 was a separate NASA experiment, not to assess the capabilities and suitability of the Mercury hardware, but to test the ground radio tracking network for later flights. At the time of the Mercury programme, geostationary communication satellites did not yet exist, so radio communications with Earth-orbiting spacecraft were handled by ground-based radio stations and ships patrolling the seas along the expected path of a later manned spacecraft. The principle was that when the spacecraft came within a few hundred kilometres of a receiving station, contact was established by shortwave (RH), ultra-shortwave (URH) or ultra-high frequency (UHF) radio bands, and C- and S-band radar signals. Outside the range of the ground receiving stations, the spacecraft flew without ground contact. The stations themselves were connected to NASA's control centre by land, submarine cables and long-wave radio links.

The plan was to use a modified Scout rocket to launch a miniature communications satellite that would simulate the Mercury spacecraft. The 67.5 kg MS-1 satellite was shaped like a square box containing two command receiver units, two mini positioning beacons, two telemetry beacons, S- and C-band radar transponders and antennas; the instruments were powered by a 1500 watt-hour battery. The first attempt to launch Mercury-Scout-1 was made on 31 October 1961, but the rocket's engine failed to fire. The crew checked the ignition wiring and scheduled a new launch for the next day. On 1 November 1961, at 10:32 UTC (15:32), the test vehicle was launched, but at the 28th second of flight, the first stage of the rocket began to disintegrate, and at the 43rd second, control issued the self-destruct command. The failure was attributed to the ineptitude of a technician who had installed one of the control system wiring harnesses the wrong way round. NASA later cancelled the Mercury-Scout tests, as other experimental flights had already succeeded in orbiting the Earth and testing the tracking system.

Because of the unreliability of the Atlas rocket - and despite the time delay - NASA's management decided that before launching a spacecraft with an astronaut on board, they would follow the same schedule as for space jumps, and test fly a chimpanzee first. To do this, they have prepared an Atlas rocket (Atlas 93-D) and a Mercury spacecraft (No. 9) for the flight, and deployed a team of five monkeys and their trainers, veterinarians, from Holloman Air Force Base to Cape Canaveral. The monkeys were put through a so-called four-problem cycle, which simulated working in space and which they would later have to perform on a space flight. In it, the monkeys had to pull two levers with their left or right paw in response to different light signals, with a weak electric shock for a wrong response. Then, following a green light, a lever had to be pulled after a 20-second delay, after which the monkey was given water (no shock was given if it failed, but it had to be repeated until the timing was correct). Thirdly, a lever had to be pulled exactly 50 times, after which the monkey was given a piece of banana. Finally, in the fourth test, the display flashed triangles, squares and circles (three in a row, two identical and one different), and the subject had to select the symbol that did not fit in the row, again, of course, punished by electric shock for getting it wrong. From the group of five monkeys, the doctors finally selected Enos, the male chimpanzee (Enos means "man" in Hebrew and Greek, before that the chimpanzee was only known by its registration number, 81).

Mercury-Atlas-5 lifted off on 29 November 1961 and orbited the Earth normally, with only minor sensor errors that did not affect the flight significantly. Enos continued the exercises as he had been trained for the above four problem cycles. In the second orbit, however, a series of problems began to occur. The most troublesome was that the monkey began to be electrocuted even when it answered correctly, so the test began to produce false results, and when the monkey tore off the sensors measuring vital signs in anger, medical data collection stopped. However, a more serious problem was the failure of one of the steering jets. A piece of metal shrapnel in the fuel line caused the nozzle to malfunction, causing the spacecraft's spatial position to deviate from the correct one. The automatic system corrected this from time to time with the other jets, but this resulted in more fuel being used than expected. The failure threatened that by the end of the planned third orbit, the propellant that powered the thrusters would run out and the spacecraft could not be positioned properly for braking and thus could not be brought out of orbit on schedule. Chris Kraft, the flight director, therefore decided at the end of the second orbit to shorten the flight and bring Enos down. The landing was a perfect success, with Mercury landing in the Atlantic Ocean after two orbits and 3 hours 20 minutes 59 seconds of flight off the island of Bermuda. Post-flight evaluations deemed the flight a success, paving the way for human orbital flight.

Human flights

Following preparatory unmanned flights, Mercury-Redstone-3 became NASA's first attempt to launch an American astronaut into space. The programme had earlier branched out into orbital and suborbital space jumps, on the news of the Soviets' advanced and successful space experiments, and the first flight with a human in the spacecraft was planned as a space jump. American ambitions were for the first American astronaut to be the first man in space, but Soviet engineers beat NASA to the punch and launched Vostok-1 with Yuri Gagarin on board on 12 April 1961, and the United States lost this chapter of the space race. The Soviet flight only increased the pressure on NASA, with John F. Kennedy urging the US to put a space shuttle into space as soon as possible as a response.

Alan Shepard was nominated for the historic flight as a result of a special selection process - NASA crew selection manager Robert Gilruth voted on the astronaut candidates themselves, who they considered most qualified to be the first to fly, in addition to themselves.

The flight took place on 5 May 1961. Shepard's mission was a flight of about 15 minutes, during which he had to cross the so-called Carmine Line, the theoretical boundary of space at an altitude of 100 kilometres, while monitoring the spacecraft's systems and reporting its operational parameters. He also had to monitor his own body's reactions to prove that the flight would not put an unbearable strain on the human body. According to the flight plan, the launch was scheduled for around 7:00 a.m., but this was delayed by hours due to repeated launch delays. This is one of the strangest design errors in the history of spaceflight. During the launch preparations, which were eventually extended by nearly 3 hours, the astronaut had an urge to urinate, which was followed by a long discussion within the control room on how to deal with it (as no urine collection system was designed into the spacesuit). In the end, as the least bad thing, control 'allowed' the astronaut to urinate.

Finally, the Freedom 7 radio call sign spacecraft successfully launched from Cape Canaveral LC-5. The Redstone rocket put the Mercury spacecraft into a parabolic orbit with a top altitude of 187 kilometres, making Shepard the first American to step out into space. The flight lasted 14 minutes 49.41 seconds, while Shepard reported on the spacecraft's operational characteristics, observing the Earth's surface. The only minor malfunction occurred on landing: while the rocket pack used for braking was detached correctly, the cabin indicator light showed the opposite. The spacecraft successfully landed in the Atlantic Ocean northeast of the Bahamas and was taken on board by the aircraft carrier USS Lake Champlain.

Following the success of the flight, President John F. Kennedy had the right reference point to expand the US space programme, announcing the Apollo programme, which he did 20 days later before the US Congress. Alan Shepard was awarded the NASA Distinguished Service Medal by the President for his accomplishments, and media reports made him a national hero.

Mercury-Redstone-4 became NASA's second space flight to put a man into space. The main purpose of the flight was to repeat Alan Shepard's journey in six weeks, to demonstrate its confident capability. The spacecraft was modified in a number of ways, two of the most important of which were the installation of a demountable cabin door and a large window. The door could speed up emergency rescue while being lighter in weight than the alternative (a more complex locking mechanism), and the window was both a design philosophy change and a practical observation point. Previously, the astronaut had been seen by engineers as a passenger rather than the driver of the spacecraft, with little concern for his or her view, but the astronauts' assertive action has changed this perception.

Astronaut Virgil "Gus" Grissom was assigned to the flight (his backup was John Glenn). The flight was due to have taken off on 18 July 1961, but due to adverse weather conditions the launch had to be postponed until the following day, and then for another two days due to the same bad conditions a day later. Finally, on 21 July 1961, conditions were right for the launch of Grissom at 7:20:36 local time (12:20:36 UTC). The spacecraft's call sign was Liberty Bell 7. The acceleration phase lasted 142 seconds, the time it took for the Redstone rocket to accelerate the spacecraft, which was 2 km

Grissom's tasks began after the propulsion stopped, in the zero gravity phase. First he had to perform manual control tests of the spacecraft, nodding, fan movement and rotation around the axis (the latter was not performed due to lack of time), followed by minutes of observation of the Earth's surface. The astronaut spent about 5 minutes in zero gravity and reached a maximum altitude of 190 kilometres. Then the braking manoeuvre was initiated to steer the capsule towards the designated landing point. The spacecraft passed through the atmosphere without any particular problems, then at 6300 metres the deployment parachute deployed and at 3700 metres the main parachute deployed and Liberty Bell 7 landed smoothly in the Atlantic Ocean, northeast of the Bahamas. Following the landing, Grissom began preparing for a rescue helicopter extraction, but then unexpectedly the newly developed collapsible cabin door broke down and water began to enter the cabin, which began to sink. The astronaut was evacuated from the capsule, and one of the helicopters that arrived began to lift the capsule and Grissom out. The helicopter that lifted the capsule first had an oil pressure problem, then the mass of the flooded capsule could not be supported by the helicopter, which had to release the Liberty Bell 7, which sank in a matter of moments. Grissom also ran into trouble, with the suit's neck section not sealing properly, causing the air to escape and keeping the astronaut afloat, and the rotor blades of the two helicopters hovering above him whipping the water around him so much that he was repeatedly submerged and nearly drowned. He was eventually rescued, but the sunken cabin took with it the valuable data recorded by the flight data recorders. One of the most important questions was to find out why the door exploded and whether this solution could be used safely in future expeditions, but both the cabin and the door sank to a depth of 4500 metres, and only Grissom's account could be relied on, who claimed that the door had been accidentally activated without his involvement. The astronaut's claim was doubted, especially in view of the fact that a test example of the cabin door had failed to trigger an accidental explosion, significantly exceeding the operating parameters, but Grissom insisted that the door had malfunctioned and this version was finally accepted as the official version.

The cabin had been lying at the bottom of the ocean for 38 years, at a depth of around 4,500 metres, when the Oceaneering company, led by Curt Newport, first searched for it and then brought it to the surface using deep-sea exploration robotic submersibles as part of an expedition sponsored by the Discovery Channel television network. Three previous attempts by Oceaneering to locate the cabin using technology developed to recover the wreckage of the Challenger space shuttle and data from NASA failed in 1987, 1992 and 1993. Newport later persuaded the Discovery Channel television company to fund a separate expedition solely to search for and recover the spacecraft, and the expedition, which went to sea in the second half of April 1999, discovered the relatively intact 'wreckage' on 1 May 1999 and brought it to the surface on 20 July 1999 (the 30th anniversary of the moon landing). The capsule was transported to the Kansas Cosmosphere and Space Center for display.

Mercury-Atlas-6 was the third human space flight in the programme and the first by the United States to place a human spacecraft in orbit. The flight also ranked third in the history of orbital flights, having been preceded only by Yuri Gagarin and German Tyitov. For the American public, this third place was also a setback, as it failed to 'make up' for Gagarin's another space race first, and Tyitov's 17-orbit, one-day flight spectacularly demonstrated the extent of the American gap. For a while, the only hope that remained in the public eye was the faint hope of an orbiting flight in 1961, but this hope was dashed by the continuing delay in preparations for orbital flight. The key to the flight, the brand-new Atlas rocket, the only one in the US capable of accelerating a 1.5-2 tonne object to its first cosmic velocity, was highly unreliable and test flights were plagued by a series of failures that prevented NASA from authorising the first live human experiment. In a series of test flights, Mercury-Atlas-1 exploded in the 58th second of the flight, presumably due to a structural weakness in the rocket, and Mercury-Atlas-2 made up for the failure with a successful flight. Subsequently, the structurally strengthened Atlas rocket failed again on Mercury-Atlas-3 flight, having to be remotely detonated due to a failure in its guidance system. The Mercury-Atlas-4 was luckier, and with the robotic spacecraft on board, the Mercury capsule completed an orbit around the Earth.

NASA decided that, due to poor reliability, one more test flight had to be included in the programme before a human was allowed on board: a monkey was used to simulate a human flight. On the model of Mercury-Redstone-2, when Ham the chimpanzee flew and solved tasks, a male chimpanzee named Enos was trained for a relatively complex task and launched on 29 November 1961 on Mercury-Atlas-5. The test was a success, although a fault in the steering system meant that the spacecraft had to be brought down at the end of the second orbit instead of three. NASA management nominated John Glenn, who had been the backup astronaut for the two space jumps and had therefore participated in the training for two specific flights, to fly the mission (Scott Carpenter was nominated as backup this time). Glenn, exercising his prerogative, chose the call sign Friendship 7, thus also choosing the name of the spacecraft.

After several delays, the launch took place on 20 February 1962 at 9:47:39 (14:47:39 UTC), Florida time. This time the Atlas worked perfectly and the spacecraft was in an elliptical orbit of 159×265 km, almost exactly as planned. Glenn's tasks were to monitor instruments, observe the Earth's surface, perform various body movements and visual observation exercises, and manually steer the spacecraft. In the first orbit, the spacecraft worked perfectly, but at the end of the orbit a minor problem arose, one of the rudder jets began to malfunction, and Glenn had to compensate manually from time to time. In addition, in Australia, the city of Perth was observed and mysterious sparks (Glenn called them "fireflies") appeared around the spacecraft over the Pacific Ocean (it was only much later that the phenomenon was deciphered, which were ice shards formed by the detachment of frozen slush on the walls of the spacecraft by the sunlight, which shone brightly in the sunlight like sparks). At the end of the first orbit, an instrument showed that the heat shield was not in a fixed position and could have come off during the braking for re-entry. From then on, control worked to solve the problem.

The second and third rounds were similar to the first, with visual observations and manual compensation for the deflection effect of the faulty nozzle. However, the continuous counter-steering consumed too much propellant, and after a while the spacecraft was left to drift. At the end of the third orbit, it was time to land. Control instructed Glenn not to detach the so-called landing package (a braking rocket package attached by leather straps to the heat shield), but to leave it in place until the heat generated by the re-entry burned off and detached it, allowing the heat shield to remain attached as long as possible once the air forces could hold it in place. The solution worked, Glenn demonstrated a smooth landing despite the concerns that the spacecraft failed to stabilise on landing due to premature propellant exhaustion and Friendship 7 swayed far beyond its design. Finally, the spacecraft landed in the Atlantic Ocean near the Turks and Caicos Islands, 64 kilometres from the planned landing point, after a flight of 4 hours 55 minutes 23 seconds. The spacecraft was taken aboard the destroyer USS Noa.

Following the flight, President John F. Kennedy awarded Glenn the Distinguished Service Medal.

Mercury-Atlas-7 was NASA's fourth flight with a human on board, and the second to fly the spacecraft in Earth orbit, completing three orbits. With Vostok-1 and -2 and Mercury-Atlas-6, it had already been decided that the chapter of the space race to send the first astronaut into space had been decided in favour of the Soviet Union, but the US wanted to continue the programme, partly to prove that the first American orbital flight was not a fluke, and partly to gain the experience needed to reach the all-time high of the Moon. In any case, the purpose of the flight was changed in that the astronaut was to carry out more scientific tasks during the three orbits, as opposed to the engineering observations and tasks planned for Glenn. The newly formed Ad Hoc Committee on Scientific Assignments and Training for the Man in Space Programme Committee planned five new tasks for the astronaut: releasing a coloured balloon from the spacecraft, which flew tethered to Mercury during the flight, observing the behaviour of a liquid in a sealed bottle in zero gravity, using a light meter to observe a flash of light on the surface of the Earth, taking meteorological photographs with a hand-held camera and studying the glow of the atmosphere. In addition to the changes to the tasks, changes were made to the spacecraft: to save weight, some devices were dropped that proved to be unnecessary over-protection or no longer provided additional data compared to previous flights, and changes were made to the wiring of the landing package to avoid a repeat of the problem experienced during Mercury-Atlas-6, where it was thought throughout the flight that Glenn's heat shield might come off prematurely and the spacecraft would burn up during atmospheric entry.

The astronaut assigned to the flight was the subject of an unexpected complication in March 1962. The next astronaut nominated for the flight was Deke Slayton, who was publicly named by Robert Gilruth at a press conference on 29 November 1961. Earlier, however, Slayton had been diagnosed with a heart condition called idiopathic ventricular fibrillation, which was the subject of divided medical opinion, but at the end of a multi-stage investigation was not considered to be a barrier to astronaut activity. In early 1962, however, NASA chief James Webb ordered a new investigation, which again produced conflicting medical opinions, but Webb accepted the opinion of a three-man panel of doctors, some of the most eminent in the US, who deemed it unsafe to launch Slayton into space, and the decision was taken on 15 March 1962 to replace the originally appointed astronaut. Interestingly, he was replaced not by his officially appointed reserve, Wally Schirra, but by Glenn's former reserve, Scott Carpenter.

The spacecraft, named Aurora 7 by its occupant, was launched from Cape Canaveral's launch pad 14 on 24 May 1962 at 7.45:16 local time (12.45:16 UTC). Carpenter completed three orbits, carrying out previously planned experiments and testing a new type of astronaut food. Several of the experiments failed (clouds prevented observation of the light rockets launched from the surface, the balloon in the balloon experiment did not inflate properly and its tether got tangled on the spacecraft) and the new food did not test well, crumbling, which could have been a source of problems in zero gravity. Carpenter also had problems handling the spacecraft. In general, the time allocated to tasks was shorter than necessary, which led to a rush on the part of the astronaut, which in turn led to mistakes. He activated unnecessary modes on the steering system and then left systems running in parallel, consuming fuel unnecessarily. As a result, much more fuel was consumed than planned, which compromised control during re-entry.

The return became the most problematic part of the flight. Preparation for re-entry began with the spacecraft being positioned correctly (the operational plan called for the cockpit to be set at 34 degrees), but Carpenter did not do this accurately, so the thrusters did not put Mercury on the desired parabolic path, In addition, Carpenter's observation of what he previously thought were mysterious glowing particles and their identification as frozen debris on the side of the spacecraft caused him to delay the ignition of the braking ignition, which further deviated the trajectory from the planned one. The atmospheric braking phase was accomplished without problems, but the landing was far from the planned point. Carpenter touched down in the Atlantic Ocean not far from the Turks and Caicos Islands, but 405 kilometres from the expected landing point. Radio contact with the astronaut was lost during the final stages of the landing, and the press covering the landing feared the astronaut had been lost. At 1 hour 7 minutes after the landing, a frogman was discovered and dropped off to Carpenter, who had meanwhile climbed out of the spacecraft in a small life raft. A helicopter later arrived on the scene to extract him and the spacecraft and placed the astronaut aboard the USS Intrepid mothership 4 hours and 15 minutes after landing.

After the flight, Carpenter was awarded NASA's Distinguished Service Medal, but due to errors discovered during the flight's evaluation, he was not subsequently nominated for another flight.

Mercury-Atlas-8 was the Mercury programme's fifth flight with an astronaut on board. It was also the third flight to successfully place a spacecraft in orbit around the Earth. The flight was also known as Sigma 7, as the commander of the spacecraft (exercising his prerogative) chose this as his radio call sign. The Mercury spacecraft was launched on 3 October 1962 from Cape Canaveral Launch Pad 14 with astronaut Wally Schirra, a Navy flight pilot and member of the Original Seven, on board.

The flight lasted 9 hours 13 minutes 11 seconds, completing six orbits of the Earth. This was essentially double the performance of the previous two Mercury flights, although the original plan was for seven orbits, but due to the finite amount of rescue capacity available for deployment at sea and the resulting optimisation, the final flight plan was reduced to six orbits. The spacecraft flew in an elliptical orbit of 285×153 kilometres, completing each orbit in 89 minutes.

For Schirra, NASA developed a series of operations whose main objective was to save as much manoeuvring fuel as possible. To achieve this, the spacecraft drifted a lot without correction (in Schirra's words, "chimpanzee mode") and, when the astronaut manually controlled the thrusters, the main objective was to achieve maximum economy of operations. For most of the journey, the spacecraft's automatic control system was tested. Meanwhile, the astronaut carried out navigation experiments based on the positions of stars. Apart from some initial problems with the temperature control of Schirra's spacesuit, the operations were perfect, with the spacecraft consuming less manoeuvring fuel than on any previous flight.

The flight concluded with a first-ever landing in the Pacific Ocean (near the dateline at the Midway Islands). The first longer-duration US space mission was also hailed by post-landing analysis as the first Mercury flight to be flawless in every detail. After the landing, Schirra received the President's Distinguished Service Medal,

Mercury-Atlas-9 was the last flight of the Mercury programme on 15 May 1963. NASA crossed the one-day time limit for the first time with a flight that ultimately lasted 34 hours 19 minutes 49 seconds and orbited the Earth 22 times. The passenger on board the Faith 7 spacecraft was Gordon Cooper - the last astronaut from the Original Weeks who had not yet flown and was free of health problems - who had solved a number of problems and achieved a model flight. The mission was longer than all the previous Mercury flights combined.

The spacecraft had to undergo minor redesign and modifications at the manufacturer McDonnell to meet the requirements of the extended flight time. NASA had originally planned an 18-orbit flight, but six months before the launch it was decided to send the spacecraft and its passenger on a 22-orbit flight. Gordon Cooper (and Alan Shepard as his backup) was then assigned to the flight. The launch finally took place on 15 May 1962, after a postponed launch attempt on 14 May. The orbit was perfect, followed by the scientific programme, the orbiting of a nanomatellite, the observation of light sources on it or at various points on Earth, radiation measurements, medical measurements and meteorological photographs. Cooper was also the first American to be required to sleep during the flight, which did not go smoothly due to the excitement of being an astronaut.

The most complicated part of the flight occurred around the 19th orbit, when some of the spacecraft's systems started to fail. As a result, Cooper lost the ability to perform an automatic controlled re-entry and had to perform the landing himself using manual control (the manual method was incomparably less accurate than the automatic, creating a dangerous situation). Despite this, Cooper performed a perfect landing in the Pacific Ocean in close proximity to the rescue teams sent to retrieve him.

The prestige loss of the Mercury programme was finally complete, because this flight represented the peak performance of the programme, while the Soviet Union had already launched Vostok-3 on 11 August 1962 and Vostok-4 a day later, which had completed 65 and 48 orbits respectively in a simultaneous flight, a performance far below that of the Mercury spacecraft and astronauts.

The Vostok programme provides a benchmark for understanding the Mercury programme and evaluating its performance. While President Eisenhower announced the satellite as the US Attraction of the International Geophysical Year, he also launched a strange competition between American and Soviet high technology. In terms of satellites, the Soviets kept launching important landmark space devices (the first satellite, the first living creature, the first probe to reach the Moon, etc.), while the Americans lagged behind Soviet achievements. The Mercury programme was intended to reverse this situation, and was given a competitor in the form of the Soviet Vostok programme (although the Vostok programme was prepared in complete secrecy by the Soviets, neither its name nor its expected performance were made public).

But in the race to put the first man into space, the Americans lost again, despite Mercury's efforts. On 12 April 1961, as preparations were well under way for the first Mercury space jump, the Soviet Union launched the Vostok-1 spacecraft into orbit with the world's first astronaut, Yuri Gagarin, on board. Vostok-1's one-orbit journey also far exceeded the upper limit of American suborbital spaceflight capabilities, and on the very first (announced) attempt the Soviets made an orbital flight. The American goal of putting the first man into space was lost again, and before the public could see any success on the part of the Mercury team, the Soviets had once again reaped the firsts.

To add insult to injury, in response to Gagarin's flight, the Soviets, with great difficulty, produced the meagre space jumps of Alan Shepard and then Gus Grissom, and on 6 August 1961, the Soviets launched Vostok-2, with German Tyitov on board, who orbited in space for more than a full day. Then, on 11-15 August 1962, the Mercury programme was dealt another blow by its rival, when first Vostok-3 was launched, and then Vostok-4 was launched shortly afterwards, and Andriyan Nikolayev and Pavel Popovich performed the world's first simultaneous space flight, bringing the two spacecraft within 5 km of each other. In addition, the two Soviet astronauts spent 3 and 4 days in space, beating by far Tyitov's space record, while the Mercury programme was then in its third orbit, a few hours' flight by John Glenn and Scott Carpenter. On 15 May 1963, the Mercury programme reached its climax with Gordon Cooper's flight, which lasted one and a half days in space, but the Soviets came up with an even bigger space sensation a month later: in 1963, the Mercury programme was completed by the first American astronaut, Scott Glenn and John Lennart. On 14 June 1963, the Soviets launched Vostok-5 with Valery Bikovsky on board, which in itself would not have been a major event, but two days later they launched Vostok-6 with Valentyina Tyershkova, the world's first female astronaut, on board. The two astronauts flew in space for 3 and 5 days respectively (3 days simultaneously), further extending the record for the duration of a space flight.

In the light of these facts, the Mercury programme has failed to achieve its objective and has been completely outclassed by its rival, the Soviet Vostok programme.


There were no predefined flight plans during the programme, but during the resource allocation (production and assignment of rockets and spacecraft to specific flights), an eighth (or sixth if we consider only orbital flights) flight was also envisaged, designated Mercury-Atlas-10. The manufacturer's McDonnell series 15 spacecraft was intended for a long-duration flight - initially a full day - which, after the necessary modifications, arrived at Cape Canaveral on 16 November 1962. After the Mercury-Atlas-8 flight, it was considered that a simultaneous flight should be carried out using the Mercury-Atlas-10 - and its spare capsule, designated Mercury-Atlas-11 - as a model for the Soviets' simultaneous flights of Vostok-3 and Vostok-4. However, this remained an idea and preparations for the flight continued as a one-day, solo flight. At the beginning of 1963, the idea of extending the flight to three days was mooted, the pilot was unofficially named, the rotation between the Original Weeks would start from the beginning with Alan Shepard, and unofficial sources named the flight mark: Freedom 7 II.

In April 1963, however, the future Mercury plans changed, and NASA's communications increasingly referred to Mercury-Atlas-9 as the culmination of the programme. On 11 May 1963, NASA finally ruled out another flight altogether. President Kennedy then left the matter to the discretion of NASA, who finally decided in the summer of 1963 not to waste resources on another flight but to concentrate on the Gemini and Apollo programmes.

Gemini programme

Originally, in 1961, when the Mercury programme was still in its early stages, NASA considered the continuation of the programme, and the management concluded that the one-man orbital flights should be continued with a two-man spacecraft. At the end of 1961, the Space Task Group within NASA was given the task of developing plans for post-Mercury space programmes (in particular the Apollo programme, the moon launch programme) and representing NASA with aerospace manufacturers in the design of space vehicles. Thus, this group laid the theoretical foundations for the post-Mercury follow-up. The initial plans were for the further development of Mercury spacecraft: during the working years, a possible new programme was referred to as 'two-man Mercury', 'improved Mercury', 'Mercury Mark II' or simply 'Mark II'. However, the needs outlined by the moon missions, such as the manoeuvrability of spacecraft, space rendezvous and docking, were such a major change that they departed from the technical foundations of Mercury and laid completely new foundations, but of course using the experience gained with Mercury. The program was given a new name and new technical content at the suggestion of Alex P. Nagy, NASA's Hungarian-born Deputy Director of Outreach. The Gemini programme, as a preparatory companion programme to the Apollo programme, was announced on 7 December 1961 by Robert Gilruth, head of the Space Task Group. After two and a half years of planning and preparation, Gemini-1 was launched with an unmanned test flight on 8 April 1964.


  1. Project Mercury
  2. Mercury-program
  3. Dancsó, Béla. Holdséta. Novella Kiadó, 14. o. [2004]. Hozzáférés ideje: 2014. április 10.
  4. A Szovjetunió Kommunista Pártjának 139/1955. augusztus 8 sz. határozata (orosz nyelven). SZKP. [2008. április 8-i dátummal az eredetiből archiválva]. (Hozzáférés: 2014. április 10.)
  5. ^ Designed in 1964 from Mercury Seven astronaut memorial
  6. ^ The project was delayed by 22 months, counting from the beginning until the first orbital mission.[2] It had a dozen prime contractors, 75 major subcontractors, and about 7200 third-tier subcontractors.[2] The cost estimate made by NASA in 1969 was $392.6 million, 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.[3][4]
  7. ^ 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 ($13.9 billion adjusted for inflation), and be launched by a "Super Titan" rocket.[9]
  8. ^ 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.[34]
  9. Mais D. Eisenhower repousse le projet de débarquement sur la Lune proposé par la NASA dès 1960 (Source J. Villain).
  10. La NASA avait envisagé de recruter pour leurs aptitudes des sous-mariniers, des grimpeurs de haute montagne, des spécialistes du vol en ballon à haute altitude. Elle avait également étudié de recruter des volontaires.
  11. Pour arriver à départager les candidats également méritants on fit passer des tests physiologiques particulièrement pénibles et des tests psychologiques « expérimentaux » ; c'était la première fois qu'on recrutait des astronautes. Finalement le comité sélectionnera principalement ses candidats à partir d'entretiens classiques.
  12. Pour les communications entre le support au sol et la capsule Mercury un réseau de stations radio était nécessaire. Une couverture totale des latitudes survolées n’étant pas possible, la trajectoire était calculée de manière à survoler le plus grand nombre de stations disponible. Mais à chaque révolution de la capsule la trace au sol se décalait et la couverture radio diminuait
  13. a b c d e f T. A. Heppenheimer: Podbój Kosmosu. Tajne epizody amerykańskich i radzieckich programów kosmicznych.. Warszawa: Wydawnictwo Amber Sp. z o.o., 1997, s. 190-193. ISBN 83-7169-852-6.
  14. a b c d e f g h i j k l m n o p q r s t u Steve Whitfield: Mercury. Warszawa: Prószyński Media Sp. z o.o., s. 3-8, seria: Historia podboju Kosmosu. ISBN 978-83-7648-722-9.
  15. a b c d e Andrzej Marks: Podbój Księzyca trwa. Warszawa: Wydawnictwa Naukowo-Techniczne, 1967, s. 312-313.

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