“WE GAVE IT AWAY”

As Kennedy battled through the closing months of his election campaign, NASA battled with similar tenacity and vigour to launch the first man into space. Many in the United States, however, were already echoing Louise Shepard’s sentiment that the Soviets remained in pole position to accomplish the historic feat. Project Mercury, Time magazine told its readers in September I960, “is not far behind, but it will be at least nine months before a US astronaut will enter orbit’’. ‘Orbit’ would prove the pivotal point, for neither America’s first man in space, nor even its second, would achieve orbit – they would experience little more than 15-minute suborbital arcs over the Atlantic Ocean, into space and back down – and the nation’s first piloted circuit of the globe would not come until February 1962. Still, in the weeks after Kennedy’s inauguration, Al Shepard and John Glenn were dividing their time between Langley Research Center in Virginia and the swamp-fringed Cape Canaveral launch site in Florida, familiarising themselves with ‘Spacecraft No. 7’: the vehicle which, since October of the previous year, had been earmarked for the first mission.

Unlike the huge spherical Vostok which had ferried Yuri Gagarin into space, the Mercury capsule was a cone-shaped machine, 1.9 m across the blunt, ablative heat shield at its base and 2.9 m tall, with a total habitable volume of just 1.6 m3 and an approximate weight at launch of 1,930 kg. The idea that a blunt cone was the most suitable shape to prevent a rocket-carried warhead from burning up in the atmosphere had arisen in the early Fifties, thanks to the work of NACA engineers Julian Allen and Al Eggers. Attached to its nose was a cylindrical parachute compartment and at its base a cylindrical package of three retrorockets. Its cramped nature prompted the astronauts to smirk that, far from ‘flying’ the spacecraft they actually ‘wore’ it. ‘‘You get in with a shoehorn,’’ added McDonnell’s pad leader Guenter Wendt, ‘‘and get out with a can opener!’’ During the early stages of ascent, capsule and astronaut would be protected by a pylon-like, solid-fuelled Launch Escape System (LES), capable of whisking them away from an exploding or malfunctioning rocket. This measured 5.15 m tall and produced 23,580 kg of thrust. Under normal circumstances, however, it was intended that the LES would be jettisoned shortly after the burnout of the rocket, although many engineers doubted its effectiveness and felt that a catastrophic failure would give an astronaut little chance of survival.

The Mercury capsule was equipped with attitude-control thrusters to enable yaw, pitch and roll exercises, but was incapable of actually changing its orbit. The three solid-fuelled retrorockets provided an ability to return to Earth, firing in sequence at five-second staggered intervals, in a ‘ripple’ fashion, although one was sufficient to complete this task if the others failed. To guard against temperatures as high as 5,200°C at its base during re-entry, a heat shield composed of fibreglass, bonded with a modified phenolic resin, was employed. By charring, melting and peeling off, taking heat with it, this ‘ablative’ material would protect the structure of the spacecraft from the high heat flux of hypersonic re-entry into the atmosphere. It was first tested atop an Atlas rocket in September 1959, surviving re-entry in remarkably good condition. The heat shield was not, in fact, an integral part of the spacecraft, but was held in place by a series of hooks. Between it and the base of the capsule was a folded rubber-and-glass-resin ‘landing bag’, 1.2 m deep, which would unfold and fill with air shortly before splashdown in the ocean. This would act as an absorber,

The Mercury spacecraft. Note the parachute container at the top and the retrorocket package at the base of the capsule.

softening the shock of landing from 45 G to 15 G, before filling with water to provide a kind of ‘sea-anchor’.

Mercury was the brainchild of NACA aerodynamicist Max Faget, adapted from Allen and Eggers’ blunt-cone design, and received the go-ahead on 7 October 1958, only six days after NASA’s birth. The name arose from that of the fleet-footed messenger of Roman mythology and, wrote Loyd Swenson in ‘This New Ocean’, a seminal 1966 work on Project Mercury, ‘‘seemed too rich in symbolic associations to be denied. The esteemed Theodore von Karman had chosen to speak of Mercury, as had Lucian of Samosata, in terms of the ‘re-entry’ problem and the safe return of man to Earth’’. By mid-January 1958, McDonnell had been awarded the $18.3 million contract to build the spacecraft, beating Grumman, which was heavily loaded with conceptual naval projects at the time. Faget’s original design for a ballistic capsule envisaged that it would re-enter the atmosphere at an attitude 180 degrees from that of launch, such that the G forces would be imposed on the front of the body under acceleration and deceleration; in effect, its ‘tail’ during launch would become its ‘nose’ during the journey back to Earth. Initial sketches from late 1957 revealed a squat, domed body with a nearly flat heat shield, the former slightly recessed from the perimeter of the latter, leaving a narrow ‘lip’ to deflect airflow and minimise heat transfer. However, this configuration proved dynamically unstable at subsonic speeds, so Faget’s group lengthened the capsule and removed the heat shield lip.

By March of the following year, the design resembled an elongated cone, which provided dynamic stability, but hypersonic wind tunnel tests showed that too much heat would be transferred by turbulent convection. Further, engineers could not figure out how to incorporate parachutes into the upper part of the nosecone, prompting its redesign into a rounded shape with a short cylinder attached to the top. Heat-transfer concerns, however, remained, and it was not until the late summer that the design, incorporating maximum stability, relatively low heating and a suitable parachute compartment, had been finalised. Faget’s team argued that by launching the capsule on a ballistic trajectory, its automatic stabilisation, guidance and control equipment could be minimised and the only manoeuvre it would be required to make would be to fire the retrorockets to decelerate and dip into the atmosphere for aerodynamic drag. In fact, added Faget, even that manoeuvre did not need to be too precise to accomplish a successful recovery.

In theory, Spacecraft No. 7 – the seventh of 20 Mercury capsules built by McDonnell – should have been capable of flying Shepard almost immediately, but after delivery to Cape Canaveral on 9 December 1960, it became necessary to implement 21 weeks’ worth of unexpected tests, repairs and rework. Additionally, the landing bag, beneath the heat shield, which would cushion its splashdown in the Atlantic Ocean, had to be installed and communications hardware checked. Its reaction-control system needed attention, whilst damaged and corroded hydrogen peroxide fuel lines required replacement and a variety of other obstacles surrounded equipment, minor structural defects and even the need to install a manual bilge pump to remove seawater. The need for the latter had been compounded by the successful, though harrowing, flight of a chimpanzee named Ham. He had been launched atop a Redstone in late January, but his capsule had suffered a multitude of niggling malfunctions. Firstly, a faulty valve had fed too much fuel into the rocket’s engine, causing Ham to fly too high and too far, whereupon the tanks ran dry, the spacecraft separated too early and re-entered the atmosphere too fast and at the wrong angle. Temperatures soared and a glitch ‘rewarded’ Ham not with banana pellets for pulling the right levers and pushing the right buttons, but with electric shocks. At the end of the mission, with the capsule filling with seawater and about to sink, ‘‘a very pissed-off chimp’’ was safely fished from the Atlantic by the recovery forces.

Wernher von Braun, whose team had designed and built the Redstone, feared that Shepard’s mission, then scheduled for March, could be similarly affected and opted for one final unmanned launch. The astronaut, however, pushed NASA officials and even von Braun himself to go ahead with his mission, regardless of the risk, feeling that he could handle and overcome any Ham-type problems. The German stood firm, though, and a nervous NASA stood beside him.

‘‘We were furious,’’ remembered Chris Kraft. ‘‘We had timid doctors harping at us from the outside world and now we had a timid German fouling our plans from the inside.’’ Furthermore, Jerome Wiesner, recently picked by President Kennedy as his science advisor, warned of the harm a dead astronaut could cause the new administration and pressed for another test flight. In addition, having inherited chairmanship of the President’s Science Advisory Committee (PSAC), he convened a panel of experts to assess the situation and recommend whether or not to proceed with Shepard’s launch. After viewing astronauts ‘flying’ in the simulators, whirling in the MASTIF and pulling up to 16 G in the centrifuge, the panel concluded that the manned mission should proceed. Their report, ironically, landed on Kennedy’s desk on the afternoon of 12 April 1961.

By this point, Shepard’s launch had already been postponed until the end of the month and, despite the crushing disappointment of Vostok 1, both he and Glenn continued to train feverishly, rehearsing every second of the 15-minute ‘up-and – down’ mission that would arc 188 km into space and back to Earth, splashing into the Atlantic some 200 km downrange of the Cape. It would be a suborbital ‘hop’: the Redstone, capable of accelerating to around 3,500 km/h, lacked the impulse to deliver Shepard into orbit – an Earth-girdling flight would have to await the Atlas – but the mission would prove to the world that the United States was in the game. Today, wrote Chris Kraft in his foreword to Neal Thompson’s biography of Shepard, it is easy to dismiss it and, when placed alongside Vostok 1, it was insignificant, but in the spring of 1961 it captivated not only America, but the world. ‘‘Add to this the fact that the reliability of a rocket-propelled system in 1961 was not much better than 60 per cent,’’ wrote Kraft, ‘‘and you may begin to have a feel for the anxiety all of us were experiencing.’’

The Redstone itself was a direct descendant of the infamous V-2, used by Nazi Germany with such devastating effect in the Second World War, and had been employed as a medium-range ballistic missile to conduct the United States’ first live nuclear tests during Operation Hardtack in August 1958. It remained operational within the Army until 1964, gaining a reputation as the service’s workhorse and, as a non-military launcher, as ‘Old Reliable’. Initial production, under the auspices of prime contractor Chrysler, had gotten underway at the Michigan Ordnance Missile Plant in Warren, Michigan, in 1952. Meanwhile, the Rocketdyne division of North American Aviation built its Model A-7 engine, Ford Instrument Company supplied its guidance and control systems and Reynolds Metals Company fabricated its fuselage. As a weapon, it could be armed with an atomic warhead with a yield of 500 kilotons of TNT or a 3.75 megaton thermonuclear warhead and, indeed, batteries of Redstones were stationed in West Germany until as late as 1964.

A direct outgrowth of the Redstone was the Jupiter-C intermediate-range ballistic missile, which, some observers believe, could have beaten Sputnik 1 by orbiting an artificial satellite in August 1956, had the political will been there. President Eisenhower’s administration, however, preferred to launch America’s first satellite atop a civilian rocket named Vanguard, rather than with a modified military weapon, and the chance was lost. The Vanguard failed spectacularly in December 1957, exploding on the pad, but less than two months later a Jupiter-C successfully lofted the United States’ first satellite, Explorer 1, into space.

A number of modifications were incorporated into the Redstone from 1959 onwards to complete the metamorphosis from a warhead-laden weapon to a man­rated launch vehicle; its reliability as a tactical missile, though high, was inadequate for an astronaut. Since redesigning it to provide the required assurances could have meant implementing a totally new, expensive and lengthy development programme, it was decided instead to adapt the existing model with only the changes needed for a manned flight. In January 1959, the Army Ballistic Missile Agency (ABMA) received the go-ahead to convert the rocket and, two months later, the Space Task Group requested the implementation of an effective abort system. By June, ABMA had submitted its response and, throughout the remainder of the year and into 1960, the design was finalised and implemented: an automatic system, capable of shutting down the Redstone’s engine and transmitting separation abort signals to the Mercury capsule and its attached LES tower. Had the rocket veered off-course, a range safety officer at the Cape would have had little option but to remotely destroy it. However, a three-second delay existed between the transmission of the abort command and the actual destruction of the Redstone, offering a hair’s breadth of time for the capsule to be pulled clear of the conflagration.

It had long been recognised that some emergencies could develop too rapidly for a mission to be manually aborted and, moreover, the astronaut’s own performance under the dynamic conditions of a launch were not known. During their analysis of this problem, ABMA engineers studied 60 Redstone flights, identifying a huge number of components which could conceivably fail. It would be impractical to accommodate them all. However, the study did find that many malfunctions – loss of attitude control and velocity, a lack of proper combustion chamber pressure in the engine or perhaps power supply problems – led to similar results, thus permitting the inclusion of relatively few abort sensors.

Constructed from aluminium alloy, the single-stage Redstone measured 25.4 m long and weighed 3,720 kg. Ignition of its engine was initiated from the ground and liftoff occurred when approximately 85 per cent of its rated thrust had been achieved. During ascent, carbon jet vanes in the exhaust of its propellant unit, coupled with air rudders, served to control its attitude and stability. Its Model A-7 engine, fuelled by a mixture of ethyl alcohol and liquid oxygen, together with a hydrogen peroxide-fed turbopump, yielded 35,380 kg of thrust and was essentially the same as that used by the military Redstone, although a number of improvements had been implemented for efficiency and safety. The Jupiter-C’s use of a highly-toxic propellant mixture called hydyne had been ruled out in favour of alcohol, although the use of the latter was more erosive of the jet vanes. Engine operations continued until the Redstone had reached a pre-determined velocity, at which stage an integrating accelerometer emitted a signal to initiate shutdown by closing off the hydrogen peroxide, liquid oxygen and fuel valves. As pressures in the thrust chamber decreased, a timer started in the Mercury capsule which triggered its separation from the tip of the Redstone.

Other modifications included lengthened tanks, the walls of which were thickened to handle the increased loads of the capsule and heavier propellant haul, and changes were made to increase the reliability of critical electronic components in the Redstone’s instrument section. Indeed, the entire layout of this section was extensively revamped to accommodate new control and abort systems. The elongated propellant tanks and increased payload weight, however, meant that the rocket tended to become more unstable in the supersonic region of flight, around 90 seconds after liftoff, and necessitated the inclusion of 310 kg of steel ballast. Stringers were also added to the inner skin of the Redstone’s aft section to support the weight of the Mercury capsule. The overall ‘burn time’ of the engine for suborbital launches was shortened by 20 seconds to 143.5 seconds in total, prompting the addition of heat-resistant stainless steel shields for the stabilising fins. Additionally, nitrogen-gas purging equipment was added to the tail to prevent an explosive mixture from accumulating in the engine compartment whilst the Redstone sat on the pad.

The first three unmanned test flights evaluated each of these modifications and the combined performance of both the rocket and the capsule under real mission conditions. The first, named Mercury-Redstone 1 (MR-1), was intended to put the abort system fully through its paces, in addition to achieving the kind of velocities – around Mach 6.0 – that the suborbital astronaut would experience and demonstrating the ability of the capsule to separate satisfactorily from the rocket. A launch attempt on 7 November 1960 was scrubbed due to low hydrogen peroxide pressures in the capsule’s thrusters and was rescheduled for the 21st. At 8:59 that morning, ignition occurred on time, but as the Redstone made to leave the pad, a shutdown signal was initiated. The thrust buildup was sufficient for the rocket to rise 10 cm, before it settled back onto its pedestal. However, the shutdown signal had caused the LES tower to fire, producing huge clouds of smoke which momentarily hid the Redstone from view. Flight Director Chris Kraft, watching the proceedings, was astonished by the tremendous acceleration, thinking it to be the actual liftoff. . . ‘‘but then the smoke cleared and the missile was still there!’’ Wally Schirra described the fiasco as ‘‘a memorable day, especially for someone who likes sick jokes’’.

The rocket swayed slightly, but remained upright and did not explode. Worryingly, though, the LES – which shot 1.2 km high and landed 360 m from

In full view of the world’s media, the Redstone carries its first human passenger into space.

the pad – had not pulled the Mercury capsule clear of the Redstone and, as the shocked flight controllers watched, the drogue parachute popped out of its nose, followed by the main canopy and lastly, accompanied by a green cloud of marker dye, an auxiliary chute. All three fluttered pathetically down onto the pad. The rocket, meanwhile, was left alone as its liquid oxygen and high-pressure nitrogen were drained, its fuel and hydrogen peroxide tanks emptied, its circuits deactivated and its destruct arming devices removed. (Initial suggestions to relieve the pressurised propellant tanks by shooting holes in them with a rifle, thankfully, were squashed.)

“The press had a field day,” Kraft recalled later. “It wasn’t just a funny scene on the pad. It was tragic and America’s space programme took another beating in the newspapers and in Congress.’’ Time magazine bemoaned ‘Lead-Footed Mercury’ and ridiculed Wernher von Braun for downplaying the MR-1 fiasco, although a New York Times journalist urged President-elect Kennedy to persevere.

Investigators would find that the shutdown had been triggered by a ‘sneak’ circuit, created when two electrical connectors in a two-pronged booster tail plug separated in the wrong order. And why did the capsule fail to separate along with the LES? According to NASA’s investigation report, it was because the G load sensing requirements had not been met. Ordinarily, after an engine cutoff, a ten-second timer was initiated and, upon its expiration, was supposed to separate the capsule if acceleration was less than 0.25 G. However, MR-1 had settled back onto the pad before the timer expired and the G-switch, sensing 1 G of acceleration, blocked the separation signal. On-board barostats, meanwhile, properly sensed that the rocket’s altitude was less than 3 km and therefore activated the parachutes. ‘‘Once we realised that the capsule had made the best of a confusing situation and had gone on to perform its duties just as it would have on a normal flight,’’ John Glenn said later, ‘‘we were rather proud of it.’’ However, to avoid a recurrence, a ‘ground strap’ was added to maintain grounding of the vehicle during all umbilical disconnections and changes to the electrical network distributor prevented a cutoff signal from jettisoning future LES towers prior to 130 seconds after liftoff.

The undamaged spacecraft would be recycled and reused on the MR-1A flight just four weeks later. Despite some difficulties with a leakage in the capsule’s high – pressure nitrogen line and a faulty solenoid valve in its hydrogen peroxide system, the mission was launched successfully at 11:15 am on 19 December. Thankfully, the abort system performed as advertised, although a malfunction of the velocity integrator caused the Redstone’s velocity cutoff to occur 78 m/sec higher than planned, thus boosting the capsule 9.6 km above its intended 205 km altitude. Accelerations during re-entry were correspondingly more severe and high tail winds during the final portion of the flight led to MR-1A splashing into the Atlantic 32 km further downrange than anticipated. The source of the velocity integrator problem was traced to excessive torque against the pivot of the accelerometer, caused by electrical wires; five of these were replaced and a softer wire material was implemented. This solved the problem, as the chimpanzee Ham’s MR-2 flight at the end of the following month would demonstrate.

Ham was not the first animal to have been launched by the United States. A pair of Rhesus monkeys, nicknamed ‘Sam’ and ‘Miss Sam’, from the School of Aviation

Ham, the chimpanzee occupant of MR-2.

Medicine in San Antonio, Texas, had been launched atop Little Joe rockets in December 1959 and January I960, respectively. Although neither of their Mercury capsules reached space (Sam achieved an altitude of 88 km, Miss Sam of 15 km), their flights demonstrated that living creatures could survive a launch and return alive. Unfortunately, the flights of the Rhesus monkeys and chimpanzees, though significant, would offer an excuse for some test pilots to heap further ridicule on the Mercury Seven. When asked if he was interested in riding a capsule into orbit, Chuck Yeager had laughed. “It doesn’t really require a pilot,” he said, “and, besides, you’d have to sweep the monkey shit off the seat before you could sit down!’’

Ham – the name was an acronym for the Holloman Aerospace Medical Center, based at Holloman Air Force Base in New Mexico, which prepared him for his mission – was launched at 11:54 am on 31 January 1961. Chosen specifically because of their close approximation to human behaviour, a colony of six chimpanzees, four female and two male, accompanied by 20 medical specialists and handlers from Holloman, had arrived at Cape Canaveral’s Hangar S a few weeks earlier. The chimps were split into two groups to prevent the spread of any contagion and were led through training exercises with the help of Mercury capsule mockups in their compounds. By the end of the month, each of the chimps was somewhat bored, but nevertheless an expert at pulling levels and pushing buttons in the right order, receiving either banana pellets or mild electric shocks for doing the right (or wrong) thing. The day before launch, James Henry of the Space Task Group and Holloman veterinarian John Mosely examined the six chimps and settled on a particularly frisky and good-humoured male as the prime candidate, with a female as his backup. Both were put on low-residue diets, instrumented with biosensors and, early on the 31st, outfitted in their space suits, placed in their contoured couches and taken to the launch pad. With 90 minutes to go, Ham, described as “still active and spirited’’, was inserted inside the MR-2 capsule.

His home for the 16-minute mission boasted a number of significant innovations, including an environmental control system, live retrorockets, a voice communica­tions device and the accordion-like pneumatic landing bag. The latter was attached to the heat shield and shortly before splashdown, the pair would drop 1.2 m, filling with air to help cushion MR-2’s impact. In the water, the deflated landing bag and heat shield were intended to serve as an anchor, keeping the spacecraft upright.

Ham’s liftoff was successful, although his Mercury capsule, programmed to travel 183 km into space and 468 km downrange of the Cape, actually flew 67 km higher and 200 km further downrange than intended. The chimp experienced six and a half minutes of weightlessness and endured 14.7 times the force of normal terrestrial gravity at one point during his re-entry. He survived and seemed to be in good spirits, despite having to wait for several hours before being picked up by the dock landing ship Donner. After splashdown, his heat shield had skipped on the water, bounced against the capsule’s base and punched two holes in the pressure bulkhead. As MR-2 capsized, the open cabin pressure relief valve let in yet more seawater. By the time he was rescued, it was estimated that there was around 360 kg of seawater inside the capsule. Ham, however, seemed in good cheer, gobbling down a pair of apples and half an orange on the recovery ship’s deck.

Post-flight analysis would reveal that the Redstone’s mixture ratio servo control valve failed in its full-open position, causing early depletion of the liquid oxygen supply; consequently, the propellant consumption rate increased, the turbopump ran faster and led to higher thrust, an earlier-than-scheduled engine shutdown and the inadvertent ‘abort’ of the MR-2 spacecraft. Nonetheless, the basic controllability and habitability of Mercury was deemed a success. In the wake of Ham’s flight, the reliability of the booster-capsule combination was reassessed, culminating in an estimated probability of success at somewhere between 78 and 84 per cent. However, many components had been designed to parameters which exceeded those demanded by the Space Task Group and launch operations personnel had devised their own methods which were more conducive to flight success. Taking this into account, the overall reliability of the system was judged at 88 per cent for launch and 98 per cent for the survival of the astronaut. These assurances were confirmed by one final test prior to Shepard’s mission – the Mercury-Redstone Booster Development (MR-BD) flight, launched at 12:30 pm on 24 March.

Although it was doubtful that any of the problems experienced on either MR-1A or MR-2 would have endangered Shepard, had he been aboard, the Space Task Group’s scrupulous attention to reliability meant that all significant outstanding modifications to the Redstone had to be dealt with. Von Braun also invoked one of the original ground rules, which insisted that no manned flight would be attempted until all responsible parties felt assured that everything was ready. Shepard’s mission was fatefully postponed until 25 April. The MR-BD test, meanwhile, was perfect: the Redstone flew flawlessly, with its thruster control servo valve’s closed position adjusted to 25 per cent open and flight sequencer timer changes prevented a recurrence of the problems on Ham’s flight. Control manoeuvres were executed to evaluate the effect of higher-than-normal angles of attack, confirming that the Redstone could withstand additional aerodynamic loads. No attempt was made to separate rocket and capsule and they splashed down together, some eight and a half minutes after launch, before sinking to the bottom of the Atlantic. The success of MR-BD had cleared the way for MR-3 – the first manned mission – to launch.

To help them prepare more effectively for the flight, Shepard and Glenn had, since February, been using a pair of McDonnell-built Mercury simulators for 55-60 hours per week. They went through flight plans together and, indeed, Shepard ‘flew’ more than 120 simulated Redstone launches during this period. As February wore into March, the training became yet more exacting: both men even went through the ritual of their pre-flight medical examinations, just as they would on launch morning, and were instrumented with biosensors and outfitted in their silver pressure suits. A week after Gagarin’s mission, on 19 April, Shepard sat in the actual capsule, atop its Redstone, on Pad 5 at the Cape, with the hatch open, meticulously plodding through each of the procedures he would follow.

By this time, he had nicknamed his tiny spacecraft ‘Freedom 7’ – not, as some observers would hint, in honour of the seven Mercury astronauts, but rather to reflect its status as the seventh capsule off the McDonnell production line. According to assistant flight director Gene Kranz, the name was adopted during the final Freedom 7 training exercises. On later missions, each member of the Mercury Seven

would suffix their own spacecraft with the number as something of a good-luck charm.

By now, the launch was officially scheduled for 7:00 am on 2 May and, in late April NASA timetabled a full dress rehearsal, with Gordo Cooper standing in for Shepard. He duly suited-up, rode the transport van out to the base of Pad 5 and jokingly bawled “I don’t want to go! Please don’t send me!” before being shoved into the elevator. The assembled journalists, apparently, did not appreciate Cooper’s gallows humour and the following morning’s newspapers even went so far as to criticise NASA for its astronaut’s inappropriate horseplay at such a tense moment. Meanwhile, Shepard checked out of a Holiday Inn where he had been staying with his wife, dropped her at the airport and drove to the astronaut quarters in the three – story Hangar S at the Cape. Since they were still required to maintain the official ‘secret’ that the first American in space could be any one of them, Shepard, Grissom and Glenn shared the same air-conditioned quarters, which had been specially decorated for them by their nurse, Dee O’Hara.

The heavens opened to heavy rain and storms early on 2 May, as the trio arose and ate a breakfast of bacon-wrapped filet mignon and scrambled eggs, together with orange juice and coffee. Since defecation in the spacecraft was, at best, difficult, such ‘low-residue’ launch-morning diets had been enforced by NASA. (Indeed, the astronauts’ lawyer and agent, Leo D’Orsey, when told about the diet, had exclaimed ‘‘No shit?’’ Shepard responded with a grin, ‘‘Exactly!’’)

The intention was that the public ‘final choice’ of who was to fly would be made that morning, with some officials even suggesting bringing all three men out of their quarters wearing hoods to keep the charade going until one of them boarded the Pad 5 elevator. Shepard, wrote Neal Thompson, opposed this lunacy and opted instead to emerge from Hangar S in his pressure suit and wade through the teeming journalists. It made little difference: the rain was so bad that the launch was scrubbed, although not before the identity of America’s first astronaut became known to the newsmen. ‘‘An alert reporter standing by the hangar door,’’ wrote Gene Kranz, ‘‘had seen him and broke the story. The secret was out.’’

Originally planned as a 48-hour postponement, it was soon realised that an attempt early on 4 May would be impossible, so foul was the weather. However, at 8:30 that night, the two-part, ten-hour-long countdown began for a launch the following morning. The stunted nature of this countdown owed itself to past experience, which showed that it was preferable to run it in two short segments to permit the launch crews responsible for both Freedom 7 and the Redstone to be adequately rested and ready. A built-in hold of some 15 hours was called when the clock hit T-6 hours and 30 minutes, during which time various pyrotechnics were installed into the capsule and the hydrogen peroxide system to feed Freedom 7’s thrusters was serviced. The countdown resumed at 11:30 pm and proceeded smoothly until another hour-long built-in hold at T-2 hours and 20 minutes, intended to check that all preparations had been made before Shepard’s departure for the launch pad.