E&T celebrates the 50th anniversary of Yuri Gagarin's pioneering space flight and highlights the technology that made it possible
We live in an age when the ability to conduct successful and repeated flights into orbit around the Earth is largely taken for granted. The International Space Station has been occupied continuously for more than a decade, and the Russian Soyuz rocket, which launches satellites and ferries astronauts to the station, has made more than 1,760 flights.
When cosmonaut Yuri Gagarin boarded his capsule on a Vostok rocket on 12 April 1961, the world was very different. Computers were typified by IBM's room-sized 1400 mainframe; telephones had rotary dials and plugged into the wall; and the ultimate in performance cars was the newly introduced Jaguar E-Type, costing just £2,200.
More importantly, though, the world was in the midst of the Cold War – a notional hiatus in hostilities that pitched the USA and the USSR into a battle for technological supremacy, with spaceflight as a key political tool. The space race began with the launch of the first artificial satellite, Sputnik 1, on 4 October 1957 – an event that struck fear into the heart of mainstream America.
While President Eisenhower had dismissed Sputnik as 'one small ball in the air', President Kennedy's reaction to Gagarin's mission was quite different: he was impatient for an equitable response. At a meeting with advisors and senior Nasa officials two days after the flight, he implored 'Just tell me how to catch up. Let's find somebody. Anybody. I don't care if the janitor over there has the answer, if he knows how.'
Kennedy had little knowledge of the technology required for manned spaceflight, but he had no difficulty recognising its importance for America and the world at large. In that sense, it was Gagarin's mission that triggered the second phase of the space race – that of landing a man on the Moon – and the raft of technologies: from propulsion systems to guidance computers - that would make it possible.
Launch and the R-7
The initial challenge of spaceflight is to overcome the pull of gravity, and the heavier the payload the more powerful the rocket required. In fact, it is the opposing design philosophies of the superpowers, in their ICBM developments of the 1950s, that led to the Soviet lead in the race to conquer space.
While America concentrated on reducing the size and mass of its nuclear payloads to match the capabilities of its rockets, the Soviets opted to build rockets capable of lifting their large, heavy payloads. This led to the R-7 vehicle, the brainchild of Russia's mysterious chief designer, Sergei Korolev, whose identity was unknown in the West until his death in 1966.
The R-7 comprised four multi-engined boosters grouped around a central core, which were ignited at launch to provide maximum thrust. After about two minutes of flight, the boosters were jettisoned, leaving the core stage to sustain thrust for an additional 150s and boost the payload (depending on its mass) to orbital velocity.
In fact, the R-7 was sufficiently powerful to place the 83.6kg Sputnik in orbit without the need for an upper stage. By contrast, the rockets that launched America's early satellites could place only a few kilograms in orbit: its first, Explorer 1, weighed 14kg with its solid propellant upper stage which also entered orbit, while its second, Vanguard 1, was a miniscule 1.5kg.
Statistics of power
Indeed, even the US response to Gagarin's flight was hobbled by a lack of raw power. The Mercury flights of Alan Shepard on 5 May 1961 and Virgil Grissom on 21 July were merely 'suborbital hops' because the Redstone booster was insufficiently powerful to deliver their capsules to orbit.
In Shepard's case, it reached an altitude of 187km at the peak of its parabolic trajectory before succumbing to the Earth's gravity and landing 15 minutes and 22 seconds after lift-off. Compare this with Gagarin's orbital flight, which varied between a perigee of about 180km and an apogee of some 300km on a mission lasting an hour and 48 minutes.
As Aerojet propulsion engineer Joseph Cassady explains, the energy required is 'between five and eight times lower for suborbital than for orbital flight'. A suborbital flight to a peak of 200km requires a delta-V (or change in velocity) of about 1,650m/s, compared with 7,780m/s to achieve a 200km-high circular orbit.
The impact on the design requirements of a launch vehicle for orbital flight is significant, confirms Cassady, since it must carry more propellant in larger, heavier tanks and requires bigger engines to deliver the increased thrust.
For the Soviets, when it came to launching a cosmonaut it was largely a matter of adding an upper stage to the R-7 to form the RNV, or Rakyeta Nosityel Vostok, variant. Naturally, it also had to be made reliable enough to launch humans, a process known as 'man-rating', but this was made easier by its design.
One of the keys to success was the clustering of a number of simple, identical propulsion units. Having four chambers on each booster was inherently more reliable than using a single, larger rocket engine. Moreover, igniting all the engines on the ground, as opposed to requiring air-starts, enhanced reliability because, in the event of a misfire, the launch could be abandoned while the vehicle was still on the pad.
Beyond that, the man-rating procedure involved a rigorous testing schedule and, of course, the development of a spacecraft to house and protect the occupant from the airless cold of space and the heat of re-entry into the Earth's atmosphere.
Manned space flight
Gagarin's spacecraft, Vostok (or 'East'), comprised a 2.3m-diameter sphere – the 'descent module' in which the cosmonaut travelled – mounted on an 'instrument module' housing the retro-rocket, life-support consumables and other support systems. Manned spacecraft brought about an increase in complexity, while at the same time demanding improved reliability.
Half a century later, it is difficult to fully appreciate the enormity of the achievement of Gagarin's flight. The catalogue of different technologies that had to work perfectly was immense: from the turbopumps and stage separation devices of the launch vehicle to the guidance system and heat shield of the descent module, there was precious little margin for error. Only three-and-a-half years had passed since the first man-made device had been placed in orbit and there had been many launch and in-orbit failures to undermine the confidence of the designers; in fact, of 106 space missions conducted before Vostok 1, no fewer than 56 failed in some manner.
America's successful launch of chimpanzee Ham in January 1961, on the same type of booster that would launch its first astronauts, added to the pressure on Korolev's team. Indeed, the degree to which the space race was hotting up was shown by the fact that only 18 days separated the success of test-flight KS5 (carrying a dog and a dummy) and the launch of Gagarin.
One of the key engineering requirements for the mission was the life support system, which comprised a pressurised cabin and a spacesuit. The main components were built into the cosmonaut's seat, while tanks containing compressed air (to maintain suit pressure) and oxygen were installed outside on the instrument module.
A fan supplied the cosmonaut with air via separate feeds to the helmet and the rest of the suit and a system of pipes and valves ran from the helmet, via a reservoir, to the cabin, which meant that under normal conditions cabin air was provided by the suit system. Nominal flight conditions simply required the ventilation of the suit 'to remove heat, sweat, carbon dioxide and other gas discharges of the human body', as Abramov and Skoog put it in their book 'Russian Spacesuits'.
Cabin air was circulated through a heat exchanger which transferred any excess heat to a liquid circuit connected to a radiator on the instrument module. The cosmonaut was able to set the initial temperature, which was then maintained by a thermostat, even during the period of re-entry heating.
Gagarin was little more than a passenger on the first manned spaceflight, and had very little to do except look out of the window and make the occasional report. Indeed, he was not even in control of the spacecraft, which was being operated remotely from the ground because officials were unsure whether a cosmonaut would be able to operate controls in this new and unknown environment. However, as a precaution, Gagarin carried a three-digit code in a sealed envelope, which he could use to unlock the manual controls if the radio link with ground control was lost.
After the launch itself, the most testing time was the period of re-entry, when an unprotected object could reach temperatures high enough to vaporise metal. The engineering solution was the ablative heat shield, which would disintegrate in a controlled manner.
The descent module was considered too heavy to land safely with a cosmonaut inside, the designers decided to incorporate an ejection seat. According to Russian spacecraft designer Boris Chertok's memoirs, 'optimising the circuits involved in blowing out the hatch, ejecting the cosmonaut and deploying the parachutes caused the electricians more trouble than all the other systems. Here, there were no manual systems to save the cosmonaut's life in the event of a random failure'.
In fact, the use of the ejection seat was not confirmed until the dissolution of the Soviet Union allowed Soviet authors to write authoritatively about the programme. As it turned out, the ejection issue was part of a deliberate Soviet obfuscation to ensure that they entered the record books: since the rules of the Fédération Aéronautique Internationale (FAI) required a pilot to be in – if not in control of – a craft from take-off to landing, admitting to the ejection could have nullified the record.
The world's press had been informed of the flight while Gagarin was still in orbit, not only for propaganda value, but also to avoid him being arrested as a spy should he land on foreign soil. Ironically, on his return to Soviet soil, he was, reportedly, greeted with pitchforks and stakes when local farmers suspected exactly that. It probably helped that 'CCCP' had been painted onto his helmet just before the flight.
Historically, there were several reasons why America was in the doldrums in early 1961, but the achievement from what many considered a nation of tractor drivers had a palpable effect on the Kennedy regime. Just six weeks after Gagarin's triumphant orbit, and 20 days after Shepard's 15-minute suborbital hop, Kennedy made his famous commitment to land a man on the Moon before the end of the decade.
Integrated circuits were not available commercially until 1961, but by the summer of 1963 some 60 per cent of US output was being used in prototypes of the Apollo guidance computer. An analogue world had become digital and the rest is history.