It was back in 1865 that the visionary French novelist, Jules Verne, described an incredible voyage to the moon in his thriller ‘From the Earth to the Moon’. Later, at the turn of the century, H G Wells, inspired by the writings of Verne, produced a string of prophetic works that accurately envisaged interplanetary space travel. By the 1930s, the inter-stellar escapades of Buck Rogers were thrilling the imaginations of a whole generation of pre-war schoolboys. However, it was to be the second half of the 20th century before science fact caught up with science fiction.
Of course, man’s eventual foray into the fathomless depths of space was not so much a sudden leap forward as the fruition of decades of technical progress. Von Braun’s pioneering work in rocketry during the Second World War is perhaps the most widely documented, but there were many other facets of essential development that took place in the years before the first tentative flights of Gagarin and Shepard. Being, literally, an ‘alien’ field of endeavour, the conquest of space required an unprecedented fusion of often previously unrelated technologies. Manned space flights, for example, could not have progressed very far without the development of suitable protective clothing to combat the airless vacuum of space.
While Verne and Wells may have been the first to envisage the need for special clothing for space travel, it was not until high altitude flight became a possibility in the 1930s that a real need emerged. As the stunt pilots of the day soared ever higher, the low atmospheric pressures encountered at altitudes of over 40,000 feet started to dictate the need for a pressurised suit, or cabin, for breathing.
The first attempts at manufacturing a space suit drew inspiration from two unlikely technologies: deep-sea diving gear and pneumatic vehicle tyres. In some respects, it was felt that the problem of controlling pressure had already been addressed in designing the armoured suits necessary for deep water diving. By the early 1930s, divers were already exploring the oceans in rudimentary armoured suits like that worn by Jim Jarratt in his explorations of the wreck of the Lusitania in 1934. At depths of more than 30 metres, the problems for the diver start as soon as he leaves the high pressures of deep water. As he ascends, bubbles of gaseous nitrogen are released into the blood from body tissues as the pressure drops, resulting in the agonising condition variously known as dysbarism, decompression sickness or simply ‘the bends’.
The same phenomenon occurs as a human leaves the atmospheric sanctuary of mother earth. From a pressure of 14.7 pounds per square inch (psi) at sea level, air-pressure reduces to 1 psi at a height of 20 miles and to just 0.001 psi at 50 miles. At 300 miles, it is virtually zero. For the body, the first effects of altitude take place at less than 3 miles (15,885 feet) from sea level, as mountain climbers can testify. At this point, the body suffers the first effects of oxygen deficiency (hypoxia). It begins with a slowing down of both physical and mental faculties, effects which accelerate rapidly as height is gained. Further up, at around 25,000 feet, the body starts to suffer the ‘bends’, the same decompression effects encountered by unlucky deep sea divers.
Higher still, at the extremely low pressures encountered above 50,000 feet, the human body is incapable of breathing without assistance, since the air pressure is insufficient to feed the lungs. At 60,000 feet and above, the vital blood vessels and organs of an unprotected body simply expand and rupture. Death at these altitudes is virtually inevitable.
To withstand the high internal suit pressures necessary to combat these frightening effects, it was felt that pressure suits for high altitude pilots might be manufactured according to the same principles used for pneumatic car tyres. So, the first high altitude suits were produced in the mid-1930s by an American tyre company, which incorporated a man-shaped inner tube inside a rubber outer shell. Although these early ‘tyre’ suits provided a reasonably habitable environment, they were very difficult to wear. The high internal pressure of the cumbersome shells meant they were extremely stiff, a drawback exacerbated by the rudimentary arm and leg joints. Getting into the suits was a feat in itself and once inside, pilots had limited function. Extricating oneself from them could be even harder – sometimes the suits had to be cut off!
However, by the dawn of the space era in the1950s, high altitude suits had undergone a radical transformation. Although they were still made of rubber, nylon – the man-made wonder fibre – was now being used as a reinforcement net to provide pressure restraint. Being soft and flexible, nylon provided the flexibility that had been lacking in previous suits. In 1961, Allan Shepard, wearing one of these suits with a specially aluminised heat and ultraviolet-reflective surface, became America’s first astronaut.
Now, 40 years later, today’s orbiting astronaut wears a normal flight suit within the Space Shuttle’s pressurised cabin. However, when the astronaut engages in a space walk, or what NASA calls an ‘Extra Vehicular Activity’, he swaps his ‘casuals’ for an ‘Extravehicular Mobility Unit’, or ‘EMU’, which is a completely self-contained unit and is sometimes described as ‘the world’s smallest spacecraft’.
Combining a spacesuit with a life support system, the EMU was originally developed to cope with the early, often emergency, space walks and the lunar landings. ‘Although space is a vacuum, it is far from empty,’ says Bill Higgins, EMU engineering manager at Hamilton Sundstrand, the American space suit manufacturer. ‘Apart from radiation waves and charged particles, the unimaginably huge expanses of intergalactic space are filled with matter ranging from tiny grains of cosmic dust to large meteoroids and the stars and planets themselves. The EMU must protect against the highly penetrative effects of micro-meteoroids.’
The EMU must also protect the space walker from extreme temperatures ranging from –250°F to +250°F (-157°C to +121°C), and be capable of encapsulating the fragile environment essential for life.
To cope with this multiplicity of demands in space requires a highly complex suit, which is made up of more than 2000 inter-related components across a number of elements and sub-assemblies. All of these must work together in complete harmony to provide a space suit of the necessary quality and reliability. ‘An EMU has to work and go on working,’ says Higgins. ‘There is simply no room for equipment malfunction in the vast expanse of space.’
Only ten thin layers lie between a space walking astronaut and eternity. The defining barrier is a multi-layer spacesuit construction combining a number of advanced fabrics which encapsulate the astronaut’s liveable inner space. ILC Dover, based in Dover, Delaware, is the major subcontractor to Hamilton Sundstrand for these space suit assembly fabrics.
Immediately next to the skin, the astronaut wears a Thermal Comfort Undergarment (TCU) under a Liquid Cooling and Ventilation Garment which incorporates no less than 100 metres of flexible tubing through which water circulates to maintain a constant internal temperature. Above this is the pressure barrier bladder which is covered by a pressure-restraining reinforcement mesh of DuPont Dacron. Next comes an inner liner followed by five layers of aluminised Mylar for insulation.
This outer layer of the suit is called Ortho Fabric, which is a special woven composite of Gore-Tex, and DuPont’s Teflon, Nomex and Kevlar brand fibres. The Gore-Tex element imparts flexibility, while the Kevlar performance technology provides mechanical strength and micro-meteoroid penetration protection. ‘As the aramid fibre used to provide ballistic protection in bullet-resistant vests, Kevlar is ideal for this,’ says Higgins. ‘The effects of sudden decompression that might result from a tear or penetration would be catastrophic.’
The Nomex thermal technology gives additional abrasion resistance and provides protection from heat and flames in the event of exposure to fire, as could occur in an accident involving rocket propellant. The Teflon part of the suit, apart from providing a chemical-resistant outer shield, provides a low friction surface to ease the passage of the bulky suit and its occupant through hatches and air-locks.
Snagging is not the only danger in these confined spaces, however. Reportedly, cosmonaut Alexei Leonov, when re-entering his spacecraft after successfully completing the world’s first space walk in March 1965, found that the rigidity of his pressurised suit prevented him from bending to seal the airlock behind him. Only by manually lowering the pressure in his suit to a hazardous level could he complete the operation and re-enter the relative safety of the spacecraft.
Since then, space suits have had to become more versatile in both design and fabric to permit the greater manual dexterity required by ongoing construction and maintenance duties during prolonged space station occupancies and flights. They are also being designed for greater durability, a requirement necessitated by the longer tours of duty in space and the cost of the suits. ‘The suits are certified for 25 space walks,’ says Higgins. ‘And they cost about USD 12 million each.’
That is a lot of money for something to wear to work.