When, on 29 May 1953, Sir Edmund Hillary and Tenzing Norgay became the first people to reach the summit of the world’s highest mountain, their achievement was rightly hailed as a triumph of human endurance and skill.
But alongside the planning, skill and mountaineer’s luck that helped them to the top of Mount Everest, their expedition also made practical use of some of the most advanced technologies available to climbers at the time.
In June 1953, just a few weeks after their historic success, The Engineer took an in-depth look at a key item of equipment: the specially designed oxygen breathing apparatus that was used by the climbers to overcome the effects of the rarefied atmosphere at high altitudes.
As the article reports, the system was developed for the expedition by UK firm Normalair Ltd, which specialised in manufacturing high-altitude life-support equipment for the aerospace industry. The firm still exists as a division of Honeywell Aerospace in Yeovil.
Based on a design developed by Farnborough Royal Aircraft Establishment, the equipment represented a significant advance on earlier breathing devices, which were unreliable and therefore mistrusted by many climbers.
The device was a so-called ‘open-circuit’ system, whereby reserves of oxygen carried in canisters on the climber’s back were inhaled via a system of regulators, while the climber’s exhaled breath was vented out into the atmosphere.
Consisting of three oxygen cylinders carried on a light-tubular carrier frame, the apparatus weighed 18.1kg and was designed to provide a total of 2,400 litres of oxygen. The rate at which this was used up would vary depending on the flow rate selected by the climber. They had a choice of either two or four litres per minute.
It was: wrote The Engineer, extremely simple to set up and use. “The user merely has to don his mask and turn the regulator valve to the ‘on’ position. The high-pressure oxygen is then reduced to a normal pressure and passes through flexible braided rubber tubing to a dual manifold assembly.”
This assembly had two outlets – one for a low flow of oxygen and one for a higher flow. Oxygen then passed through one of these outlets to the economiser which ensured that whenever the climber began to breathe in, oxygen was automatically fed into the face mask.
When the oxygen supply ceased or the pressure dropped, the climber had to disconnect the empty bottle, discard it on the mountainside, and reconnect a fresh bottle to the system.
One particularly innovative design tweak saw the adaptors for the system altered so that the climbers would be able to make use of high-pressure oxygen bottles left on the mountain by earlier expeditions.
While Hillary and Norgay opted for an ‘open-circuit’ system, the 1953 attempt took place at a time when some were considering the potential benefits of closed-circuit systems that save on weight by recycling the climber’s exhaled air. “Should a lighter set be necessary perhaps the best method would be to adopt the use of the closed-circuit system,” wrote The Engineer. “But this means the ‘unused’ oxygen exhaled would not be wasted and only the relatively small percentage of oxygen used would need to be made good.”
Interestingly, just days before Hillary and Norgay reached the summit, English climber Tom Bourdillon came tantalisingly close using just such a system. Had he succeeded, it’s possible that the history of breathing apparatus for high-altitude mountaineers would have taken a different path.
Today, most climbers attempting Everest use oxygen canisters. Indeed, until relatively recently an oxygen-free ascent was considered impossible.
To date, of the approximately 4,000 climbers to have reached the summit, only around 200 have climbed without supplemental oxygen and a number have died trying.