The problem at altitude
Since the early days of powered flight, and long before anyone flew in space, pilots were already running into its basic problem: thin air. As an aircraft climbs, the outside air pressure drops. At very high altitudes there is too little oxygen to breathe, and below a certain pressure body fluids can form gas bubbles, a condition that is serious or fatal. A pilot who wanted to fly in the stratosphere needed to carry an artificial atmosphere around the body.
There were two broad answers. One was a pressurized cabin, which became standard on high-flying aircraft. The other was a garment that held pressure around the person, which is the idea that led to the spacesuit. A suit is the backup for a cabin and a necessity when a cabin is not possible.
Early experiments
Several people worked on this at about the same time, so no one name should be treated as the sole originator. In the early 1930s, balloon and aircraft pioneers experimented with sealed suits and helmets. The American pilot Wiley Post developed a pressurized suit for his high-altitude flights in the aircraft Winnie Mae in the mid-1930s, working with a rubber company and a designer, Russell Colley, who later contributed to other American suit projects. The suit was hard to move in, and the helmet had a small window, but it showed the idea could work.
In Spain, the engineer and officer Emilio Herrera designed a stratospheric suit in the mid-1930s for a planned balloon flight. The flight was not carried out, in part because of the Spanish Civil War, but the design is often cited in histories of the topic. In the Soviet Union and elsewhere, designers explored similar ideas.
From partial to full pressure
Military aviation pushed the technology forward. Two approaches emerged:
- Partial-pressure suits. These used tubes or bladders that squeezed the body when the cabin lost pressure, helping the pilot to breathe against pressurized oxygen delivered to the mask. They were lighter but offered limited protection above a certain altitude.
- Full-pressure suits. These enclosed the whole body in a pressurized garment, with a sealed helmet, gloves and boots. They were heavier and stiffer, but gave protection at the altitudes where partial suits stopped working.
Pressure suits are different from anti-gravity suits. The latter squeeze the legs and abdomen to reduce blood pooling under high acceleration, and they do not hold a pressurized atmosphere.
A key ingredient was material. Rubber coated fabrics and later synthetic fibers could hold gas pressure and still bend. The idea of sealing rubber into airtight layers draws on the older chemistry of vulcanized rubber, while nylon and other synthetic fibers provided strong restraint layers.
Jets, rocket planes and the Navy suit
After World War II, faster aircraft engines and rocket aircraft brought pilots to altitudes where pressure suits were a necessity. During the 1950s, the United States Navy developed a full-pressure suit called the Mark IV, and test pilots flying high-altitude research aircraft used pressure suits of various designs. The X-15 rocket plane, which reached the edge of space in the 1960s, used a pressure suit as part of its safety system.
Many of the same companies and engineers who made the aviation suits became involved in the first space programs. Their experience in bending joints, sealing gloves and managing heat inside a sealed garment was exactly what spaceflight needed.
From the stratosphere to orbit
When American planners picked the clothing for the Mercury astronauts, they did not begin from nothing. They modified an existing Navy pressure suit, and the Soviet Union likewise adapted its high-altitude suits for the Vostok program. Yuri Gagarin’s April 1961 flight used a suit designed so that he could eject from the capsule at low altitude during descent and parachute to the ground.
This is why historians often say that the first spacesuit grew out of aviation rather than being invented all at once. The step from a pilot’s pressure suit to a spacesuit was an extension and an improvement, with fewer new ideas than one might expect. A later suit, such as the Mercury suit, was a refined version of what pilots had already worn.
What changed for space
Pressure suits for pilots only had to survive a rare emergency, since pilots normally relied on the cabin. Spaceflight added new demands, which later suits had to meet:
- longer wear times
- protection from temperature extremes
- the ability to work outside the spacecraft, which led to the lunar spacesuits
- lighter weight and better mobility
The line from the stratosphere to the lunar surface is continuous. The principle of holding a bubble of oxygen at a safe pressure around a person did not change, even as the materials and the surrounding systems did.