One of the most challenging parts of the human exploration of the skies and beyond, was how to ensure that the human body could continue to function normally at higher altitudes. Although the machines needed to be developed to get humans off the ground, it also needed to be addressed that life support at higher altitudes was an essential part of this.
Jet planes that flew at higher altitudes were often tested, especially during the Cold War. Being able to fly high was something that could give you an advantage over an enemy, and of course there is always that human desire to go higher and to break records.
Flight suits needed to be developed for pilots that would help to keep them safe if the air pressure in the cabin became damaged or stopped working for some reason. The suit would be attached to the plane with a hose to provide the pilot with oxygen to breathe, and the suit itself could be inflated in order to push pressure to the pilot, replicating conditions on the ground.
Of course, the even more ambitious quest to break free from the Earth completely and launch manned missions into space, meant that this was something that needed to be thought of. The first flights into space used designs that were basically the same as the flight suits used by pilots in high altitude planes.
However, as the next phase of space exploration came with the Gemini program, the demands on the suit would be higher, and the old suits would need to be completely redesigned. In order to meet the requirements of a spacewalk, the suit would need to be able to provide greater mobility once it was pressurised.
As well as this, the suit would need to provide astronauts the protection from all of the dangers of space that we are usually protected from by the atmosphere of the earth. Things like micro-meteorites and cosmic radiation also had to be considered when designing a space suit that allowed the astronaut to walk out of their ship and into space.
Rubber moulding like this www.meadex.co.uk/rubber-moulding/ was needed in order to make the precise seals for the suits, and materials like Teflon would help to keep the astronaut safe in the vacuum. It was also designed so that the astronaut could remain tethered to the ship and the oxygen and water could then be moved to the suit via a connecting hose.