From Star Trek: Theurgy Wiki
An environmental suit, also known as an EVA suit or pressure suit, is a special form of clothing designed to be used for protection or life support in inhospitable environments. With the advent of space travel came the need to perform tasks outside the controlled atmosphere of space vessels. Consequently, the EVA suit was developed. As planets and other stellar objects came within the reach of Human space explorers, their EVA suits became necessary for them to explore environments with different atmospheric conditions than those on Earth.
The design of the helmet allowed an almost normal field of view to the wearer. Though the vertical field of view was limited to eight degrees, the amount of room inside the helmet allowed the wearer to compensate by simply moving his or her head. The helmet had a clear visor integrated into the front that could not be opened separately. It featured two outside lights, one on either side, and two ambient lights inside to illuminate the wearer's face. When the helmet was sealed, the ambient lights would activate. Audio equipment, like a microphone and speaker, were integrated.
Located on the back of the helmet were air hoses to an oxygen supply, and an electrical connector for light, communication, and propulsion units. The helmet connected to the life support and propulsion unit via a secondary connection ring and not to the EVA suit directly. Padding within the helmet made sure the wearer could not touch the visor with his or her face.
The EVA suit was made as one full piece that closed at the front via a zip fastener and ended just below the elbow. The suit was self-sealing, meaning that if it were punctured or damaged in some way, sealant would be automatically applied to prevent the suit from decompressing. Although the suit was solid enough to protect its wearer from the rigors of space, a hypospray could still penetrate it in case of an emergency.
Life Support & Propulsion
The life support and propulsion unit (or "LSPU") consisted of a hard upper torso body-shell and a harness. This unit contained the essentials for survival in space: communication equipment, oxygen, propulsion unit, EVA controls, and the power supply. It was padded to give the wearer some extra comfort. The LSPU also held an extra oxygen hose for refilling or sharing the oxygen supply. This extra hose allowed oxygen to be replenished from any device that held liquid oxygen, provided the physical connection would fit.
On the front of the unit, the following switches were present: communications, oxygen transfer, lighting and propulsion activation.
On the back were the incoming and outgoing oxygen connections. These hoses were fastened via a bayonet joint to prevent accidental release. Below one of the oxygen connections was an air supply indicator, divided into eight equal parts. This indicated the level of oxygen by means of color coding – green, yellow, and red. In 2154, this air supply indicator was removed and replaced by an analog indicator on the right side of the LSPU. The back of the unit also contained an electrical cord, which transferred power and communications from the LSPU to the electrical connector at the back of the helmet.
The harness consisted of two leg bands that were connected to each other via a belt that was also used to hold small tools as necessary. The LSPU was secured to the harness at four attachment points to keep the unit in place.
Gloves & Boots
The gloves had five digits and were connected to the EVA suit via a zip fastener just below the elbow. They were also self-sealing. The boots were made out of the same material as the EVA suit and could be magnetized.
Wearers were kept alive by the backup system of their environmental suits, by "keeping their vital functions going" while unconscious. The system kicked in due to an environmental seal in their suits had been compromised, depleting the oxygen.