The Mark III or MK III (H-1) is a NASA space suit technology demonstrator built by ILC Dover. While heavier than other suits (at 59 kilograms (130 lb), with a 15 kilograms (33 lb) Primary Life Support System backpack), the Mark III is more mobile, and is designed for a relatively high operating pressure.[1]
The Mark III is a rear-entry suit, unlike the EMU currently in use, which is a waist-entry suit. The suit incorporates a mix of hard and soft suit components, including hard upper torso, hard lower torso and hip elements made of graphite/epoxy composite, bearings at the shoulder, upper arm, hip, waist, and ankle, and soft fabric joints at the elbow, knee, and ankle.
The Mark III was originally designed to an 8.3 pounds per square inch (57 kPa) operating pressure, which would make the Mark III a "zero-prebreathe" suit. For a vehicle with a one atmosphere, mixed-gas environment, such as that on the International Space Station, the suit could be donned and ready for an EVA within the normal donning and checkout period without risk of the bends, which can occur with rapid depressurization from an atmosphere containing nitrogen or another inert gas. Currently, ISS astronauts must spend several hours in a reduced pressure, pure oxygen environment before EVA to avoid these risks.[1]