On June 3, 1965, Edward H. White II became the first American astronaut to “walk in space” when he opened the hatch of Gemini 4 and floated alongside the spacecraft for 22 minutes. For the first time, an American was protected from the harsh environment of space by only a few layers of fabric. Extravehicular activity (EVA), or walking in space, was one of the major objectives for the two-man Gemini flights. White wore a space suit produced by the David Clark Company in Worcester, MA.

Project Gemini was the intermediate step between Mercury’s initial forays into space and Apollo’s moon landing goal. To explore the moon, astronauts would have to work outside the confines of their landing craft, so EVA was a technique that had to be proven during the Gemini missions. Other Gemini goals included long duration flights, orbital rendezvous and docking.

The space suits worn by Mercury astronauts were a backup to the capsule life support system. In contrast, the Gemini suits would be the primary protection for an astronaut while he worked outside the spacecraft. B. F. Goodrich Company produced the suits for Project Mercury, which were based on the US Navy Mark IV full pressure suit. When the time came to create a suit for Gemini, B.F. Goodrich submitted an advanced version of the Mercury suit; David Clark Company proposed a derivative of the US Air Force A/P 22S-2. After evaluating both suits, NASA managers selected the David Clark suit.

The A/P-22S suit was a descendant of the pressure garment worn by X-15 pilots. From the inside out, the A/P 22S-2 had four layers: an oxford nylon comfort layer, a neoprene-coated ripstop nylon pressure bladder, a restraint layer, and a nylon outer cover. For the Gemini space suits, the David Clark Company used HT-1 Nomex for the outer cover and braided HT-1 for the restraint layer. The restraint layer was one of the key design elements of the Gemini suits. Called Link-Net, the restraint layer resembled a fish net and kept the pressure bladder from inflating too much. The net construction permitted the astronaut to move his limbs even when the suit was inflated. When inflated, the Gemini space suits were pressurized to 3.7 pounds per square inch.

On the first piloted Gemini flight, Astronauts Gus Grissom and John Young wore G3C model suits, which was the intravehicular version. The G3C weighed 25 pounds and was similar in structure to the A/P 22S-2 garment in that it comprised the comfort layer, pressure bladder, Link-Net restraint layer, and outer cover. The G4C suits that Ed White and James McDivitt wore weighed 35 pounds. Most of the increased weight was from the addition of an extravehicular coverlayer that comprised layers of nylon felt, aluminized mylar, unwoven dacron and HT-1 Nomex.

NASA launched Gemini 4 on June 3, 1965. On the third revolution of the Earth, White opened the hatch and floated out. As the spacecraft approached the tracking station in Guaymas, Mexico, Mission Control reported: “This is Gemini Control, Houston. Gus Grissom has just established contact with the spacecraft. McDivitt confirmed that White did leave the spacecraft. He said he looks great. He’s outside working his maneuvering unit and Jim is quite exuberant about the performance that he’s witnessing at this time.”

White tested a device called the Hand Held Maneuvering Unit, or HHMU. It comprised two oxygen bottles attached to a handle with small jet nozzles. Squeezing the handle squirted oxygen through the nozzles to produce thrust for maneuvering. White depleted the HHMU’s gas supply after traveling the length of the spacecraft. For 21 minutes, he floated alongside the spacecraft, attached to it by a 25-foot gold-covered umbilical. Then, it was time to come in. “The saddest moment of my life,” according to White as he climbed back inside the cabin. At first, he could not lock the hatch, and McDivitt had to reach over and help. Working together, they secured the hatch and settled in for the rest of the 4-day mission.

The next two flights did not include EVAs so the astronauts on these flights wore G3C suits. On Gemini 5 in particular, this was a severe test of the comfort of these suits because Astronauts Cooper and Conrad wore them for 8 days. Gemini 7 presented an even more extreme test for the astronauts and spacecraft: Frank Borman and James Lovell were to spend two weeks in orbit. David Clark Company fabricated a new light-weight space suit for Gemini 7, the G5C suit. The G5C comprised just two layers: a neoprene coated nylon pressure bladder and an HT-1 nylon restraint and coverlayer. The suit had a large, soft hood-like helmet with a built-in clear visor. Underneath the soft helmet, the astronaut wore a standard US Navy crash helmet for impact protection. The G5C ensemble weighed 16 pounds. The astronauts could remove the G5C during flight and wear only the one-piece cotton “constant wear garment.”

Subsequent Gemini astronauts all wore G4C suits because there were EVAs planned for each flight. On Gemini 9, Gene Cernan was supposed to test the Astronaut Maneuvering Unit (AMU), which used hydrogen peroxide thrusters. To protect the suit from the hot exhaust gases from the thrusters, woven stainless steel fabric called Chromel-R covered Cernan’s legs. Layers of aluminized H-film and fiberglass cloth underneath the steel fabric provided additional insulation from the AMU exhaust, which could reach 1,300 degrees F.

On the Gemini 4 EVA, White wore a small chest pack called the Ventilation Control Module, or VCM. The VCM controlled suit pressure with oxygen supplied from the spacecraft via a 25-foot umbilical. The VCM also housed a 9-minute emergency oxygen supply. Later Gemini astronauts used a larger chest pack called the Extravehicular Life Support System (ELSS) that provided greater oxygen reserves and better heat and moisture removal than the VCM. The ELSS was also designed to function independent of the spacecraft with oxygen being supplied from a backpack like the AMU. It contained a 30-minute emergency oxygen supply.

The A/P 22S-2 suit which spawned the G3C and G4C suits evolved into the S-1035 full pressure suit that is worn by pilots flying U-2 aircraft. This was the basis for the Advanced Crew Escape Suit (ACES) worn by Space Shuttle astronauts during launch and reentry and the Commercial Hypobaric Astronaut Protective Suit (CHAPS) being proposed by the David Clark Company for commercial space flight use.