Hamilton Standard had overall development responsibility for the Apollo suit and associated Portable Life Support System (PLSS). A subcontract was awarded to International Latex Corporation (ILC) for development of this suit. After suit development was completed, the production contract was awarded to International Latex, and the initial suit was designated A5L. The A6L design incorporated a thermal/ meteoroid garment. This was never flown. Following the Apollo fire, the suit was redesigned to eliminate flammable materials and was designated A7L (designation A8L was never used). Each Apollo astronaut had three custom fitted A7L suits - one for flight, one for training, and one for flight back-up. The Apollo suit massed 49 lbm (22 kg) and its PLSS, 57lbm (26 kg)*. The A7LB modification was used for Apollo J series lunar landing missions. The A7LB with an additional thermal garment was used for Skylab. Apollo ASTP, with no EVA requirements, reverted to the original design.

*[lbm means pound-mass, e.g. the PLSS only weights 57 lb when gravity is equal to 1-G (32 ft/s^2 or 9.81 m/s^2), as it is on earth. On the moon the PLSS weights less than 57-lb, BUT it still has a mass of 57lbm. Kilograms (kg) are a unit of mass, like lbm. instead of weight, like lb, so they avoid this confusion remain the same in different gravities.]

The hazard of micrometeoroids that constantly pelt the lunar surface from deep space was met with an outer protective layer on the Apollo spacesuit. A backpack PLSS provided oxygen for breathing, suit pressurization, and ventilation for moonwalks lasting up to 7 hours; Apollo spacesuit mobility was improved over earlier suits by use of bellows-like molded rubber joints at the shoulders, elbows, hips and knees.

From the skin out, the Apollo A7LB spacesuit began with an astronaut-worn liquid-cooling garment, similar to a pair of long-johns with a network of spaghetti-like tubing sewn onto the fabric. Cool water, circulating through the tubing, transferred metabolic heat from the Moon explorer's body to the backpack and thence to space.

Next came a comfort and donning improvement layer of lightweight nylon, followed by a gas-tight pressure bladder of Neoprene-coated nylon or bellows-like molded joints components, a nylon restraint layer to prevent the bladder from ballooning, a lightweight thermal superinsulation of alternating layers of thin Kapton and glass-fiber cloth, several layers of Mylar and spacer Material, and finally, protective outer layers of Teflon-coated glass-fiber Beta cloth.

Apollo space helmets were formed from high-strength polycarbonate and were attached to the spacesuit by a pressure-sealing neck ring. Unlike Mercury and Gemini helmets, which were closely fitted and moved with the crewman's head, the Apollo helmet was fixed and the head was free to move within. While walking on the Moon, Apollo crewmen wore an outer visor assembly over the polycarbonate helmet to shield against eye-damaging ultraviolet radiation, and to maintain head and face thermal comfort. Completing the Moon explorer's ensemble were lunar gloves and boots, both designed for the rigors of exploring, and the gloves for adjusting sensitive instruments.

The lunar surface gloves consisted of integral structural restraint and pressure bladders, molded from casts of the crewmen's hands, and covered by multi-layered superinsulation for thermal and abrasion protection. Thumb and fingertips were molded of silicone rubber to permit a degree of sensitivity and "feel." Pressure-sealing disconnects, similar to the helmet-to-suit connection, attached the gloves to the spacesuit arms. The lunar boot was actually an overshoe that the Apollo lunar explorer slipped on over the integral pressure boot of the spacesuit. The outer layer of the lunar boot was made from metal-woven fabric, except for the ribbed silicone rubber sole; the tongue area was made from Teflon-coated glass-fiber cloth. The boot inner layers were made from Teflon-coated glass-fiber cloth followed by 25 alternating layers of Kapton film and glass-fiber cloth to form an efficient, lightweight thermal insulation.

Nine Skylab crewmen manned America's first space station for a total of 171 days during 1973 and 1974.

They wore simplified versions of the Apollo spacesuit while doing the historic repair of the Skylab and changing film canisters in the solar observatory cameras. Jammed solar panels and the loss of a micrometeoroid shield during the launch of the Skylab orbital workshop necessitated several spacewalks for freeing the solar panels and for erecting a substitute shield.

The spacesuit changes from Apollo to Skylab included a less expensive to manufacture and lightweight thermal micrometeoroid overgarment, elimination of the lunar boots, and a simplified and less expensive extravehicular visor assembly over the helmet. The liquid-cooling garment was retained from Apollo, but umbilicals and astronaut life support assembly (ALSA) replaced backpacks for life support during spacewalks.

Apollo-type spacesuits were used again in July 1975 when American astronauts and Soviet cosmonauts rendezvoused and docked in Earth orbit in the joint Apollo-Soyuz Test Project (ASTP) flight. Because no spacewalks were planned, U.S. crewmen were equipped with modified A7LB intravehicular Apollo spacesuits fitted with a simple cover layer replacing the thermal micrometeoroid layer.

The space suit is an airtight anthropomorphic structure called the Pressure Garment Assembly or PGA. There are two basic configurations of the suit used to support Apollo Missions: an Intravehicular (IV) configuration designated as the CMP A7LB PGA, and an Extravehicular (EV) configuration identified as the EV A7LB PGA. The CMP A7LB pressure garment configuration is worn by the Command Module Pilot. The EV A&B configuration is worn by the Crew Commander and the Lunar Module Pilot. A slightly modified version of the EV A7LB PGA is planned for use during Skylab missions.

The Extravehicular Mobility Unit (EMU) configured for Skylab missions. The pressure garment assembly interfaces with the spacecraft environmental control system, or the Apollo Portable Life Support System (PLSS) or the Skylab Astronaut Life Support Assembly (ALSA). The pressure garment is operational at differential pressures of 3.70 to 3.90 psi (25.5 to 26.9 KPa); temperatures of -290 to +310 degrees Fahrenheit (94.3 to 428 degrees Kelvin) for Apollo missions or -180 to +277 degrees Fahrenheit (155 to 409 degrees Kelvin) for Skylab missions; and In micrometeoroid flux densities normally expected within the lunar orbit perimeter about the earth or a 300,000 mile (480000 km) orbit.

Entrance Into the suit is made through restraint and pressure- sealing zippers. The entrance opening used In the CMP A7LB assembly extends down the center of the back, from the neck area to the front crotch area. The EV AMB suit employs entrance zippers that extend from the left side of the waist, around the back to the right side of the waist, and diagonally up to the right chest area of the suit. Routing of the zippers in the EV A7LB suit was changed from that employed in the CMP model to accommodate the new neck and waist joints. The entrance zippers can be operated by the crewman if required, but zipper actuation is normally done with the assistance of a fellow crewmember.

There are two protective envelopes employed in the space suit: an Inner pressurizable envelope, and an outer thermal and micrometeoroid protective envelope. The inner pressurizable envelope Is called the Torso and Limb Suit Assembly (TLSA); this assembly Interfaces with a detachable helmet, and a pair of removable gloves. The outer envelope used for thermal and micrometeoroid protection Includes an Integrated Thermal Micrometeoroid Garment (ITMG), a Lunar Extravehicular Visor Assembly (LEVA) or Skylab Extravehicular Visor Assembly (SEVA),and a pair of lunar boots that are used for Apollo Lunar missions only. The torso and limb suit consists of an inner comfort liner, a rubber-coated nylon bladder, and an outer nylon restraint structure with the exception of the shoulder, elbow, wrist, thigh and knee joints. These joints are single wall, integrated restraint and bladder, bellows-like structures.

The Thermal Micrometeoroid Garment (ITMG) Is composed of an inner layer of rubber-coated nylon, alternate layers of aluminized material separated by a low-heat-conducting spacer fabric, and an outer layer of fire and abrasion resistant material. This thermal cross section employs the same Insulation principle as the "Thermos" bottle when the suit is exposed to the near vacuum of space. The Lunar Extravehicular Visor Assembly (LEVA) or Skylab Extravehicular Visor Assembly (SEVA) includes a shell assembly that fits over the helmet, and that clamps around its base. Two visors, two side-eyeshades, and a center eyeshade are supported by the shell. The outer sun visor employs a gold coating that reflects solar heat and light from its surface. The inner protective visor is transparent, although it includes an Inner coating that retains heat being emitted from the face. The protective visor is used without the sun visor during operations in shadow areas where visibility through the dark sun visor would not be adequate. The visors and eyeshades are adjustable and can be moved to positions selected by the crewman for his comfort and safety.

The Lunar Boots are slip-on assemblies that include a cross section of materials similar to those In the ITMG. There are additional layers of materials used in the boot sole as necessary to reduce the transfer of heat from the lunar surface to the foot. Metal-woven fabric or "Chromel-R" forms the outer shell of the boots to resist high lunar surface temperatures and surface abrasion. The outer structure of the boots in the sole consists of silicone rubber that is sewn to the outer metal fabric shell and affords Improved wear and thermal protection to the boots.

For each PGA, there are two pairs of gloves used to support Apollo and Skylab missions: Intravehicular (IV) Gloves and Extravehicular (EV) Gloves. The IV Glove is a single-wall restraint and bladder structure formed to fit the crewman's hand. For scuff protection and added structural support, an outer gauntlet and palm restraint system is fitted over the glove. The palm restraint affords Improved hand dexterity for operating spacecraft controls and special devices. The EV Glove Includes an IV Glove that Is fitted with an outer thermal glove that employs a similar cross section to that of the ITMG. For abrasion and thermal protection, the outer shell is constructed of metal-woven fabric, and the fingertips are fitted with silicone rubber caps.

The outer thermal glove extends well back over the IV glove-TLSA juncture. Gaseous oxygen is circulated through the suit by the PLSS (backpack) or ALSA, or the spacecraft environmental control system for respiration, pressurization, and ventilation purposes. The oxygen is directed to the helmet from Inlet gas connectors on the suit, down over the body, to the arm and leg extremities, and then is directed through ducts to the exhaust gas connectors. The Impurities are removed from the gas stream as it passes through the spacecraft environmental control system or portable life support system, and then is recirculated through the suit. The ventilation system removes body heat from within the suit during lV operations, or when free space EV activities are performed remote from the spacecraft.

During lunar surface excursions the metabolic heat generated by the body exceeds the capability of the ventilation system, so a liquid cooling system Is employed which removes the major portion of body heat from within the PGA; thereby reducing fatigue as a result of body dehydration through perspiration.

The Liquid Cooling Garment (LCG) consists of a network of polyvinyl tubing that is supported by spandex fabric. The garment is worn next to the skin and covers the entire body exclusive of the head and hands. A liquid coolant or water is circulated through the tubing from the portable life support system. In the suit, heat is transferred from the body to the liquid through the tubing wall, and in the portable life support system, the heat is removed from the liquid before it is recirculated back to the LCG.

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