Spacesuit Guidebook is designed to supplement Spacesuit wall chart (VVAL-114), published by the Educa- tional Affairs Division, January 1990. The wall chart depicts Astronuat Bruce McCandless on his historic first untethered spacewalk using the Manned Maneuvering Unit. He flew on Shuttle mission 41 -B (February 3-1 1, 1984), and ventured 100 meters from the Shuttle's cargo bay and returned safely. The guidebook explains in depth the elements depicted on the wall chart in see-through and cut-away perspectives. Together the wall chart and guidebook show as well as explain the inside workings of the spacesuit and its various components. Forty separate elements are identified with an accompanying numerical legend. Those elements are further ex- plained in this guidebook along with their functions and how they work in relation to other elements. Additional chapters discuss essential compo- nents of the spacesuit such as the Primary Life Support System and the Manned Maneuvering Unit, and the method for donning the spacesuit. The original manuscript for this guidebook was written by Greg Vogt, Oklahoma State University. It was expanded and edited into this format by Robert Haynes, NASA Headquar- ters. The oil painting, around which the wall chart was designed, was painted by American artist Bruce Wolfe. Many people assisted in reviewing this guidebook from the early stages up to the final booklet. Special thanks go to Keith Hudkins, NASA Headquarters, for identifying the 40 spacesuit components; and to James Poindexter, Johnson Space Center for reviewing the manuscript. pacesuit components

The EMU is what Space Shuttle systems. Items 1 and 2 are explained around y axis), pitch (z axis), and astronauts call their spacesuit. EMU more fully in their own chapters. yaw (x axis). stands for Extravehicular Mobility 1. Primary Life Support System 3. Thruster Lights Unit. It is what protects astronauts This portable life support system While flying the Manned Maneu- from the harsh environment of space is an essential component of the vering Unit, the astronaut keeps outside the Space Shuttle's crew spacesuit. It is the backpack unit track of propellant with two cabin. The EMU includes many that the astronaut is wearing (it is gauges located on either side of individual components that, when only partially visible in the paint- the helmet's face plate. An assembled, form a single spacesuit. ing, shown on either side of the astronaut needs to know how Making the EMU is an exacting astronaut's helmet). The life much propellant is left in the unit, process. Pressure and restraint layers support system contains all the because when the propellant is are enclosed by thermal insulating control and monitoring systems gone, the astronaut is no longer and tear and puncture resistant layers. required to sustain the astronaut's able to maneuver. The astronaut One layer's function is just to keep the life while in space. It supplies needs to keep enough fuel in astronaut from overheating. Suit oxygen for breathing and for suit reserve to return safely to the layers are joined to metal connecting pressurization, and cleans carbon Shuttle. Generally, this means an rings and a hard fiberglass upper dioxide and odors from the air astronaut can use up half the fuel torso. Each layer and each compo- inside the suit. A tiny built-in to maneuver away from the nent must pass stringent inspections computer warns the astronaut of Shuttle and keep the remaining before a human life is entrusted to it. problems. half for the return. When fully assembled, the EMU 2. Manned Maneuvering Unit 4. Extravehicular Mobility Unit becomes a nearly complete short- Thruster Lights term, "soft," spacecraft for one A series of 24 thrusters is located EMU lights are found on either person. It provides pressure, thermal, on the Manned Maneuvering Unit side of the astronaut's helmet and and micrometeoroid protection, (MMU). The astronaut controls are used to shine light on objects oxygen, cooling water, drinking water, them with hand controllers at the in space. The small built-in flood food, waste collection (including ends of the MMU's two arms. lamps light up places sunlight and carbon dioxide removal), electrical (See item 40.) The thrusters may lights in the cargo bay do not power, and communications. The also be operated automatically by reach. The EMU lights have their only thing lacking in the EMU is pro- turning on an automatic attitude own battery system and are pulsion, but this can be added by hold system. Compressed nitro- needed for work in the Shuttle fitting a gas-jet-propelled Manned Ma- gen is moved through feed lines cargo bay or for repairing satel- neuvering Unit. On Earth the suit and to varying combinations of the 24 lites in space. When the astro- all its parts weigh about 112 kilo- nozzles. The nozzles are arranged nauts are building the Space grams. In orbit, they have no weight in clusters of three each on the Station Freedom, the EMU lights at all, but do retain their mass, which eight corners of the maneuvering will help them assemble the astronauts feel as a resistance to a unit, and are aimed along three pieces of the Station while in orbit change in motion. axes perpendicular to each other above Earth. The list that follows corresponds (x, y, and z) and permit six de- 5. Color Television Camera to the numerical legend on the wall grees of freedom of movement. The camera's lens system is chart. Some items will be self-ex- Movements in space are ex- about the size of a postage stamp, planatory, while others are parts of plained by the terms roll (rotation and mounted just over the helmet. Television monitoring is neces- Communications Microphone power from the Shuttle itself. In sary for certain communications Voice communication with the this manner the "consumables" with the Shuttle and Mission Shuttle and Mission Control are stored in the Primary Life Sup- Control. The camera is situated essential at all times. The micro- port System are conserved in line of view with the astro- phone inside the helmet con- during the prebreathing activity naut's own line of vision and is nects to the radio module located that is needed before an astro- equipped with its own batteries in the life-support unit of the naut can leave the Shuttle crew and RF transmitter so that the spacesuit. Covering the astro- cabin. The umbilical remains crew inside the Shuttle and naut's head is the communica- connected to the spacesuit until mission controllers on Earth can tions carrier assembly, or the astronaut disconnects it after get an astronaut's eye view of the "Snoopy Cap" as it is sometimes moving from the airlock into the spacewalk. During complicated called. The assembly is a fabric cargo bay. At the time the spacewalks, viewers may be able skull cap with built-in earphones umbilical is released, the space- to provide assistance. and a microphone for use with walk begins. The Service and 6. Helmet Solar Shield the spacesuit's radio. Cooling Umbilical is also used to Shown in the wall chart as a cut- 35mm Still Camera recharge batteries and replenish away, the solar shield is actually Views of the Shuttle, its cargo consumables. part of an entire assembly that bay, satellites, Earth, and other 11. Emergency Relief Valve covers the helmet. The visor as- phenomena are captured for Should the Primary Life Suport sembly contains a metallic gold- study by the 35mm camera. The System malfunction, the astro- coated Sun-filtering visor, a clear camera is attached to the naut can survive for 30-60 thermal impact protection visor, Manned Maneuvering Unit and is minutes by using the secondary and adjustable blinders that situated in line of view with the oxygen pack (see chapter 3, attach over the helmet. These astronaut's own line of vision. "Primary Life Support System"). shields are necessary to protect Camera Switch This system is activated by astronauts from harmful light The 35mm still camera is oper- opening the purge valve. This and radiation emitted by the Sun. ated by a cabled switch con- valve, which has a set of pinch- The helmet itself is a plastic nected to the camera and the ers on either side of it, allows the pressure bubble with a neck dis- glove of the EMU. The astronaut astronaut to let some of the connect ring and ventilation merely needs to press a button pressure out of the EMU. To distribution pad. The helmet has on the end of the cable attached activate the valve, the astronaut a backup purge valve (for use to his or her glove, and the simply squeezes the pinchers with a secondary oxygen pack camera automatically focuses, with the EMU glove, and air worn beneath the Primary Life snaps the picture, and advances pressure is released through the Support System backpack) and the film for the next picture. tube-like extension on the EMU is used to remove expired carbon Spacecraft Life-Support chest plate. dioxide. (See item 11.) A tube Connector 12. Water Cooling Control Valve projects into the helmet near the Long before donning the upper The astronaut is able to control astronaut's mouth from a plastic half of the EMU, the Shuttle's his or her body temperature water pouch attached inside the Service and Cooling Umbilical is inside the spacesuit by control- spacesuit's hard upper torso. plugged into the dispays and ling the temperature of water cir- The tube allows the astronaut to control module panel on the culating through the Liquid drink from it as if from a straw, front of the upper torso. Five Cooling and Ventilation Garment.

, providing him or her with fresh connections within the umbilical The garment (item 29) is laced water. Also mounted inside the provide the suit with cooling with an intricate network of helmet near the water tube is an water, oxygen, and electrical astronaut snack food bar. plastic tubing, through which control module on the hard upper The mirror reflects the numbers in water is circulated to keep the torso prevents the astronaut from their correct position. Whenever astronaut cool and to help control being able to bend down to look an astronaut must adjust a switch perspiration. at the controls when he or she or valve that is not otherwise Note that the numbers on the needs to adjust them. If you look visible, the mirror helps in Water Cooling Control Valve are just to the right of the control locating and adjusting it. printed backwards. The reason is valve, you'll see a small mirror Push-to-Talk Switch that the location of the display strapped to the astronaut's arm. This switch operates the micro-

Extended view of the upper part of the EMU phone inside the helmet. The ing a task requiring it, and to spacesuit. It comprises the outer voice radio works much as a CB remove it when no longer needed. layer of the Thermal Micromete- radio works. The talk button must 21. Manned Maneuvering Unit oroid Garment. This layer is of be pushed to talk, and released to (MMU) Release Ring Ortho FabricTM,a blend of woven receive voice messages. When it is not in use and during NomexTMand TeflonTMwith 14. Fan Switch the donning procedure, the MMU KevlarTMRip Stops. It protects This switch turns on and off a fan is stowed in the flight support subsequent layers of the space- inside the EMU to circulate air station. In this location, astro- suit, namely the Pressure Re- through the helmet and other nauts prepare the MMU for flight, straint Layer and the Pressure areas of the spacesuit. charging batteries and replenish- Bladder from abrasions and tears. 15. Caution and Warning Switch ing propellant tanks. In donning 25. Super insulation Layers (Alumin- This switch starts the caution and the MMU, the astronaut backs ized MylarTM) warning system to display states into it while it is secured on the The next five layers of the Ther- of various functions within the flight support station. The MMU is mal Micrometeoroid Garment EMU. released from the flight support provide the astronaut with 16. Communications Volume station via these two release rings thermal protection. The material Controls and the astronaut maneuvers in these layers is Aluminized Volume controls are required to away using the MMU propulsion MylarTMFilm, which is reinforced keep some messages from power. with DacronTMScrim. blaring in the astronaut's ears, 22. Safety Tethers 26. Second Micrometeoroid Layer and to better tune in faint ones. When astronauts work in the (NeopreneTM) 17. Computer Screen Intensity Shuttle's cargo bay, they need to As the inner lining for the Thermal Controls keep from floating too far away Micrometeoroid Garmet, this layer This switch controls the intensity from the spacecraft. Sometimes is the final barrier of micromete- of the readout on the computer they work in stations with foot oroid protection. The material is display (see item 18). restraints, but mostly they wear NeopreneTMcoated NylonTMcloth. 18. Computer Display safety tethers. These tethers can 27. Pressure Restraint Layer The computer display atop the be moved from location to loca- (DacronTM) display and control module shows tion along the cargo bay to This layer is composed of syn- an alpha and numeric readout for provide the astronaut with a full thetic fabric placed over the pres- monitoring by the astronaut. The range of mobility, while still sure bladder fabric to give it addi- readout shows levels of oxygen, keeping the astronaut within safe tional support and shape. (See fuel, and power remaining in the working distance of the cargo also items 28 and 31 .) EMU'S Primary Life Support bay. 28. Pressure Bladder (Polyurethane- System. 23. Locator Strobe Lights coated MylarTM) 19. Oxygen Pressure Actuator Strobe lights are used on the Pressure bladders are much like This switch allows the astronaut MMU to help EVA astronauts today's tubless tires, composed of to select the internal oxygen pres- locate each other's position, as rubber (urethane) to seal in the air sure of the EMU. well as to help crew members on pressure and NylonTMto restrain 20. Mini-workstation Connector the Shuttle keep track of EVA expansion. For the bladder in the Often the astronaut works in or progress. Strobe lights are spacesuit, NylonTMis dipped in around the Shuttle's cargo bay, effective means for locating polyurethane a minimum of six performing tasks that require objects in poorly lit regions. times to create an impermeable tools. These EMU connections 24. Micrometeoroidflear Protection barrier between the pressure of allow the astronaut to attach a Layer the pure oxygen inside the small workstation while perform- This is the outermost layer of the spacesuit and the vacuum of space on the outside. (See also touching the astronaut's skin. It is Joints for the lower and upper items 27 and 31 .) made of NylonTMchiffon, a light- torsos represent an important 29. Liquid Cooling and Ventilation weight material, to be as comfort- advance over those of previous Garment (Ethelene Vinyl Acetate able as possible. It is positioned spacesuits. The EMU joints Tubing) between the astronaut and the maintain nearly constant volume Almost like a pair of longjohns, Liquid Cooling and Ventilation during bending. As the joints are the Liquid Cooling and Ventilation Garment. bent, reductions in volume along Garment covers the astronaut's 31. Pressure Restraint System the inner arc of the bend are upper and lower body. The The materials used for the EMU equalized by increased volume garment itself contains ethelene pressure restraint system are a along the outer arc of the bend. vinyl acetate tubing, through composite of items. Airtight 32. Boot Disconnect which water is circulated to linings with comfort fabrics are a All suit openings have locking control the temperature. significant part, but the spacesuit provisions that require a mini- 30. Body Comfort Lining (NylonTM must also be flexible and retain its mum of three independent Chiffon) shape as well as inside pressure. motions to open. This feature This is the first layer of fabric (See also items 27 and 28.) prevents any accidental opening

uminized Mylar Film Rein- Thermalinsulation Micrometeoroid protection as part of rmced with Dacron Scrim Thermal Micrometeoroid Garment V' astronaut locks the two body-seal e, a /

*.-%-l. closure rings together, sometimes "/ with the help of another crew -'*-~.~4 member. Shown here, the restraint layer of the EMU glove is placed over the bladder. The bladder is formed when a ceramic cast of a hand is dipped seven or eight times into a vat containing urethane. Then the hand-shaped bladder is stripped from the cerammic cast and inflated to check for defects and leaks. 36. Manned Maneuvering Uni% 38. Waist Bearing that regulate various life-support Safety Belt The upper torso and lower torso functions of the EMU on the front This safety belt harness secures sections of the EMU are joined by of the display and control module the astronaut into proper position a metal body-seal closure. Two are out of the astronaut's vision while wearing the Manned rings - one on the upper torso range. The mirror permits the Maneuvering Unit. and one on the lower torso - astronaut to read the knob 37. Tool Tether lock together in a fashion similar settings, which are written on the While in space orbiting Earth, the to other ring-seals. There is also a spacesuit backwards to make astronauts experience near large waist bearing that permits them easy to read with the mirror. weightlessness. For instance, in astronauts mobility at the waist. 40. Rotational Hand Controller the Shuttle's cargo bay, anything This permits them to make twist- A hand controller is built into each that is not secured by some ing motions when their feet are arm of the Manned Maneuvering method tends to float off. This is secured by foot restraints on sta- Unit. The hand controllers allow true of the small tools required for tionary work platforms. the astronaut to direct the firing of work in the cargo bay or for 39. Procedure Check List different combinations of MMU repairing satellites in space. The A small, spiral-bound, 27-page thrusters for nearly complete astronauts cannot simply lay the checklist for various spacewalk controll over his or her move- tool down when it is not being procedures is mounted on the left ments. In space, there is no up or used. The tool tether keeps small arm of the upper torso. There is down, the direction of movement tools from drifting away, holding also a small wrist mirror. The is discussed with the terms roll, them within working range of the mirror was added to the space- pitch, and yaw. astronaut's grasp. suit because some of the knobs Power Mode Switch (SCUIBatt) I

An extended view of the display and control module acesu

The EMU can be donned in about pressure is reduced from the normal 10 to 15 minutes. But preparing to 101 kilopascals to 70.3 kilopascals, go outside the Shuttle crew cabin and the percentage of oxygen is takes about two hours and twenty slightly increased. By the end of this minutes. Inside the crew cabin, phase, much of the nitrogen has been astronauts breathe a mixture of cleared from the astronauts' blood- nitrogen and oxygen at the same air streams and the two astronauts can pressure as at sea level on Earth (I 01 remove their launch and entry hel- kilopascals). But inside the space- mets. When they put on their space- suit, astronauts breathe pure oxygen suits and seal the helmets, the astro- at a much lower pressure (29.6 nauts prebreathe pure oxygen for an kilopascals, or roughly one-third the additional 30 to 40 minutes before cabin pressure). If an astronaut goes pressure inside is lowered to 29.6 directly from the cabin into the kilopascals. spacesuit, the rapid drop in pressure After prebreathing, the first items around the body could cause caisson to be put on are the urine collectors. disease. Also known as "the bends," The device for males is called the this disease happens when the Urine Collection Device and is simply external pressure around the body an adaptation of a device used for The fabric of the Liquid and Cooling Garment is laced drops too quickly, causing bubbles of people who have kidney problems. It with plastic tubing to circulate cooling water nitrogen to form and expand in a is a pouch that can contain approxi- person's bloodstream. It is the same mately one quart of liquid and is wear. It is a one-piece suit with a debilitating problem that underwater attached via a roll-on connector cuff. zippered front and is made of stretch- divers sometimes experience if they For females, the urine collector is able SpandexTMfabric laced with 91.5 rise to the surface too quickly. The called the Disposable Absorption and meters of plastic tubing. When the disease can cause severe pains in the Containment Trunks. These trunks are EMU is completely assem bled, joints, cramps, paralysis, and even multilayered shorts that hold a highly cooling and ventilation become death if pressure around the person absorptive powder, and are also significant problems-body heat, is not gradually returned to normal. capable of containing about a quart of contaminant gases, and perspiration To prevent caisson disease, the liquid. all must be removed. astronauts (a team of two) intending Most of the EMU donning process Cooling of the crew members is to go EVA must remove nitrogen takes place inside the orbiter's airlock. accomplished by circulating chilled from their bloodstreams. They do The airlock is a cylindrical chamber water through the plastic tubes in the this by spending time breathing pure located on the orbiter's mid-deck; one garment. Chilling the water is one of oxygen. Called "prebreathing," this hatch leads from the mid-deck into the functions of the Primary Life activity begins when the two astro- the airlock and a second hatch leads Support System. Oxygen and expired nauts don their special launch and from the airlock out to the unpressur- carbon dioxide are drawn from the entry helmets. They breathe pure ized cargo bay. suit's atmosphere through ducts into oxygen from the orbiter oxygen Inside the airlock, the astronauts the Primary Life Support System for supply system for one hour. Ap- put on the Liquid Cooling and Ventila- purification and recirculation. Body proximately 12 hours before the tion Garment. The garment has the perspiration is also drawn away from astronauts exit into space, the cabin general appearance of long under- the suit by the venting system. ORIGINAL PAGE SLACK AND WHITE PHOTOGRAPH

The upper torso of the EMU is pre- The Service and Cooling Umbilical of The lower torso of the EMU is donned With a diving motion, the astronaut pared for donning. the orbiter is hooked up to the upper dons the upper torso. torso. Purified oxygen from the Primary Life The electrical harness provides Voice communications are also Support System reenters the suit biomedical and communications carried on this circuit. through a duct in the back of the hookup with the Primary Life Sup- Next, several simple tasks are helmet, which directs the flow over port System. The biomedical performed. Antifog compound is the astronaut's face to complete the hookup monitors the heart rate of rubbed on the inside of the helmet. circuit. the astronaut, and radios this The wrist mirror and checklist are put Next, the EMU electrical harness information via a link with the on the left arm of the upper torso. is attached to the hard upper torso. orbiter to Mission Control on Earth. Also at this time a food bar and

The Liquid Cooling and Ventilation The upper and lower rings of the The EMU gloves are donned. The helmet and visor assembly is Garment is connected. waist entty closures are joined and donned. sealed 8RBGINAL PAGE BMeu .ARID WHITE PHOIOGMPH

The Biomedical An EVA checklist is Unit is connected. attached to the upper torso's left sleeve.

A food bar and the An antifog com- In-suit Drink Bag pound is applied are inserted inside inside the helmet. the neck ring of the upper torso.

water-filled In-suit Drink Bag are Next, the communications carrier upper torso is multilayered. The inner inserted inside the front of the hard assembly or "Snoopy Cap" is con- layer is a pressure bladder made of upper torso. The food bar, of com- nected to the EMU electrical harness urethane-coated NylonTM.Above this pressed fruit, grain, and nuts, is and left floating above the hard upper layer is a restraining layer of Da- wrapped in edible rice paper and its torso. The communications carrier cronTM. Enclosing this layer is an upper end extends into the helmet assembly earphones and micro- outer thermal garment of neoprene- area near the astronaut's mouth. phones are held by the fabric cap. coated NylonTM,five layers of alumin- When the astronaut is hungry, he or After the astronaut dons the EMU, the ized MylarTMlaminated with DacronTM she merely bites the bar and pulls it cap is placed on the head and ad- scrim, and the outermost layer, a upward before breaking off a piece to justed. combination of GortexTM,KevlarTM, and chew. In that manner, a small piece When the tasks preparatory to NomexTM. of the bar remains extended into the donning the suit are completed, the Long before donning the upper helmet for the next bite. It is neces- lower torso, or suit pants, are pulled half of the EMU, the airlock's Service sary to eat the entire bar at one time, on. The lower torso comes in various and Cooling Umbilical is plugged into because saliva quickly softens the sizes to meet the varying size require- the displays and control module panel protruding food bar piece, making it ments of different astronauts. It on the front of the upper torso. Five mushy and impossible to extract. The features the pants with boots, joints in connections within the umbilical In-suit Drink Bag is placed just over the hip, knee, and ankle, and a metal provide the suit with cooling water, the bar. The bag is filled with up to body-seal closure for connecting to oxygen, and electrical power from the 0.65 liters of water from the water the mating half of the ring mounted orbiter itself. In this manner, the supply in the Shuttle's galley prior to on the hard upper torso. The lower "consumables" stored in the Primary entering the airlock. A plastic tube and torso's waist element also contains a Life Support System will be conserved valve assembly extends up into the large bearing. This gives the crew during the lengthly prebreathe period. helmet, and a drink can be taken member mobility at the waist, permit- The Service and Cooling Umbilical is whenever needed. Both the food bar ting twisting motions when the feet also used for recharging batteries and and drink bag are held in place by are held in workstation foot restraints. replenishing consumables between VelcroTMattachments. The fabric of both the lower and EVAs. With the lower torso in place and naut to move his or her head around. or yawning, or by pressing their noses the orbiter providing consumables to With the donning of the helmet on an optional sponge mounted to the the suits, each astronaut "dives" with and gloves, the spacesuits are now left on the inside of the helmet ring a squirming motion into the upper sealed off from the atmosphere of the and blowing. This forces air inside torso. To dive into it, each astronaut airlock and the astronauts are being the ears and sinus cavities to equalize maneuvers under the body-seal ring supported by the oxygen, electricity, the pressure. of the upper torso and assumes a and cooling water provided by the During the next several minutes diving position with arms extended Shuttle. A manual check of suit seals the two spacesuits are purged of any upward. Stretching out, while at the is made by pressurizing each suit to remaining oxygen/nitrogen atmos- same time aligning arms with the suit 29.6 kilopascals d. (The "d" stands phere from the cabin, which is re- arms, the astronaut slips into the for differential.) Inside the airlock the placed with pure oxygen. Additional upper torso. pressure is either 70.3 or 101 kilopas- suit checks are made while the final Two connections are made. The cals. The suit's pressure is elevated oxygen prebreathe takes place. first joins the cooling-water tubing an additional 29.6 kilopascals, giving The inner door of the airlock is and ventilation ducting of the Liquid it a pressure differential. Once sealed and the airlock pressure bleed- Cooling and Ventilation Garment to pressure reaches the desired level, the down begins. A small depressuriza- the life support system. The second oxygen supply is shut off and the tion valve in the airlock latch is connects the biomedical monitoring digital display on the chest-mounted opened to outside space, permitting sensors to the EMU electrical harness control module is read. To assist in the airlock atmosphere to escape. that is connected to the life-support reading the display, an optional When the airlock pressure reaches unit. Then the astronaut locks the two Fresnel lens inside the space helmet 34.48 kilopascals, the bleed-down is body-seal closure rings together, may be used to magnify the numbers. temporarily stopped to check for usually with the assistance of another Some leakage of spacesuit pressure is leaks. If the EMU is found to have any crew member who remains on board. normal. The maximum allowable rate leaks, the airlock is repressurized, One of the most important of leakage of the Shuttle EMU is 1.38 permitting astronauts and crew features of the upper half of the suit is kilopascals per minute and this is members to reexamine the EMU seals. the hard upper torso, a hard Fiber- checked before the suit is-brought If there are no leaks, final depres- glasTMshell covered by the fabric back down to airlock pressure and the surization is begun. The outer airlock layers of the Thermal Micrometeoroid oxygen supply is turned back on. hatch is then opened and the suited Garment. The hard upper torso is As the suit pressure is elevated, astronauts prepare to pull themselves similar to the breast and back plates the astronaut may experience discom- out into the cargo bay. As a safety of a suit of armor. It provides a rigid fort in the ears and sinus cavities. measure, they attach tethers to the and controlled mounting surface for The astronauts compensate for the orbiter to prevent floating away as the Primary Life Support System on pressure change either by swallowing they move from place to place by the back and the display and control hand holds. At this point, the astro- module on the front. nauts disconnect the Orbiter Service The last EMU gear to be donned and Cooling Umbilical from the EMU includes eyeglasses, if needed, the and pull themselves through the outer communications carrier assembly, airlock hatch. The Primary Life Sup- comfort gloves, the helmet with lights port System begins using its own and optional TV, and gloves. The supplies. The EVA begins. When in connecting ring of the helmet is space, the two astronauts are identi- similar to the rings used for the body- fied by the use of red stripes on the seal closure. Mobility is not needed in EMU pants legs. One EMU will have this ring because the inside of the stripes and the other will not. The Communications Carrier Assembly is placed helmet is large enough for the astro- over the head. ife suppor system

During the Apollo Moon walks, where it is directed over the head and taminants are filtered out by lithium astronauts experienced their first real then downward along the inside of the hydroxide and activated charcoal freedom inside spacesuits because of helmet face plate. Before passing into layers. The gas stream then travels a portable life support system worn the helmet, the oxygen warms suffi- through a heat exchanger and on their backs. Up to that time all ciently to prevent fogging the visor. sublimator for chilling and 'removal EVAs were tethered to the spacecraft As the oxygen leaves the helmet and of humidity. The heat exchanger and by an umbilical line that supplied travels into the rest of the suit, it picks sublimator also chills water that runs oxygen and kept astronauts from up carbon dioxide from the astro- through tubing in the Liquid-Cooling drifting away. naut's respiration. Humidity from and Ventilation Garment. The EVAs aboard the Space Shuttle perspiration, some heat from physical humidity in the gas stream con- allow astronauts greater freedom. activity, and trace contaminants are denses in the heat exchanger and Because Shuttle EVAs take place in also picked up by the oxygen as it is sublimator and relatively dry gas the near weightless environment of drawn into the ducting built into the (now cooled to approximately 13" space, astronauts do employ tethers, Liquid Cooling and Ventilation Gar- Celsius) is directed through a carbon but these act only as safety lines and ment. A centrifugal fan, running at dioxide sensor before recirculating do not provide life support. nearly 20,000 rpm, draws the con- through the suit. Oxygen is regu- The freedom of movement taminated oxygen, at a rate of about lated by the Primary Life Support afforded Shuttle astronauts is owed to 0.1 7 cubic meters per minute, back System as needed. In the event of the Primary Life Support System into the Primary Life Support System, an emergency, a purge valve in the carried on their backs. The Primary where it passes through a filtration suit can be opened. The purge valve Life Support System provides life cartridge. opens the gas flow loop, permitting support, voice communications, and Carbon dioxide and trace con- the moisture and the carbon dioxide- biomedical telemetry for EVAs lasting as long as 7 hours. Within its dimen- Electronics Module sions of 80 by 58.4 by 17.5 centime- \ Time ters, the system contains five major groups of components for life sup- MMU Mount~ng port. These are the oxygen ventilat- ing, condensate, feedwater, liquid transport, and primary oxygen circuits. The oxygen ventilating circuit is a closed-loop system. Oxygen is supplied to the system from the primary oxygen circuit or from a secondary oxygen pack that is added to the bottom of the Primary Life Support System for emergency use. The circulating oxygen enters the suit through a manifold built into the hard upper torso. Ducting carries the .z2 oxygen to the back of the helmet, Antenna , rich gas to dump outside the suit just before it reaches the contaminant Oxygen Tank Manual Override control cartridge. \ \ Shut-off Valve Frame and \ \ / Button Protect Cover I A byproduct of the oxygen venti- lating circuit is moisture. The water, which is produced by perspiration and breathing, is withdrawn from the oxygen supply by being condensed in the sublimator and is carried by the condensate circuit. (The small amount of oxygen that is also carried by the condensate circuit is removed by a gas separator and returned to the oxygen ventilating system.) The water is then sent to the water storage tanks of the feedwater circuit and added to their supply for eventual use in the sublimator. In this manner, the system is able to maintain suit cooling for a longer period than would be Extended view of the secondary oxygen pack. possible with just the tank's original water supply. system that is connected to the plastic primary oxygen circuit. Its two tanks The job of cooling the astronaut is tubing of the Liquid Cooling and contain a total of 0.54 kilograms of the function of the feedwater and the Ventilation Garment. Water in this oxygen at a pressure of 5,860.5 liquid transport circuits. circuit, driven by a pump, absorbs kilopascals, enough for a normal 7- Using the pressure of oxygen body heat. As the heated water hour EVA. The oxygen of this circuit from the primary oxygen circuit, the passes to the heat exchanger and is used for suit pressurization and feedwater circuit moves water from sublimator, heat is transferred breathing. Two regulators in the the storage tanks (three tanks holding through the aluminum wall to the circuit step the pressure down to a total of 4.57 kilograms of water) to chamber with the porous wall. The usable levels of 103.4 kilopascals and the space between the inner surfaces ice formed in the pores of that wall is 29.6 kilopascals. Oxygen coming of two steel plates in the heat ex- sublimated by the heat directly into from the 103.4 kilopascal regulator changer and sublimator. The outer gas, permitting it to travel through the pressurizes the water tanks, and side of one of the plates is exposed pores into space. In this manner, oxygen from the 29.6 kilopascal regu- directly to the vacuum of space. That water in the transport circuit is cooled lator goes to the ventilating circuit. plate is porous and, as water evapo- and returned to the Liquid Cooling and To insure the safety of astronauts rates through the pores, the tempera- Ventilation Garment. The cooling rate on EVAs, a secondary oxygen pack is ture of the plate drops below the of the sublimator is determined by the added to the bottom of the Primary freezing point of water. Water still work load of the astronaut. With a Life Support System. The two small remaining on the inside of the porous greater work load, more heat is tanks contain 1.2 kilograms of oxygen plate freezes, sealing off the pores. released into the water loop, causing at a pressure of 41,368.5 kilopascals. Flow in the feedwater circuit to the ice to be sublimated more rapidly and The Secondary Oxygen pack can be heat exchanger and sublimator then more heat to be eliminated by the used in an open-loop mode by stops. system. activating a purge valve or as a On the opposite side of the other The last group of components in makeup supply should the primary steel plate is a second chamber the main life support system is the system fall to 23.79 kilopascals. through which water from the liquid transport circuit passes. The liquid transport circuit is a closed-loop maneuverin

Battery (2)

Thrusters (24). , I The Manned Maneuvering Unit Locator light switch (MMU) of the Space Shuttle is de- MMU Release ring (2) I signed to operate in the weightless environment of outer space and under the temperature extremes found there. The MMU is operated by a single spacesuited astronaut and has six degrees of freedom of movement. The unit features re- dundancy to protect against failure of individual systems. It is de- signed to fit over the life support system backpack of the EMU. The first flight test of the Shuttle MMU took place on flight 41-B. On the fifth flight day of the February 1984 mission, astronauts Bruce McCandless (depicted in the wall chart) and Robert Stewart suited up and entered the payload bay. McCandless got into the MMU and moved away from the Shuttle to a distance of 45.75 meters. He returned to the cargo bay and then moved out again to more than twice the earlier distance, all the time checking out the MMU's capabilities. Later, he used a Arm angle adjustment lever (2) 1 Y/ special latching mechanism with a External power connector practice target. This was an important test on preparation for The MMU is approximately 127 astronaut backs into the unit and the planned capture and repair of centimeters high by 83 centimeters snaps the life support system into ailing satellites on future missions. wide by 69 centimeters deep. When place, the arms are unfolded. Fully Stewart also tested the MMU carried up into space by the Shuttle, it extended, the arms increase the depth on the same mission, and on the is stowed in a support station at- of the MMU to 122 centimeters. To seventh flight day, both tested a tached to the wall of the cargo bay adapt for astronauts with different second MMU for precision in ma- near the airlock hatch. Two MMUs arm lengths, controller arms can be neuvering and stopping. The MMU are normally carried on a mission, adjusted over a range of approxi- proved itself, paving the way for with the second unit mounted across mately 13 centimeters. The MMU is future satellite repair and retrieval, from the first on the opposite cargo small enough to be maneuvered with space construction, and possible bay wall. The MMU controller arms ease around and within complex rescue of astronauts from disabled are folded for storage, but when an structures. With a full propellant load space vehicles. its mass is 148 kilograms. Preparations for The MMU is towed in Astronaut prepares the MMU Astronaut backs into the MMU Astronaut releases the MMU from the a flight with the the flight Support Station for flight and charges propel- and prepares for release. flight support station and maneuvers MMU begin with for launch and reentry /ant tanks or changes batteries away using the MMU's power. the astronaut and for on-orbit if necessary. donning an servicing. EMU.

Gaseous nitrogen is used as the and other equipment or by changes in Shuttle during maneuvering is propellant for the MMU. Two alumi- the center of gravity are automatically through the EMU radio voice commu- num tanks with KevlarTMfilament countered when sensed by small nication equipment. overwrappings contain 5.9 kilograms gyros. Generally, a total velocity change of nitrogen each at a pressure of of 20.1 meters (66 feet) per second is 20.68 kilopascals, enough propellant Using the MMU possible on one flight. Furthermore for a 6-hour EVA depending upon the When it becomes necessary to use the that "delta velocity", as it is called, amount of maneuvering done. Under MMU, an astronaut first enters the must be divided in half so that propel- normal operation, each tank feeds on orbiter's airlock and dons a spacesuit. lant will be available for the trip back. a system of thrusters. In the event of Exiting into space, the astronaut It is divided in half again to allow for some failures, crossfeed valves may attaches a safety tether and moves rotational accelerations. Generally, be used to connect the two systems, along hand holds to the MMU. The astronauts fly the MMU at velocities of permitting all propellant from both maneuvering unit is attached to the only 0.3 to 0.6 meters per second tanks to be used. The right hand cargo bay wall with a framework that relative to the Shuttle. While these controller produces rotational accel- has stirrup-like foot restraints. Facing velocities may seem small, they ac- eration for roll, pitch, and yaw. The the MMU, with both feet in the re- complish much in the weightless left controller produces translation straints, the astronaut visually in- environment of Earth orbit. Once an acceleration in the degrees of for- spects the unit. If the battery needs astronaut begins moving in a new ward-back, up-down, and left-right. replacing or if the propellant tanks direction or at a new velocity, that Hand controller inputs pass through a need recharging, these tasks can be astronaut will keep moving indefi- small unit that operates the appropri- done at this time. When ready, the nitely until an opposing thrust is ate thrusters for achieving the desired astronaut turns around and backs into applied. acceleration. Coordination of the two position. The life support system of Upon completion of assigned controllers produces intricate move- the EMU locks into place, hand tasks, the astronaut returns to the ments in the unit. Once a desired controller arms are unfolded and payload bay and reverses the unstow- orientation has been achieved, the extended, and the MMU is released ing procedure. To assist in realign- astronaut can engage an automatic from the frame. ment with the mounting frame, large attitude-hold function that maintains During the maneuvering, the mushroom-like knobs, built into the the inertial attitude of the unit in flight. astronaut must use visual cues to frame, are available for grasping by This frees both hands for work. Any move from one location to another. the crew member to push backwards induced rotations produced by the No other guidance system is neces- onto the frame. astronaut's manipulating of payloads sary. The only contact with the acesu

The EMU represents more than 50 During the next 30 years, pres- pressure inward on the astronaut. years of development and testing by sure suits evolved in many directions, Mobility for the head and hands was the United States, France, Italy, and technical manufacturing help was provided by rigid bearings. In spite of Germany, and other countries. It all gained from companies that made the bearings, the limbs of the suit did began with high-altitude flyers, and armor, diving suits, galoshes, and not bend in a hinge fashion as do among the first of them was an even girdles and corsets. Designers human arms and legs. Instead, the American, Wiley Post. Post was an learned in their search for the perfect fabric arms and legs bent in a gentle aviation pioneer of the 1930s and was suit that it wasn't necessary to provide curve that restricted movement. seeking to break high-altitude and full sea-level pressure. A suit pres- When the astronaut moved an arm, speed records. Post, as well as sure of 24.13 kilopascals would the bending creased or folded the others, knew that pressure protection suffice quite nicely if the wearer fabric inward near the joints, decreas- was essential. Through experience, breathed pure oxygen. Supplying ing the volume of the suit and increas- aviators had learned that Earth's pure oxygen at this low pressure ing its total pressure slightly. Fortu- atmosphere thins out with altitude. actually provides the breather with nately for the comfort of the Mercury At 5,500 meters, air is only one- more oxygen than an unsuited person astronauts, the Mercury suit was half as dense as it is at sea level. At breathes at sea level. (Only one fifth designed to serve only as a pressure 12,200 meters, the pressure is so low of the air at sea level is oxygen.) backup if the spacecraft cabin decom- and the oxygen present is so scarce Various techniques were used for pressed. No Mercury capsule ever that most living things perish. For constructing pressure garments. lost pressure during a mission, and Wiley Post to achieve the altitude Some approaches employed a rigid the suits remained uninflated. records he sought, he needed protec- layer with special joints of rings or The six flights of the Mercury tion. (Pressurized aircraft cabins had cables, or some other device to permit series were followed by ten flights in not yet been developed.) Post's limb movements. Others used the Gemini program. Suit designers solution was a suit that could be nonstretch fabrics-laced up corset- were faced with new problems. Not pressurized by his airplane engine's fashion. only would a Gemini suit have to supercharger. With the advent of pressurized serve as a pressure backup to the First attempts failed when it was aircraft cabins, unpressurized comfort spacecraft cabin, but also as an discovered that Post's pressure suit and mobility became prime objectives escape suit if ejection seats had to be became rigid and immobile when in spacesuit design. Suits served as fired for an aborted launch, and as an inflated. He couldn't move inside the pressure backups should the aircraft EMU for extravehicular activity. To suit, much less work airplane con- cabin lose pressure. increase mobility and the comfort of trols. A later version succeeded when By the time NASA began the the suit for long-term wear, designers the suit, as constructed, was already Mercury manned space-flight pro- departed from the Mercury spacesuit in a sitting position. This allowed gram, the best full-pressure suit concept. Instead of fabric joints, they Post to place his hands on his air- design consisted of an inner gas- chose a construction that employed a plane controls and his feet on the barrier layer of neoprene-coated bladder restrained by a link net. The rudder bars. Moving his arms and fabric, and an outer restraint layer, of bladder was an anthropomorphic- legs was difficult, but not impossible. aluminized NylonTM. The first layer shaped layer of NeopreneTM-coated To provide visibility, a rigid helmet retained pure oxygen at 34.5 kilopas- NylonTM.That was covered in turn with a viewing port was placed over cals and the second prevented the with a layer of TeflonTM-coatedNy- Post's head. The port was small, but first from expanding like a balloon. IonTMnetting. The netting, slightly a larger one was unnecessary because The restraint layer directed the oxygen smaller than the pressure bladder, Post had only one good eye! limited inflation of the bladder and that a better method of cooling the This was followed by a multi-layered retained the pressure load in much the astronaut was required. The gas outer suit. The innermost layer of this same way automobile tires retained cooling system could not remove heat garment was a NeopreneTM-coated the load from inner tubes in the days and moisture as rapidly as the astro- NylonTMbladder surrounded by a before tubeless tires. The new naut produced them. Particularly the NylonTMrestraint layer. Improved spacesuit featured impro&d mobility inside of the helmet visor quickly mobility was achieved by bellows-like in the shoulders and arms and was fogged over, making it difficult to see joints of formed rubber with built-in more comfortable to wear unpressur- through. restraint cables at the waist, elbows, ized during space flights lasting as The Apollo program following shoulders, waist, knees, and ankles. long as 14 days. Gemini added a new dimension in On top of that was a layer consisting The first Gemini astronaut to "go spacesuit design. Although the term of a chloroprene-coated NylonTMrip EVA" was Ed White. White exited "spacewalk" was coined for the stop that protected against microme- from the Gemini 4 space capsule on Gemini program, no actual walking teoroids. Next came two layers of June 3, 1965. For a half hour, White was involved. Actual spacewalks KaptonTMand BetaTMMarquisette and tumbled and rolled in space, con- would not occur until the Apollo EVAs five layers of aluminized MylarTM,al- nected to the capsule only by an on the Moon. ternated with nonwoven DacronTM oxygen feed hose that served secon- As with the Mercury and Gemini spacing material. The outermost layer dary functions as a tether line and a spacesuits, Apollo suits had to serve of the suit was white TeflonTM-coated communication link with the capsule. as a backup pressure system to the BetaTMglass-fiber cloth. This last On his "spacewalk," White used a space capsule. Besides allowing layer was flame resistant; it also small hand-held propulsion gun for flexibility in the shoulder and arm served as a protection against heat maneuvering in space. The gun areas, they also had to permit move- and cold and the wear and tear of released jets of oxygen that propelled ments of the legs and waist. On the walking on the Moon. him in the opposite direction when he Moon, bending and stooping were Capping off the suit was a com- pulled a trigger. It was the first necessary to pick up samples. Suits munications headset and a clear poly- personal maneuvering unit used in had to function both in near-weight- carbonate-plastic pressure helmet. space. lessness and in the one-sixth gravity Slipped over the top of the helmet was At completion of the Gemini pro- on the Moon's surface. Furthermore, an assembly consisting of sun- gram, NASA astronauts had logged when walking on the Moon, Apollo filtering visors and adjustable blinders nearly 12 additional hours of EVA astronauts needed the flexibility to for sunlight protection. The final experience. Approximately one-half of roam freely without dragging a cum- items of the Apollo spacesuit were that time was spent merely "standing bersome, combination oxygen line custom-sized gloves with molded up" through the open hatch. and tether. A self-contained Portable silicone-rubber fingertips that pro- One of the most important (Primary) Life Support System was vided some degree of fingertip lessons learned was that EVAs were needed. sensitivity in handling equipment, not as simple as they looked. Moving Donning an Apollo spacesuit lunar boots, and a portable life around in space required a great deal began with a cooling garment, similar support system. The backpack unit of work. The work could be lessened, to long johns, which was laced with a provided oxygen for breathing and however, by extensive training on network of thin-wall plastic tubing. pressurization, water for cooling, and Earth. The most effective training This tubing circulated cooling water radio communications for lunar took place underwater. Wearing a around the astronaut to prevent surface excursions lasting up to 8 specially weighted spacesuit while in a overheating. On top of this layer was hours. Furthermore, back inside the deep tank of water gave later Gemini the pressure garment assembly. The lunar lander the life-support unit could crew members adequate practice in innermost layer of this assembly was be recharged for additional Moon the maneuvers they would soon a comfort layer of lightweight NylonTM walks. perform in space. It was also learned fabric with fabric ventilating ducts. During the Apollo program, 12 umbrella-like portable heat shield filtering and heat-transferring effects astronauts spent a total of 161 hours through the scientific airlock to cover of an atmosphere, at Earth's distance of EVA on the Moon's surface. An the area where the original shield was from the Sun, the sunlit side of additional 4 hours of EVA were spent torn away. Later, on an EVA, the objects in space may climb to over in weightlessness while the astronauts metal holding the jammed solar arrays 120" Celsius while the shaded side were in transit from the Moon to was cut, and the panel was freed to may plummet to lower than -100" Earth. During those EVAs a single open. During an EVA by the second Celsius. Maintaining a comfortable astronaut, the command module pilot, crew to occupy Skylab, an additional temperature range becomes a signifi- left the capsule to retrieve photo- portable heat shield was erected over cant problem. graphic film. There was no need for the first. Enhancing the Shuttle's overall the life-support unit, because those The Skylab EMU was a simplified capabilities is the EMU. Like the astronauts were connected to the version of the Apollo Moon suits. spacecraft itself, the Shuttle EMU is spacecraft by umbilical tether lines There was no need for a life-support reusable. Spacesuits used in previous supplying them with oxygen. system, because the astronaut was manned space flight programs were NASA's next experience with attached to the station by an umbilical custom built to each astronaut's body EVAs came during the Skylab pro- tether that supplied oxygen and size. In the Apollo program, for gram. The need for astronauts on a cooling water. An astronaut life- example, each astronaut had three spacecraft was convincingly demon- support assembly, consisting of a custom suits-one for flight, one for strated. Spacesuited Skylab astro- pressure-control unit and an attach- training, and one for flight backup. nauts literally saved the Skylab ment for the tether, was worn on the Shuttle suits, however, are tailored program. chest and an emergency oxygen from a stock of standard-size parts to Skylab was NASA's first space package containing two supply bottles fit astronauts over a wide range of station. It was launched in 1973, six was attached to the right upper leg. A individual variations. months after the last Apollo Moon simplified visor assembly was used In constructing the Shuttle landing. Trouble developed during the over the pressure helmet, and lunar spacesuit, developers concentrated all launch when a micrometeoroid shield protective boots were not needed. of their designs toward a single ripped away from the station's outer Skylab astronauts logged 17.5 hours function-going EVA. Spacesuits surface. This triggered the premature of planned EVA for film and experi- from earlier manned space flight deployment of two of the six solar ment retrieval and 65 hours of un- programs had to serve multiple panels, resulting in one being ripped planned EVA for station repairs. functions. They had to provide away by atmospheric friction. The Outer space is just what its name backup pressure in case of cabin second was jammed in a partially implies. It is the space, or vacuum, pressure failure, protection if ejection opened position by a piece of bent beyond the uppermost reaches of the became necessary during launch, EVA metal. In orbit, Skylab received atmosphere of Earth, surrounding our in weightlessness, and EVA while insufficient electrical power from the planet and all other objects in the uni- walking on the Moon in one-sixth remaining solar panels; the station verse. Although it is a void, outer Earth's gravity. Suits were worn was overheating due to the missing space can be thought of as an envi- during lift-off and reentry and had to shield. Instead of scrapping the ronment. Radiation and objects pass be comfortable under the high g mission, the crew was assigned the through it freely. An unprotected forces experienced during accelera- task of repairing the crippled station. human or any other unprotected living tion and deceleration. Shuttle suits While still on board the Apollo com- being placed in the outer space are worn only when it is time to mand module, Paul Weitz unsuccess- environment would perish in a few venture outside the orbiter cabin. At fully attempted to free the jammed brief, agonizing moments. other times, crew members wear solar panel as he extended himself The temperature range found in comfortable shirts and slacks or through the open side hatch. On outer space provides a second major coveralls. board Skylab, the crew poked an obstacle for humans. Lacking the During the first American EVA ence. Furthermore, precise motions nitrogen gas were released from (Gemini 4) Ed White experimented were difficult to achieve and maintain, various nozzles spaced around the with a personal propulsion device, the and using the unit proved physically unit. The nozzles, fourteen in number, Hand-Held Maneuvering Unit. The exhausting. were arranged to aim top-bottom, unit White tested was a three-jet ma- On the Gemini 9 mission, a front-back, and right-left to produce neuvering gun. Two jets were located backpack maneuvering unit was six degrees of freedom in movement. at the ends of rods and aimed back, carried. However, problems with the The AMRV could move forward and so that firing them pulled White unit prevented Gene Cernan from back, up and down, and side to side, forward. A third jet was aimed testing it. and could roll, pitch, and yaw. With forward to provide a braking force. Following the Gemini program, the eleven additional nozzles, precise By holding the gun near his center the next space experiments that tested positioning with the AMRV was far of mass and by aiming it in the maneuvering units for EVAs took simpler than with the Hand-Held direction in which he wanted to travel, place during the second and third Maneuvering Unit of the Gemini pro- he was able to propel himself forward. manned Skylab missions. The gram. The astronaut was surrounded Stopping that movement required experiments were dubbed M-509. by the unit, taking the guesswork out firing the center jet. Five of the six astronauts who flew in of determining center of mass and The propulsive force of the Hand- those two missions accumulated a making control much more accurate. Held Maneuvering Unit was produced total of 14 hours testing an advanced The astronaut could translate closely by releasing compressed oxygen from device called the AMRV, or Astronaut along the surface of a curved or two small built-in tanks. Although the Maneuvering Research Vehicle. The irregularly shaped object without unit worked as intended, it had two AMRV was shaped like a large version making contact with it. During the disadvantages. To produce the of a hiker's backpack. Built into the Skylab experiments with the EMU, the desired motion, it had to be held as frame was a replaceable tank of device was tested only inside the near to the astronaut's center of mass compressed nitrogen gas. Controls spacecraft, but the experiment as possible. Determining the actual for the unit were placed at the end of confirmed that a maneuvering device position was difficult because of the "arm rests." To move, the astronaut of that design was both feasible and bulky spacesuit White wore, and was worked rotational and translational desirable for future EVAs. a matter of guesswork and experi- bank controls. Propulsive jets of National Aeronautics and Space Administration