Apollo/Skylab spacesuit: Difference between revisions

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[[File:Apollo 11 space suit.jpg|thumb|200px|[[Neil Armstrong]] described his Apollo 11 A7L suit as "tough, reliable and almost cuddly."<ref>{{cite news|title=Science Friday Archives: How to Dress for Space Travel |url=http://www.sciencefriday.com/program/archives/201103256 |newspaper=NPR |date=March 25, 2011 |url-status=dead |archiveurl=https://web.archive.org/web/20111010145433/http://www.sciencefriday.com/program/archives/201103256 |archivedate=October 10, 2011 }}</ref>]]

The '''Apollo/Skylab space suit''' is a class of [[space suit]]s used in [[Apollo program|Apollo]] and [[Skylab]] missions. The names for both the Apollo and Skylab space suits were Extravehicular Mobility Unit (EMU).<ref name="us">{{cite book |title= US Spacesuits |author1=Kenneth S. Thomas |author2=Harold J. McMann |year= 2006 |publisher= Praxis Publishing Ltd. |___location= Chichester, UK |isbn= 0-387-27919-9 | pages = 428–435 | url= https://books.google.com/books?id=cdO2-4szcdgC&source=gbs_navlinks_s }}</ref> The Apollo EMUs consisted of a Pressure Suit Assembly (PSA) aka "suit" and a Portable Life Support System (PLSS) that was more commonly called the "backpack".<ref name="us1">{{cite book |title= US Spacesuits |author1=Kenneth S. Thomas |author2=Harold J. McMann |year= 2006 |publisher= Praxis Publishing Ltd. |___location= Chichester, UK |isbn= 0-387-27919-9 | pages = 428–433 | url= https://books.google.com/books?id=cdO2-4szcdgC&source=gbs_navlinks_s }}</ref> The A7L was the PSA model used on the Apollo 7 through 14 missions.<ref name="us2">{{cite book |title= US Spacesuits |author1=Kenneth S. Thomas |author2=Harold J. McMann |year= 2006 |publisher= Praxis Publishing Ltd. |___location= Chichester, UK |isbn= 0-387-27919-9 | pages = 428–429 | url= https://books.google.com/books?id=cdO2-4szcdgC&source=gbs_navlinks_s }}</ref>

The subsequent Apollo 15-17 lunar missions,<ref name="us3">{{cite book |title= US Spacesuits |author1=Kenneth S. Thomas |author2=Harold J. McMann |year= 2006 |publisher= Praxis Publishing Ltd. |___location= Chichester, UK |isbn= 0-387-27919-9 | pages = 430–431 | url= https://books.google.com/books?id=cdO2-4szcdgC&source=gbs_navlinks_s }}</ref> Skylab,<ref name="us4">{{cite book |title= US Spacesuits |author1=Kenneth S. Thomas |author2=Harold J. McMann |year= 2006 |publisher= Praxis Publishing Ltd. |___location= Chichester, UK |isbn= 0-387-27919-9 | pages = 432–433 | url= https://books.google.com/books?id=cdO2-4szcdgC&source=gbs_navlinks_s }}</ref> and [[Apollo-Soyuz]] used A7LB pressure suits.<ref name="us5">{{cite book |title= US Spacesuits |author1=Kenneth S. Thomas |author2=Harold J. McMann |year= 2006 |publisher= Praxis Publishing Ltd. |___location= Chichester, UK |isbn= 0-387-27919-9 | pages = 434–435 | url= https://books.google.com/books?id=cdO2-4szcdgC&source=gbs_navlinks_s }}</ref> Additionally, these pressure suits varied by program usage. For the Skylab EMU, NASA elected to use an umbilical life support system named the Astronaut Life Support Assembly.

== Basic design <!--DO NOT capitalize the word "design" here -- see the Manual of Style---> ==

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In October 1964, NASA elected to split the spacesuit program into three parts. David Clark would provide the suits for the "Block I" early missions without extra-vehicular activity (EVA). The Hamilton/ILC program would continue as "Block II" to support the early EVA missions. The pressure suit design for Block II was to be selected in a June 1965 re-competition. To assure Block II backpack success, AiResearch was funded for a parallel backpack effort. The later, longer-duration Apollo missions would be Block III and have more advanced pressure suits and a longer duration backpack to be provided by suppliers selected in future competitions. To reflect this new start in the program, the PGA was renamed the Pressure Suit Assembly (PSA) across the programs and the Block II and III SSAs were renamed Extravehicular Mobility Unit (EMU).

Hamilton and International Latex were never able to form an effective working relationship. In March 1965, Hamilton switched to B. F. Goodrich as suit supplier.<ref name=tjtm>{{cite book |title= The Journey To Moonwalking |author=Kenneth S. Thomas |year= 2017 |publisher= Curtis Press |___location= Great Yarmouth, Norfolk, UK |isbn= 9-780993-400223 | pages = 99–103 | url= https://books.google.com/books?id=cdO2-4szcdgC&source=gbs_navlinks_s }}</ref> International Latex, in July 1965, won the Block II suit competition with its A5L design. This forced NASA to assume management of the Block II EMU program directly.<ref name=tjtm88-114>{{cite book |title= The Journey To Moonwalking |author=Kenneth S. Thomas |year= 2017 |publisher= Curtis Press |___location= Great Yarmouth, Norfolk, UK |isbn= 9-780993-400223 | pages = 88–114| url= https://books.google.com/books?id=cdO2-4szcdgC&source=gbs_navlinks_s }}</ref> Before the end of 1965, Hamilton Standard completed certification of its new backpack.<ref name=tjtm80-87>{{cite book |title= The Journey To Moonwalking |author=Kenneth S. Thomas |year= 2017 |publisher= Curtis Press |___location= Great Yarmouth, Norfolk, UK |isbn= 9-780993-400223 | pages = 80–87 | url= https://books.google.com/books?id=cdO2-4szcdgC&source=gbs_navlinks_s }}</ref> NASA subsequently terminated the Block II AiResearch backpack, thus completing the selection of the suit/backpack designs and suppliers to support man's first walking on the Moon. However, this was not to be without improvements. The Apollo 11 EMU featured an A7L suit with a -6 (dash six) backpack reflecting seven suit and six backpack design iterations.<ref name="us2"/> The A7L was a rear entry suit made in two versions. The Extra-vehicular (EV), which would be used on the Moon and the Command Module Pilot (CMP) that was a simpler garment.<ref name="us"/>

The A7L pressure suits reached space flight in October 1968 aboard Apollo 7.<ref name=tjtm155-162>{{cite book |title= The Journey To Moonwalking |author=Kenneth S. Thomas |year= 2017 |publisher= Curtis Press |___location= Great Yarmouth, Norfolk, UK |isbn= 9-780993-400223 | pages = 155–162 | url= https://books.google.com/books?id=cdO2-4szcdgC&source=gbs_navlinks_s }}</ref> These were used as launch and reentry emergency suits. Also in 1968, NASA recognized that with modifications, the Block II EMU could additionally support the later EVA missions that involved a Lunar Rover Vehicle (LRV). This resulted in the termination of Apollo Block III in favor of an Apollo 15 through 17 EMU using an A7LB suit and a "-7" long duration backpack.<ref name="us"/>

The complete Apollo EMU made its space debut with Apollo 9 launched into space on March 3, 1969.<ref name=tjtm162-169>{{cite book |title= The Journey To Moonwalking |author=Kenneth S. Thomas |year= 2017 |publisher= Curtis Press |___location= Great Yarmouth, Norfolk, UK |isbn= 9-780993-400223 | pages = 162–169 | url= https://books.google.com/books?id=cdO2-4szcdgC&source=gbs_navlinks_s }}</ref> On the fourth day of the mission, Lunar Module Pilot Russell Schweickart and Commander James McDivitt went into the Lunar Module. The astronauts then depressurized both the Command and Lunar Modules. Schweickart emerged from the Lunar Module to test the backpack and conduct experiments. David Scott partially emerged from the Command Module's hatch supported by an umbilical system connected to the Command Module to observe. The EVA lasted only 46 minutes but allowed a verification of both EVA configurations of the EMU. This was the only Apollo spacewalk prior to the Apollo 11 lunar landing mission.

Apollo 11 made the A7L the most iconic suit of the program. It proved to be the primary [[pressure suit]] worn by [[NASA]] astronauts for [[Project Apollo]]. Starting in 1969, the A7L suits were designed and produced by [[ILC Dover]] (a division of [[Playtex]] at the time). The A7L is an evolution of ILC's initial A5L, which won a 1965 pressure suit competition, and A6L, which introduced the integrated thermal and micrometeroid cover layer. After the deadly [[Apollo 1]] fire, the suit was upgraded to be fire-resistant and designated A7L.<ref name='SP-4011:Skylab A Chronology'>{{cite web|url=https://history.nasa.gov/SP-4011/part2c.htm |title=SP-4011:Skylab A Chronology |accessdate=2007-07-07 |year=1977 |publisher=[[NASA]] | archiveurl= https://web.archive.org/web/20070717011524/https://history.nasa.gov/SP-4011/part2c.htm| archivedate= 17 July 2007 | url-status= live}}</ref><ref name='EMU Development'>{{cite web|url=http://www.hq.nasa.gov/alsj/tnD8093EMUDevelop.html |title=Development of the Extravehicular Mobility Unit|publisher=NASA |author1=Charles C. Lutz|author2=Harley L. Stutesman |author3=Maurice A. Carson |author4=James W. McBarron II |year=1975 |accessdate=10 January 2016 | archiveurl= https://web.archive.org/web/20070801204432/http://www.hq.nasa.gov/alsj/tnD8093EMUDevelop.html| archivedate= 1 August 2007 | url-status= live}}</ref>

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===Portable Life Support System===

At the beginning of the Apollo spacesuit competition, no one knew how the life support would attach to the suit, how the controls needed to be arranged, or what amount of life support was needed. What was known was that in ten months, the Portable Life Support System, aka "backpack", needed to be completed to support complete suit-system testing before the end of the twelfth month. Before the spacesuit contract was awarded, the requirement for normal life support per hour almost doubled. At this point, a maximum hourly metabolic energy expenditure requirement was added, which was over three times the original requirement.<ref name=tjtm34-39>{{cite book |title= The Journey To Moonwalking |author=Kenneth S. Thomas |year= 2017 |publisher= Curtis Press |___location= Great Yarmouth, Norfolk, UK |isbn= 9-780993-400223 | pages = 34–39 | url= https://books.google.com/books?id=cdO2-4szcdgC&source=gbs_navlinks_s }}</ref>

In late 1962, testing of an early training suit raised concerns about life support requirements. The concerns were dismissed because the forthcoming Apollo new-designs were expected to have lower effort mobility and improved ventilation systems. However, Hamilton took this as a strong indication that Apollo spacesuit life support requirements might significantly increase and initiated internally funded research and development in "backpack" technologies.

In the tenth month, the first backpack was completed. Manned testing found the backpack to meet requirements. This would have been a great success but for the crewed testing confirming that the 1963 life support requirements were not sufficient to meet lunar mission needs. Early in 1964, the final Apollo spacesuit specifications were established that increased normal operations by 29% and increased maximum use support 25%. Again, the volume and weight constraints did not change. These final increases required operational efficiencies that spawned the invention of the porous plate sublimator<ref name=tjtm58-59>{{cite book |title= The Journey To Moonwalking |author=Kenneth S. Thomas |year= 2017 |publisher= Curtis Press |___location= Great Yarmouth, Norfolk, UK |isbn= 9-780993-400223 | pages = 58–59 | url= https://books.google.com/books?id=cdO2-4szcdgC&source=gbs_navlinks_s }}</ref> and the Apollo liquid cooling garment.<ref name=tjtm-lcg>{{cite book |title= The Journey To Moonwalking |author=Kenneth S. Thomas |year= 2017 |publisher= Curtis Press |___location= Great Yarmouth, Norfolk, UK |isbn= 9-780993-400223 | pages = 59–65, 81–83 | url= https://books.google.com/books?id=cdO2-4szcdgC&source=gbs_navlinks_s }}</ref>

The porous plate sublimator had a metal plate with microscopic pores sized just right so that if the water flowing under the plate warmed to more than a user-comfortable level, frozen water in the plate would thaw, flow through the plate, and boil to the vacuum of space, taking away heat in the process. Once the water under the plate cooled to a user-comfortable temperature, the water in the plate would re-freeze, sealing the plate and stopping the cooling process. Thus, heat rejection with automatic temperature control was accomplished with no sensors or moving parts to malfunction.

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=== ASTP Spacesuit ===

[[Image:Astp-KSC-75PC-409HR.2.jpg|thumb|200px|right| The ASTP crew, entering the transfer van]]

For the [[Apollo-Soyuz Test Project]], NASA decided to use the A7LB CMP pressure suit assembly worn on the J-missions with a few changes to save cost and weight since an EVA was not planned during the mission. The changes included a simplified cover layer which was cheaper, lighter and more durable as well as the removal of the pressure relief valve and unused gas connectors. No EVA visor assemblies or EVA gloves were carried on the mission.<ref name="ASTP Press">{{cite web|title=Apollo ASTP Press Kit|url=https://history.nasa.gov/astp/documents/astp%20press%20kit%20(us).pdf|publisher=NASA|accessdate=4 March 2014|page=53|format=PDF|date=10 June 1975}}</ref>

The ASTP A7LB suit was the only Apollo suit to use the [[NASA logo|NASA "worm" logo]], which was introduced in 1975 and used extensively by NASA until 1992.