Apollo oxygen - Revision history

Washcarso: moving main article redirect to correct section

2026-10-14T08:12:34Z

moving main article redirect to correct section

← Older revision		Revision as of 04:12, 14 October 2026
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	== Command module and lunar module ==		== Command module and lunar module ==
	{{main article\|Apollo command module oxygen\|Apollo lunar module ~~oxygen\|Apollo PLSS~~ oxygen}}		{{main article\|Apollo command module oxygen\|Apollo lunar module oxygen}}

	[[File:Apollo oxygen tank cutaway S71-16745.jpg\|right\|frame\|Cutaway of a service-module oxygen tank, drawn for the Apollo 14 redesign. The fans were removed and a third heater was added after Apollo 13. NASA S71-16745.]]		[[File:Apollo oxygen tank cutaway S71-16745.jpg\|right\|frame\|Cutaway of a service-module oxygen tank, drawn for the Apollo 14 redesign. The fans were removed and a third heater was added after Apollo 13. NASA S71-16745.]]
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	== Suits on the Moon ==		== Suits on the Moon ==
			{{main article\|Apollo PLSS oxygen}}
	On a walk the suit was a closed loop inside the backpack. A fan pulled gas from the suit, through a lithium hydroxide and charcoal cartridge, through a cooler, and back to the helmet. The primary bottle added only makeup gas: oxygen the crewman consumed, plus leakage. The bottle on the earlier flights held 1.12 pounds at 850 [[Pounds per square inch\|psi]]. The bottles on Apollo 15, 16, and 17 held 1.75 pounds at 1,410 [[Pounds per square inch\|psi]]. A second supply, the oxygen purge system, was mounted on top of the pack and was open-loop if the backpack failed. The regulator, the purge valve, and the refill from the lunar module are on [[Apollo PLSS oxygen]].		On a walk the suit was a closed loop inside the backpack. A fan pulled gas from the suit, through a lithium hydroxide and charcoal cartridge, through a cooler, and back to the helmet. The primary bottle added only makeup gas: oxygen the crewman consumed, plus leakage. The bottle on the earlier flights held 1.12 pounds at 850 [[Pounds per square inch\|psi]]. The bottles on Apollo 15, 16, and 17 held 1.75 pounds at 1,410 [[Pounds per square inch\|psi]]. A second supply, the oxygen purge system, was mounted on top of the pack and was open-loop if the backpack failed. The regulator, the purge valve, and the refill from the lunar module are on [[Apollo PLSS oxygen]].

Flerf Whisperer: Link the oxygen chart

2026-10-14T00:20:32Z

Link the oxygen chart

← Older revision		Revision as of 20:20, 13 October 2026
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	== See also ==		== See also ==
			* [[Apollo oxygen chart]]
	* [[Apollo fuel cells]]		* [[Apollo fuel cells]]
	* [[Apollo command module cooling]]		* [[Apollo command module cooling]]

Flerf Whisperer: Link the cooling article from the glycol warmer

2026-10-13T23:25:55Z

Link the cooling article from the glycol warmer

← Older revision		Revision as of 19:25, 13 October 2026
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	=== Command module ===		=== Command module ===
	Service-module oxygen arrived at about 900 [[Pounds per square inch\|psi]]. Capillaries wound on the hot water-glycol line warmed it and limited the flow. A surge tank in the command module stayed near 900 [[Pounds per square inch\|psi]]. The main regulator dropped the line to 85 to 110 [[Pounds per square inch\|psi]], and the cabin regulators held about 5 [[Pounds per square inch\|psi]]. The suit regulator held the suits just under cabin pressure, or near 3.75 [[Pounds per square inch\|psi]] if the cabin was dumped. The handbook wording, the valves, and photographs of the hardware are on [[Apollo command module oxygen]].		Service-module oxygen arrived at about 900 [[Pounds per square inch\|psi]]. Capillaries wound on the hot water-glycol line warmed it and limited the flow. That coolant system is [[Apollo command module cooling]]. A surge tank in the command module stayed near 900 [[Pounds per square inch\|psi]]. The main regulator dropped the line to 85 to 110 [[Pounds per square inch\|psi]], and the cabin regulators held about 5 [[Pounds per square inch\|psi]]. The suit regulator held the suits just under cabin pressure, or near 3.75 [[Pounds per square inch\|psi]] if the cabin was dumped. The handbook wording, the valves, and photographs of the hardware are on [[Apollo command module oxygen]].

	=== Lunar module ===		=== Lunar module ===
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	== See also ==		== See also ==
	* [[Apollo fuel cells]]		* [[Apollo fuel cells]]
			* [[Apollo command module cooling]]
	* [[Apollo command module oxygen]]		* [[Apollo command module oxygen]]
	* [[Apollo PLSS oxygen]]		* [[Apollo PLSS oxygen]]

Washcarso at 23:25, 13 October 2026

2026-10-13T23:25:37Z

← Older revision		Revision as of 19:25, 13 October 2026
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	== Command module and lunar module ==		== Command module and lunar module ==
	{{main article\|Apollo command module oxygen\|Apollo lunar module oxygen}}		{{main article\|Apollo command module oxygen\|Apollo lunar module oxygen\|Apollo PLSS oxygen}}

	[[File:Apollo oxygen tank cutaway S71-16745.jpg\|right\|frame\|Cutaway of a service-module oxygen tank, drawn for the Apollo 14 redesign. The fans were removed and a third heater was added after Apollo 13. NASA S71-16745.]]		[[File:Apollo oxygen tank cutaway S71-16745.jpg\|right\|frame\|Cutaway of a service-module oxygen tank, drawn for the Apollo 14 redesign. The fans were removed and a third heater was added after Apollo 13. NASA S71-16745.]]

Flerf Whisperer: Link the backpack article where the moonwalk suits are described

2026-10-13T23:14:27Z

Link the backpack article where the moonwalk suits are described

← Older revision		Revision as of 19:14, 13 October 2026
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	{{series apollo}}		{{series apollo}}

	'''Apollo oxygen''' is the breathing supply for the Apollo command module, the lunar module, and the suits worn on the Moon. The service-module tanks also fed the fuel cells. Carbon dioxide was removed with lithium hydroxide. The crews changed those cartridges on a schedule. The oxygen tanks themselves were filled before launch and were not replaced in flight.		'''Apollo oxygen''' is the breathing supply for the Apollo command module, the lunar module, and the [[Apollo PLSS oxygen\|suits worn on the Moon]]. The service-module tanks also fed the fuel cells. Carbon dioxide was removed with lithium hydroxide. The crews changed those cartridges on a schedule. The oxygen tanks themselves were filled before launch and were not replaced in flight.

	== Command module and lunar module ==		== Command module and lunar module ==
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	Lunar-module suits used the demand regulators on [[Apollo lunar module oxygen]]: 4.8 [[Pounds per square inch\|psi]] in the cabin, 3.8 [[Pounds per square inch\|psi]] once the cabin was dumped for a walk.		Lunar-module suits used the demand regulators on [[Apollo lunar module oxygen]]: 4.8 [[Pounds per square inch\|psi]] in the cabin, 3.8 [[Pounds per square inch\|psi]] once the cabin was dumped for a walk.

	On the walk the backpack did the drop in one step, from a bottle of warm compressed gas rather than from the cold service-module supply. A single-stage regulator took the bottle, several hundred [[Pounds per square inch\|psi]] up to about 1,400 [[Pounds per square inch\|psi]] depending on the flight, down to about 3.85 [[Pounds per square inch\|psi]] in the suit. The purge bottle on top of the pack had its own single-stage regulator and held the suit near 3.7 [[Pounds per square inch\|psi]] if the backpack failed. An early purge-system design heated the gas before the regulator, to keep what reached the suit above 30 degrees Fahrenheit. Manned tests showed the flow and the suit stayed warm enough without it, and the flight purge system flew without that heater.<ref>J. C. Beggs and F. H. Goodwin, [https://ntrs.nasa.gov/citations/19720019459 ''Apollo PLSS: Environmental Control of the Smallest Manned Space Vehicle''], Hamilton Standard (1972).</ref>		On the walk the [[Apollo PLSS oxygen\|backpack]] did the drop in one step, from a bottle of warm compressed gas rather than from the cold service-module supply. A single-stage regulator took the bottle, several hundred [[Pounds per square inch\|psi]] up to about 1,400 [[Pounds per square inch\|psi]] depending on the flight, down to about 3.85 [[Pounds per square inch\|psi]] in the suit. The purge bottle on top of the pack had its own single-stage regulator and held the suit near 3.7 [[Pounds per square inch\|psi]] if the backpack failed. An early purge-system design heated the gas before the regulator, to keep what reached the suit above 30 degrees Fahrenheit. Manned tests showed the flow and the suit stayed warm enough without it, and the flight purge system flew without that heater.<ref>J. C. Beggs and F. H. Goodwin, [https://ntrs.nasa.gov/citations/19720019459 ''Apollo PLSS: Environmental Control of the Smallest Manned Space Vehicle''], Hamilton Standard (1972).</ref>

	== In flight ==		== In flight ==

Flerf Whisperer: Point the backpack section at the PLSS oxygen article

2026-10-13T22:34:37Z

Point the backpack section at the PLSS oxygen article

← Older revision		Revision as of 18:34, 13 October 2026
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	== Suits on the Moon ==		== Suits on the Moon ==
	[[File:Apollo PLSS interior S68-34582.jpg\|right\|frame\|Portable life support system with the cover off, 1968. The backpack held the oxygen supply, the carbon-dioxide cartridge, and the cooling water. NASA S68-34582.]]		On a walk the suit was a closed loop inside the backpack. A fan pulled gas from the suit, through a lithium hydroxide and charcoal cartridge, through a cooler, and back to the helmet. The primary bottle added only makeup gas: oxygen the crewman consumed, plus leakage. The bottle on the earlier flights held 1.12 pounds at 850 [[Pounds per square inch\|psi]]. The bottles on Apollo 15, 16, and 17 held 1.75 pounds at 1,410 [[Pounds per square inch\|psi]]. A second supply, the oxygen purge system, was mounted on top of the pack and was open-loop if the backpack failed. The regulator, the purge valve, and the refill from the lunar module are on [[Apollo PLSS oxygen]].
	On a ~~moonwalk~~ the suit was a closed loop inside the backpack. A fan pulled gas from the suit, through a lithium hydroxide and charcoal cartridge, through a cooler, and back to the helmet. The primary ~~oxygen~~ bottle added only makeup gas: oxygen the crewman consumed, plus leakage. The bottle on the earlier flights held 1.12 pounds at 850 [[Pounds per square inch\|psi]]. The ~~backpacks~~ on Apollo 15, 16, and 17 held 1.75 pounds at 1,410 [[Pounds per square inch\|psi]]. After reserves, about 1.3 pounds remained for the walk, which covered excursions planned up to about seven hours. The cartridge on those flights held about 3.1 pounds of lithium hydroxide.<ref>Hamilton Standard, [https://ibiblio.org/apollo/Documents/apollo_portable_life_support_and_oxygen_purge_systems.pdf ''Apollo Portable Life Support and Oxygen Purge Systems''] (early backpack: 1.12 lb oxygen, 2.85 lb purge oxygen).</ref><ref>Hamilton Standard, [https://ibiblio.org/apollo/Documents/apollo_portable_life_support_systems.pdf ''Portable Life Support System''] (J-mission backpack: 1.75 lb at 1,410 [[Pounds per square inch\|psi]]).</ref>

	A second ~~bottle~~, the oxygen purge system, was mounted on top of the pack~~. It held 2.85 pounds at about 5,880 [[Pounds per square inch\|psi]]~~ and was open-loop~~: oxygen passed through the suit and out a purge valve. It was the backup~~ if the backpack failed. ~~It was not used to extend a normal walk.~~

	~~Packs for the first walk were filled before launch. Between later walks~~, ~~inside~~ the lunar module, each crewman serviced his own pack. He removed the spent hydroxide cartridge, locked in a fresh one, and exchanged the battery. He connected the descent-stage oxygen hose and filled the backpack bottle, ~~then let it cool~~ and ~~topped it off, because compression heats~~ the ~~gas and the pressure falls as the bottle cools. Cooling water was refilled~~ from the ~~descent tank, and wastewater was drained. The work took about half an hour a suit.<ref>~~[~~https://www.apollojournals.org/alsj/a11/a11FinalEVAProc_HSI-38438.pdf Apollo 11 final EVA procedures], cartridge change and oxygen fill.</ref><ref>Eric M. Jones,~~ [~~https://apollojournals.org/alsj/plss.html ''~~Apollo PLSS ~~Images''~~]~~, Apollo Lunar Surface Journal. Recharge between walks.</ref>~~

	If a backpack failed away from the lunar module, that crewman opened the purge bottle. The working backpack could share cooling water through a buddy hose. Walks were planned so the ride back still fit that emergency oxygen.

	== See also ==		== See also ==
	* [[Apollo fuel cells]]		* [[Apollo fuel cells]]
	* [[Apollo command module oxygen]]		* [[Apollo command module oxygen]]
			* [[Apollo PLSS oxygen]]
	* [[Apollo lunar module oxygen]]		* [[Apollo lunar module oxygen]]
	* [[Pounds per square inch]]		* [[Pounds per square inch]]

Flerf Whisperer: Link the fuel-cell article from the oxygen pipeline

2026-10-13T21:10:01Z

Link the fuel-cell article from the oxygen pipeline

← Older revision		Revision as of 17:10, 13 October 2026
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	The command module drew oxygen from cryogenic tanks in the service module. Flights through Apollo 13 carried two. Apollo 14 and the later landings carried three, with the extra tank plumbed so a failed tank could be shut off.<ref name="trw">R. K. M. Seto, C. E. Barton, and J. E. Cunningham, [https://ntrs.nasa.gov/citations/19710015627 ''Apollo Cryogenic Integrated Systems''], TRW for NASA Manned Spacecraft Center (1971, changed 1972). Table 2.1: 330.1 lb stored, 323.45 lb usable, 4.75 cubic feet, about 900 [[Pounds per square inch\|psi]].</ref> Each tank held about 330 pounds in 4.75 cubic feet, kept near 900 [[Pounds per square inch\|psi]] by electric heaters. The oxygen was supercritical: denser than a gas, and not a boiling liquid. A surge tank of 3.7 pounds and a repressurization bottle of 3 pounds, both in the command module, covered short peaks in demand.<ref name="csm">F. H. Samonski Jr. and E. M. Tucker, [https://ntrs.nasa.gov/citations/19720012252 ''Apollo Experience Report: Command and Service Module Environmental Control System''], NASA TN D-6718 (1972).</ref>		The command module drew oxygen from cryogenic tanks in the service module. Flights through Apollo 13 carried two. Apollo 14 and the later landings carried three, with the extra tank plumbed so a failed tank could be shut off.<ref name="trw">R. K. M. Seto, C. E. Barton, and J. E. Cunningham, [https://ntrs.nasa.gov/citations/19710015627 ''Apollo Cryogenic Integrated Systems''], TRW for NASA Manned Spacecraft Center (1971, changed 1972). Table 2.1: 330.1 lb stored, 323.45 lb usable, 4.75 cubic feet, about 900 [[Pounds per square inch\|psi]].</ref> Each tank held about 330 pounds in 4.75 cubic feet, kept near 900 [[Pounds per square inch\|psi]] by electric heaters. The oxygen was supercritical: denser than a gas, and not a boiling liquid. A surge tank of 3.7 pounds and a repressurization bottle of 3 pounds, both in the command module, covered short peaks in demand.<ref name="csm">F. H. Samonski Jr. and E. M. Tucker, [https://ntrs.nasa.gov/citations/19720012252 ''Apollo Experience Report: Command and Service Module Environmental Control System''], NASA TN D-6718 (1972).</ref>

	Most of the oxygen went to the three fuel cells, ~~which produced electricity~~ and water. The environmental-control budget for a 14-day, three-man design mission was about 173 pounds, including cabin leakage and repressurization. Crew use was figured at 1.8 pounds per man per day.<ref name="csm" /> In flight the cabin was held at 5 [[Pounds per square inch\|psi]] of pure oxygen. On the pad the mix was about 60 percent oxygen and 40 percent nitrogen, then bled down after launch.		Most of the oxygen went to the three fuel cells. Those plants turned hydrogen and oxygen into electricity and drinking water. The cells, the reaction, and the water path are on [[Apollo fuel cells]]. The environmental-control budget for a 14-day, three-man design mission was about 173 pounds, including cabin leakage and repressurization. Crew use was figured at 1.8 pounds per man per day.<ref name="csm" /> In flight the cabin was held at 5 [[Pounds per square inch\|psi]] of pure oxygen. On the pad the mix was about 60 percent oxygen and 40 percent nitrogen, then bled down after launch.

	The lunar module had no fuel cells and no cryogenic tanks. One descent-stage tank held 48 pounds of oxygen at about 3,000 [[Pounds per square inch\|psi]]. Two ascent-stage tanks held 2.4 pounds each and were saved for the climb back to orbit. The descent tank also refilled the backpacks. Cabin pressure was about 4.8 [[Pounds per square inch\|psi]], pure oxygen.<ref name="lm">R. J. Gillen, J. C. Brady, and F. Collier, [https://ntrs.nasa.gov/citations/19720013195 ''Apollo Experience Report: Lunar Module Environmental Control Subsystem''], NASA TN D-6724 (1972).</ref><ref>NASA Office of the Chief Health and Medical Officer, [https://www.nasa.gov/wp-content/uploads/2023/03/apollo-lunar-lander-technical-brief-ochmo.pdf ''Apollo Lunar Lander'' technical brief] (2023).</ref>		The lunar module had no fuel cells and no cryogenic tanks. One descent-stage tank held 48 pounds of oxygen at about 3,000 [[Pounds per square inch\|psi]]. Two ascent-stage tanks held 2.4 pounds each and were saved for the climb back to orbit. The descent tank also refilled the backpacks. Cabin pressure was about 4.8 [[Pounds per square inch\|psi]], pure oxygen.<ref name="lm">R. J. Gillen, J. C. Brady, and F. Collier, [https://ntrs.nasa.gov/citations/19720013195 ''Apollo Experience Report: Lunar Module Environmental Control Subsystem''], NASA TN D-6724 (1972).</ref><ref>NASA Office of the Chief Health and Medical Officer, [https://www.nasa.gov/wp-content/uploads/2023/03/apollo-lunar-lander-technical-brief-ochmo.pdf ''Apollo Lunar Lander'' technical brief] (2023).</ref>
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	== See also ==		== See also ==
			* [[Apollo fuel cells]]
	* [[Apollo command module oxygen]]		* [[Apollo command module oxygen]]
	* [[Apollo lunar module oxygen]]		* [[Apollo lunar module oxygen]]

Washcarso at 23:50, 12 October 2026

2026-10-12T23:50:11Z

← Older revision		Revision as of 19:50, 12 October 2026
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	== Command module and lunar module ==		== Command module and lunar module ==
			{{main article\|Apollo command module oxygen\|Apollo lunar module oxygen}}

	[[File:Apollo oxygen tank cutaway S71-16745.jpg\|right\|frame\|Cutaway of a service-module oxygen tank, drawn for the Apollo 14 redesign. The fans were removed and a third heater was added after Apollo 13. NASA S71-16745.]]		[[File:Apollo oxygen tank cutaway S71-16745.jpg\|right\|frame\|Cutaway of a service-module oxygen tank, drawn for the Apollo 14 redesign. The fans were removed and a third heater was added after Apollo 13. NASA S71-16745.]]
	The command module drew oxygen from cryogenic tanks in the service module. Flights through Apollo 13 carried two. Apollo 14 and the later landings carried three, with the extra tank plumbed so a failed tank could be shut off.<ref name="trw">R. K. M. Seto, C. E. Barton, and J. E. Cunningham, [https://ntrs.nasa.gov/citations/19710015627 ''Apollo Cryogenic Integrated Systems''], TRW for NASA Manned Spacecraft Center (1971, changed 1972). Table 2.1: 330.1 lb stored, 323.45 lb usable, 4.75 cubic feet, about 900 [[Pounds per square inch\|psi]].</ref> Each tank held about 330 pounds in 4.75 cubic feet, kept near 900 [[Pounds per square inch\|psi]] by electric heaters. The oxygen was supercritical: denser than a gas, and not a boiling liquid. A surge tank of 3.7 pounds and a repressurization bottle of 3 pounds, both in the command module, covered short peaks in demand.<ref name="csm">F. H. Samonski Jr. and E. M. Tucker, [https://ntrs.nasa.gov/citations/19720012252 ''Apollo Experience Report: Command and Service Module Environmental Control System''], NASA TN D-6718 (1972).</ref>		The command module drew oxygen from cryogenic tanks in the service module. Flights through Apollo 13 carried two. Apollo 14 and the later landings carried three, with the extra tank plumbed so a failed tank could be shut off.<ref name="trw">R. K. M. Seto, C. E. Barton, and J. E. Cunningham, [https://ntrs.nasa.gov/citations/19710015627 ''Apollo Cryogenic Integrated Systems''], TRW for NASA Manned Spacecraft Center (1971, changed 1972). Table 2.1: 330.1 lb stored, 323.45 lb usable, 4.75 cubic feet, about 900 [[Pounds per square inch\|psi]].</ref> Each tank held about 330 pounds in 4.75 cubic feet, kept near 900 [[Pounds per square inch\|psi]] by electric heaters. The oxygen was supercritical: denser than a gas, and not a boiling liquid. A surge tank of 3.7 pounds and a repressurization bottle of 3 pounds, both in the command module, covered short peaks in demand.<ref name="csm">F. H. Samonski Jr. and E. M. Tucker, [https://ntrs.nasa.gov/citations/19720012252 ''Apollo Experience Report: Command and Service Module Environmental Control System''], NASA TN D-6718 (1972).</ref>

Flerf Whisperer: Terse lunar-module oxygen rundown, with a link to the detailed page

2026-10-12T19:02:51Z

Terse lunar-module oxygen rundown, with a link to the detailed page

← Older revision		Revision as of 15:02, 12 October 2026
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	=== Lunar module ===		=== Lunar module ===
	~~[[File:Apollo 17 oxygen control module.jpg\|right\|frame\|Apollo 17~~ lunar module ~~Challenger. The~~ oxygen ~~control module~~. ~~Regulators~~ A ~~and B are the knobs marked cabin, egress, direct oxygen, and close. Those two take the 900 [[Pounds per square inch\|psi]] supply down to cabin pressure. Close~~-~~out photo from the Apollo Lunar Surface Journal.]]~~		The lunar module stored warm compressed oxygen. A descent-stage regulator dropped about 2,800 [[Pounds per square inch\|psi]] to about 900 [[Pounds per square inch\|psi]]. Two demand regulators then held the cabin near 4.8 [[Pounds per square inch\|psi]], or the suits near 3.8 [[Pounds per square inch\|psi]] for a walk. Before a moonwalk the crew dumped the cabin. After the walk they filled it again from the descent tank. The trips between the command module and the lunar module used the command module's oxygen through the docking tunnel. The valves, the checklists, and the photographs are on [[Apollo lunar module oxygen]].
	~~The lunar module did not carry cryogenic oxygen, so it had no glycol warmer. The descent tank was compressed gas near~~ 2,800 [[Pounds per square inch\|psi]]~~. A high-pressure regulator in the descent stage dropped that~~ to about 900 [[Pounds per square inch\|psi]] before the line came up into the cabin.<ref name="lmoxy">[https://apollojournals.org/alsj/alsj-ECSFunDesOxy.html Oxygen supply and cabin pressure control], Apollo Lunar Surface Journal, from the lunar module news reference.</ref> That 900 [[Pounds per square inch\|psi]] line refilled the backpacks. It is also the supply the cabin regulators used.

	~~The step from 900 [[Pounds per square inch\|psi]] to cabin pressure is two oxygen~~ demand regulators ~~in the oxygen control module. The module is on the suit-circuit package, at the right rear of~~ the ~~lunar module pilot's station. Besides the regulators it holds the descent and ascent shutoff valves, the backpack fill valve, and a~~ cabin repressurization valve.<ref name="lmequip">[https://www.apollojournals.org/alsj/alsj-ECSEquipOxy.html Oxygen supply and cabin pressure control equipment], Apollo Lunar Surface Journal, from the lunar module news reference.</ref>

	Each regulator has one handle: cabin, egress, direct oxygen, or close. A sense line brings suit-loop pressure back to an aneroid bellows, and the bellows moves a poppet against a spring. Cabin and egress are the same valve with a different spring. Cabin holds the loop at 4.8 [[Pounds per square inch\|psi]], ~~within 0.2 [[Pounds per square inch\|psi]]. Egress holds it at~~ 3.8 [[Pounds per square inch\|psi]]~~, within 0~~.~~2 [[Pounds per square inch\|psi]]. Direct oxygen opens~~ the ~~poppet all~~ the ~~way~~. ~~Close shuts that regulator off. Either one can feed~~ the ~~loop by itself~~. ~~At 900 [[Pounds per square inch\|psi]] and 70 degrees Fahrenheit, one of them can flow about 7 pounds an hour.<ref name="lmequip" /><ref name="lm" />~~

	~~While~~ the ~~cabin is sealed, the suit loop~~ and the ~~cabin are connected, so~~ the ~~pressure~~ the ~~regulators hold in the loop is the cabin pressure~~. ~~For a moonwalk the crew sets both handles to egress~~, ~~closes~~ the ~~cabin return~~, and ~~dumps~~ the ~~cabin. The suits stay at 3.8 [[Pounds per square inch\|psi]]. Relief valves~~ on ~~the hatches open if the cabin rises about 5.6~~ [[~~Pounds per square inch\|psi~~]] ~~above the pressure outside~~.~~<ref name="lm" /><ref name="lmoxy" />~~

	=== Suits ===		=== Suits ===
	Command-module suits took oxygen that had already been warmed and dropped to about 100 [[Pounds per square inch\|psi]]. Demand regulators fed that loop only when suit pressure sat a few [[Pounds per square inch#Inches of water column\|inches of water column]] below cabin pressure, a fraction of a [[Pounds per square inch\|psi]], and they vented the suits if suit pressure rose above cabin pressure, so the suits stayed soft. If the cabin was depressurized below 3.5 [[Pounds per square inch\|psi]], the same regulators held the suit loop at 3.75 [[Pounds per square inch\|psi]], within 0.25 [[Pounds per square inch\|psi]].<ref name="csm" />		Command-module suits took oxygen that had already been warmed and dropped to about 100 [[Pounds per square inch\|psi]]. Demand regulators fed that loop only when suit pressure sat a few [[Pounds per square inch#Inches of water column\|inches of water column]] below cabin pressure, a fraction of a [[Pounds per square inch\|psi]], and they vented the suits if suit pressure rose above cabin pressure, so the suits stayed soft. If the cabin was depressurized below 3.5 [[Pounds per square inch\|psi]], the same regulators held the suit loop at 3.75 [[Pounds per square inch\|psi]], within 0.25 [[Pounds per square inch\|psi]].<ref name="csm" />

	Lunar-module suits used the demand regulators ~~above~~: 4.8 [[Pounds per square inch\|psi]] in the cabin, 3.8 [[Pounds per square inch\|psi]] once the cabin was dumped for a walk.~~<ref name="lmoxy" />~~		Lunar-module suits used the demand regulators on [[Apollo lunar module oxygen]]: 4.8 [[Pounds per square inch\|psi]] in the cabin, 3.8 [[Pounds per square inch\|psi]] once the cabin was dumped for a walk.

	On the walk the backpack did the drop in one step, from a bottle of warm compressed gas rather than from the cold service-module supply. A single-stage regulator took the bottle, several hundred [[Pounds per square inch\|psi]] up to about 1,400 [[Pounds per square inch\|psi]] depending on the flight, down to about 3.85 [[Pounds per square inch\|psi]] in the suit. The purge bottle on top of the pack had its own single-stage regulator and held the suit near 3.7 [[Pounds per square inch\|psi]] if the backpack failed. An early purge-system design heated the gas before the regulator, to keep what reached the suit above 30 degrees Fahrenheit. Manned tests showed the flow and the suit stayed warm enough without it, and the flight purge system flew without that heater.<ref>J. C. Beggs and F. H. Goodwin, [https://ntrs.nasa.gov/citations/19720019459 ''Apollo PLSS: Environmental Control of the Smallest Manned Space Vehicle''], Hamilton Standard (1972).</ref>		On the walk the backpack did the drop in one step, from a bottle of warm compressed gas rather than from the cold service-module supply. A single-stage regulator took the bottle, several hundred [[Pounds per square inch\|psi]] up to about 1,400 [[Pounds per square inch\|psi]] depending on the flight, down to about 3.85 [[Pounds per square inch\|psi]] in the suit. The purge bottle on top of the pack had its own single-stage regulator and held the suit near 3.7 [[Pounds per square inch\|psi]] if the backpack failed. An early purge-system design heated the gas before the regulator, to keep what reached the suit above 30 degrees Fahrenheit. Manned tests showed the flow and the suit stayed warm enough without it, and the flight purge system flew without that heater.<ref>J. C. Beggs and F. H. Goodwin, [https://ntrs.nasa.gov/citations/19720019459 ''Apollo PLSS: Environmental Control of the Smallest Manned Space Vehicle''], Hamilton Standard (1972).</ref>
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	== See also ==		== See also ==
	* [[Apollo command module oxygen]]		* [[Apollo command module oxygen]]
			* [[Apollo lunar module oxygen]]
	* [[Pounds per square inch]]		* [[Pounds per square inch]]
	* [[Moon landings]]		* [[Moon landings]]

Flerf Whisperer: Link psi, psia, and psig, and call the suit difference inches of water column

2026-10-12T18:03:41Z

Link psi, psia, and psig, and call the suit difference inches of water column

Show changes