As a result of the Apollo 1 spacecraft fire, the use of a pure oxygen atmosphere during launch and ascent of Saturn V was abandoned by the U. S. space program, according to NASA.
According to the Apollo Lunar Surface Journal, for Apollo 12, values given for cabin pressure are 4.8 psi, and for normal operating suit pressure, 3.8 psi. This suggests a pure oxygen environment for the Lunar Module.
For Apollo 11, 12, & 14, during EVA preparation, the suit relative pressures were 4.6 to 5.2 psi when the LM cabin pressure was 3.5 psi, giving suit absolute pressures of 8.1 to 8.7 psi pure oxygen. At earth's atmospheric pressure of 14.7 psi, this correlates to 55% to 60% oxygen content, which gives an oxygen partial pressure of 8.1 to 8.7 psi.
According to the Apollo 12 ALSJ, the suits were already difficult to bend at 3.8 psi relative pressure (when the LM cabin pressure was 3.5 psi). When the suit pressures were at about 4.5 psi relative pressure, the suits were very stiff.
The following quotes are from a March 11, 1968 Aviation Week & Space Technology article headlined "Flammability Tests Spur Two-Gas Apollo".
"Washington - Decision to use a two-gas atmosphere (60% oxygen, 40% nitrogen) during manned Apollo on-the-pad preparations and in pre-orbital flight reflects a basic inability to make the spacecraft flameproof after 14 months of redesign that cost more than $100 million and added about 2,000 lb. to the system.
"The decision (AW&ST, Mar. 4, p. 21) was forced on the National Aeronautics and Space Administration after three series of flammability tests on an Apollo command module boilerplate failed to satisfy officials that changes would prevent the spread of fire under a pure-oxygen environment."
The article goes on to mention how a 95% oxygen system at 6.2 psi which would be orbital configuration developed problems in fire propagation tests.
Would not there have been serious flammability problems of such an environment in the lunar module? The article concludes:
"By switching to a two-gas system for pre-flight and immediate post-launch activities, NASA is willing to accept an added problem. Astronauts will be breathing pure oxygen during that phase and they will have to vent the spacecraft cabin during boost to orbit and repressurize to 6 psi with oxygen to permit them to remove their helmets and work in relative comfort.
"Possibility of the 40% of nitrogen causing bends if an emergency escape has to be made during the launch phase was considered by officials less hazardous than that of fire propagation in a one-gas system."
A Feb. 6, 1967 article in AW&ST indicates that when the Apollo program was being planned, the primary reason for choosing a 5-psi cabin oxygen system was weight considerations. Added weight (with a two-gas system) would come from a mixture control system to keep the proper gas ratio. Also, introduction of an oxygen-nitrogen or oxygen-helium environmental control system for Apollo would have meant the addition of an airlock.
Just how dangerous was a pure oxygen environment in the ascent and descent lunar module considered to be?
Here on earth, increasing the percentage of oxygen to slightly above 21% dramatically increases probability of fires. According to The Anthropic Cosmological Principle (p. 567) by Barrow and Tipler, "...the probability of a forest fire being started by a lightning-bolt increases 70% for every 1% rise in oxygen concentration above the present 21%. Above 25% very little of the vegetation on land would survive the fires...". "At the present fraction of 21%, fires will not start at more than 15% moisture content. Were the oxygen content to reach 25%, even damp twigs and the grass of a rain forest would ignite."(p. 568).
Ralph René, in his book NASA Mooned America, provides a list of government-sponsored testing that resulted in oxygen fires. René extracted this information from Appendix G in Mission To The Moon by Kennan & Harvey. Here are some tests on that list:
"September 9, 1962 - The first known fire occurred in the Space Cabin Simulator at Brooks Air Force Base in a chamber using 100% oxygen at 5 psi. It was explosive and involved the carbon dioxide scrubber. Both occupants collapsed from smoke inhalation before being rescued."
"November 17, 1962 - Another incident using 100% oxygen at 5 psi in a chamber at the Navy Laboratory (ACEL). There were four occupants in the chamber, but the simple replacing of a burned-out light bulb caused their clothes to catch on fire. They escaped in 40 seconds but all suffered burns. Two were seriously injured. In addition an asbestos 'safety' blanket caught fire and burned causing one man's hand to catch fire."
"April 28, 1966 - More Apollo equipment was destroyed as it was being tested under 100% oxygen and 5 psi at the Apollo Environmental Control System in Torrance, CA."
"January 1, 1967 - The last known test was over three weeks before Grissom, Chaffee & White suffered immolation. Two men were handling 16 rabbits in a chamber of 100% oxygen at 7.2 psi at Brooks Air Force Base and all living things died in the inferno. The cause may have been as simple as a static discharge from a rabbit's fur ... but we'll never know."
NASA subjected Grissom, White and Chaffee to over 90% pure oxygen at over 16 psi in a test with live electrical circuits and switches being thrown, and with a hatch that took more than three minutes to open, resulting in the fatal Apollo 1 fire.
Bill Kaysing, in his book We Never Went To The Moon, states, in Chapter 9 titled "Murder By Negligence On Pad 34", "If any two documents lend credibility to the contention that the Apollo flights were faked, they are most certainly the Baron Report and the Phillips Report. They were authored by two men of obvious integrity and dedication. Although from diverse backgrounds, both Tom Baron and Sam Phillips were in total agreement on one basic premise, i.e., that North American Aviation and its sponsor, NASA, were totally unequal to the task of assuring even one successful flight to the moon!"
Why did NASA decide to subject Grissom, White and Chaffee to more than
90% pure oxygen at over 16 psi in a test with live electrical circuits
and switches being thrown, and with a hatch that took more than three minutes
to open, resulting in the fatal Apollo 1 fire?
Apollo Lunar Module Lack of Flame and Exhaust and Other Anomalies
Apollo Internet Images and Videos with Anomalies and Inconsistencies
Various Other Apollo Image Anomalies
Deadly Radiation At and Beyond the Van Allen Shields
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