Jarrah asked: During his testimony, Frank Borman told Congress: "I dont believe that any of us recognized that the test conditions for this test were hazardous." He also told the US Senate: "None of us were fully aware of the hazard that existed when you combine a pure-oxygen atmosphere with the extensive distribution? of combustibles and the likely ignition...and so this test...was not classified as hazardous."
Yet in his on pages 162 and 163 of his book, Men From Earth, Buzz Aldrin writes: "The only serious hazard of the pure-oxygen environment was fire. As every high school student learns, when a smoldering match is put into a beaker of oxygen, it blazes into a spectacular flame. The Apollo cabin was also an oxygen-rich container, and the spacecrafts many switches, electrical equipment, and over 15 miles of wiring could easily short-circuit, providing a glowing match".
They either didn't know the risk, as Borman stated. Or they knew the risk and considered it acceptable, as Aldrin says. Which is it?
This is where we see an example of the incorrect interpretation Jarrah often makes. We have to look at three parts: what was the hazard, what risk was associated with the hazard, and what are the consequences.
Firstly what was the hazard? The hazard was the use of 100% oxygen in the spacecraft.
What was the risk? The risk was fire in the spacecraft.
Now, and most importantly, what are the consequences? The consequence depended on the phase of flight, and ranged from loss of cabin pressure and possible mission abort, to loss of the crew .
Well, that's obvious, isn't it? 100% oxygen posed an unacceptable risk. NO - you have to look deeper. If a fire had occurred in space and the astronauts were in their suits, the immediate action would have been to depressurize the cabin. Remove the oxygen and they fire goes out. If they weren't in their suits, the plan was to use the water gun to put out the fire. The option still existed for them to don the emergency masks and partially depress the cabin, helping put out the fire. They would have had to abort the mission, but the crew would have a high probability of survival.
This was the case through the majority of the flight. It would not be available if there were a fire on the pad. The length of time on the pad, however, was small compared to the total mission time.
Now what was the risk of a fire happening? There was some risk of an electrical short happening, but it was considered low; after all, this was a US spacecraft not some cheap radio from Japan. Besides, design rules meant that there was not to be any flammable material within 12 inches of any possible ignition source.
So the hazard was known, but the risk of an event with catastrophic consequences was low... or so it was believed. That's why the test was not considered to be hazardous. There were no fuels loaded, there were no explosives, even the launch escape system rocket was safed.
So what changed this? There were a number of factors, the most importantly being the spacecraft the spacecraft being pressurized to nearly 20 psi. This drastically increased the the consequences of any fire; it would burn with greater intensity. What also was not properly considered was the increased risk of an electrical short because of faulty wiring, poor workmanship.
NASA knew there were problems; so did the astronauts. It was just they believed that the problems would be solved. No aircraft, no complex technical system ever develops trouble-free; there are always faults, always problems.
NASA - and the astronauts - got lulled into a false sense of security.
They had used 100% oxygen in Mercury and Gemini without problems. The Apollo spacecraft, pressurized with near 20 psi of 100% oxygen, had been tested four times previously in a test chamber with no problems. They just didn't completely consider everything, and got caught out.
Page 87 of Volume I to the INVESTIGATION INTO APOLLO 204 ACCIDENT before the US House of Representatives subcommittee on NASA oversight illustrates this:
Mr Gurney: Colonel, we all recognize, I think I state this correctly, that the use of pure oxygen does present, severe fire hazards. I think actually that is the language used in the report and I guess there has been a great deal of discussion between using pure oxygen or some other combination in the cabins of spacecraft and yet it puzzles me when you say that under these specific test conditions you never considered fire as a hazard. Now, what generally do you consider as a fire hazard in this kind of atmosphere? Then let me say in trying to illustrate, if you were going into a filling station to have car serviced you wouldn’t light a match and have a cigarette while the gas was going into the tank. What areas do you identify as rather severe risks in this business of working in a pure oxygen atmosphere?
Colonel Borman: I think what you say about going into the gas station and striking a match is true. Mr. Rumsfeld can tell you when he flew in the Navy in jets he was using 100% oxygen all the time. There is oxygen right above your head when striking matches on a commercial airliner. Oxygen per se is not dangerous, only when associated with a fuel and an ignition source. Quite frankly we did not think, and this is a failing on my part, and on everyone associated with us; we did not recognize the fact that we had the three essentials, an ignition source, extensive fuel, and of course we knew we had the oxygen.
Why didn't they realise the danger? Part of the reason was because fire propagation data was misleading:
Dr Thompson: Could I interject a comment? Prior to the accident review, a great deal of dependence had been placed on information for flame propagation obtained from small laboratory samples of burning rates, some burning horizontal and some vertical, some burning upward and some burning downward, and some at 45 degree angles, and all kind of results were obtained. One of the outstanding accomplishments of this review has been the development of a procedure for obtaining valid information on the flame-propagation problem. The results obtained from these small samples are shown to possibly downright misleading...
Mr Davis: Thank you, Sir. There is one other question and that is this: The decision to raise the capsule atmosphere to 16.7 pounds per square inch was entirely predicated upon the assumption that you could rely upon the fact that there would be no arcing within the capsule. That is correct, is it not? And if that assumption had not been wrong, then nothing else would have been the matter?
Dr Thompson: Yes.
Mr Davis: The fact that the assumption was wrong is the whole trouble?
Dr Thompson: That is correct.
So Jarrah - they knew about the hazards but the risks were not properly appreciated.