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Richard Lamb wrote:
In the aftermath of the Apollo 1 fire, NASA took a year (and $75 mil) to redesign the space craft, mature their mental attitudes, and yes, did come back with a much safer vehicle. Yes, but I still wonder how anyone in their right might would use a nearly pure oxygen atmosphere in a vehicle full of humans and electrical equipment... Matt |
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Matt Whiting wrote:
Richard Lamb wrote: In the aftermath of the Apollo 1 fire, NASA took a year (and $75 mil) to redesign the space craft, mature their mental attitudes, and yes, did come back with a much safer vehicle. Yes, but I still wonder how anyone in their right might would use a nearly pure oxygen atmosphere in a vehicle full of humans and electrical equipment... Matt Probably because it might be possible to run at a lower pressure in flight and keep the crew alive. This _was_ one of the very first corrections made to the design. 60% O2 /40% N |
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Matt My computer bombed so this may go as a dup? I have thousands of hours in jet fighters breathing 100% oxy. We had all kinds of electrical stuff in cockpit(s) and aircraft. High power Radar, Radio's, etc., etc. .. Big John ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~ On Wed, 23 Jun 2004 18:28:37 -0400, Matt Whiting wrote: Richard Lamb wrote: In the aftermath of the Apollo 1 fire, NASA took a year (and $75 mil) to redesign the space craft, mature their mental attitudes, and yes, did come back with a much safer vehicle. Yes, but I still wonder how anyone in their right might would use a nearly pure oxygen atmosphere in a vehicle full of humans and electrical equipment... Matt |
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Matt Whiting wrote in message ...
Richard Lamb wrote: In the aftermath of the Apollo 1 fire, NASA took a year (and $75 mil) to redesign the space craft, mature their mental attitudes, and yes, did come back with a much safer vehicle. Yes, but I still wonder how anyone in their right might would use a nearly pure oxygen atmosphere in a vehicle full of humans and electrical equipment... Matt If the Russians had just informed us of their loss due to the same problem earlier it may not have happened. Harry K |
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On Wed, 23 Jun 2004 18:28:37 -0400, Matt Whiting
wrote: Richard Lamb wrote: In the aftermath of the Apollo 1 fire, NASA took a year (and $75 mil) to redesign the space craft, mature their mental attitudes, and yes, did come back with a much safer vehicle. Yes, but I still wonder how anyone in their right might would use a nearly pure oxygen atmosphere in a vehicle full of humans and electrical equipment... Just got done reading _Angle of Attack_, the biography of North American VP Harrison Storms, who led the NA Apollo program. Since he got fired (actually, transferred to headquarters) as a result of the Apollo I fire, it goes into the situation with considerable detail. Early in the life of the program, the decision as to what to use for air in the cabin fell to two basic issues: The known fire danger of a pure oxygen atmosphere, and the fact that equipment did not then exist to sense and maintain a nitrogen/oxygen atmosphere. Other than the CO2 scrubbers (needed with either scheme) all that would be necessary for the pure-oxygen system would be a simple valve allow oxygen into the spacecraft when the pressure dropped. With 5 PSI pressurization, occupants have the same partial pressure of oxygen as at sea level, and the fire danger isn't too severe. There was the rather low danger of the 5 PSI pure 02 system, vs the potential schedule risk of the control system and the known weight penalties of the 14 PSI N/O2 mix. North American favored the normal-air mix, but the ultimate decision was NASA's. Also in their proposal, North American specified an outward-opening hatch with an explosive device to get rid of it in a hurry. Two things worked against this part of the design. First, NASA had gained a considerable black eye with the loss of Gus Grissom's Liberty Bell 7. Whether you believed that Grissom blew the hatch himself or a technical fault caused the mechanism to fire, the basic fact was that the accident would not have happened if an emergency eject mechanism had not been installed. And...according to _Angle of Attack_, the NASA manager in charge of the Command Module program was ex-Navy. An ex-Navy submariner, in fact. And anyone wearing dolphins will insist that pressure on a hatch should cause it to close *tighter*. He was dead-set against an outward-opening hatch, and his background also gave him a negative view of things like explosive hatches. After all, the main danger was a loss of pressurization on orbit. Either way the hatch worked, the astronauts would be able to open it in the case of a pad emergency. But if a hatch failed once the rocket was in orbit, the astronauts would be dead. An inward-opening hatch was obviously less risk, on-orbit. So... Apollo was directed to make the hatch open inward, to not include an emergency jettison function, and to use a pure-oxygen atmosphere (IIRC, the pure-oxy atmosphere was NASA Change Order #1). Mercury and Gemini had used 100% oxygen systems, and no problems had occurred. Then came the Plugs-Out test of Apollo 1. The Plugs-Out test was basically a full test to see if all the spacecraft systems would support launch. The crew was in place, the hatch would be closed, the capsule would be pressurized, and all the umbilicals normally used to connect the capsule to the pad would be disconnected. Unfortunately, the test required the capsule to be pressurized to ensure that everything sealed properly. Since it was on the ground, not in space, they had to pressurize it to about two PSI over ambient. And, of course, they used the only breathable gas aboard: 100% oxygen. A pure-oxygen atmosphere at 5 PSI has its dangers, but a pure-oxygen atmosphere at 16 PSI is pure horror. No one really knows what started the fire. What I found interesting is that the capsule wasn't completely ready for flight...some items were still in work. For instance, one piece of cabin equipment had been removed for repair. Its power connector was left in place, energized. It was located in close to the area where they determined the first started: near one of the astronaut's feet. But whether the cause was a kicked connector, scraped insulation, or any of the myriad other possibilities, a fire started. The crew started the painful, awkward process of opening the inward-swinging hatch. But within about ten seconds, the fire had built the internal pressure to the point where the hatch could *not* have been budged...either by the crew, nor by any of the pad support personnel with the equipment they had available. After I read _Angle of Attack_, I re-watched the Apollo 1 fire episode of HBO's series, "From the Earth to the Moon." The series shows Frank Borman testifying to Congress about the fire. I don't know if the dialog used in the series was directly from Borman's actual testimony, but one line really rang true: "The cause of this accident was a failure of imagination." Everyone worried about what would happen during a failure in space, but nobody thought about the mundane problems that might occur during a simple, routine pad test...or how a chain of seemingly logical design decisions could result in disaster. Ron Wanttaja |
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