originally posted by: RossWellOldMexico
How could the the inside survive the blast as the exterior blew open? There had to be some form of manipulation of the explosion to be done that way.
Even the astronauts thought they were goners.
You have to understand the design.
The place the astronauts are in is called the command module. It's shaped sort of like a Hershey's kiss. The LM was attached at the pointy end. At the
bottom, there's a big garbage can shaped part called the service module. It's pretty much separate from the command module, except for some plumbing
and connections that can be detached.
The service module has all the lumpy stuff in. Like most of the batteries, the fuel cells, a biggish rocket motor, oxygen tankage and the like. The
command module has enough of that to run by itself for the duration of the re-entry.
The problem was in the service module. The service module is made up, to an extent, of frames that have equipment bolted on, then you bolt the frames
together. There was a frame that was dropped in construction. The frame had some stuff already bolted on, and one of them was an o-tank. That o-tank
had, as part of its design, a siphon tube that ran to the bottom, for emptying the thing in test. The tube was dislodged, and the tank could not be
emptied using the siphon. The flaw was decided to be not worth disassembling the SM to replace, and it was decided that the tank could be emptied by
opening the vent and turning on the tank heater, boiling the liquid O2 out the vent.
This was done. However. there were two more things that hadn't been dealt with. One was, the design team had decided early on that the thermostats on
the o-tanks should operate properly with a higher voltage supply which was available on the ground (60V?) as well as the 28V craft supply. This design
change was sent to the tank manufacturer (Beech?) but not incorporated in the tankage design. No one caught it, either at NASA or at Beech.
So, now you've got the world's only o-tank that has to be boiled dry on the ground, and it's got a thermostat that can't handle the voltage. So right
off the bat, the thermostat fused shut. This was verified (obviously you couldn't get the bad one) by trying it on various spares, and there was a
fair number that did the same. So if you put the power to it, it would boil the O2 out alright, but the thing would just get as hot as it could, as
there wasn't a cutout that worked anymore.
The second thing no one thought about, was that even with the thermostats fused shut, the test operators would be able to tell by just watching the
thermocouple indicators in the tanks which tell you the temperature of the tank's insides. However, the designers of that console just KNEW the tanks
couldn't go over about 80C on the internal heaters, because they had a thermostat that opened to protect them at that temperature. So the gauge
wouldn't indicate any temperature higher than that. So the test guys were fat dumb and happy boiling the thing out, thinking it was maxing out at
It went a lot higher.
These tanks were amazingly insulated. Any heat you put in there basically stayed in there. And the heaters were running full bore with no place for
the heat to go. And it went up high enough to melt the Teflon insulation, because that's what happened on the ground when they tried to replicate this
So now you've got a nice O2 tank that will still hold the O2 just fine, until you turn on the tank heater or run the stirrers. At which point the bad
insulation will cause a spark, and Teflon will burn just FINE in liquid O2. In fact, as an example, combat aircraft countermeasure flares often use
Teflon as a thermite component, which should give you a feel for how hot Teflon burns with a really aggressive oxidizer present.
When the tanks were stirred, that one lit up the insulation inside. The pressure went sky high, and the tank blew. When it did, it blew the plumbing
all to hell and popped a panel off the service module, screwed up the engine and who knows what else. There is a pretty good photo of the inside of
it, it's mangled all to hell.
But that's the SERVICE MODULE. Nothing in there but tanks and batteries and support doodads. The place where the astronauts are is the COMMAND MODULE.
A totally different part of the thing, and not directly connected to it in terms of a tunnel or access hatches or the like.