reply to post by Chadwickus
Just to jump in, in case others are confused by Chad's point:
One must consider the entirety of the Space Program, starting with Mercury in the early 1960s, continuing with Gemini and ultimately Apollo.
A bit of History: Everyone is, (or should be) aware of the tragedy of Apollo One. It was called a 'plugs-out' test of the proto-type of the Apollo
CM design, as mated to the Saturn IB lift rocket.
Here's something that needs to be explained: Earth's normal atmosphere at Sea Level is about 14.7 PSI. It is about 20% oxygen, the rest mostly
Nitrogen and other trace gases.
To save weight, in the Space Missions of the 1960s, as well as on Apollo, the capsules' life-support environments were pressurized to about 3.5 PSI,
but with pure oxygen. This, the same with the EVA suits (which blows away one idiot's video of why the gloves wouldn't work in a vacuum, but, I
digress...)
Duriing Apollo One's test....the idea was that they HAD to pressurize the CM capsule to simulate the same PSID as they'd experience in a
vacuum...but, at the Earth's surface. (PSID = pounds/sq/inch differential)
This means they pumped the cabin up to over 18 PSI....(14.7 + 3.5) of pure oxygen.
Certainly, the O2 wasn't harmful in any way to a Human....they had already purged the nitrogen out of their systems (any Scuba Divers know what I'm
talking about).
Two things: It was not necessary to pressurize like that....(could have used normal air for this particular test) and, the egress hatch was a
'plug-type' (as used on jet airliners) but with no explosive bolts for quick exit.
Ironic, that Gus Grissom died on Apollo One, after having been blamed for 'blowing' the hatch on his Mercury capsule (later deemed to be false)
during his recovery from splashdown, thusly losing the capsule. (It was recovered, using modern technology, and he was exonerrated post-humously).
SO, the proto-type Apollo CM had no explosive bolts. A fire started, and with the increased pressure in the capsule, and a hatch which had to open
iniward before it could open outward to provide escape....there was no escape.
BUT, the very high-pressure O2 environment proved to be a hazard that no one had predicted -- the newly invented 'Velcro' material. Specifically,
the 'fuzzy' part of Velcro....the 'loops' (not the 'hooks') turned out to be very flammable in a high-pressure pure O2 environment.
The Velcro didn't start the fire, but it burned readily once the flames hit it.
The CM was re-designed.....and the next vehicle to fly was designated Apollo 7, launched just into Earth orbit on a Saturn IB....but, despite that
early tragic set-back, the program recovered. As it is in all experimental flight testing.
BTW, the Saturn V lift vehicle was needed to accomplish launch of Apollo to reach the Moon. The Saturn IB was part of the experimentation as the
program progressed. Each step, once shown successful, was built upon and tested, again and again and again...and again....
[edit on 3/28/0909 by weedwhacker]
second edit.....I write off the top of my head....I invite anyone with further interest to visit Wikipedia. Lotsof good info there.....
[edit on 3/28/0909 by weedwhacker]