Author Topic: Apollo capsule with sea level air cabin pressure ?  (Read 4645 times)

Offline Michel Van

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Re: Apollo capsule with sea level air cabin pressure ?
« Reply #20 on: 05/02/2018 04:05 PM »
Another reason why they never developed an upgraded Apollo was the shuttle was already in development  and it was expect the new vehicle would be flying before the end of 1977.

NAA worked for NASA on Apollo CSM block III for Apollo Application Program in 1966
it feature operational time up to 45 days, increase hydro lox load for Fuelcells power output 4,000 W.
increased in RCS propellant from 790 to 2500 lbs.
Atmosphere would be 70% oxygen 30% nitrogen at 5 psi co2 removal would be molecular sieve device

in 1966 NAA expected the first Block III would launch ready in case summer of 1969.
But in 1967 happen Apollo one fire and AAP got slaughtered in congress
Apollo Application Program survived as Skylab and it use remaining CSM Block II


I not don't know about Big Gemini cabin pressure
« Last Edit: 05/02/2018 04:10 PM by Michel Van »

Offline ThereIWas3

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Re: Apollo capsule with sea level air cabin pressure ?
« Reply #21 on: 05/02/2018 06:09 PM »
Considering all the follow-on complications, that really endanger the viability of the entire project, what was the reason for hanging on to the sea-level pressure requirement for Orion?
"If you want to build a ship, don’t drum up people to collect wood and don’t assign them tasks and work, but rather teach them to long for the endless immensity of the sea" - Antoine de Saint-Exupéry

Offline Michel Van

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Re: Apollo capsule with sea level air cabin pressure ?
« Reply #22 on: 05/02/2018 07:22 PM »
Considering all the follow-on complications, that really endanger the viability of the entire project, what was the reason for hanging on to the sea-level pressure requirement for Orion?

Simple: International Space Station.
the entire system including the Shuttle  and the Soyuz capsule use sea level air cabin pressure.
since Orion had to fly also to ISS it needed sea level air pressure

For Apollo style capsule
into ISS was easy 5 minute adaption fron low pressure rich oxygen to sea level atmosphere 
But the crew needed adaption time of 2 hours to return to that Apollo via special docking Airlock.
to get dissolved nitrogen out there body

Source:
Skylab Reuse study special about different Air pressure in Shuttle and Skylab itself. 
Apollo Soyuz Test Program and its need for airlock module 

Offline Hitech

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Re: Apollo capsule with sea level air cabin pressure ?
« Reply #23 on: 05/02/2018 08:32 PM »
I think they "demo'd the dangers of testing at sea level 100% O2 :(

Offline Fequalsma

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Re: Apollo capsule with sea level air cabin pressure ?
« Reply #24 on: 05/04/2018 04:41 AM »
There are A LOT of other knock-on effects besides the ones that you mention.  A new tank for N2, a larger, heavier tank for more O2, a manifold and regulator to mix them, etc., etc., etc.  It's a pretty long list!
F=ma

a Back note

With Apollo CM internal pressure shell increased from 582 to 1571 kilogram
will increase also other components weight like Windows and Hatches
and special the Parachute because it carry a heavier capsule down

i understand why was never a study for Apollo with sea level air cabin pressure.
simply the CSM would be to heavy for Saturn Ib or Titan IIIM
« Last Edit: 05/04/2018 04:45 AM by Fequalsma »

Offline Michel Van

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Re: Apollo capsule with sea level air cabin pressure ?
« Reply #25 on: 05/04/2018 01:37 PM »
Found this PDF about Two Gas Atmosphere for CSM under Apollo Application Program

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19700025125.pdf

the pressure remain 5 psia
studies were Oxygen/Nitrogen and Oxygen/Helium  with option to get on 100% oxygen
also include data about additional mass of Tanks and systems for CSM

Offline buel

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Re: Apollo capsule with sea level air cabin pressure ?
« Reply #26 on: 05/18/2018 03:10 PM »
I've just read this fascinating thread and I have a naive question - during the Apollo 1 fire, they were testing at 15psi. Inflight, the pressure would have been 5psi. Why weren't they using 5psi during the test?

Online e of pi

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Re: Apollo capsule with sea level air cabin pressure ?
« Reply #27 on: 05/18/2018 03:46 PM »
I've just read this fascinating thread and I have a naive question - during the Apollo 1 fire, they were testing at 15psi. Inflight, the pressure would have been 5psi. Why weren't they using 5psi during the test?
The cabin absolute pressure was 16.7 psi, meaning it was just slightly over the ambient pressure outside the capsule (atmospheric pressure is ~14.7 psi at sea level at standard conditions). If it was to be at 5 psi, it'd have to be pumped down to a vacuum, which is a loading the structure wasn't designed for (its pressure vessel was optimized to hold pressure in, not keep pressure out).

They were simulating the launch procedure, where the 14.7 ambient air would be pumped out and a pure-oxygen atmosphere at 16.7 psi pumped in, creating positive pressure and ensuring no ambient air could leak back in. During ascent, then, the cabin would bleed down in stages until the ambient pressure was below the 5 psi it would maintain in vacuum, which is when it would hold at 5 psi.
« Last Edit: 05/21/2018 04:37 PM by e of pi »

Offline Proponent

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Re: Apollo capsule with sea level air cabin pressure ?
« Reply #28 on: 05/19/2018 11:59 AM »
By the way, how much of a hazard would pure oxygen at 5 psi be on the ground?  The partial pressure of oxygen would be about 60% higher than in air, so that obviously increases the risk.  But the lack of nitrogen would also reduce convective cooling, which I presume would increase the risk as well.

For that matter, what about in orbit?  There is no convection, which reduces cooling but also reduces the supply of oxygen to a flame.  What's the net effect on inflammability?

Offline Michel Van

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Re: Apollo capsule with sea level air cabin pressure ?
« Reply #29 on: 05/22/2018 11:33 AM »
By the way, how much of a hazard would pure oxygen at 5 psi be on the ground?  The partial pressure of oxygen would be about 60% higher than in air, so that obviously increases the risk.  But the lack of nitrogen would also reduce convective cooling, which I presume would increase the risk as well.

For that matter, what about in orbit?  There is no convection, which reduces cooling but also reduces the supply of oxygen to a flame.  What's the net effect on inflammability?

See what happen with Apollo one

After that NASA removed everything inflammable from capsule
Make sure that Electronic not produce Sparks anymore.
the Crew got new Spacesuits were the coating made from "Teflon-coated yarn Beta fiberglass fabric"

Max Faget made proposal to replace 100% Oxygen at 16 Psi with a mixed gas atmosphere,
Either oxygen-nitrogen or oxygen-helium in a 60:40 ratio.
That mixed atmosphere will be bled out Capsule during ascent into orbit and replaced with pure oxygen.
While the Astronauts are sealed in there Spacesuits breading already 100% Oxygen.

NASA chose oxygen-nitrogen as easy part.

source
https://www.popsci.com/why-did-nasa-still-use-pure-oxygen-after-apollo-1-fire
http://ocii.com/~dpwozney/apollo2.htm

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