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-   -   Apollo: One gas environment? (http://www.spacebanter.com/showthread.php?t=49632)

Bill May 1st 04 01:57 AM

Apollo: One gas environment?
 
Were all the Apollo flights made in a one-gas (pure oxygen)
environment? It seems that the thin skin of the LM made it necessary
to limit the cabin pressure to 3.5 psi and required a one-gas system.
Is this correct?

Henry Spencer May 1st 04 03:18 AM

In article ,
Bill wrote:
Were all the Apollo flights made in a one-gas (pure oxygen)
environment? It seems that the thin skin of the LM made it necessary
to limit the cabin pressure to 3.5 psi and required a one-gas system.


That, plus the need to do spacewalks without lengthy prebreathing, plus
the much greater complexity of two-gas life-support systems.

Post-fire, Apollo used 60% oxygen 40% nitrogen as the *cabin* atmosphere
on the pad, but the crew always breathed pure oxygen, and the cabin
shifted to pure oxygen during ascent.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |

Rocky Top May 1st 04 03:57 AM


"Bill" wrote in message
...
Were all the Apollo flights made in a one-gas (pure oxygen)
environment? It seems that the thin skin of the LM made it necessary
to limit the cabin pressure to 3.5 psi and required a one-gas system.
Is this correct?


Yes.



Greg D. Moore \(Strider\) May 1st 04 04:03 AM


"Rocky Top" wrote in message
news:[email protected]

"Bill" wrote in message
...
Were all the Apollo flights made in a one-gas (pure oxygen)
environment? It seems that the thin skin of the LM made it necessary
to limit the cabin pressure to 3.5 psi and required a one-gas system.
Is this correct?


Yes.


To detail a bit more. All took off with a mixed gas atmosphere (N2 and O2)
at I believe 1 atmosphere pressure.

The N2 was bled off until the they reached the partial pressure of the O2
was left.







Doug... May 1st 04 08:34 AM

In article , says...
In article ,
Bill wrote:
Were all the Apollo flights made in a one-gas (pure oxygen)
environment? It seems that the thin skin of the LM made it necessary
to limit the cabin pressure to 3.5 psi and required a one-gas system.


That, plus the need to do spacewalks without lengthy prebreathing, plus
the much greater complexity of two-gas life-support systems.

Post-fire, Apollo used 60% oxygen 40% nitrogen as the *cabin* atmosphere
on the pad, but the crew always breathed pure oxygen, and the cabin
shifted to pure oxygen during ascent.


Pre-Fire, of course, the cabin was pressurized to roughly 17 psia of
pure oxygen. They also overpressurized the cabin at times during post-
Fire operations, but as Henry says, the air was 40% nitrogen.

The cabin pressure was maintained at roughly 5 psia in both the LM and
the CM. This was a little higher than the natural partial pressure of
oxygen in sea-level air. During EVAs (any time they were in hard
suits), the suit pressure was maintained at about 3.5 psia. You could
put more air pressure in the suits, but the higher the pressure the
"harder" the suit became... it would become very much harder to do
simple things like raise your arm to eye level in a suit pressurized to,
say 4.5 psia than in a suit at 3.5 psia. (Eric Jones discusses this in
several of the Apollo Lunar Surface Journals, and most of the Apollo
moonwalkers confirmed that they had a harder time working in such
"harder" suits.)

Doug


Nicholas Fitzpatrick May 1st 04 02:42 PM

In article ,
Doug... wrote:
In article , says...
In article ,
Bill wrote:
Were all the Apollo flights made in a one-gas (pure oxygen)
environment? It seems that the thin skin of the LM made it necessary
to limit the cabin pressure to 3.5 psi and required a one-gas system.


Post-fire, Apollo used 60% oxygen 40% nitrogen as the *cabin* atmosphere
on the pad, but the crew always breathed pure oxygen, and the cabin
shifted to pure oxygen during ascent.


Pre-Fire, of course, the cabin was pressurized to roughly 17 psia of
pure oxygen. They also overpressurized the cabin at times during post-
Fire operations, but as Henry says, the air was 40% nitrogen.


I'm sure I'm not the only one who had to look this up, not knowing
what a psi is equivalent to. I'm sure everyone knows that 1 atmosphere
= 101.3 kPA ... but many of us forget that this equals 14.7 psi

So they pressurised to 1.16 atmospheres (117.2 kPa) and then dropped
to 0.24 atm (24.1 kPa).

Nick

Brett Buck May 1st 04 07:50 PM

On 5/1/04 6:42 AM, in article , "Nicholas
Fitzpatrick" wrote:
I'm sure I'm not the only one who had to look this up, not knowing
what a psi is equivalent to. I'm sure everyone knows that 1 atmosphere
= 101.3 kPA ... but many of us forget that this equals 14.7 psi


We do? Gee, *I* got through 4th grade science!

Brett


Revision May 2nd 04 11:38 AM


"Nicholas Fitzpatrick" So they pressurised to 1.16 atmospheres (117.2
kPa) and then dropped
to 0.24 atm (24.1 kPa).


Yeah well it makes just as much sense to say they kept about a 3.5 psi of
positive pressure.....



Hans May 2nd 04 03:43 PM

I agree.

For a normal person it is almost impossible to understand all these
interesting topics when it is full of gallons, feets and psi's instead of
litres, meters and Pascals

I'm sure I'm not the only one who had to look this up, not knowing
what a psi is equivalent to. I'm sure everyone knows that 1 atmosphere
= 101.3 kPA ... but many of us forget that this equals 14.7 psi

So they pressurised to 1.16 atmospheres (117.2 kPa) and then dropped
to 0.24 atm (24.1 kPa).

Nick




Herb Schaltegger May 2nd 04 05:42 PM

In article ,
"Hans" wrote:

I agree.

For a normal person it is almost impossible to understand all these
interesting topics when it is full of gallons, feets and psi's instead of
litres, meters and Pascals


"Normal person", huh? You mean, some sort of "units snob?"

Well, since a good part of these "interesting topics" all use Imperial
measurements (the American part, of course), wouldn't it behoove you to
learn a few simple conversions so you can understand the discussion?
After all, a good many of us did so and can work fairly easily in either
system.

--
Herb Schaltegger, B.S., J.D.
Reformed Aerospace Engineer
Columbia Loss FAQ:
http://www.io.com/~o_m/columbia_loss_faq_x.html


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