Pure O2 effects in spaceflight

[SteveInNZ]

How did Apollo/Gemini astronauts get on with breathing pure O2 for nearly 2 weeks ?
Even though the ambient pressure was reduced, wouldn't it still be just as reactive in terms of Pulmonary toxicity ? Were there any observed problems attributed to the atmosphere (aside from Apollo 1) ?

Steve.

 

[Thalassamania]

The capsule atmosphere was at .2 ATA with 100% oxygen. Same oxygen level as earth.

 

[Teamcasa]

Here is a good link to more information
The Apollo Spacecraft - A Chronology. Vol. IV. Part 2 (1968 Mar)

 

[DA Aquamaster]

The 100% O2 at 3 psi versus the 21% O2 at 1 atmosphere argument was one of safety on the ground (21% O2) versus safety in flight.

The other benefit was that a lower pressure differential allowed lighter spacecraft weight and the early boosters used by NASA were pretty anemic so light weight carried the day and they went with a reduced pressure using 100% O2.

Where NASA got caught was in using a 100% O2 atmosphere at 1 atmosphere in ground tests, with fatal results on Apollo 1. In the end after the Apollo 1 fire they compromised by starting with a 21% 1 atmosphere environment and then bleeding it down and replacing it with 100% O2 at reduced cabin pressure during launch and ascent.

The Soviets had larger boosters and coudl lauche the extra weight so they tended to stay with 1 ATA cabin pressure - but they also lost astronauts do to rapid decompression so that approach was not perfect either.

The space shuttle used a 1 ATA environment as weight was not that big an issue on an already grossly inefficient spacecraft with big strap on boosters. The normal shirt sleeve environment avoids the need to pre-breathe 100% O2 for several hours prior to the flight.

 

[Dr Deco]

The oxygen is present at low pressure and thus would not result in pulmonary oxygen toxicity. The addition of nitrogen was not possible because of weight constraints in the early NASA rockets. The earlier responders were correct in their comments.

 

[Gilldiver]

The space shuttle used a 1 ATA environment as weight was not that big an issue on an already grossly inefficient spacecraft with big strap on boosters. The normal shirt sleeve environment avoids the need to pre-breathe 100% O2 for several hours prior to the flight.

When you see the early guys heading to the launch with helmets on and carrying a generation set, they are on the 100% O2 and breathing down the nitrogen so that they don't get Bent in orbit. This is still a concern when doing a EVA as the suits are only pressurized to about 3 PSI. So, even on the shuttle and the station they have to breath down for a few hours prior to going EVA.

 

[Dr Deco]

Hi Readers:

The pressure in the EVA suit is low. It is, however, 4.3 psi. Going for the cabin to the suit is equivalent from going to the top of Mt Everest from sea level. At NASA, my job was to make the change as safe and efficient as possible.

 

[Gilldiver]

Hi Readers:

The pressure in the EVA suit is low. It is, however, 4.3 psi. Going for the cabin to the suit is equivalent from going to the top of Mt Everest from sea level. At NASA, my job was to make the change as safe and efficient as possible.

Don't you mean 'Going form the cabin to the suit is equivalent of going from sea level to the top of Mt Everest?'

You are going from 1 ATM to 4.3 PSI.

 

[DandyDon]

Either way, a helluva a change! Even without N2, there has to be a lot of allow for...!

The capsule atmosphere was at .2 ATA with 100% oxygen. Same oxygen level as earth.

So the cabin is around 3 psi?

Hi Readers:

The pressure in the EVA suit is low. It is, however, 4.3 psi. Going for the cabin to the suit is equivalent from going to the top of Mt Everest from sea level. At NASA, my job was to make the change as safe and efficient as possible.

And the EVA suit is a 4.3 psi, 43% higher? That's why going from the cabin to the suit, even tho only 1.3 psi change is still like coming down from great altitude...?

Why is the suit higher pressure? I need to look at the link give; hope I don't get lost.

 

[Gilldiver]

The shuttle and Station are at 1 ATM. The low pressure of 3 PSI given is for the early projects.

Decompression sickness in flight is not a new problem, it was a big concern for the WWII flyers.

Newswise Medical News | Professor Gives Historical Look at Physiology and WWII Air War

This is one of the reasons that in the US Army Airforces it was required to go on 100% O2 above 12,000 feet. Keeping conscious was another, but most can keep going without O2 to above 14 or 16,000 feet. By going onto 100% early they had a few minutes to breath down as the bomber streams kept climbing towards 20,000 feet and higher.

Fighter pilots who could be between 25,000 and the ground in a few minutes had more problems so were told to keep on the O2 all the time.