Oxygen Fires

from
http://astronautix.com/thisday/sepber10.htm#BORN

"1962 -
• Fire in a simulated Air Force space cabin Nation: USA.
Program: Apollo. Spacecraft: Apollo CSM.
• Fire broke out in a simulated space cabin at the Air
Force School of Aerospace Medicine, Brooks Air Force Base, Tex., on the
13th day of a 14-day experiment to determine the effects of breathing
pure oxygen in a long-duration space flight. One of the two Air Force
officers was seriously injured. The cause of the fire was not
immediately determined. The experiment was part of a NASA program to
validate the use of a 5 psia pure oxygen atmosphere for the Gemini and
Apollo spacecraft."


Yet the continued to use a pure oxygen atmosphere until Apollo1 five
years later?

--
Gareth Slee

Gareth Slee wrote:
from
http://astronautix.com/thisday/sepber10.htm#BORN

"1962 -
· Fire in a simulated Air Force space cabin Nation: USA.
Program: Apollo. Spacecraft: Apollo CSM.
· Fire broke out in a simulated space cabin at the Air
Force School of Aerospace Medicine, Brooks Air Force Base, Tex., on the
13th day of a 14-day experiment to determine the effects of breathing
pure oxygen in a long-duration space flight. One of the two Air Force
officers was seriously injured. The cause of the fire was not
immediately determined. The experiment was part of a NASA program to
validate the use of a 5 psia pure oxygen atmosphere for the Gemini and
Apollo spacecraft."


Yet the continued to use a pure oxygen atmosphere until Apollo1 five
years later?

--
Gareth Slee



From a 1964 NASA report:


Space-cabin atmospheres. part ii - fire and blast hazards a literature
review

Roth, E. M.
NASA Center for AeroSpace Information (CASI)
NASA-SP-48 , 19640101; Jan 1, 1964
Fire and blast hazards in space cabin atmospheres
Accession ID: 64N20744
Document ID: 19640010830

http://ntrs.nasa.gov/archive/nasa/ca...964010830..pdf


-Rusty

In article ,
Gareth Slee wrote:
"1962 -
• Fire broke out in a simulated space cabin at the Air
Force School of Aerospace Medicine, Brooks Air Force Base, Tex., on the
13th day of a 14-day experiment to determine the effects of breathing
pure oxygen in a long-duration space flight...
The experiment was part of a NASA program to validate the use of a 5 psia
pure oxygen atmosphere for the Gemini and Apollo spacecraft."

Yet the continued to use a pure oxygen atmosphere until Apollo1 five
years later?

They continued to use a pure oxygen atmosphere *in flight* -- that's the
5-psi atmosphere referred to -- throughout Apollo. There were important
reasons for this; it was not just some careless whim.

The conditions of the simulated cabin were not considered representative
of actual spaceflight or of actual space hardware. Most everyone
understood that there was some fire hazard associated with the in-flight
atmosphere, but the combination of free fall (suppressing convection) and
an effort to exclude ignition sources from the Apollo cabin was thought
sufficient to control the hazard. The issue was not ignored; serious
attention was given to fire hazards during planning.

Unfortunately, the combination of a poorly-run development process and a
steady stream of uncontrolled engineering changes undermined this
somewhat. There was much more flammable material in the cabin than had
originally been intended, and the already-optimistic goal of excluding
ignition sources was compromised by sloppy workmanship.

But the big flaw was simply that all the work on fire hazards had focused
on *in-flight* fires. Nobody thinking about fire prevention noticed that
Apollo testing and ground operations were being done with pure oxygen at
16 psi, which is *much* more dangerous than 5 psi, especially in 1 G.
(There were again real reasons for this choice of atmosphere, but people
would nevertheless have thought twice about it if the added hazard had
been noticed.)

After the fire, they *didn't* change the in-flight atmosphere, because the
technical reasons for pure oxygen there remained compelling. They did
change a fundamental assumption: ignition sources were now assumed to be
present, so fire could start, but it must not spread enough to be
dangerous. Flammable materials were eliminated wherever possible, and
drastically restricted if they could not be eliminated (there simply
weren't any non-flammable substitutes for some things). And after a lot
of effort, they ended up having to accept a different cabin atmosphere
(the suits still had pure oxygen in them) for ground operations, with a
transition to pure oxygen during ascent, because fireproofing the cabin
well enough for 16-psi oxygen just didn't end up being practical.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |

(Henry Spencer) writes:


After the fire, they *didn't* change the in-flight atmosphere, because the
technical reasons for pure oxygen there remained compelling. They did
change a fundamental assumption: ignition sources were now assumed to be
present, so fire could start, but it must not spread enough to be
dangerous. Flammable materials were eliminated wherever possible, and
drastically restricted if they could not be eliminated (there simply
weren't any non-flammable substitutes for some things). And after a lot
of effort, they ended up having to accept a different cabin atmosphere
(the suits still had pure oxygen in them) for ground operations, with a
transition to pure oxygen during ascent, because fireproofing the cabin
well enough for 16-psi oxygen just didn't end up being practical.

How did they avoid killing the crew with that 16psi pure O2?

ISTM there are lots of nasty side effects of too much O2...and
100% 16ps is way too much...
--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

David Lesher writes:
How did they avoid killing the crew with that 16psi pure O2?

ISTM there are lots of nasty side effects of too much O2...and
100% 16ps is way too much...

Oxygen toxicity at 16 psi of 100% O2 don't show up for quite some time
(12-16 hours). By then, they'd already be launched and running at
lower pressure (around 4 psi, IIRC).

--
Richard W Kaszeta

http://www.kaszeta.org/rich

In article ,
David Lesher wrote:
...they ended up having to accept a different cabin atmosphere
(the suits still had pure oxygen in them) for ground operations...

How did they avoid killing the crew with that 16psi pure O2?
ISTM there are lots of nasty side effects of too much O2...and
100% 16ps is way too much...

As witness hospital oxygen tents, breathing pure oxygen at around 1 atm
pressure for a little while is not grievously harmful. It's not something
you want to do for weeks on end if you can avoid it, but the Apollo crews
typically got it for only a few hours. (E.g., on a launch day, between
suiting up and the middle of ascent.)

They had to pre-breathe pure oxygen for a while before launch anyway, to
flush the nitrogen out of their bodies, since they were going to be
decompressing to 5 psi during ascent. (And might have to decompress
further, to suit operating pressure, in the event of (say) cabin damage
during initial docking with the LM.)
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |

On 11 Sep 2006 07:38:52 -0500, Richard Kaszeta
wrote:

ISTM there are lots of nasty side effects of too much O2...and
100% 16ps is way too much...

Oxygen toxicity at 16 psi of 100% O2 don't show up for quite some time
(12-16 hours). By then, they'd already be launched and running at
lower pressure (around 4 psi, IIRC).

Weren't they in their suits for launch, anyway?

Brian

Henry Spencer wrote:

After the fire, they *didn't* change the in-flight atmosphere, because the
technical reasons for pure oxygen there remained compelling. They did
change a fundamental assumption: ignition sources were now assumed to be
present, so fire could start, but it must not spread enough to be
dangerous. Flammable materials were eliminated wherever possible, and
drastically restricted if they could not be eliminated (there simply
weren't any non-flammable substitutes for some things). And after a lot
of effort, they ended up having to accept a different cabin atmosphere
(the suits still had pure oxygen in them) for ground operations, with a
transition to pure oxygen during ascent, because fireproofing the cabin
well enough for 16-psi oxygen just didn't end up being practical.



Thank you Henry for clearing up my misconceptions.

--
Gareth Slee

"Gareth Slee" wrote in message
. ..
Yet the continued to use a pure oxygen atmosphere until Apollo1 five
years later?

That's why they were no-smoking flights. With the pure oxygen added to the
excessive hydrogen in the water produced by the fuel cells...

That's the *real* cause of Apollo 13- with those harsh arc lights simulating
the sun, one of the stage hands lit up too close to the CM simulator, and
....

Brian Thorn wrote:
Weren't they in their suits for launch, anyway?

Remember, inside a cabin pressurized to 16 psi, any suit would be
pressurized to at least 16 psi as well (for comfort if nothing else),
and also at 100% oxygen--otherwise, why bother?

Also, IIRC the 16 psi was for a leak check, and was depressurized back
to 14.7 psi sea level pressure for launch.

John Charles
Houston, Texas