Atmosphere in Shuttle / Iss

OK, I've tried to understand exactly what the atmosphere in the Shuttle and
ISS is, but am presented with a bewildering set of figures....

I was wondering whether any of the assembled folk would care to explain the
pressure and make up and how much it differs from the Earth's and the
pressurisation in a typical high flying jet.

I was interested mainly because of the implications in a fire. I noted in
some reports from the Iss, for instance, that current spikes were seen from
a fan motor, which must mean, I'd say that its a brushed motor and that the
brushes/comutator are getting worn and probably sparking a lot!

Brian

--
Brian Gaff....
graphics are great, but the blind can't hear them
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"Brian Gaff" writes:

OK, I've tried to understand exactly what the atmosphere in the Shuttle and
ISS is, but am presented with a bewildering set of figures....

I thought it essentially an O2 and N2 mix at very nearly the mixture
and pressure found on Earth at sea level. Is this not the case?

Jeff
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Remove "no" and "spam" from email address to reply.
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"jeff findley" wrote in message
...
"Brian Gaff" writes:

OK, I've tried to understand exactly what the atmosphere in the Shuttle
and
ISS is, but am presented with a bewildering set of figures....

I thought it essentially an O2 and N2 mix at very nearly the mixture
and pressure found on Earth at sea level. Is this not the case?

It is. Especially on ISS they want to replicate it fairly close to
sea-level air-pressure. It makes experiments easier to control.

Also, you can rely on convection for cooling.

The shuttle will lower pressure to I think around 10psi before a spacewalk
to reduce pre-breath time for the astronauts performing the EVA.




Jeff
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Remove "no" and "spam" from email address to reply.
If it says "This is not spam!", it's surely a lie.

In article ,
jeff findley wrote:

"Brian Gaff" writes:

OK, I've tried to understand exactly what the atmosphere in the Shuttle and
ISS is, but am presented with a bewildering set of figures....

I thought it essentially an O2 and N2 mix at very nearly the mixture
and pressure found on Earth at sea level. Is this not the case?

Jeff

It is nominally (within a small range of variability) 20% O2, 80% N2 at
14.7 pisa. The next-highest levels of trace constituents are H20 vapor
and CO2, both of which are actively (and specifically) controlled. All
other trace gases (methane, some CO, ammonia, and more than a few
others) are actively reduced and controlled by the station ECLSS.

A standard commercial aircraft pressurization system will maintain the
aircraft at approximately 8,000 feet ASL-equivalent pressure.

--
Herb Schaltegger, Esq.
Chief Counsel, Human O-Ring Society
"I was promised flying cars! Where are the flying cars?!"
~ Avery Brooks

[what is] the pressure and make up and how much it differs
from the Earth's and the pressurisation in a typical high flying jet.


The air on the shuttle is kept close to sea level conditions on Earth,
with 14.7 pounds per square inch of pressure, and an oxygen/nitrogen
mixture that contains 21% oxygen.

I believe it's about the same on the ISS.

A high-flying commercial jet doesn't try to maintain sea-level pressure
(14.7 pounds) because the pressure differential would add strain to the
fuselage and would require a stronger, more expensive fuselage, so
they just pressurize it to what you'd find at an an altitude of 5,000 to
8,000 feet.


I was interested mainly because of the implications in a fire.

Fire is indeed a major concern on spacecraft. The most famous and
tragic incident was the Apollo 1 fire that resulted in the death of 3
astronauts while on a training exercise on the pad. But in that
instance, the capsule was pressurized to a much higher oxygen
content than normal (90% pure oxygen at over 16 psi, I think), causing
the fire to burn much more intensely than it normally would.

Another major incident was a fire on board the Mir space station. Although
downplayed by officials at the time, it was actually a very serious incident
and the astronauts and cosmonauts initially thought that they'd probably
have to abandon ship. Their fire extinguishers had little effect and dense
smoke filled the station, but the fire eventually burned out on its own.

Jim

Another major incident was a fire on board the Mir space station. Although
downplayed by officials at the time, it was actually a very serious incident
and the astronauts and cosmonauts initially thought that they'd probably
have to abandon ship. Their fire extinguishers had little effect and dense
smoke filled the station, but the fire eventually burned out on its own.

Jim


The problem was the fire was between the astronauts and their soyuz escape
craft. It was a very bad problem nd they were very lucky.

"Greg D. Moore \(Strider\)" wrote in message .. .
"jeff findley" wrote in message
...
"Brian Gaff" writes:

OK, I've tried to understand exactly what the atmosphere in the Shuttle
and
ISS is, but am presented with a bewildering set of figures....

I thought it essentially an O2 and N2 mix at very nearly the mixture
and pressure found on Earth at sea level. Is this not the case?

It is. Especially on ISS they want to replicate it fairly close to
sea-level air-pressure. It makes experiments easier to control.

Also, you can rely on convection for cooling.

Not in microgravity, you can't. Convection requires a gravity
field. Of course, you can still get cooling via conduction, and
fans can create airflow that makes it still more effective, but
strictly speaking, convection won't happen without gravity.

Jim Lovell talks about this in his "Lost Moon" book. When the
Apollo 13 astronauts were fighting cold, trying to sleep in the
CM, they could stay warmer by remaining as still as possible.
The air around them would be warmed by body heat, and with
no convection to carry it away, the warm layer would stay
right there. But any slight movement would disturb this
thin layer of warm air.

--Rich

On 18 Jul 2003 17:37:06 GMT, oSpam (HOST Comp
JimS) wrote:


I was interested mainly because of the implications in a fire.

Fire is indeed a major concern on spacecraft. The most famous and
tragic incident was the Apollo 1 fire that resulted in the death of 3
astronauts while on a training exercise on the pad. But in that
instance, the capsule was pressurized to a much higher oxygen
content than normal (90% pure oxygen at over 16 psi, I think), causing
the fire to burn much more intensely than it normally would.


Jim
IIRC, the atmosphere on Apollo 1 was 100% oxygen at 5psi. This was
maintained throughout the program, although it was changed for ground
testing.

Regards,

Bob Bernatchez

"Richard Cochran" wrote in message
om...

Not in microgravity, you can't. Convection requires a gravity
field. Of course, you can still get cooling via conduction, and
fans can create airflow that makes it still more effective, but
strictly speaking, convection won't happen without gravity.

Conduction is what I mean. :-)

"Bob Bernatchez" wrote in message
...
| On 18 Jul 2003 17:37:06 GMT, oSpam (HOST Comp
| JimS) wrote:
|
|
| I was interested mainly because of the implications in a fire.
|
| Fire is indeed a major concern on spacecraft. The most famous and
| tragic incident was the Apollo 1 fire that resulted in the death of 3
| astronauts while on a training exercise on the pad. But in that
| instance, the capsule was pressurised to a much higher oxygen
| content than normal (90% pure oxygen at over 16 psi, I think), causing
| the fire to burn much more intensely than it normally would.
|
|
| Jim
| IIRC, the atmosphere on Apollo 1 was 100% oxygen at 5psi. This was
| maintained throughout the program, although it was changed for ground
| testing.
|
| Regards,
|
| Bob Bernatchez
OK, so that would rule out the Apollo being used as a lifeboat on the Iss,
if that is so, and the Soyuz is used, does that imply that the Soyuz uses
the same pressurisation as the ISS? However, it cannot or the link up
between that Soyuz and Apollo who's anniversary we just went through, would
not have worked, would it?

Are you still with me?

Are we saying that the Soyuz can stand the pressure, but the Apollo could
not, or was the atmosphere just such a low pressure for weight reasons?

Brian

--
Brian Gaff....
graphics are great, but the blind can't hear them
Email:
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