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-   -   How is Spaceshuttle pressurised? (https://www.pprune.org/tech-log/318054-how-spaceshuttle-pressurised.html)

chornedsnorkack 14th March 2008 19:47

ISA at tropopause (11 km) is about 220 mb. If you filled your plane with pure oxygen, you could fly unpressurized to FL370 or above (how high?)

moggiee 15th March 2008 01:05


Originally Posted by mgTF (Post 3978060)
but how can they seal the ship? and why our planes compared to, look more like swiss emmental?

Very good seals and strong locks/latches.

There are also fewer holes built into it in the first place - aeroplanes have basin drains, outflow valves, lots more doors and hatches unlike spacecraft which are more like a baked bean tin with a single door in.

To be brutally honest, I would have thought it was obvious! :)

mgTF 15th March 2008 11:46

here's another question,
how does it work when they go outside for a walk, is there a sort of mini room with a vacuum system preventing internal air to dispel outside?

wiggy 15th March 2008 12:40

There have been some good replies here but the answer to most of this can be best found on the NASA shuttle pages... try typing "Space shuttle" into Google and then going into the NASA pages - I think, mgTF, that 'external airlock" might be the answer to your question.

moggiee - to be brutally honest I agree:ok:, I'm just trying to be kind:O

B Fraser 15th March 2008 12:48


If you filled your plane with pure oxygen, you could fly unpressurized to FL370 or above (how high?)
You would have to pre-breath neat O2 for a couple of hours beforehand and all the way up to altitude until your body was free of nitrogen. Decompression sickness can ruin your whole day.

Tinstaafl 15th March 2008 14:36

Capster, the change in pressure is not that high. Rather less than what your car tyres have to hold.

Your car's tyre is at something like 50 psi total pressure - more after a long drive when the tyre has been heated by friction - the atmosphere around it is at ~15 psi (slightly less & variable so rounded for convenience) so the tyre's difference is ~35 psi. That 35 psi (or 32 or whatever you usually inflate your tyre to) is what we usually think of when we think about how much pressure the tyre holds. We tend to forget this measurement is relative to the atmosphere, not absolute.

Meanwhile, both relatively & absolutely, the shuttle's interior is held at 14.7 psi, the exterior is at 0 psi (near enough) so the difference is......14.7 psi!

moggiee 15th March 2008 15:02


Originally Posted by mgTF (Post 3980468)
here's another question,
how does it work when they go outside for a walk, is there a sort of mini room with a vacuum system preventing internal air to dispel outside?

You don't watch enough telly!

UFO, Space 1999, Star Wars, 2001, Alien, Solaris etc. - any of those will give you your answer.

Tinstaafl 15th March 2008 16:31

You must mean they have teletransporters to beam them outside, Moggiee! Amazing. I mean, how else could it be done? :8

rsuggitt 15th March 2008 20:21

In a word, airlocks.

TURIN 15th March 2008 21:31


In a word, airlocks.
There's no need for that sort of language. :)

moggiee 15th March 2008 22:08


Originally Posted by Tinstaafl (Post 3980953)
You must mean they have teletransporters to beam them outside, Moggiee! Amazing. I mean, how else could it be done? :8

Transporters are "Star Trek" and "Blake's 7" - all my references are clearly airlock users!

james ozzie 16th March 2008 11:12

Breathing pure oxygen
 
Although a pure oxygen atmosphere allows lower cabin pressure & and solves lots of engineering problems, the fire hazard gets way too high. The deadly Apollo 1 launch pad fire ended pure oxygen cabins. By the way, track down (Wiki) the transcript of Flight Director Gen Kranz's address to the team after the accident - an excellent speech that is as good and relevant today as it was 40 years ago.

wiggy 16th March 2008 22:56

james ozzie
 
"The deadly Apollo 1 launch pad fire ended pure oxygen cabins"...Er, no it didn't, or at least not immediately - all the subsequent Apollo missions flew, manned, with pure Oxygen enviroments. What did stop post Apollo 1, amongst other things, was the procedure of pumping the Cabin up to greater than 15 psi with pure Oygen pre-launch ( Or in Apollo 1's case, a launch rehearsal). That, procedure, plus the uncontrolled spread/use of infalammable material in the Command Module (e.g. velcro), played a major part in the spread of the fire in Apollo 1.

ShyTorque 16th March 2008 23:16


baked bean tin
I thought baked beans were a banned substance on all space flights. :ooh:

hedgehopper 17th March 2008 20:20

Parp:

Pardon me...

Capt Pit Bull 17th March 2008 20:46

I'd like to take this opportunity to recommend the HBO series 'From the earth to the moon', (one episode of which, incidentally, cover the Apollo 1 accident.)

I found this to be a very interesting, well made and also deeply moving series and an absolute must for anyone interested in space flight. Each episode considers different aspects of the Gemini and Apollo programmes.

BTW I don't get a cut from HBOs DVD sales, though perhaps I ought to!

pb

chris weston 17th March 2008 21:07

Lithium compounds
 
I'm pretty sure its Lithium Peroxide not Hydroxide that's used as the peroxide scrubs to the carbonate and oxygen in 2:1 redox stoichiometry.

The Hydroxide simply neutralises to the carbonate.

Forgive the lack of subscripts and yes I know it's ionic really but it goes like this

2Li2O2 + 2CO2 = 2Li2CO3 + O2

cf

Li(OH)2 + CO2 = LiCO3 + H2O


CW

chris weston 17th March 2008 21:11

An unbalanced posting
 
Try

2LiOH + CO2 = Li2CO3 + H2O

Clicked too fast

Sorry pardon

CW

Spanner Turner 18th March 2008 00:50

From Space Shuttle Reference Manual (available at NASA website),


The cabin air from the cabin fan is ducted to the two lithium hydroxide canisters, where carbon dioxide is removed and activated charcoal removes odors and trace contaminants. An orifice in the duct directs a specific amount of cabin air through each lithium hydroxide canister. The canisters are also located under the middeck floor. They are changed alternately every 12 hours through an access door in the floor. For a flight crew of seven, the lithium hydroxide canisters are changed alternately every 11 hours. Replacement canisters are stored under the middeck floor between the cabin heat exchanger and water tanks.


:ok:

Wyle E Coyote 18th March 2008 01:16

This'll keep the boys and girls happy,


......activated charcoal removes odors and trace contaminants
"change the filter lads, it baked beans tonight"


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