Reduced Atmospheric Pressure Query

[Kilgs]

One of the interesting things in Jovian Chronicles is that all orbitals and vessels maintain a standard atmosphere of 34 kilopascals (0.335 standard atm). There are no inert gases so Oxygen is at 24kp and nitrogen is the remaining 10kp.

Is this valid? The pressure is lower but all of the components are present. I don't do science so I'm appealing to you folks...

 

[Vladika]

The only thing that matters, to a human, is the oxygen. At that percentage, even at 1/3 atmosphere, it should be enough, though the breathing might feel "thin".

As an aside, 100% oxygen is poisonous to humans, and death will usually occur in 24 hours. This is significant to scuba divers, at 5 atmospheres, as the oxygen content of compressed air is an equivalent of 100%, though the "mix" is still 20/80.

The replacement of helium for nitrogen is for other reasons, not pertinent to the topic here, but of possible interest nonetheless.

 

[Timerover51]

One of the interesting things in Jovian Chronicles is that all orbitals and vessels maintain a standard atmosphere of 34 kilopascals (0.335 standard atm). There are no inert gases so Oxygen is at 24kp and nitrogen is the remaining 10kp.

Is this valid? The pressure is lower but all of the components are present. I don't do science so I'm appealing to you folks...

I have not read the Jovian Chronicles, but at that atmospheric pressure, cooking is going to be a problem as water is going to boil at a much lower temperature than at normal Earth surface pressure, which I know as 14.7 pounds per square inch. Microwaving food with a high water content may result in steam explosions. The pressure equates to about 8000 meters in altitude or a bit over 26,000 feet. Water will boil at about 74 degree Celsius and 166 degrees Fahrenheit.

That is not a good atmosphere from a fire standpoint either.

 

[Kilgs]

That is not a good atmosphere from a fire standpoint either.

Interesting... an added side-benefit for orbital living? Safety first, colonists!!

 

[McPerth]

One of the interesting things in Jovian Chronicles is that all orbitals and vessels maintain a standard atmosphere of 34 kilopascals (0.335 standard atm). There are no inert gases so Oxygen is at 24kp and nitrogen is the remaining 10kp.

Is this valid? The pressure is lower but all of the components are present. I don't do science so I'm appealing to you folks...

Never thought about it, but remember what inflates the lungs is athmospheric presure against the vaccum produced by the diafragma (and other muscles) movements. I'm not sure if this presure would be enough to overcome the lungs' elasticity and inflate them...

This aside, for the same reasons Timerover51 tells, I guess it will produce more evaporation of liquids, so drying the mucoses (most notable eyes, nose and mouth). While this would probably not be harming, it will be at least uncomfortable for unprotected people...

 

[Zutroi]

Never thought about it, but remember what inflates the lungs is athmospheric presure against the vaccum produced by the diafragma (and other muscles) movements. I'm not sure if this presure would be enough to overcome the lungs' elasticity and inflate them...

This aside, for the same reasons Timerover51 tells, I guess it will produce more evaporation of liquids, so drying the mucoses (most notable eyes, nose and mouth). While this would probably not be harming, it will be at least uncomfortable for unprotected people...

That shouldn't be an issue... Mercury and Gemini vehicles ran a pure oxygen atmosphere at 0.34 bar pressure.

 

[Spinward Scout]

That shouldn't be an issue... Mercury and Gemini vehicles ran a pure oxygen atmosphere at 0.34 bar pressure.

Yes, but Mercury and Gemini were manned by Military personnel who were in excellent physical condition. Anyone who has any lung capacity problems would start to have a problem with the lowered air pressure and possibly end up with the symptoms of altitude sickness.

EDIT: Of course when you are talking rpg characters, it would probably effect a character with a lower than average stamina/endurance (I can't remember what Jovian Chronicles calls it).

 

[Timerover51]

Thinking further about the implications of a lower boiling point of water, you would also have an increased risk of disease from inadequately sanitized cooking and eating utensils.

Also, as indicated, for some people, altitude sickness is going to be a problem regardless of the adequate oxygen supply.

 

[Carlobrand]

That shouldn't be an issue... Mercury and Gemini vehicles ran a pure oxygen atmosphere at 0.34 bar pressure.

Ho!! Pure oxygen atmosphere's what killed the Apollo 1 team! Stuff doesn't behave the way you're used to in that kind of setting - in fact, they seem downright eager to burn.

 

[aramis]

Ho!! Pure oxygen atmosphere's what killed the Apollo 1 team! Stuff doesn't behave the way you're used to in that kind of setting - in fact, they seem downright eager to burn.

It only became a major problem during the pressure test to 1 atm...

 

[Carlobrand]

An O2 atmosphere fire took the lives of two airmen and a bunch of test rabbits in a research facility. Pure O2 at half an atmosphere:

http://news.google.com/newspapers?n...apVAAAAIBAJ&sjid=J-EDAAAAIBAJ&pg=4871,6525686

Mishap 6 (Page 157) in this study is of interest. Hypobaric chamber studying effects of a low pressure environment, pure oxygen at a third of an atmosphere. A spark triggered a fire that spread to the men's clothes. An asbestos safety blanket, used to try to smother the fire, itself caught fire. Mishap 9 (Page 158) recounts the death of the two airmen with the rabbits noted above.

http://c.ymcdn.com/sites/membership.../safety_docs/hyperbaric_and_hypobaric_cha.pdf

Pure oxygen is not the only threat. You can get some radically increased odds of combustion and burn rates just by doubling the partial pressure. Fire safety code for storage of oxygen containers requires some sort of ventilation to prevent O2 build-up in the room being used to store the oxygen, and of course warning signs.

This industry training PDF instructs (Page 11) that O2 values above 23.5% should be considered dangerous.

http://www.asiaiga.org/docs/AIGA 005_10 Fire hazards of oxygen and oxygen enriched atmospheres.pdf

Something from a book on Google - the table on page 146 illustrates the increased flame spread rate in three materials as a function of volume of oxygen at 1 atmosphere.

http://books.google.com/books?id=wa...ge&q=oxygen percentage increased fire&f=false

Strikes me that a rather nasty way to kill someone in space is to adjust the O2 feed in his room to enrich the room air and then introduce an ignition source.

 

[JimMarn]

Ho!! Pure oxygen atmosphere's what killed the Apollo 1 team! Stuff doesn't behave the way you're used to in that kind of setting - in fact, they seem downright eager to burn.

I've watched a documentary on this fire. Many of the materials used in Apollo 1 were not treated with fire retardant. They would have caught fire under normal oxygen levels. The other problem is when the material burned, toxic fumes came off.

The investigation uncovered this, and is one of the reasons it took so long for the next Apollo capsule to be built. Materials are now designed to not spread a fire, nor to catch fire easily.

 

[savage]

Strikes me that a rather nasty way to kill someone in space is to adjust the O2 feed in his room to enrich the room air and then introduce an ignition source.

Perhaps if you're trying to destroy the ship. Environmental control must have redundant alarms by TL11 to minimize these disasters. There are too many risks allowing damage to a ship from an improper air mixture.

 

[Carlobrand]

Perhaps if you're trying to destroy the ship. Environmental control must have redundant alarms by TL11 to minimize these disasters. There are too many risks allowing damage to a ship from an improper air mixture.

Nah, I'm sure we could restrict it to the area defined by the bulkheads. Probably. :devil:

One presumes, if you're trying to kill someone, can get that kind of access to life support controls, and are choosing that method over any of several less dramatic methods, that you can also disable whatever alarms or safeties may exist and don't particularly care about the fate of others in the area or the ship as a whole. Which most likely makes you a rather sophisticated assassin or terrorist with both good technical skills and very good clandestine skills - who plans not to be aboard when it happens.

 

[savage]

Nah, I'm sure we could restrict it to the area defined by the bulkheads. Probably. :devil:

One presumes, if you're trying to kill someone, can get that kind of access to life support controls, and are choosing that method over any of several less dramatic methods, that you can also disable whatever alarms or safeties may exist and don't particularly care about the fate of others in the area or the ship as a whole. Which most likely makes you a rather sophisticated assassin or terrorist with both good technical skills and very good clandestine skills - who plans not to be aboard when it happens.

A sophisticated assassin has many more delicate methods of assault.

If we look at yachts, ships, even houses,office building, and the modern submarine the typical HVAC-type systems provide air for an entire environment not a specific room. Now in the case of research centers rooms may have their own system, but it is not feasible for a typical free trader to implement a design that sends air from the central system to each specific room. Same thing with fire and structural sheer walls. Most of the interior cabin walls will not be structured. Sabotage of the air mix system to induce flash fire will take out a portion of the ship. An architect should have independent backup monitors all over the place to look for oxygen or CO2 build up.