At what altitude would kerbals need oxygen?

[Tanner Rawlings]

A while ago I made a post about naming and climbing the tallest mountain on Kerbin (Mt. Kraken was chosen as the name), and it got me thinking, if you did all the math, at what altitude would a Kerbal need his own oxygen supply? I will start to do the math and post it as i complete it, but feel free to correct or hand out your own calculations, opinions or sites that may help, sorry if this is a weird post but i like making post that require a community effort !

Results:

Assuming kerbals need the same amount of oxygen as humans, they would need supplemental oxygen (if hiking or climbing a mountain) around 38 kPa (like humans) so instead of doing calculations and stuff, i did the testing in the most kerbal way possible, strapping a barometer to a srb and sending it straight up, at ~4,700m the pressure reached .38 atm (38 kPa) so, after 4,700m it is safe to assume that kerbal would need oxygen, but they can survive past that as have many humans have climbing mount Everest with out oxygen

(Mt Kraken Thread)

http://forum.kerbalspaceprogram.com/threads/51607-Highest-Mountain-on-Kerbin

Edited June 11, 2014 by Tanner Rawlings

[magnemoe]

Well mount everest is 0.3 bar, 15 km is the limit for only breathing oxygen, think that is around 0.1 bar.

[Kasuha]

Kerbals are wearing spacesuits all the time so they obviously have oxygen all the time. Or whatever gas they need to breathe if they breathe at all.

Since very little is known about Kerbal metabolism I'm afraid your question cannot be answered. We can only answer theoretical question at which height humans would need oxygen masks on Kerbin.

On Earth humans usually start needing oxygen at 2500 m altitude at which the atmospheric pressure is about 75 kPa. On Kerbin with its atmospheric characteristics that corresponds to approximately 1440 m.

[Jouni]

Several cities have airports at over 3.5 km, which corresponds to about 2.1 km on Kerbin. Many people flying there directly from sea level suffer from altitude sickness, but it's usually not serious.

The highest altitude to which humans can acclimatize permanently is around 5 km (2.9 km on Kerbin). If you fly directly to that altitude, there's a high risk of serious consequences, and possibly death.

Even the best mountaineers can stay only for a couple of weeks above 7 km (4.1 km on Kerbin). The human body doesn't recover that well anymore, and sleeping is difficult.

The "death zone" begins at around 8 km (4.7 km on Kerbin). People can't survive there for more than a couple of days without supplementary oxygen. Recovery is basically nonexistent, and the body shuts down unnecessary functions, such as digestion.

Passenger jets usually fly at 10-12 km (5.9-7.1 km on Kerbin). If the cabin is depressurized, people are advised to put on their own oxygen masks first before helping others, because there may not be time to do it the other way.

[Seret]

On Earth humans usually start needing oxygen at 2500 m altitude

Thereabouts. Night vision is affected more than day vision, you'll lose some even well under that altitude without oxygen.

[Jesrad]

Well mount everest is 0.3 bar, 15 km is the limit for only breathing oxygen, think that is around 0.1 bar.

Close enough, the actual figure for humans is 160 mBar

However I still believe Kerbals do photosynthesis and only need sunlight.

[teal'c]

Close enough, the actual figure for humans is 160 mBar

However I still believe Kerbals do photosynthesis and only need sunlight.

Well technically they'd need CO2 for photosynthesis as well. (And water)

[Jesrad]

Yeah but that's OK, all that stuff is within the Kerbal already, they're pretty much walking, rocket-riding, sentient ecospheres on their own. That's how they survive being stranded a couple centuries in complete vacuum.

I guess that makes them lichen-shrimps of sorts.

[MR4Y]

Well, consider the fact that Kerbals don't have noses. They either breath by their skin or some sort of similiar mechanics. Considering their big heads and small body, they probaby don't possess a very high lung capacity.

One can suggest that Kerbals are plant based life forms.

[Javster]

Personally I think that the "thick" section of the atmosphere meter is where Kerbals can breathe, so up to 10000m, they don't need oxygen.

[Jouni]

On Earth humans usually start needing oxygen at 2500 m altitude at which the atmospheric pressure is about 75 kPa.

Supplemental oxygen is rarely used below about 8 km, except in medical emergencies and other special situations. It's sometimes used when people have to ascend quickly to a high altitude, such as in the train to Tibet. Even then almost all people stop using the oxygen, when they reach the destination.

[ThinkOutsideTheHangar]

Guys, shouldn't this be in the Science Labs, where all the nerds are?

[Soda Popinski]

Guys, shouldn't this be in the Science Labs, where all the nerds are?

Shhh. This is KSP. The nerds are everywhere.

[TheDataMiner]

On Earth humans usually start needing oxygen at 2500 m altitude at which the atmospheric pressure is about 75 kPa.

I've climbed mountains much higher then this without even the slightest hint of altitude sickness and I know that there are plenty of people that live well above this altitude.

[Franklin]

Well, consider the fact that Kerbals don't have noses. They either breath by their skin or some sort of similiar mechanics.

Like, their mouths?

[problemecium]

Given my hypothesis that Kerbals are aquatic, they need a supplemental air supply at 0 meters, i.e. anywhere outside the water. Indoors they can adjust the atmosphere to their liking.

[MR4Y]

Like, their mouths?

Have you even seen any life form with a mouth and no nose?

[NoPanShabuShabu]

Have you even seen any life form with a mouth and no nose?

I've a got Mr. Bob Kerman here who'd like to have a word with you.

[LethalDose]

Well, even assuming the little green maniacs use aerobic respiration based on Oxygen and the Kreb's cycle and anything we know about life on Earth is applicable to life on Kerbin.

*breath*

there's also the issue that smaller life forms tend to require more energy/mass than larger life forms (basal metabolic requirements scale as a function of surface area, not volume). So even though they're smaller and require overall less O2/min, they require more O2/kg/min, and therefore need to move the O2 in more efficiently and hence would be more sensitive to low atmospheric oxygen concentrations.

Fun fact, It's thought that this is at least part of the reason why whales evolved to be so large on Earth: Their increased size leads to lower metabolic rates, which lets them stay submerged longer.

Anyway, Kerbin's thicker atmosphere may compensate for the larger O2 requirement. Or maybe it doesn't if the atmospheric density drops off faster than it does on Earth.

And again, this all assumes everything I said above.

[Tanner Rawlings]

assuming that kerbals need about the same oxygen as humans (about 17% minimum) or about 38 kPa (death zone begins here) ive decided to screw calculations and just send a press barometer on a srb and see at which altitude the pressure reaches 38 kpa

EDIT

i sent it up and the barometer reached .38 atm (38 kPa) at around 4700m so if a kerbal wanted to climb Mt. Kraken they most likely would want to have oxygen (they can do it with out it)

Edited June 11, 2014 by Tanner Rawlings

[Guest]

I think kerbals can't survive outside of their spacesuits. They always have it on...perhaps it is part of their body.

[Lazro]

Well, consider the fact that Kerbals don't have noses. They either breath by their skin or some sort of similiar mechanics. Considering their big heads and small body, they probaby don't possess a very high lung capacity.

One can suggest that Kerbals are plant based life forms.

I actually think that Kerbals are basically sponges with green skin. My pet theory is that their huge heads contain lots of air pockets, which they can use to store oxygen and that that spongy casing protects other vital organs they have in their heads. Not only does this allow them to go for a good long while without apparently breathing (as they so often do) this also explains why they're so resilient falling on their heads-their sheer sponginess protects them from falls.

[NERVAfan]

On Earth humans usually start needing oxygen at 2500 m altitude at which the atmospheric pressure is about 75 kPa. On Kerbin with its atmospheric characteristics that corresponds to approximately 1440 m.

Some people certainly have trouble at that altitude -- that's why passenger jet cabins (FAA rules, anyway, IIRC) aren't allowed to be depressurized below the equivalent of 8000 ft. (which is ~ 2400 m) -- but I don't think people "usually" start needing supplemental oxygen that low, at least not for short trips. Certainly I've been higher than that and not needed anything special, and I'm not super-athletic or anything.

(That's about the altitude of Machu Picchu, which lots of people visit. Pikes Peak is over 4000 meters.)

I think altitude tolerance is pretty variable among people though.

Anyway, Kerbin's thicker atmosphere may compensate for the larger O2 requirement. Or maybe it doesn't if the atmospheric density drops off faster than it does on Earth.

Kerbin's atmosphere isn't actually more dense, it has the same sea level pressure at the same gravity. The game's placeholder drag model just calculates a fake "cross-sectional area" based on mass, and uses a massively too high value of 8 square meters per ton.

And the atmospheric pressure does drop off faster, Kerbin's atmosphere scale height is 5 km while Earth's is 8.5 km (according to this NASA site)

[Jouni]

Some people certainly have trouble at that altitude -- that's why passenger jet cabins (FAA rules, anyway, IIRC) aren't allowed to be depressurized below the equivalent of 8000 ft. (which is ~ 2400 m) -- but I don't think people "usually" start needing supplemental oxygen that low, at least not for short trips. Certainly I've been higher than that and not needed anything special, and I'm not super-athletic or anything.

The Wikipedia articles on altitude sickness and similar topics are quite good:

http://en.wikipedia.org/wiki/Effects_of_high_altitude_on_humans

http://en.wikipedia.org/wiki/Acute_mountain_sickness

Some significant altitudes:

• Athletic performance and endurance begin to suffer at 1000-1500 m.
  
• Some particularly susceptible people may get altitude sickness already at 2000 m.
  
• At 2100 m, the oxygen saturation of blood starts to drop significantly.
  
• Most people can ascend to 2400 m without any problems. Beyond that, syptoms of altitude sickness may manifest 6-10 hours after the ascent.
  
• There is a rule of thumb in high altitude hiking that you should start paying attention to the altitude above 3000 m.
  
• The highest major cities are at around 4000 m.
  
• The highest permanent settlements are at around 5000 m.
  

[KerbMav]

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Thank you, all the motivation I still needed ... I am going hiking for two weeks on Corsica in a few days!