Reconciling Martian and Terran environmental needs

[vicky_molokh]

Greetings, all!

So, long story short, our team decided to live on the same space station as the little dragons*. But there's a complication. All of our bodies are meant for a Terran environment (disregarding issues of gravity). The little dragons, OTOH, are Mars-Adapted without the ability to handle a Terran environment. Specifically, the limits of their zone of comfort are 0.6 bar of pressure and +10°C / 283K / +50°F (degrees Fahrenheit). Sure, we have a sealed compartment where we can keep a Terran atmosphere for complete comfort, but we'd rather prefer to be able to share the rest of the station with them too, without denying either the humans or the dragons the ability to fly around without a vacc suit. There are two sides to reconciliation, and I have some doubts and ambiguities about both.

1. A mid-way environment.
The default Martian atmosphere has either 0.4bar, and one of: 45% carbon dioxide, 27% oxygen, 21% nitrogen, 2% argon, 5% other; OR 75% CO2, 15% O2, 5% N2, 2% Ar, 3% others.
That puts partial oxygen pressure at somewhere between 0.1 bar absolute and 0.06 bar absolute. Luckily, the dragons are okay with reducing CO2 and upping O2 to human levels. The question is, how much? The total atmospheric pressure pretty much has to be set to 0.6 bar, which counts as Thin for us, but as still okay for them. For us, a Thin atmosphere means a -1 to Vision, +1 to FP costs, and rolls for altitude sickness if we stay for 60+ minutes in the low-pressure section of the base. But that's assuming an Earthlike percentage of O2, i.e. about 21% of total pressure, which amounts to a partial pressure of 0.126 bar absolute. But this can be upped.

(Edit: we can lower CO2 to human levels, so it's not an issue.)

What are the nuances of upping partial pressure of O2 in a low-pressure atmosphere?
GURPS says that 0.8 bar at Earthlike composition, or 0.168 bar absolute partial pressure of O2 specifically, is the lower range of the human-normal O2 level. Wikipedia lists 0.16 bar absolute as the lower okay limit of partial pressure. So, should upping the partial pressure to this level (thus resulting in about 27% oxygen) get rid of the altitude sickness, the FP cost, and the Vision penalty? Or will the Vision penalty stay? Is such a relative percentage of O2 okay, or does it have some sort of threat?

Luckily, the human temperature zone in GURPS is considered to reach as low as 2°C / 275K / 35°F (degrees Fahrenheit). I guess it's somewhat (by about 10°C) optimistic, but hey, maybe it just assumes the humans are northerners - after all, it puts the upper human limit at 32°C / 305K / 90°F (degrees Fahrenheit), which seems pessimistic by almost the same 10°C.

2. Biomodification.
Full-scale biomodification is mostly out of the question: they're built such that we can't grant them temperature tolerance at all, and lung modifications would only expand their zone of comfort by 0.2 bar at most. They've also been through some other major trauma recently, so we're disinclined to put them through anything stressful at all.
Likewise, none of us is inclined to install the full Mars-Adapted biomod. First, there's the issue of straining points (we're trying to mostly avoid Mutable Point Totals), but also of monetary costs and recovery times. Also, Low-Pressure Lungs are sort of nasty when used in 1-bar atmo.

Now, Pressure-Tolerant Lungs (Perks, p.11) are totally awesome, since the perk allows a human to treat Thin atmospheres as Normal, but Normal as Normal too, all things being equal. Which is awesome, since it seems to solve the partial pressure problem all on its own. But this Perk was published waaaay later than all of THS biomods, or even the 4e Bio-Tech biomods. So I'm unsure if it's possible to get it, and how. Yes, I know it's borderline useless for a real Martian atmosphere, but for the midway environment, it seems like a perfect fit. Do you think it's an available biomod in THS, and should it be a difficult one if it is?

Thanks in advance!

* == a curiosity of a bioengineering design.

[gjc8]

Well, worst comes to worst you don't need full vacc suits. You can get by with just a respirator even on Mars.

I believe that altitude sickness (in humans) is caused by insufficient oxygenation, so if the dragons can tolerate a sufficiently high ppO2, I think that solves most of your problems, though as maybe not the vision penalty.

[Anthony]

Your mid-way environment would be toxic to humans; we can't handle more than a few percent CO2. You'll basically need the humans to be using a breathing mask and insulated clothing, and mucous membranes (such as the eyes) probably shouldn't be exposed due to formation of carbonic acid. If you're willing to wear goggles, a breathing mask, and an insulated suit, that should be adequate to handle the default Martian atmosphere (a standard smartsuit can provide all three).

[vicky_molokh]

Originally Posted by Anthony

Your mid-way environment would be toxic to humans; we can't handle more than a few percent CO2. You'll basically need the humans to be using a breathing mask and insulated clothing, and mucous membranes (such as the eyes) probably shouldn't be exposed due to formation of carbonic acid. If you're willing to wear goggles, a breathing mask, and an insulated suit, that should be adequate to handle the default Martian atmosphere (a standard smartsuit can provide all three).

Oh, sorry, I didn't make it clear: we can reduce CO2 to human levels, replacing it with Nitrogen or whatever.

[vicky_molokh]

Originally Posted by gjc8

I believe that altitude sickness (in humans) is caused by insufficient oxygenation, so if the dragons can tolerate a sufficiently high ppO2, I think that solves most of your problems, though as maybe not the vision penalty.

Sure, they can handle it just fine, GM said it's not an issue. The question is whether having a higher-than-normal percentage of O2 (while maintaining human-normal partial pressure) has any adverse effects, threats etc.?

[gjc8]

Originally Posted by vicky_molokh

Sure, they can handle it just fine, GM said it's not an issue. The question is whether having a higher-than-normal percentage of O2 (while maintaining human-normal partial pressure) has any adverse effects, threats etc.?

Small degrees of oxygen enrichment (increasing the fraction by ~5%) in enclosed spaces have been studied as a treatment for conventional altitude sickness, and the hazards I've seen mentioned are loss of acclimatization to altitude when the subject does have to work outside, rather than oxygen toxicity. There's a mention here of workers at a high-altitude telescope facility using 27% oxygen fraction for a prolonged period (though not 24/7; they commute from lower altitude residences) without mention of adverse consequence. And I know that, in medical circumstances, there's routine use of oxygen enrichment as long as the fraction is less than 0.5.

I think it's probable that .6 bar atmosphere with 30% oxygen fraction won't result in adverse consequences, even over a long period, at least if the humans sleep in a regular atmosphere. Although, for acclimatization purposes, their "regular" atmosphere should aim for about the same .18 ppO2, so about .85 bar, which is the equivalent of about 1500 m in altitude on Earth (around Denver, Colorado).

[Anthony]

Originally Posted by vicky_molokh

Oh, sorry, I didn't make it clear: we can reduce CO2 to human levels, replacing it with Nitrogen or whatever.

That's surprising; it's enough to affect the ph of the blood. In any case, the main problem with an enriched oxygen low pressure atmosphere is that it's a fire hazard, it's otherwise human breathable.

[gjc8]

Originally Posted by Anthony

That's surprising; it's enough to affect the ph of the blood.

IRC, Mars-adapted parahumans have no issues with low CO2 atmospheres.

[vicky_molokh]

Originally Posted by gjc8

IRC, Mars-adapted parahumans have no issues with low CO2 atmospheres.

Correct, but the little dragons were assembled differently, and modifying them isn't exactly feasible (at the moment, anyway). They're not human at all. We're still investigating what they were based on. Extreme xeno-mix or even heavily synthetic DNA aren't exactly out of the question.

[vicky_molokh]

Originally Posted by Anthony

That's surprising; it's enough to affect the ph of the blood. In any case, the main problem with an enriched oxygen low pressure atmosphere is that it's a fire hazard, it's otherwise human breathable.

Thanks, this is exactly the sort of thing I was wondering about. Is there a way to measure the level of this fire hazard based on oxygen content? (I'm assuming you mean specifically the %, since partial pressure is no higher than normal.)

Also, what's so surprising about being able to lower CO2 to human-acceptable levels?