Any scubadiver or biochemist to help me with my sci-fi setting?

[Turanil]

Ah the weird question!

So my problem is: I am still working on my sci-fi setting, and there is a few Earth-like planets, with humanoid species. However, I really don't like when some spacefaring dude lands on an unknown planet, and it's the same gravity, climate, atmospheric pressure, and breathable air as in California or Europe. I wanted to tweak that ludicrous staple of science fiction.

So I have a few humanoid races (humans and near-humans) who were seeded on various planets ages ago by "The Ancients". As such, those planets are very similar to Earth, but nonetheless DIFFERENT. It's hard sci-fi not Star-Wars! Hence, I wanted to have different gravity, different atmospheric pressures, and different air composition. As such, I got a look at some Scuba-Diving websites to get info, but I have difficulties to extrapolate. It's the reason I would like to ask anyone around with scientifical knowledge, or used to breathing problems of Scuba Diving, to help me create different rpg planets that would retain some verisimilitude. Thus:

Earth: has a gravity of 1 G; pressure of 1 atmosphere; and air of 20% Oxygen and 79% Nitrogen.

Mars: has been terraformed, and has now 0.38 G; 0.5 atmospheric pressure; and air with less dioxide of carbon, but well...

Planet-3: I want an heavy atmosphere for a heavy gravity world (around 1.3 to 1.5 G). Since the planet is far from sun, it would be cold, but heavy atmosphere makes a greenhouse effect, thus retains heat (by the way it is a dim and foggy sky of red color). Plus greater size and heavier gravity give more volcanism, and thus more gases into atmosphere. Hence I was seeing something like a 3 atmospheric pressure. However, how would fare non-native humans there? And how would fare native from this world when on Earth? Ideas about air composition?

Planet-4: I want a bigger but less dense planet as Earth. So 1,1 G; I was thinking of 1,3 atmospheric pressure; I don't know for air: what to have humans and the heavy-world native live without equipment there? Otherwise, it's a world with an elliptic orbit, so summers are insufferably hot, and nothing live in the deserts; sky is pale green.

Thanks for your response, if per chance you are able to give me some insight on this subject.

Okay, I know that i am making my life difficult for no real reason here, but...

 

[diaglo]

isn't that superman i see.

 

[Thanee]

There are some quite realistic (as far as that goes) sci-fi settings out there, like Traveller, which might be a good source of information. GURPS has some good sourcebooks, too, I've heard.

Bye
Thanee

 

[Turanil]

There are some quite realistic (as far as that goes) sci-fi settings out there, like Traveller, which might be a good source of information. GURPS has some good sourcebooks, too, I've heard.

I have most d20 sci-fi games. Traveller 20 has some abstract tables to create planets, but nothing that would answer my (hopeless?) questions. I also have GURPS Transhuman space, who goes for realistic descriptions, but also no answer to my question there.

isn't that superman i see.

Huh??

 

[BlackMoria]

I am not certain exactly what you are looking for but I did scuba dived some time ago.

The main thing is Boyle's Law, which dictates how gases operate under pressure. A diver going down in the depths undergoes increasing pressure and this pressure causes the nitrogen in the blood to alter properties (it becomes more gaseous). If the diver were to suddenly surface, the nitrogen does haven't have time for proper re-aborption and the nitrogen forms bubbles in the blood. This condition is called 'The Bends' or compression sickness and is a serious condition - frequently fatal. Treatment consists of taking the affected person under pressure again and then very slowly, easing the pressure so that the dangerous bubbles don't form.

To use this in your setting, anyone from a high pressure world would be in danger of compression sickness if they were in any environment that was lower pressure than if they were used to, unless they went through an adaptative process (time in a pressure chamber) to prepare them.

The effects of high pressure on a person used to 'normal' pressure would be pressure on the ears and sinuses to start. This can become painful as the pressure increases and difficulty in breathing due to a heavy feeling in the chest. Blood gas chemistry goes awry and a condition called the 'raptures' ensues - the mind experiences hallicinations and a feeling of euphoria while the body shuts down.

 

[Psion]

So my problem is: I am still working on my sci-fi setting, and there is a few Earth-like planets, with humanoid species. However, I really don't like when some spacefaring dude lands on an unknown planet, and it's the same gravity, climate, atmospheric pressure, and breathable air as in California or Europe. I wanted to tweak that ludicrous staple of science fiction.[/b]

I don't know of too many (read: any) SF RPGs that actually have a planet generation sequence that don't factor in differences in gravity and atmospheric pressure.

However I don't have the first idea of how much more pressure a human can take before experiencing physiological problems, but know that they can survive quite a bit less. Witness the altitudes at which you can find communities.

You might find that if humans settled on another planet with high pressures, they might settle in high altitudes just specifically for the lower pressures.

 

[diaglo]

Huh??

Superman... a comic book turned into a movie...

Kryptonite his weakness...

any of this ring a bell?

the premise of his powers on Earth stemming from the difference in his home planet vs. Earth.

 

[CarlZog]

Black Moria's got the general idea, but the causes are a little different. It's not the state of pressure by itself that causes problems for scuba divers, but the fact that they've been inhaling compressed gases at a reasonably constant pressure while their body is undergoing changes in pressure. Free divers don't have this problem.

In terms of your setting, it seems to me that newcomers to a planet with a higher atmospheric pressure may have some difficulty adapting. They're likely to exert themselves more easily, reducing endurance. This would obviously be compounded if the planet also had a higher gravity.

However, people from a higher pressure atmosphere may have just as much difficulty adapting to a lower pressure planet. Their lungs are used to the higher pressure, denser air. They may have trouble breathing -- also reflected in reduced endurance.

I think going from high to low would be more difficult than going from low to high. Acclimating to less air would be more difficult than acclimating to the strenuousness of pressure on the body.

Instead of diving, a more appropriate real-world analogy may be Mount Everest climbers, who have to spend long periods of time at base camps on several different levels acclimating to the lower pressure on the way up.

zog

 

[MaxKaladin]

Well, one thing to remember about SCUBA diving is that it pretty much just involves "standard" air at increased pressures. It won't be much use dealing with different atmospheric compositions and won't predict all of the problems with lower than normal pressures.

That said, I think your biggest problem will be atmosphere composition. Air with less than about 16% (IIRC) oxygen is not survivable for most humans. Then there's all the other stuff that might be in the air. Some of it might be quite harmful to humans. Issues of pressure take a back seat to atmospheric composition. With all the volcanism you mention on the one planet, I'd imagine that atmosphere is unbreathable.

At the one extreme, you have a Mars with 0.5 ATM of pressure. That's still more than at the top of Everest, so its survivable but non-natives used to a 1ATM environment will probably require occasional use of supplimental oxygen like high altitude climbers and would get winded very easily. They might have to worry about the bends if they spend long times at this pressure and then suddenly try to transfer to a normal pressure (Climbers descend too slowly for this to be a problem -- its rapid change that does it).

The other extreme, 3 ATM is about the pressure divers experience at about 100 feet underwater. A diver can only stay at this depth for a few minutes before needing to return to the surface. If they don't, they risk the bends. Even if they start to return, divers are expected to make decompression stops to give their bodies time to gradually get rid of the compressed nitrogen bubbles in their systems before they become dangerous. Even with all of this, exposure should be limited to a short time to avoid problems, which means that repeated trips in a day are pretty much out. I'd imagine your 3 ATM planet would probably not have non-natives moving around without some sort of rigid shell suit that would protect against the atmosphere. Its probably a moot point since the atmosphere would almost certainly be unbreathabe with all that volcanic activity going on. Nativse of this planet in a standard atmosphere would be about like humans at the top of Mount Everest. There would be a need for supplimental oxygen at the least and they would become tired easily, assuming they could breath the air at all.

The middle ground is at 1.3 ATM. My rough guess would be that people could move around for moderate periods of time here. A good rule of thumb in diving is that 33 feet (10.1 Meters) of water depth is equal to an additional 1 ATM of pressure, so 1.3 ATM is about like being at the bottom of a swimming pool. Its been years since I read the charts, but I think you can expect to be able to use air at that depth for over an hour without expecting any real problems, so I'd expect that people in a 1.3 ATM enviroment could probably do about the same. Without the compressed air problem, you would probably just need to worry about moving suddenly from high to low pressures .

Disclaimer: I learned SCUBA diving more than ten years ago and got a certification, but I'm really rusty on all the exact numbers and possibly on some of the theory -- especially if its relatively recent -- so all of this should go with a grain of salt.

Edited to correct myself.

 

[MaxKaladin]

Black Moria's got the general idea, but the causes are a little different. It's not the state of pressure by itself that causes problems for scuba divers, but the fact that they've been inhaling compressed gases at a reasonably constant pressure while their body is undergoing changes in pressure. Free divers don't have this problem.

Yeah, I forgot about that. Like I said, its been 15 years since I took the theory classes. I'd expect removing that factor to increase the amount of time people can operate in increased pressure enviroments a great deal. Moving between pressures rapidly will still be a problem, but it should greatly increase the amount of time one can operate at a pressure over what a SCUBA diver can expect.

Edit: Correcting myself again.