I'm currently working on a science fiction comic about humans marooned on an alien world for generations.
This world is slightly larger and more metallic than earth with greater gravity a higher percentage of oxygen (I was thinking similar levels to the Carboniferous period here on earth 35-40%) and 3-4 earth atmospheres of pressure at sea level and a more comfortable level higher up where most humans live in domed habitats and can move around outside for limited periods with some protection. Though I'm really flexible on all those numbers if they don't work or aren't actually possible.
My question is related to the people moving between higher and lower levels of pressure to scavenge materials and war with the locals. How much pressure is too much? how quickly could they move between these levels? how long could they survive in the lowlands with and without equipment? and what other unforeseen issues could I have missed?
Mainly I want to know if these issues could be resolved with cybernetic modification (particularly modifications that make them repugnant to the unmodified) to allow for a lower level of protective equipment at all pressures. I remember reading peter watts Rifters trilogy in which the deep sea divers were modified to remove all their internal pockets of gas at will and store them in a canister, presumably so nothing could rupture under the pressure.
Would something that extreme be viable or necessary? and more important would switching it on while shirtless be unsettling and cool looking?
Thanks for taking the time to read this and sorry for any errors or faux pas on my part I'm not good with words.
Please be gentle, its my first time.