Thank you Yvonm for the Youtube links you posted 7 months ago.
It seems to be the assumption that an O’Neill cylinder will have 1g gravity once spun up. This is absurd. I am 75 and feel 1g, and even when I was 18 and did much more walking, it was tiresome to climb hills. Even young people can hurt themselves if they fall over.
I suggest 0.3g. I know that astronauts in the ISS need to exercise a lot each day to avoid bone and muscle loss, before they return to Earth. I remember whenever a Russian capsule returned from the ISS, the astronauts were guided out of the capsule and onto armchairs set out for them.
At 0.3g in an O’Neil cylinder, people can cycle long distances easily. It would be absurd to live under 1g, and move about the cylinder by battery golf carts. Little or no rain, light breezes at the most and good weather. Bicycles work well, and the ease of cycling under 0.3g means people would exercise a lot without thinking much about it.
Ceilings could be another metre higher, allowing more storage higher up. Jump off the floor, rise to the ceiling, grab a grab handle and remove something from an upper cupboard, then let go and float down to the floor. A 75kg person weighs only 25 kg under 0.3g. There is little or no rain in an O’Neill cylinder, so expect flat roofs used as lounges. You may climb stairs to the roof, giving exercise, but you might come down by fireman’s pole. You would prefer not to use a fireman’s pole under 1g.
Wikipedia tells me that O’Neill’s proposed cylinder would be 8 km in diameter, or about 25 km in circumference. With 0.3g, the centrifugal force (artificial gravity) will be one third that at 1g, so the diameter could be larger. Not 3 times larger, because centrifugal force depends on angular velocity squared. Coriolis forces, such as they are, will be less.
Air pressure need not be sea level Earth pressure, which would exert a force of 14psi on the outer shell of the cylinder. Wikipedia tells me that air pressure on Earth halves with every 5500 metres of altitude, or every 18,000 feet. Air pressure on Earth is 90% of sea level at 1000 metres altitude, 80% at 2000m, and 70% at 3000m. Some people on Earth live above 3000m, or 10,000 feet, and have to move about under 1g. La Paz, Bolivia, Lhasa, Tibet, and Cuzco, Peru are all above 3000m. I suggest air pressure in an O’Neill cylinder be 70% sea level Earth pressure. People will adapt.
At 0.3g, structures will experience less force and can be lighter. I suggest aerated concrete as a building material. Not much compressive strength, but at 0.3g, no problem.
I live in Australia, and our early settlers tried to reproduce English buildings in a different climate. For one thing, the sun in Australia comes from the north, not from the south. We have, of course, adjusted, and I expect a similar adjustment on O’Neill cylinders.