So today we're talking about O'Neill Cylinders! Space settlements have always been something straight out of sci-fi, but cool to talk about nonetheless. Today, I'm going to talk about what exactly are O'Neill cylinders, and what their capabilities consist of. 😎 #scicomm (1/21) 
Physicist Gerard O'Neill had given his students a task to design large space habitats which first inspired the idea, and he then published about it in a 1974 article of Physics Today. He discussed them more in his 1976 novel The High Frontier: Human Colonies in Space. (2/21)
So, how do they work? They are a pair of two cylinders counter-rotating each other. This spin allows for the creation of artificial gravity through the fictitious centrifugal force. Think of those rides that spin really fast and make you stick to the walls. We can... (3/21)
...currently do this with space habs like the @Space_Station, but with its relatively small diameter, it would require nausea-inducing rotational speeds in order to simulate actual artificial gravity. The larger diameter, the slower the rotational speed. (4/21)
O'Neill Cylinders allow for freedom to simulate different conditions since its gravity and environmental properties can be changed. They can be tailored for specific kinds of civilizations and provides many more options than terraforming a single planet. The idea is that...(5/21)
...different cylinders could represent different aspects of life. There could be things like agriculture cylinders, suburban cylinders, vacation or getaway cylinders, etc., and transport between all the different cylinders would, in theory, be pretty efficient. We'd... (6/21)
...put the first cylinders at the L5 point in the Earth-Moon system. This is a Lagrange point, and these 5 points are places of stability. It is a great spot since it is equidistant between both the Earth and Moon, and would allow for efficient material transport. (7/21)
In the future, these cylinders could be placed at different places near planetary bodies. My vision is that people would regularly live on these cylinders, and then some people would travel down to the planetary objects to either visit or do things like science and whatnot (8/21)
Now, for the physical properties of the O'Neill Cylinders. Most construction could be done by robotic manufacturing tools, and humans can just supervise the process. O'Neill proposed that we would need to gain essential materials from the moon and nearby asteroids. (9/21)
The creation of in-space manufacturing facilities would help with the transport of materials to colonies. An interesting idea that O'Neill also proposed regarding transporting these materials was an electromagnetic catapult. It would essentially cost nothing because... (10/21)
...you would only need to supply the catapult electricity, which could come from the sun through the use of solar panels. It also wouldn't be hard to catapult objects, because the Moon has such low gravity (1/6th of Earth's). I will not lie, it's a pretty neat idea! (11/21)
These cylinders are HUGE. They were first proposed to me around 20 miles long and 5 miles wide with over 300 square miles of internal space. It was thought that over 1 million people could live in a single cylinder, so with a pair of two cylinders, over 2 million people! (12/21)
Early designs had three stips of land material, and there would be three other strips serving as large windows made of tinier windows so that in case of a meteorite impact, the entire thing wouldn't break and kill everyone. Mirrors at the ends would redirect sunlight. (13/21)
Now let's talk about the internal environment. Things like soil and animals would need to be transported in. The weather could be made to be similar to Earth, but obviously not exactly alike. The atmosphere would be at half pressure, with 20% O2 and 30% N2. (14/21)
In order to protect from cosmic rays, the immense shielding, maybe including water shielding, could protect cylinder inhabitants. Though, not all radiation can be protected from. This leads me to talk about some disadvantages that come with O'Neill cylinders. (15/21)
One of the first disadvantages is exposure to radiation from the sun, which is usually what the ozone layer in the Earth's atmosphere protects us from. People living on O'Neill cylinders will have to accept the fact that they have higher cancer risks from this radiation. (16/21)
Similar to terraforming, building these enormous structures would cost a ton of money. But each day, spaceflight is getting cheaper and cheaper, so it’s a matter of just waiting for when things are affordable enough. But we most likely won't see them in our own lifetimes. (17/21)
Then lastly, we would still need a lot of automated technology, like the electromagnetic catapult, to be developed to make the building process much more efficient and also make gathering materials easier. So things aren't looking too good for us O'Neill Cylinder fans. (18/21)
But these aren't completely out of reach, and there are companies currently working on this idea, aka Blue Origin. Jeff Bezos, who was once one of O'Neill's students, expressed his interest in these colonies during the unveiling of the Blue Moon lunar lander last year. (19/21)
O'Neill Cylinders is what I think is a better solution to continuing the human race. Even though both are still currently out of reach, I find the idea of being able to simulate your own conditions and live in different places of the solar system is much more interesting. (20/21)
So that's my thread on O'Neill Cylinders! Feel free to correct me on anything, let me know if you have questions, and keep on the lookout for a thread poll soon. (21/21)
If space exploration quickly advances, I'd love to be a science advisor for the first prototypes of these 🤔
If space exploration quickly advances, I'd love to be a science advisor for the first prototypes of these 🤔
