Rutger Hauer died on the 19th. His role in Bladerunner was one of the most famous in science fiction cinema. Today I watched the trailer for the 4th season of The Expanse. As my entry into old-man-hood at 60 approaches, the deaths of all these actors and actresses I grew up with “gives me pause.” The replicants in Bladerunner only had 5 years to live and were trying to extend their existence. In regards to The Expanse it is interesting that alien technology has allowed access to other star systems. That MacGuffin was never addressed in Bladerunner. The “Off-World Colonies” were where replicants were employed. I have always considered freezing people and then reviving them undamaged after decades to be the future of star travel. It is also the only chance I and my wife have of living more than another quarter century.
Gerard K. O’Neill envisioned a future with artificial worlds mass-produced as needed. The human race could then expand an order of magnitude. I always wonder just how big these hollow moons will be. NASA SP-413 does not address size except in terms of the minimum hull strengths required for the different types of habitats. What it does state is under one revolution per minute is likely not going to work well. To produce centripetal force equivalent to one gravity at the equator of a sphere with one revolution per minute will require a diameter of over a mile with a circumference of about 3.5 miles. Considering the supertankers, bridges, and skyscrapers we build on Earth, constructs on this scale undertaken on the Moon at one-sixth Earth gravity and then launched into space for assembly make one mile diameter hollow spheres quite reasonable projects.
It follows if the mega-constructs we build on Earth scale up in lunar gravity into 1 mile spheres then building one mile diameter spheres on Earth could scale up to six mile diameter spheres in zero gravity space. For the sake of this argument consider mass-produced six mile in diameter hollow spheres. If half of the interior surface is considered living space this would be about 50 square miles. About the size of San Francisco which has a population of over 800,000. How long could such a sphere last? If designed to constantly recycle its structure in some way then as long as it received enough solar energy and a small supply of necessary materials it would maintain integrity for thousands of years and longer. Sending such hollow moons to other star systems at a few percent of the speed of light is of course the next step for humankind. Younger versions of Earth await these arks sent to transplant species from old Earth. Or if there are no Earth analogs then new star systems as simply new asteroid belt factories to create more hollow moons.
After slow boats the most probable development to follow will be black hole starships. Nothing else has come close to this concept and may not for centuries to come. It may be that some of those asleep on those slow starships will be awakened to transfer to a much faster ride. This might have worked for Bladerunner as these ships would have taken people to the nearest star systems in as many years as light years. The amount of energy necessary to create these miniature black holes would require a truly immense solar space solar energy infrastructure. Beam propelling Bernal Spheres at a few percent of the speed of light will also require very high energies, with bombs used to slow down on arrival, but black holes are a couple orders of magnitude more energy intensive. There may be little chance of seeing fast ships overtaking slow ones until well into or near the end of the next century.
Ice on the Moon 