David L. Babcock <olb...@gmail.com> wrote: You fail to factor in the enormous sheer tonnage of steel and other metals > required.
I suppose a star ship would have to be made of stronger materials than steel. Something more like what you make a space elevator out of. > Confounding that it's not just peak oil we're at, it's peak nearly > everything. > By the time we make star ships, we will already have colonized the solar system. We will have all of the steel, carbon and other materials on all planets and asteroids, which is a far larger mass of material than we have available on earth. However, as I said, I think it would be more convenient to collect a large fraction of the sun's light and convert it back from energy into mass. Assuming this can be done. The sun loses 4 million tons per second in mass-energy conversion. If we collect and convert it back into whatever elements we need, that is enough to build any number of star ships in a short time. The largest cruise ships today are 100,000 tons and they carry 5,000 people. So we could launch 40 cruise ships per second, enough to carry 200,000 people crammed together in 21st century quarters. Say, we launch one ship per second, of 4 million tons, and it carries only 10,000 people in luxury. That would be 700,000 seconds to accommodate the entire present world population. That's 194 hours, or 8 days. > Jed would argue, I think, that enough energy combined with engineering and > plant materials -renewables- will make feasible cheap replacements for > almost any sort of spacecraft components. Not renewable. Extra-terrestrial. > I argue that the tonnage does you in. Visualize an ocean liner for every > small town, a fleet of them for every city. > Visualize 40 ocean liners per second and you will have a more realistic notion of what people will be capable of making -- a few thousand years from now. Not that people will construct such things, of course. Robots will. Trillions and trillions of robots. Most of them no larger than an insect, I suppose. Do not ask where they will come from. That is like asking where bacteria come from. From other bacteria! They are self reproducing. - Jed
