dragoongfa wrote:Space resource extraction is weird because of the inherent logistics issue on getting the raw resources to their destination. Not just 'space freight' from point A to point B but to actually get the raw resources to the manufacturing centers in enough quantities to make them worthwhile.
Yeah, I agree, and this is one reason why I think Mars with its one-third gravity will be an attractive manufacturing center for raw materials extracted from the (relatively) nearby asteroid belt.
dragoongfa wrote:The difficulty of getting even a space shuttle's worth of equipment back down to Earth without an accident is well known; imagine getting a few hundreds of tons down every few minutes in order to feed a large industrial concept.
Getting raw materials down to a planet with an atmosphere is comparatively easy; reentry is just a heat management problem. It's lifting the finished goods out of the gravity well that's the challenge. Even if you have orbital elevators, dropping bulk raw materials in cheap (and perhaps even disposable) reentry sleds might still be more economical in some cases.
dragoongfa wrote:A possible fourth solution is to go full dysonian with your spacecrafts, large planet sized motherships that would be all in one in terms of manufacturing and logistics but at that point I doubt that even an entire solar system's worth of raw resources would be able to sate the needs of an empire able to build such a craft.
If your planet-sized megaship has anything like the mass of a planet, you haven't really solved the problem.
Sweforce wrote:Am I right to assume that since spaceships are hideously expensive to build these will if possible be used for a long time?
The most expensive components of a spacecraft are going to be its powerplant(s) and drives. As long as these are still up to the task, a ship may remain in service for a long time. However, if you need new engines, it will probably be cheaper to build a new ship from scratch than to try to retrofit a new power system into an existing hull. The other problem is that space is an incredibly hostile environment, with hulls constantly subjected to hard radiation and high-velocity micro impacts; it will take constant maintenance to keep them airtight and sound, and this probably has diminishing returns of cost-effectiveness as the hull ages. But I can imagine old ship hulls being used for storage, docked in a disused wing of a space station.
Space stations probably exist on a different economic curve, as they are much more bulk than engine, and can be much more massive (they still have to move, but not very fast). A robustly built station hull (or one built into an asteroid or the like) may last for many centuries and be worthwhile to retrofit with new technology. Warships, similarly, have a variety of expensive components, which may make some refits more cost effective.
Sweforce wrote:A Star Trek (TOS, not the new movies) comparison, the vessel that Khan used to flee Earth with with his followers in the late 20th century is of a line of ships STILL used in the Kirk era, they are used interplanetary and either have a skeleton crew or are fully automated.
Well, I think this is more a case of a cash-strapped effects team reusing an existing model rather than sound science fiction (in the remastered version of the series, they used a different model for the
Woden in "The Ultimate Computer"). It's hard to imagine that a sublight atomic powered sleeper ship from the 1990's would make an economical ore freighter in the warp drive era of 2267.
There will be different sizes and configurations for different roles. Small, high-value cargoes (and passengers) may be carried by relatively small, faster transports with heated, pressurized holds. Bulk cargo will want larger hulls that may not need special environments. If the cargo destinations have full spaceports with their own orbit-to-surface infrastructure, then a cargo ship doesn't need any extra capabilities, but if it has to access the surface on its own, then it may need large hangars and a complement of heavy shuttles.