Activity for rwallace‭

Type	On...	Excerpt	Status	Date
Question	—	Durability of materials in ideal conditions How long can objects made of hard material last at room temperature in otherwise ideal conditions? If left outdoors on Earth, over the course of millions of years, any material will be eroded by wind, rain, temperature fluctuations etc. But what if you take an object of some hard ceramic like alumi... (more)	—	over 4 years ago
Question	—	Building a launch loop A launch loop https://en.wikipedia.org/wiki/Launchloop is a proposed way to put lots of things into space at lower unit cost than rockets (only need to pay the energy cost in electricity for each payload) without needing very strong materials (the exoatmospheric-height structure is supported by elect... (more)	—	over 5 years ago
Question	—	Minimum tech level to invent core memory Magnetic core memory was a critical innovation in the development of computers. Per https://en.wikipedia.org/wiki/Magnetic-corememory it was the most advanced form of memory from about the mid-fifties to early seventies. For development of a semi-steampunk setting, I'm thinking about how much earlie... (more)	—	over 5 years ago
Question	—	How much equipment would be needed to set up a mining colony? Setting: a mining colony on a distant world, exporting rare-earth minerals. As in many space opera stories, the world is a shirtsleeve environment with a reasonably pleasant biosphere. Tech level: I am making the assumption, admittedly unrealistic but commonplace because it is useful for science fic... (more)	—	almost 6 years ago
Question	—	Cost of electrolytic hydrogen Working on a future history setting; the question arises, since the world cannot run on fossil fuels forever, one way or another, something must end up replacing them; what will that something be? A co-author has suggested using nuclear energy to electrolyze water for hydrogen which is combined with... (more)	—	almost 6 years ago
Question	—	Speed of water jet driven by 300 bar In a setting where portals can be opened between one location and another, Suppose you open a portal of area one square meter, with one end at the surface and the other end at the bottom of an ocean, three kilometers down, where the pressure is three hundred bar. Obviously a jet of water will come t... (more)	—	about 6 years ago
Question	—	Practical height of towers without elevators I'm writing about a setting where building technology is quite advanced, but elevators have not yet been invented, so the limiting factor on height is ergonomic. What would be the maximum practical height for a building where the people going up the stairs are expected to be pretty fit, and where it... (more)	—	about 6 years ago
Question	—	Visibility of explosions from space I'm trying to figure out whether spacecraft could see explosions occurring on the surface of a planet, or under what conditions they could. To be specific: Given a spacecraft equipped with a duplicate of the Keck telescope, using visible light only, watching a planet similar to Earth, at what dista... (more)	—	over 6 years ago
Question	—	Drop capsule shape Sci-fi setting where cargo is being shipped to colony worlds. If a spaceship has to land and take off again, that costs a lot of money, so that mode of transport is reserved for people and urgent, high-value cargo; the plan is to get bulk cargo the last lousy few hundred kilometers in drop capsules, ... (more)	—	almost 7 years ago
Question	—	Lead as a nuclear fuel On a timescale of 1e11 years, all uranium and thorium will have decayed, but planets will still exist, orbiting red dwarf stars. Would it be possible to use lead as a nuclear fuel? In principle, the curve of binding energy says lead fission is an exothermic reaction. Is there a way to do this while ... (more)	—	almost 7 years ago
Question	—	Surveying fossil fuel deposits from the air On Earth in 2017, finding oil or coal deposits is a tall order. However, consider a science fiction scenario where we find a habitable planet that hasn't hosted an intelligent species in at least a hundred million years, so has fossil fuel deposits in easily accessible locations. Is there a way to fi... (more)	—	over 7 years ago
Question	—	How long would it take to build a spaceship? I'm working on a science fiction story which includes the following premise: Tony Stark invents an unobtainium reactionless engine, and the protagonists want to build a spaceship around it, big enough to carry a nontrivial amount of cargo. They have a company similar to SpaceX, enough money, politica... (more)	—	over 7 years ago
Question	—	Erosion of buildings on geological timescales I'm looking at a science fiction scenario similar to Lovecraft's At the Mountains of Madness where buildings are exposed to the elements for millions of years. I have a feeling they wouldn't be quite as intact as Lovecraft had it, so I want to try to figure out what's realistic. As in Lovecraft, the... (more)	—	over 7 years ago