Most of the time I'll be looking at a particular technology or trope of SF - force fields, FTL travel, interstellar empires - and analysing the way that it would effect the setting. I'll look at the science behind some of common technologies seen in 'hard' SF, and I'll make hypothetical examples, along with calculations and equations. Sometimes I might do a 'case study', starting with a set of initial assumptions, and exploring the universe that they imply.
Although I'm creating this blog with the intent that it will help other writers and fans of SF, my motives are less than altruistic. I harbour the hope that people with more knowledge than myself will stubble across it, comment, and enlighten. So if you have ideas and opinions, please comment; constructive criticism is always welcome.
But on with the fun stuff and the subject of this post: the Man in the Can.
It has been stated that SF fans, and people in general, connect better with human characters than they do with silicon chips(Bernside's Zeroth Law). Thus, while a book or movie may have robotic or AI supporting characters, the protagonist is generally human. In fact, for most of us SF addicts, the whole point of science fiction is to write, read, or watch people in various situations, especially on or around spaceships. Unfortunately for us, this is also the place people are least likely to be found in a Hard SF setting. A military ship will have crew to make the higher order strategic and tactical decisions, but even they become redundant in the heat of combat, or in navigating between planets or stars. Not that if the sole purpose of the ship is to fight, rather than gunboat diplomacy, even one human becomes pointless, as they limit acceleration, cannot themselves cope with the complex trajectories of space combat, and limit performance through the added mass of life support and extra armour. For cargo vessels the conclusion is inevitable especially at a low tech level with the sorts of performance that most projected NASA designs have. Not only does the crew take up mass budget that could be used for profitable cargo, but they force the trip time down to reduce radiation exposure and irreversible damage from zero-gee. Of course, you can add a spin hab, shielding, but this adds cost and cuts away payload. So while there might be a supervisor at the water mining station on Demios, the cargo ships will be basic drones, flowing a minimum energy, maximum time Hohmann transfer orbits. They don't even need to be AI, very basic software will do the trick. Also, much smaller spacecraft are possible, allowing external propulsion methods like mass drivers, magbeams, and solar sails to be more effective.
However, all is not lost. If there is no technical reason for the ships to be manned, a non-technical one can easily be fabricated. Say a terrorist cell manages to hijack the controls of a few ten tonne capsules of rare earth metals from the asteroids, and uses the minimal guidance thrusters they posses to cause a collision with a space station, or some other space based asset. Chaos ensues. Without enough time to react such an attack would be devastation, and no government would want the possibility of it happening again. Looking for someone to blame they settle on the transport company, and pin responsibility on them. As a security measure - any computer can be hacked, so adding more powerful software does not do the job - they decide to build manned ships. At the beginning of the flight the captain signs a document that gives him full responsibility for the ship, protecting the parent company from legal retaliation if another 'incident' occurs.
Naturally the company does not want to cut its profits by to much, so they skimp. Tiny quarters, minimal life support, one crewman, and long travel times to reduce the energy budget. The crew themselves are likely to be minimally trained, as even if something goes wrong there is little they can do; there is nowhere to pull over and top up the radiator in space. Many of them would be the anti-social misfits how like the solitude, or people who need the money, assuming high wages. Coast cutting measures also leads to story potential when a water tanker halfway between Earth and Mars begins to malfunction, and the lone crewman is caught up in a desperate struggle to stay alive. In any case, it is a far more interesting setting than one in which robotic freighters are the norm. It also suggests further antics down the track; a solar system in which ten tonnes modules are shot all over the system by magbeam is not one in which a interplanetary war is likely; one with a multitude of large, high capacity ships is. Take out the cargo, add a rack of missiles, and the United Saturn Federation has its first warcraft to fight against the Terran oppressors.
So there we have it, a reason to keep the man in the can.
Feel free to comment and add anything that I've missed.