Of course, there is no one ideal design of human spaceship. Indeed there are over a dozen types, though they are split into four main categories:
- HOOT: Human Occupied Orbital Transport
- CAT: Cargo Access Transport
- LRET: Long Range Exploratory Transport
- HIDEN: HIgh DElta-V Nuclear
HOOT units are the usual space plane many think of - sleek spearhead shaped craft that carry brave people into orbit. There are numerous ways of getting these craft off the ground - some are released from piggy-back aircraft, and others accelerated along a launch ramp like an old V-1 buzz bomb. Once airborne, the choice doesn't end, a combination of hydrogen-oxygen propellants, Bio-kerosene , or even powdered metals sublimated by a ground based laser.
All have in common, however, small size and layers of safety systems to keep humans safe during launch, maneuvers, and re-entry.
CATs are the classic "Big Dumb Rocket" or sometimes exotic launch technologies using lasers use to put large objects into space. A lack of human passengers makes them cheaper to operate, and allows for higher accelerations and faster launches.
Although citizen ships look nothing like classic flying saucers, LRETs do. These are giant wheels, spun to produce artificial gravity, thus keeping the occupants healthy for long flights.
Time is money, and if a problem were to arise on either Mars, or an asteroid mining outpost, a conventional Holman transfer orbit could take years. Thus a small number of unmanned, fission powered nuclear rockets are kept in lunar orbit, ready to run on a 2g brachistone trajectory (that is, constant acceleration until the half way point at 19.6 meters second, then reversing and breaking at that rate) to quickly move materials around the solar system.