The previous two chapters focused on how to determine travel times using the sort of locomotion available on Earth-like worlds. Space travel falls under two categories: existing technology from Earth and invented technology. As I’m not a rocket scientist, the former is best left for those in the know to explain. World builders tend to be focused on imagined technologies anyway, and there’s no telling what detail you might want to know and utilize about real technologies. More to the point, the limits of real technology eliminate interstellar travel and therefore whatever we’re hoping to achieve.
The Realities of Space
Writing fiction doesn’t free us from the realities of space, such as the intense cold or lack of oxygen. Some will think gravity doesn’t exist either, but gravity is everywhere and causes all rotation (i.e. orbits). The conceit of artificial gravity has long been accepted so that we only need to address it if we want to, such as designing a rotating ship.
The question we must address is whether to pretend certain realities are overcome by technology (or magic) or not. It’s recommended to be consistent in a single product. For example, in the Star Trek universe, food replicators that make lunch appear from thin air is as unrealistic as the teleportation devices that move matter (including people) between places. Being equally unrealistic (or realistic) is wise and helps the audience accept the reality we’re presenting; otherwise, incongruities creep in. Having food replicators and teleporters but no artificial gravity would be an example, as the gravity, or a simulacrum, would be easier to achieve from a technological standpoint.
When inventing technologies for space, creating a hierarchy of believability might be wise, if we’d like to have some things achieved while others are still imaginary, even to our advanced inhabitants. Maybe we want them to have achieved artificial gravity (so actors have a much easier time on screen) but still have the need to grow and cook food. At one time, the communication devices of Star Trek were considered fantastic but have been eclipsed by reality.
Generally, advanced communication is easier to achieve, as this often means little more than smaller devices with greater distance or computing power or capabilities, and sending of signals (not matter) long distances. Those signals can contain data just like here on Earth. This suggests that an advanced program, such as a hologram or A.I., could be sent vast distances, with the possibility of corruption in transit.
Any technology involving non-living matter is easier to create than something involving living creatures. This is especially true of transportation. Creating a new propulsion system using newly discovered elements from far flung solar systems is more believable than a technology that bends time and space and causes matter to just end up somewhere else in an instant. Such abilities are best seen as rare because making them commonplace implies the characters have other godlike abilities, too, and their lives become too easy, which reduces conflict, the heart of every story.