Free How to Write Science Fiction and Fantasy by Orson Scott Card Page A

the embryos are revived and raised to adulthood by computers or robots inside the ship. They come to the new planet as virtually new creations, having known neither parents nor any human society except the one they form. Obviously, this is a one-way trip with no hope of later visits or help from the home planet, since no one on the home world will even know whether the colony ship happened to find a habitable planet, let alone where.

    Ramdrives. Long before the personal computer culture taught us to use the term RAM drive for a virtual disk in volatile memory, science fiction readers were introduced to the ramscoop stardrive, or ramdrive, that solved
    part of the fuel problem. Instead of carrying fuel enough to handle all of a ship’s acceleration, a ramship would use conventional fuel to get up to a certain speed, then deploy a huge network like a funnel in front of it, to scoop up the loose matter that is everywhere in space. This matter would then be used as fuel, so that acceleration could continue without having to carry all the fuel along.
    There are theoretical problems-the efficient use of the loose interstellar “dust,” some structure for the net that isn’t so heavy that the matter it collects can’t provide energy enough to accelerate it, the fact that at velocities far below lightspeed the interstellar dust stops being harmless dust and starts being extremely dangerous and explosive debris that seriously harms any ship traveling that fast. But the ramdrive is fun and semiplausible, and it allows you to have a starship that isn’t the size of your average asteroid.
    Time dilation. Time dilation space travel is a sort of middle path. With this set of rules, your starship can travel at a speed so close to the speed of light (say, 99.999% of lightspeed) that, while you don’t turn into pure energy, you get from point A to point B at almost the speed of light. Relativity theory suggests that time aboard an object traveling at that speed would be compressed, so that while an outside observer might think thirty years had passed, people on the ship would only have lived through a few hours or days or weeks.
    This allows you to get people from world to world without generation ships or cryo-travel. The travelers who reach the new planet have clear memories of their home world. But they won’t be particularly eager to get back, because, while to them it has been only a few weeks since they left home, back there it has been thirty years. Anybody they left behind has aged a whole generation or died. And if they turned around and went back immediately, they would return home to find that someone who was twenty when they left is now eighty years old. To all intents and purposes, it’s still a one-way voyage-but one that allows the travelers to arrive with their society intact, relatively unchanged by the voyage.
    Still, the characters will have been cut off from anyone they knew and loved. This suggests that either the travelers will be going through some degree of grief or they will have had no close friends or family on their previous world; in either case, this will have a lot to do with how you characterize them
    And pretend not to know that to a ship traveling at such a high percentage of lightspeed, space dust would strike them like intense gamma radiation. Just say that they use a half-mile-thick layer of crushed asteroid as shielding, or that they have a force field that shields them from the radiation. Or don’t say anything at all-time dilation stories are such a staple in science fiction that you really don’t have to apologize for them anymore.
    The ansible. I first ran across this variation on time dilation in the works of Ursula K. LeGuin, and found it one of the most useful devices in space travel. In essence, the ansible is a device that allows you to communicate instantaneously, regardless of distance. Thus travelers can go on one-way time-dilation voyages, yet still report to and receive