FTL Communication refers to some sort of method for distant spacecraft or planets to stay in touch without the multi-year delays between responses that would occur if using normal radiowaves.
FTL Communication Subtypes
- FTL Radio - breaking the laws of physics for the sake or making communication simple and familiar
- Psionics - Psychics could be employed to communicate across great distances
- Tachyonic Antitelephone - a machine that allows you to talk to your own past and receive answers before you ask the question
The first two on that list generally ignore relativity. The Antitelephone doesn't ignore the laws of spacetime, and so is not only FTL communication, but also an extremely limited form of Time Machine.
If your setting doesn't have one of those methods, when you're in deep space, you're pretty much on your own. A distress call could take years to reach civilization, and more years to get a reply. Even within the solar system, there's several minutes of delay from one planet to another.
Improvising and Workarounds:
- If you can find a wormhole, normal radio could be sent through it to the other end at speeds faster than that of radio/light outside the wormhole. If the other end opens up somewhere populated, you may be able to send a message faster. It's possible that a civilization could develop a means of creating microwormholes, too small or unstable for human passage. It may be that making a portal big enough for people takes too much energy, or that wormholes have lethal effects on human physiology and damaging effects on spaceships, but are just fine for radio.
- A very clever scientist might rig up something involving one of the following scientific principles, but you'll need to research them yourself for ideas:
- If no FTL communication exists in the setting, but FTL stardrive does, there may be a spacecraft equivalent of snailmail or the pony express. Not that it would do you any good when it comes to sending a distress call, but it may at least allow for planets to interact a bit. Probably darned pricey, though, unless FTL Travel is itself really cheap and easy.
Game and Story Use
- There's a few possible permutations, a setting could have (FTL Communication, but no FTL Travel), (No FTL Comm or Travel), (No FTL Comm, but yes FTL Travel) or (Yes to both FTL Comm and FTL Travel).
- Even then you have a chance to play about with some factors such as bandwidth - if you allow narrow bandwidth FTL comms, you'll have a system of communications that feels more like the telegraph than radio, which is great for "colonial era in space" settings - fairly laconic messages can be sent FTL, everything else must travel by "post" (or at least be uploaded onto a ship for FTL transport). For bonus points, even these narrow-band coms may require something similar to a stardrive to transmit, making FTL signal stations expensive, cumbersome and potentially vulnerable. Especially if a stardrive can't be safely operated planetside.
- Without FTL communication, space is really lonely and isolated. A ship in trouble is totally on it's own. Space is so big and empty, the probability of rescue would strain belief.