So, something I was working with, but a primary concept of the setting I'm working on is the idea that FTL travel and communications are not necessarily set in stone, or more specifically, they are in terms of the underlying “sciences” behind them but different races and different civilizations have developed different types of FTL drive and even variations within those types and sub-types based on their needs, access to resources, etc. I wanted to run this past some people to kinda put forth the ideas for a prospective setting development in hopes of both finding the possible extensions and flaws. And hey if anyone has any other ideas they want to throw out, that would help too. I also wanted to see if a genuine “mix” of FTL systems instead of having just one and nothing else would work since most series only have one like Warp Drive and EVERYONE uses it and never go beyond that. So a genuine question I would ask is, what do you think of a series which has many different, overlapping FTL systems that function in various ways. Anyway, one of the major types of interstellar travel in 20,000 years from now is relativistic. Basically, a wide variety and family of drives that allow near-light travel exist, some more realistic than others perhaps but they all let a ship reach a high level of relativistic speed. This includes one type, widely used by the human factions of the galaxy, which lets a ship reach ACTUAL lightspeed, so if a star or planet is like forty LY away they can reach it in forty years straight, but most are not THAT fast but still relativistic speeds. This ties into two other major plot elements: firstly FTL communications are surprisingly easy to build, as humanity discovers, and some exist naturally, like “subspace radio” which is basically a term for actual radio frequencies discovered in the future which perpetuate at “tachyonic speeds”; secondly, tachyons actually exist, a FAMILY of particles called “tachyonic” in fact which travel at different velocities (Tachyon-A and Tachyon-A* both travel at a bare minimum of fifteen times faster-than-light, while Tachyon-B particles are five times slower but more common, etc) and can be widely used. This means that even relativistic travel can be linked by FTL communications of various types so a fleet lightyears away, or a solar system separated form Earth by lightyears, can directly communicate with the “Homeworlds” in real-time. This interstellar internet means that while worlds may be separated or ships separated from one another there is no real distance. By the time most of the series is set real-time communications between star systems is considered a matter of course by literally every civilization in the galaxy, with maybe seconds of “time debt” at most, usually instant or real-time. This also ties into another type of FTL: Free Boosting. Free Boosters are basically teleportation technology writ large. In the (relatively) near future of the 2100s humankind develops the technology to upload minds into computers. And coupled with FTL comms, this means that minds can be transmitted over interstellar distances instantly or near instantly, and THAT is combined with being able to upload a mind into a new body (be it fully mechanical or bio-engineered or “flash cloned”) means that Free Boosting is an alternative kind of FTL: send out a ship, once it gets there it can either set up a Free Booster terminal or carry Free Boosters on-board, and this becomes a military strategy for many races. Generally, the technology only allows a specific number, and at the top end of the scale Free Booster termini allow 3000 people to “jump in” every hour due to the speed of manufacturing bodies for them. BUT if a ship is big enough, it can hold a TON of termini. The upper end of this is a “battle planetoid” which are planets converted into ships (yes I stole that idea from Lensmen, mock me as you will lol) which hold three-hundred thousand Free Booster termini that can port in three-thousand people an hour, or almost a billion people an hour. Most worlds in the Empire of Mankind have...well probably millions of termini, some single-person booths and some for many thousands, meaning with FTL comms billions or tens of billions can travel between worlds instantly. This is also connected to the Everlasting, a system of quasi-post-scarcity production that exists across most of the Empire of Mankind. It's complicated but it involves a combination of holographs, augmented reality and 3D printing (“flash forging”) that takes concepts like Amazon or Twitter and expands it to the point that virtual reality cybercosms with real matter now exists, meaning a person can buy something and have it instantly forged in their hand in seconds, and on like 80% of the Empire's planets this is commonplace. Those that lack it either choose to not use the Everlasting or are too far on the fringes for it to realistically reach them, but direct connection to the Everlasting is common for almost everyone. Most other interstellar capable races have similar (or better!) systems, and galactic economics are kinda built on it. Now it's not infinite or infallible, and resources are still mined and needed to supply matter for “flash forging” or energy for the planetwide AR/holographic systems. During wars, planets disconnect from the Everlasting, so the enemy can't just make weapons or robot soldiers on the fly, but neither can the Imperial Army so like I said resources are still necessary; it's not ACTUAL post-scarcity but it's as close as I figure we'll ever get even by the year 20,000 A.D. There are other races, like Mankind's ally the Aeon Empire, who are genuinely post-scarcity however. (Take note this, and Free Boosting, also is why people have absurd lifespans in the 21st millennium. There are realistically people upwards of 1500-2000 years old, considered “elderly”, but still hanging in there) Other, more “traditional” kinds of FTL include DeSynch Drives, Rifts and Free Lanes. DeSynch Drives, more formally called “Dimensional DeSynchronization Drives”, are a kind of FTL that allows a ship to skip back and forth between different regions of subspace (a lower plenum of spacetime also used as a means of FTL communication) and hyperspace (a higher realm where tachyons originated, made of pure energy with no natural matter) and real space, like a sine wave. This accelerates the ship faster and faster almost ad infinitum. Kind of a super-relativistic drive. The more energy you put in the faster you can go, so larger ships with more reactor cores and greater capacity for energy generation can achieve speeds upwards of ten times the speed of light. Now this requires the energy of a star, but at the far end of space ships this is some what possible, since they have multiple reactor cores which combined are like small suns. The fact this is fairly common in the galaxy, and that ships can be fucking HUGE, makes this easier than it sounds. The Citadel are an example of a race that has this technology and the hub of the civilization, the eponymous Citadel, is a mobile megastructure the size of a Dyson sphere built around a literal star and can reach ten times the speed of light; on the lower end of the scale, the average Imperial super dreadnaught is 50-75 miles in scale and has four reactors with one-half of a star's output combined and can reach five to seven times the speed of light. The biggest problem with DeSynch is that there is time debt incurred, so one day of ship-time is a week of real time. So if you're going at seven times lightspeed and traveling say five-hundred lightyears, that would take 300 years of ship-time using DeSynchronization, but would, in real space, be two-thousand years. So it's not THAT fast, and that's why other kinds of FTL are necessary. Rifts are naturally occurring events which CAN be produced artificially but it's not easy. Rifts are just what it sounds like, a Rift is a fancy term for a wormhole. The number in a system varies, for example, Sol has just one orbiting Mercury while another system, Ares, has FORTY. Also you have no idea where it leads to, you have to map them all out. But it's instantaneous, literally like teleportation, so when you map out enough Rifts, you can travel from one end of the Rift network to the other in minutes or hours. Last but not least, Free Lanes are artificial devices built by a race now extinct that used to rule the galaxy called the Priory, who it is believed directly created mankind to take their place explaining our unusually (in the series) fast development and evolution. Free Lanes are gigantic structures, basically artificial singularities, which are linked by massive jets of FTL particles like highways. Ships with special Star Sails, which have to be the size of a city, can “ride” these Free Lanes from one point to the next, and there are literally millions spread across three galaxies—the Milky Way and two of our Satellite Galaxies. Once a ship reaches the end of a Free Lane path, they can use relativistic travel or other kinds of FTL to go where they please, so these Hub Systems are extremely important, and overflowing with trade ports and colonies from thousands of races, basically imagine a system where every planet is a city-world and every moon is converted into Babylon 5 and you imagine what a Hub System looks like. Interestingly, it seems many of these systems were artificial in the first place, and expanded upon by other races, and the Priory made them specifically to be trade hubs and economic centers. So any thoughts appreciated, like is there a huge plot hole I missed or something, anything maybe I should add or explore more? I didn't go into precise details on some parts but I could so feel free to ask.