...Which sounds remarkably similar to Honorverse Apollo when being run by ships that can't run them directly from their own computers. Like the battlecruisers in the latest book, blowing up that Solie task force.
OK, exposition time- it's the (late) twenty-first century, and humanity's got small colonies going on mars and Jupiter's larger moons, and scientific bases elsewhere, as we finally got fusion working so Orion drives became viable again. But fusion this time. Someone finally got something along the lines of a quantum 'entaglement' com going -it isn't really, because it has 'frequencies' which aren't really frequencies, but close enough- and is cruising the 'frequencies' as a form of SETI. And lo and behold, he hears a signal on one of them.
Cut forward a few years. It's a Contact-style message, basically a huge engineering diagram. We can build it, but we really don't know what it does. Fortunately, once we suceed in decoding a certain bit that looks like an explanation, we find out. Simply put, it says, more or less, "This is an FTL drive. Here's how to use it." Cue massive skepticism... until a ship winds up flying from the Earth/Moon L1 point to Jupiter at ~1000 C.
Skip forward a few decades. Humanity's got a few interstellar colonies going, we've met an alien race on one of our scouting missions, and all is going pretty well. The FTL drive lent itself quite nicely to modification to an FTL detector, so we can see stuff coming in. Then a scouting fleet stops sending back messages. And that's where the thing starts.
Ok, back to the tech- FTL drive is about twice the size of a school bus and requires about 1 GW of power while operating. FTL sensors, the best we can build see about five light-years out. And our FTL comm is similar to our radio now, as in, we can do short range- in this case Earth can talk to Alpha Centauri, but nothing else, at least for a shipboard transmitter- but we can recieve from much farther. Depending on the size of the reciever. So messages from ships back to Earth are usually sent back by (very large) messenger drones. They're basically an FTL drive, a hard drive, a radio, a fusion generator, and the stuff you need to use some of that output for thrust. Basically venting a bit of the explosion behind the drone. That's how ships do it too, at this point.
I'm hoping to find a reasonable way to get very short effective range, I.E. a thousand kilometers being a long-range engagement. Any ideas on that? And thanks for all the help so far.
