So imagine humanity is an interstellar species and we have hit peak rocket fuel and we have to find a renewable form of propulsion and furries have taken over the world and now theres an excess of dogs, so we make an experimental space ship that has a bunch of breeding pits and arms like the canadaarm on the ISS which is like a big robotic arm that can manipulate shuttle sized objects, so we scale it down so it can hold a large dog, like a saint bernard ok and then we throw all the dogs out the back of the space ship for sustained propulsion and its called the dog engine and we solved the rocket fuel crisis by throwing dogs really fast away from us its cruel but if you dont listen to them barking its almost like its ok for them to be dumped into the dark and empty vacuum of space but we also need to consider that we need more matter to make dogs to hurl them backwards so we farm hydrogen from gas clouds and we collect carbon from dogs that other dog engines have left behind and we have a dog engine highway that has a trail of dogs that dog engines swim through