First of all this is not a perpetual motion machine and is not the previous U Reusable Fuel Transit Drive I designed earlier. This type of transit drive, which doesn't reuse fuel, works in theory by having two combustion chambers and their respective exhaust nozzles positioned parallel to the spacecraft's length and perpendicular to its width. Fuel is pumped into the combustion chambers and goes out the two exhaust nozzles at high velocity (the fuel exhausts push the ship forwards when they hit the bulkhead positioned at the fore part of the combustion chambers which is forces 1 and when they exit through the exhuast nozzles which is forces 2), and each fuel exhuast half next travels through a C shaped loop (which is forces 3 & 4 that cancel each other and forces 5) around nearest combustion chamber and then each fuel exhaust travels through its respective symmetrically backwards C shaped loop (which is forces 6 - forces 5 & 6 cancel each other and forces 7 & 8 that cancel each other) until both fuel exhausts hits the ship's bulkhead (forces 9) pushing it more forwards (that bulkhead is parallel to the ship's width and perpendicular to its length). The fuel exhausts don't exit the spacecraft. The structure of the tunnels, combustion chambers, exhaust nozzles, etc. are made up of a theorized new super element I call superglass (the superglass structure negates the necessity of magnetic fields to contain the fuel exhaust particles to keep them from melting spacecraft structure). You'll note that I didn't describe pushing fuel exhausts back into the combustion chambers along the ship's width when they're at forces 9 to become forces 1 again to design this quad thrust fuel transit drive as a perpetual motion machine.