J85s are old technology. They're a turobjet, not a turbofan, nor do they have any electronics on board. This makes them highly inefficient engines. They're chea

J85s are old technology. They're a turobjet, not a turbofan, nor do they have any electronics on board. This makes them highly inefficient engines. They're cheap, there are plenty lying around from old 4th gen fighters, and plenty of old guys who know how to work on them. I suspect they used these just to get the XB-1 airborne, making progress while they find a better engine.