No, there is one mount just on one side and the engine also has to be prepared for ferrying. There are quite a few planes which can do this, sometimes the engines have a pod put around them, in this case I think the fans are removed to reduce drag.
In all cases, the engine isn't working. Think of it more like putting an engine on your car roof rack.
Ah, OK. I read it as upgrading it to a six engine bomber and carrying the load internally - that would require significant airframe modifications though so probably a silly idea.
Given the rest of the Air Force fleet I can't see that a 747 with one bomb would the that useful, but it's one more airframe I suppose. It would also need to be fitted with the arming and release mechanisms so quite a lot of additional work involved there too.
Yeah, that was my thought. I bet you could fit an awfully big bomb under there... or a long range tank with enough fuel in it to keep you in the air for a day or more.
747 was developed in the 60s when it was clear that ICBMs were the future of long-range bombing. I doubt they were thinking of military applications with this. The only long-range bomber missions envisioned by that time were super-sonic deep penetration designs (e.g., see XB-70 bomber), and even those were abandoned in the face of improving anti-aircraft missile tech (see: when the Soviet Union shot down a U-2).
I dunno, something the size of a 747 is probably already flirting with the limits of diminishing returns. It's not unlike the rocket equation. Fuel is very heavy, so adding more fuel means you burn more fuel, meaning you need to carry more fuel...
In all cases, the engine isn't working. Think of it more like putting an engine on your car roof rack.