Ah ha! In the back of my mind I knew this wasn't entirely unprecedented, just couldn't remember where. The scheme, as described in more details by you, is a l

Ah ha! In the back of my mind I knew this wasn't entirely unprecedented, just couldn't remember where. The scheme, as described in more details by you, is a lot simpler, and less concerning than I was envisioning (figures, given this is Space X). There's no cross tanking, that is, feeding the tanks of the central core from the sides. Hmmm, although as I remember, when they had to shut down one engine during an ascent, it shed debris because of the pressure imposed by the adjacent engines. But I note the Merlin 1D, while producing significantly more thrust at sea level (nearly 50%), can throttle between 70-100 percent. Obviously they've thought through these stresses, and of course there are structural implications in making them highly reusable, they're willing to trade off weight penalties for durability, and therefore likely strength. Anyway, thanks for the details, and all the contributions you've made to this topic!