It's also useful to sort of run a gedankenexperiment and visualize the whole flow of landing three cores from an FH launch, all at LZ-1.



The cores come in translating from east to west; they don't even cross the shoreline until after the landing burn starts, I don't believe (though that is for the traditional single-engine landing burn; we've not witnessed a landing burn that uses three engines on approach to LZ-1 yet). You really want to stagger the landings by at least 30 seconds, maybe more -- something that can be designed into the boostback and entry burns.



So, you land your first core. It comes in from offshore and rounds out, in terms of a straight vertical descent, no higher in altitude than 100 meters, maybe less. (Close enough to the ground that the engine exhaust will trace a blast pattern from the edge of the pad into the center, meaning the core translated into its vertical descent after the exhaust began to impinge on the pad surface.)



That core, it seems to me, had better land on the westernmost pad of the pads available. You do not want either of the subsequent stages to try to overfly a landed core, that way lies almost certain damage to the landed core and the possibility of interfering with the core in flight, maybe even enough to cause it to crash. I'd imagine the second and third pads will be east of, and well north and south, respectively, of the far westernmost pad.



So, your first core lands on the western point of your pad triangle, and here comes your second core. If it comes in wobbling for any reason, tips and RUDs, you want the third pad far enough away from the debris radius so that it will be "clean" enough for a successful landing of the third core. You also want it far enough away from the first landed core to avoid flying debris from being likely to damage that one.



That's the worst case scenario. You also have the scenarios of:



- the first core to arrive hitting and crashing,



- the first two cores crashing,



- the second and third crashing,



- just the third crashing, and



- all of the cores crashing.



The scenario I described, though, when the first arrival lands successfully and the second RUDs, is the one where you endanger both a successfully landed stage and the potential safe landing of a subsequent arrival.



That scenario is the best reason why you don't want to try and land all three cores on the present LZ-1 pad. Remember, these are still labeled by SpaceX as experimental landings...