This engineering question got me wondering. If cross feed technology were sufficiently developed, and stresses could be managed (these are big if's, and there are more I'm sure), how would these various configurations roughly compare?
Are there numbers out there, or could someone ballpark them, or tell me a simple way to ballpark the missing values?
The first two are copied from Wikipedia's Falcon Heavy. They are tons to LEO. They also agree with the numbers in this Reddit which is probably not independent, but that table also gives the third number as well.
F9 FT: 22.8 FH: 54.4 FH w/cf: 64.5 FQH: ? FQH w/cf: ?
In my very unofficial acronyms, FQH = 'Falcon Quad Heavy' - four F9-like boosters, and w/cf = 'with cross feed'.
Cross feed for FQH might have boosters 1 and 3 feeding into 2 and 4, and dropping off first, while boosters 2 and 4 are also simultaneously feeding the core. It's a mess of engineering - I'm not proposing it as a real solution - it's more of a best possible (or best imaginable) upper limit.
edit: I'm starting to rethink this question; The potential benefit of the "FQH" might be better realized by optimizing throttling and even staggering engine starts. In other words, maybe this is more difficult to even "ballpark" than I first realized.