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Comment by chasd00 | Hacker News Reader

yeah i think BFR and the upgraded Falcon 9 pretty much obsoletes Falcon Heavy almost immediately. The Heavy just took so long to put together, it was suppose to fly 4 or 5 years ago right? I've heard it reported that the Falcon Heavy engineering was much harder than anticipated. Does anyone know what some of the major obstacles were? The concept seems straightforward but where did they start getting into trouble?

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I remember reading a quote from Elon where he says that at some point, they realised it's less "strapping three cores together" than "flying three cores in very close formation"

The stresses involved are truly enormous, and the whole thing must be very well balanced to avoid putting even more stresses on the frame.

Something as stupid as fueling the rocket needs to be done with care, as they're dealing with super-chilled liquid oxygen: The cold temperatures make the rocket contract a little bit, you have to make sure all three boosters contract exactly the same otherwise you can break the attachment points.

After countless hours of experimenting with additional struts in KSP to keep my rockets from going through RUD I have a weird feeling as if I understand this on some level. Rationally, I don't think that I have any real understanding of rocket science from KSP - but that weird feeling just won't go away.

My understanding is that the center core was nearly a complete redesign because of the greatly increased load from the side boosters.

The structure in the core is beefed up a lot, but I wouldn't call it nearly a complete redesign as the other functions remain basically the same. Nearly complete structural redesign, I agree.

One of the things that slowed it down a lot was the continual development of the Falcon 9.

With the Block 3/4/5 series of the Falcon 9 (5 is the final design and mostly focused on reusability upgrades, 4 is interim) they have a relatively stable base rocket to develop the Heavy variant against.

Yeah, the regular Falcon 9 is so much stronger nowadays, it can basically do what was planned for Heavy back in ~2015. Just at the thrust difference between Merlin engine iterations (https://en.wikipedia.org/wiki/Merlin_(rocket_engine_family) ), and add the fact that the stage is longer than before, and you have a pretty capable base rocket.

You can read about the dramatic improvements here too: https://en.wikipedia.org/wiki/Falcon_9

BFR could easily run into similar delays giving Falcon Heavy a longer useful life.

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