Falcon Heavy has too many engines.

[Frozen_Heart]

Where do you hear that?

The raptor engine is for the new type of massive launcher that is in current design.

Not for the falcon9 or falcon heavy. neither the second stage.

It does make sense. With the current engine thrust numbers, a 9 Raptor, single core design will have a similar thrust to a Falcon Heavy. A single core simplifies things and a more powerful and higher ISP upper stage provided by a Raptor would make full reusability much more viable.

However nothing like that has been confirmed. The only use of the Raptor that's been announced is on the BFR.

[Kryten]

Falcon heavy is already too big and expensive for the current market, at least without dual-launch or reusability. Given the way both reusability and FH flights are moving, I see it being replaced by a Raptor-powered vehicle before it's flown all that much. A 5-engine design would fulfill the market needs and still have plenty of margin for reusability.

[DerekL1963]

The reason they use 9 small instead of one or two large engines is redundancy.

While there ends up being some advantages (as well as some disadvantages) to having multiple small engines, one of the key reasons Falcon has multiple small(er) engines is that small simple engines are cheaper, simpler, and faster to develop and manufacture.

If your only engine fails, your rocket is ....ed. If one of nine engines fail, you might not be able to land the rocket, but it'll still reach orbit.

A properly designed modern engine fails very rarely. (And having multiple engines actually *increases* your chances of having a single engine fail.)

Multiple engines also require more complex piping, a heavier and more complex thrust structure, more effort (read, $$) to install and checkout.... Some of that can be recouped through economy of scale, yes, but that doesn't mean the issues aren't there.

Engineering is always about tradeoffs, and while SpaceX has chosen a route different than that generally followed by the other players (which tend towards fewer, larger, engines) - that doesn't make their approach intrinsically better or right, just different.

[SargeRho]

Indeed, if however one of your nine engines is, say, 25% more likely to fail than your one engine, and one of nine fails, it's not a big deal, and the one engine failure becomes almost inconsequential. If however, your one engine fails, it's a total loss of vehicle.

[Kryten]

Indeed, if however one of your nine engines is, say, 25% more likely to fail than your one engine, and one of nine fails, it's not a big deal, and the one engine failure becomes almost inconsequential. If however, your one engine fails, it's a total loss of vehicle.

Only if you assume the engine failure is benign enough not to severely damage other systems. That's rarely the case.

[SargeRho]

The Falcon 9 is built to withstand the most likely engine failure modes, and has withstood one such failure mode, I think during CRS-2, when one of the engines lost pressure.

[sgt_flyer]

The Falcon 9 is built to withstand the most likely engine failure modes, and has withstood one such failure mode, I think during CRS-2, when one of the engines lost pressure.

It was for CRS-1 according to the investigation, the combustion chamber was breached because of material flaws - a jet of hot gases then damaged the engine's fuel line, resulting in the engine losing pressure (so it was shut down, and the mission continued)

CRS-2 had a problem with the dragon's draco thrusters when it separated from the upper stage (but they managed to correct it)