Falcony Heavy with Raptor centre core and Merlin side boosters

[gin455res]

SpaceX always optimizes for cost.

I fail to see how either the OP's mix of raptor and merlin cores or shifting to a Nitrox/RP-1 mixture is going to be cheaper for SpaceX to implement than the company's current plans.

It's like the Mini-ITS idea - I can see the benefits of having one but I can't see SpaceX building one because I don't see them building something that's not on their critical path. SpaceX doesn't need Mini-ITS so why spend the money to build one?

Has anyone Modeled a sustainer core with 2-4 over-expanded + 1 standard central merlins?


Could this reach orbit without an upper-stage?


Re-entry may be interesting as the angle of entry will be much flatter, the core will initially be weightless, and the grid fins will enable a high-lift entry, surfing a very narrow shockwave.  (Can a core become a true hypersonic glider with the greater control authority of the larger grid fins.)


How would the 'wing-loading' of a 3-5 engined core compare to a capsule, or the shuttle orbiter?


Current entries the booster weighs nearly all 100% its empty mass and it is coming in much more steeply.

[Lars-J]

Has anyone Modeled a sustainer core with 2-4 over-expanded + 1 standard central merlins?

How and where would those over-expanded Merlins fit?

[rakaydos]

Has anyone Modeled a sustainer core with 2-4 over-expanded + 1 standard central merlins?

How and where would those over-expanded Merlins fit?

Take out 2 regular merlins to fit 1 slightly overexpanded one between them. Probably have to kill the center gimbal too.

[watermod]

Despite describing the Block 5 as the final version of the Falcon 9, Shotwell hinted at the possibility of a future version of the rocket that could use the Raptor engines designed for transportation to Mars. Shotwell said Raptor, a liquid methane and oxygen engine for SpaceX’s interplanetary spaceship, has undergone “many dozens of tests” and is progressing well.

“The original idea for those engines were to serve as a propulsion system for the big Mars system, but we are looking at the utility of it on the Falcon program,” she said.

http://spacenews.com/spacexs-final-falcon-9-design-coming-this-year-two-falcon-heavy-launches-next-year/?utm_content=buffered598&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

[whitelancer64]

Despite describing the Block 5 as the final version of the Falcon 9, Shotwell hinted at the possibility of a future version of the rocket that could use the Raptor engines designed for transportation to Mars. Shotwell said Raptor, a liquid methane and oxygen engine for SpaceX’s interplanetary spaceship, has undergone “many dozens of tests” and is progressing well.

“The original idea for those engines were to serve as a propulsion system for the big Mars system, but we are looking at the utility of it on the Falcon program,” she said.

http://spacenews.com/spacexs-final-falcon-9-design-coming-this-year-two-falcon-heavy-launches-next-year/?utm_content=buffered598&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

To me, "looking into the utility" is a way of saying "we're confirming that it's not going to work."

Much like NASA "looked into the possibility" of putting crew on the EM-1 mission but concluded that it wasn't feasible.

[gin455res]

Has anyone Modeled a sustainer core with 2-4 over-expanded + 1 standard central merlins?

How and where would those over-expanded Merlins fit?

Take out 2 regular merlins to fit 1 slightly overexpanded one between them. Probably have to kill the center gimbal too.

Yes, or just remove engines 2, 4, 6, 8  and move 1,3,5,7 inboard slightly and add a larger bell
perhaps for the three engine version have two pumps feeding four bells, plus the central standard engine