Falcon 9 and Falcon Heavy

jmattingly13 said:

I suppose you're implying staging here, because each F9 boost core has nine Merlin engines (and the second stage a single MVac). I'm currently building a nine-motor cluster F9 with a core 24mm and 8 18mm mounts in the Octaweb configuration. All to scale. It's hard to cram all those motors in--a 3" airframe is just barely enough to place the cluster of 8 18mm motors. I thought about doing second stage, but determined it would just be too hard to stabilize the whole thing. Transition and nosecone are in the process of being printed. Given how hard I think it's going to be to light a single core, I don't think I'll be strapping any more boosters on. (On the other hand, I am doing that for the F9 kit they sell...)

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mad4hws said:

I was thinking about a cluster of 9 18mms. with C6s, this would allow for about 70 newtons of impulse, which would be enough to get the bird airborne to about 1000 feet. For the second stage, I agree with you on stability. I'm thinking about having spring loaded fins of some sort pop out of the upper stage when it releases from the sustainer. Even with this, it would be difficult to stabilize because of it being so short. Still, it would be really excellent to see and would be a challenge to build. if I could pull off the Falcon 9, then the next logical step would be the Heavy. I haven't clustered that many motors before - I'll need to figure that out too.

to get the motors in the 3x3 configuration, the airframe would need to be a little bigger than 3". I was thinking about getting 3" PVC pipe and using as a mandrel for a fiberglass lay-up. it's outside diameter is 3.5".

you said you're printing your nose cone and transition? Would love to see some pics.

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JRThro said:

If you're going for scale, the engine arrangement isn't 3x3 anymore, it's what SpaceX calls the Octaweb arrangement, which I think is just the 8 engines in an octagon.

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luke strawwalker said:

And one in the center... thus nine engines... just not in a cube arrangement anymore...

Later! OL JR

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JRThro said:

Oh. Yeah. Duh. :blush:

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jmattingly13 said:

The 3x3 configuration for F9 is no longer in use. The new(er) F9 v1.1 uses the Octaweb, as SpaceX calls it, which makes it easier to shove 9 motors into a 3" airframe. The combo of the short length of the second stage and the ~4" diameter of the fairing has led me to forgo a second stage. The fins would just need to be too large.

I'll start a build thread with good pics when I get the nose cone and transition, so probably some time next week or, more realistically, the week after (next week is finals...).

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