Booster Motor Distance From 2nd Stage Motor - How Far Is To Far?

For a LPR D-12 booster motor, how far can the booster be from the 2nd stage motor and still ignite the motor?

Is 9" away too far? Would putting a smaller "umbilical tube" inside the BT-50 body tube keep the volume down and help?

I could bench test it but was hoping some folks here had some first hand knowledge.

I'm planning to build a TIE Fighter as a booster stage for my X-Wing, but I'm not wanting to experience a lawn dart.

Not interested in air starting the 2nd stage... trying to keep it simple.

Thanks in advance!

I've done a C6-0 booster to sustainer at 10 inches and had no problems. The secret is to have vent holes up near the sustainer motor so the air can leave the tube and let the hot burning parts of the booster motor reach the sustainer motor.

Calling @BABAR (I think)

Gap staging needs a vent near the sustainer motor so the dead air is pushed out and the hot burnthrough gas can get to the upper nozzle easier.

Handeman said:

I've done a C6-0 booster to sustainer at 10 inches and had no problems. The secret is to have vent holes up near the sustainer motor so the air can leave the tube and let the hot burning parts of the booster motor reach the sustainer motor.

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Ignition isn’t the problem. I have done D12-0 up to 51 inches gap. Problem is, once you go much beyond the length of your booster fins, you need to come up with a recovery system for the booster because tumble won’t work over certain length.

Put your vents just aft of the sustainer motor. The vents relieve the pressure of the booster motor burn through (prevents it from blowing off the sustainer/premature separation) but let the hot gas go all the way forward to illuminate the sustainer nozzle. It’s the photons that ignite the sustainer, not particles. (Stine wrote a great book but was proven wrong on that particular point.)

lakeroadster said:

For a LPR D-12 booster motor, how far can the booster be from the 2nd stage motor and still ignite the motor?

Is 9" away too far? Would putting a smaller "umbilical tube" inside the BT-50 body tube keep the volume down and help?

I could bench test it but was hoping some folks here had some first hand knowledge.

I'm planning to build a TIE Fighter as a booster stage for my X-Wing, but I'm not wanting to experience a lawn dart.

Not interested in air starting the 2nd stage... trying to keep it simple.

Thanks in advance!

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how well will your TIE fighter fare tumbling from say 100 feet up?

BABAR said:

how well will your TIE fighter fare tumbling from say 100 feet up?

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We'll see..... Probably not well since the launch field is basically like concrete (hard to find a soft spot in The Rocky Mountains). Something about a TIE fighter crashing appeals to me on some level. I seem to recall a movie where it spun out of control.

My version of the TIE Fighter is made from all balsa. Maybe I should bump the solar array wings up to 1/4" (made from laminated 1/8").. or make them from basswood. I am planning to paper the wings also.

lakeroadster said:

We'll see..... It's made from all balsa. Maybe I should bump the solar array wings up to 1/4".. or make them from basswood.

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This may add more weight, which will make it fall faster.

My first thought was foam presentation board. It’s foam sandwiched between paper, you could buy a black one, cut the gray details out of gray paper and glue em on, if you roll the paper over the foam boards edges it will add a lot strength as well.

Amsterdam said:

This may add more weight, which will make it fall faster.

My first thought was foam presentation board. It’s foam sandwiched between paper, you could buy a black one, cut the gray details out of gray paper and glue em on, if you roll the paper over the foam boards edges it will add a lot strength as well.

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Thanks.. the more I think of your foam concept the more I like it.

For the round fuselage section I could bore a 1" hole through styrofoam, glue the body tube in it, then chuck the body tube in the lathe and sand the spherical portion to shape.

Yeah! They sell styrofoam balls too, all kinds of diameters, shapes are usually true on the “spikey texture” foam, I have no idea what kind of foam it is but it’s sold at craft stores, oddl rockets Sputnik is made from one, apogee-link.

I have no idea how to get a smooth finish with foam other than sheeting or laminating it, im sure there’s lightweight alternatives that would conform to the ball shape.

As for fins I’ve also seen people trim foam board fins with dowels or carbon rod to add round edges, and protect from dings.

Would be an engineering feat (but as a mechanical engineer who better prepared to do it!), but CATO recovery would be perfect functionally AND thematically.

Make it out of foam board and styrofoam. At staging, breaks into three parts, but would be attached by Kevlar.

https://www.rocketryforum.com/threa...th-rarely-intentionally-used-recovery.154004/

https://www.rocketryforum.com/threads/mayday-mayday-gone-fission.35512/

https://www.rocketryforum.com/threads/rebuilt-viagara-better-flight.151946/

I am currently building a Double Mean Machine. It is 2 Mean Machines gap staged. The distance between motors is nearly 70 inches.

Padseven said:

I am currently building a Double Mean Machine. It is 2 Mean Machines gap staged. The distance between motors is nearly 70 inches.

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Holy moly... you must document this.

I can't imagine how the airframe would even be rigid enough to stay straight and vertical.

Oh wow, I want to see details as well. Have you gap staged that distance before? What BP motor(s) are you using in the first stage to get enough thrust? Minimum diameter? Stuffer tube? Very cool.....

Padseven said:

I am currently building a Double Mean Machine. It is 2 Mean Machines gap staged. The distance between motors is nearly 70 inches.

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Please post your results!
I would love to see what the edge of the envelope is.

I will definitely be documenting this. I plan on using a 12ft 1010 rail to keep it vertical through the booster phase at least. I have built gap staged rockets with 28 inches between stages. I have a static test planned for a 60 inch gap.

Padseven said:

I will definitely be documenting this. I plan on using a 12ft 1010 rail to keep it vertical through the booster phase at least. I have built gap staged rockets with 28 inches between stages. I have a static test planned for a 60 inch gap.

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So the stack on the rail will have buttons on sustainer as well as the booster? I ask, because if there is much wind at all, there is a lot of lateral force on the sustainer at the coupling point. So it really helps if the sustainer is on the rail too.

Yes, buttons on both the sustainer and the booster. A standard Mean Machine is tough to manage on the pad by itself.

Are you going to use a smaller diameter tube “chimney” to duct the ejection gas from the booster to the sustainer?

BABAR said:

... It’s the photons that ignite the sustainer, not particles. (Stine wrote a great book but was proven wrong on that particular point.)

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Where would I find more info on this? I have Stine's book, I'm just intrigued by that particular study.

Funkworks said:

Where would I find more info on this? I have Stine's book, I'm just intrigued by that particular study.

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Great video on gap staging that debunks “particle theory”

BABAR said:

Great video on gap staging that debunks “particle theory”

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Thanks for posting this BABAR.. Emma did an amazing job on this.

I have created a separate thread for the documentation of the Double Mean Machine Build. https://www.rocketryforum.com/threads/double-mean-machine.154262/