multi-stage ignition tips wanted!

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Lamp
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Re: multi-stage ignition tips wanted!

Postby Lamp » Mon Aug 09, 2010 11:17 pm

I don't think the vent holes really matter that much for motors taped together or butting against each other, especially C's as the flame front would be right at the nozzle to light the second motor. for smaller motors or if they are separated at all the vent holes are required to allow the air between the motors to vent and therefore prevent the possibility of the air acting like a compressible barrier, stopping the flame from reaching the second motor.

I had one of the motors in a BP 2 motor cluster fail to ignite on Saturday. Fortunately all that happened was it flew lower than expected and ejected a second or two after apogee. It was my first cluster ignition failure but next time I'll give the BP in the nozzle a little scrape for added insurance.
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OverTheTop
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Re: multi-stage ignition tips wanted!

Postby OverTheTop » Wed Aug 18, 2010 2:58 pm

I would imagine as the BT diameter gets larger it would be moderately beneficial to promote flame travel.


The vent holes between the two stages allow hot gas to flow from the booster in the direction of the sustainer. Apparently it is burning particles of BP flying forward rather than pure flame or hot gas that causes the ignition of the sustainer. The vent holes help encourage the gas flow forward (carrying the burning bits) when the booster burns through, and also assist in making sure the sustainer is held in place for the 30ms or so for ignition, rather than being blown off by the pressure.

I suspect the vent holes become more necessary as the separation between motors increases.
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Jackwolf
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Re: multi-stage ignition tips wanted!

Postby Jackwolf » Tue Dec 05, 2017 11:45 am

Just a quick question, do you need any certification to build and fly multistage rockets?

Thanks

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kopius
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Re: multi-stage ignition tips wanted!

Postby kopius » Tue Dec 05, 2017 12:00 pm

Jackwolf wrote:Just a quick question, do you need any certification to build and fly multistage rockets?

Thanks

That depends on what impulse you are planning on flying. If the total impulse is going into HPR, then yes.


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Jackwolf
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Re: multi-stage ignition tips wanted!

Postby Jackwolf » Thu Dec 07, 2017 10:23 am

Great, Thanks


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