That drawing shows a cutaway view, showing the forward end of the motor. The "Igniter" is installed in the forward end of the motor.

This Nike Booster image shows a similar arrangement.

Dave F.

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Not sure exactly how many, but the vast majority of large solid rocket motors that I have seen cutaway views of (like these and the shuttle SRBs for instance) are ignited from the head end to ensure good, swift flame propagation down the entire core all at once, or as close to that as it can be.

Seems like I recall hearing way back when that the shuttle SRB igniter threw a flame more than 100 feet long. And as many of us recall from shuttle launches, when the SRBs ‘lit’ they lit quick with almost an explosive blast off the pad; basically, ‘instant on’ ignition.

‘Chuffing’ of mid-to-highpower hobby motors on the pad can be a minor nuisance most of the time; with larger motors like these it could very easily be catastrophic.

Earl

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Earl L. Cagle, Jr.
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One major point of difference between model rockets and their full size counterparts is that most full-sized rockets are filled with propellant and oxidizer. Most model rockets have a much smaller because of their smaller motors. A very large part of the tubular section of a real Black Brant III (or any other sounding rocket, for that matter) will contain propellant. If we tried to do that with a model rockets, recovery would be and is very difficult. Think of the Estes Mosquito, Streak, Scout, etc. if you fly one of those models with the largest motor that fits in it.

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Mike Toelle

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It's called a head-end igniter.
-JH

Then I wonder if the solid rocket boosted SUBROC’s we carried on the sub had a forward igniter. Since I wasn’t a torpedoman I wouldn’t have had a need to know about the innards of a nuke weapon. Two dangers of the SUBROC that we ALL were aware of was the Tritium in the warhead and the fact if the rocket motor ever started in the torpedo room or in the tube it would incinerate the boat.

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All composite propellant motors, whether hobby or professional, are ignited from the top, with very, very few exceptions. There aren't many end burner composites in the world. Almost all composites are some sort of core burner, either c-slot for small hobby motors, bates grain, etc, and then you add star cores, multi cores, etc. If you don't ignite from the top, you get chuffing at the very least, not a good thing for big steel cased rockets with warheads! The thrust of a composite motor has to do with the total surface area that is burning at any given time. With various core burners, bates, etc. they are working out a surface area to match the empty volume of the casing as the propellant burns away, keeping as close to optimal thrust as possible. Ignite farthest away from the nozzle and let the flame front ignite the rest of the length. Ignite near the nozzle, and the top part doesn't ignite immediately so you get low initial thrust and "chuffs" or worse.

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SUBROC . . .

Dave F.

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The only ones I can think of are the Aerotech Warp 9 end-burners.

Dave F.

Yup, that’s the one. Confidentially, we hated carrying the SUBROC. It required an extra guard in the Torpedo Room and the kill radius of the weapon would probably take out the firing sub.

__________________
Never trust an atom. They make up everything.

4 out of 3 people struggle with math.

Chemically, alcohol IS a solution.

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Another exception is the Aerotech/Apogee E6 Blue Thunder motors (both the 24/40RC loads Frank Burke's rocket gliders use and the single use motors Apogee sells). I suspect but don't know for sure that the Apogee F10s are also.

Definitely niche motors.

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Bernard Cawley
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