Fast / slow APCP clustering

[Feckless Counsel]

TRF,

Anyone have experience clustering fast APCP propellant, say Cesaroni V-Max, with long burn APCP propellants? Interest is getting mass to that fin-stable velocity and then a nice long coast.

Specifically lets consider one central Aerotech N1000 and three Cesaroni J1055 as closely spaced radials.

Feckless

 

[edwinshap1]

well the ultimate wildman used 3 K2045s clustered around an O motor. the problem is igniting a larger motor will take longer, and the K motors burnt out before the O came to pressure, so the rocket actually began to fall before the O ignited. luckily it was pretty stable so it didn't land shark.

fast motors will ignite and burn way faster than slow motors, but the slow motors will hopefully ignite before the rocket drops too slow.

 

[Feckless Counsel]

edwinshap1,

You've captures the essence of my question.

Those fast motors burn in 700mS. Delay among motor starts could be as much as 125mS. So clusters of fast and slow APCP motors are impractical / impossible even with CuO thermite ignition?

Comments?

Feckless

 

[cjl]

1) I wouldn't use thermite in a 54mm Vmax. That's just asking for trouble
2) You can absolutely cluster them. It just takes some careful planning

For your proposed setup (3 J1055s and an N1000), I would set it up with the N1000 alone hooked to the ground system with a standard igniter. I would set up the J1055s with dowels and dipped ematches (which is the stock igniter, with a dowel), and hook them to a raven or similar device. It would basically be the same as wiring airstarts. I would then program the raven to ignite the J1055s after a zero second delay from liftoff. This is because the J1055s come up to pressure very quickly even with the stock igniter (<200ms typically). This would allow the central N1000 plenty of time to get up to pressure, and as soon as the rocket began to move, the three J1055s would be lit. They would probably ignite within the first two feet of travel on the rail, giving the rocket the kick it needed to become stable without the risk of the N coming up to pressure late.

 

[Agent Titan]

Amen, CJL. I was just about to post almost the same exact thing.

 

[bobkrech]

As the previous two responders stated, you need to make sure the central N1000 is up to pressure before you ignite the J1050s otherwise you will ignite the outboard and in the worst case not ignite the central N1000 at all.

Many CTI motors use a BP starter pellet so these CTI motors should only be ignited with the CTI igniters they were designed for. The starter pellet is designed to ignite the motor quickly and a more energetic igniter may overpressurize them.

Bob

 

[cjl]

Bob: the 54mm Vmax motors do not contain a starter pellet due to the large core size. Instead, they ship with dipped ematches. I still wouldn't use any particularly energetic igniters though.

 

[ClayD]

If you ignite the N1000, you can airstart the others at launch detect. if they are fast and light easy, shouldnt be a problem