Compound motor.

[tan]

I was wondering if anyone has experimented with using in the same motor different types of propellant arrangement. If the core of the motor was APCP and the outer half be candy propellant!
The APCP would give the initial fast burn and high blast off speed and the candy would take over with its longer burn!

Sorry if I am not using the correct technical terms as I am very new to this!
:sigh:

 

[CarVac]

There are dual thrust motors, where one grain is extremely fast and the rest are slow, like the Aerotech K375: one grain of Warp-9 and the rest are White Lightning.

 

[ClayD]

There are dual thrust motors, where one grain is extremely fast and the rest are slow, like the Aerotech K375: one grain of Warp-9 and the rest are White Lightning.

Additionaly there are taylored grian geometry using the same propellant to provide boost sustain using the same propellant... https://pro38.com/products/pro54/motor/MotorData.php?prodid=2772L640-P

For instance, if you had a 4 grain motor that has a neutral thrust curve... take the top 2 grains, and double them to 4 grains... now you have 4 grains at the top and 2 long ones at the bottom.
this requires a propellant that is forgving to the drop in chamber pressure, and needs to burn stable across the varying KN.

Probably better odds at gaining success with the same "genus" of propellant. I wouldnt go as far as to say it wont work , but would be darn difficult to make work.

 

[CarVac]

Is that how the L640 works?

Somehow I doubt that that simple geometry change can produce such a marked dual-thrust step. Short grains would normally regress, but the boost part of the thrust curve is clearly progressive. Plus there's the oddity that the L640 has more impulse than the standard 54/6GXL Classic...

 

[ClayD]

Is that how the L640 works?

Somehow I doubt that that simple geometry change can produce such a marked dual-thrust step. Short grains would normally regress, but the boost part of the thrust curve is clearly progressive. Plus there's the oddity that the L640 has more impulse than the standard 54/6GXL Classic...

My Bad........

I just remember seeing this, and mixed up the info on 1/2 grain vs. "Fast" Grains...
https://www.pro38.com/pdfs/Pro75_notes_V1.8.pdf

On a side note, i have some motors that i have burn profiles where very noticable "grain shut down" steps occur. Very prominent.(but no, nothing like the L640... that is a very stark step.)

 

[McKailas Dad]

I had thought of mixing grains in a AT 29/40-120 case. Baybe a partial grain of an F22, and a part of a F40 to make a 'Jack White' motor. Or even make up some 'Thunder and Lightening' burns?

Of course that would not be legal per NAR, but could it be done? Maybe split the difference between the nozzle sizes?

Oh, how 'bout a 'Patriotic' motor with red, white and blue? :eyeroll:


Just thinking out loud....

 

[ClayD]

i have heard of red/white/blue motors...

 

[Loki Research]

Back in my early EX years I did this a few times.
This is a 54/2000 test. Yea, I was a little excited.

Oh, how 'bout a 'Patriotic' motor with red, white and blue?

Oh it can be done. Having enough patience to do it right is another. :wink:

 

[johnclifton]

I've done this, I call them bi-propellant motors. I've made two 76mm with 20" propellant, the cores were diamondback and Mr. clean with the outer layer of both being a pourable black sparky. Called them L-somethings.
Both worked fine.

Next came a 98mm 15XXX with the outer layer being a poured monolith sparky. Didn't work so well. I now have a minute and a half, plus, road flare gloriously enshrined on Justin's MWP 9 DVD (this was at night).

Gonna try it again at MWP 10. Same case 98mm 15XXX with different core propellant and different processing.
Go to this thread and down almost to the bottom to see a pic that Manny posted of the load.

https://www.rocketryforum.com/showthread.php?41727-What-are-you-flying-at-MWPX

 

[oddmanrockets]

years ago i saw a launch of alternating k550 and k1100 grains launched and it flew really nice. they called it Puff the magic dragon because it made smoke rings on the way up