Long burn grains or moon burner

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A moon burner as the hole offset near the side, I get the drawing on Google forget the 2 type of grains on the drawing, it's just to show the hole position



drawing.jpg
 
Excluding formulations, long burns are typically end grain burners or shallow cored and moonburns are regressive as a function of core geometry where the flame face increases during the middle of the burn resulting in a 'cresent' of propellant that tapers off from both ends, the thrust curve has a noticable 'hump' in it-thus the 'moon' analogy.
 
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All moonburners are long burn, but not all long burn are moonburners.

Very few long-burn composite motors are end-burning (I can only think of the Aerotech Warp9-based motors like the I49, G69, I59); most are either moonburners or C-slot, both using a small offset core.
 
Very few long-burn composite motors are end-burning (I can only think of the Aerotech Warp9-based motors like the I49, G69, I59)

And Warp9 is the polar opposite of a long burn motor.
 
I find this interesting, in the TRA level 2 study guide there is a question:

Most APCP (ammonium perchlorate composite propellant) rocket motors are central-burning rather than
endburning:

and the answer is:

Because most APCP has a burn rate that is too low for useful endburners.

So your statement:
And Warp9 is the polar opposite of a long burn motor.

Should read "And Warp9 is the polar opposite of a long burn propelant" which would allow it to work for an end-burning configuration like a 8 second I49.
 
Long burners and moonburners - I love 'em both, whether or not they are the same thing.

s6
 
I've been want to cast a gpu moonburners, my question is are they a single grain, or multiple Bates grains. I cou see it be a problem aligning all the cores
 
I cou see it be a problem aligning all the cores
Larger commercial moonburners are usually made in multiple grains for shipment and have to be glued back together and yes, aligning the cores is kind of a pain, especially if the grains are tight in the liner (I'm looking at you, AT M685). Smaller ones like the AT K185 and CTI K300 are shipped as single large grains. I don't know how much more complex casting monolithic grains is.
 
Should read "And Warp9 is the polar opposite of a long burn propelant" which would allow it to work for an end-burning configuration like a 8 second I49.

It took a couple of re-reads to get what you are saying here. Yes, the Warp9 is the exact type of propellant needed for an end-burning application. Unlike most APCP propellants, it burns very fast. When used with the normal bates grains, it makes motors like the I1299 with a burn time of 0.3 seconds. In an end-burner like the I49, it will take 7.7 seconds to burn all the way through the 5.563 inch propellant grain. That means it burns about 18mm per second, which is very fast for APCP.
 
I've been want to cast a gpu moonburners, my question is are they a single grain, or multiple Bates grains. I cou see it be a problem aligning all the cores

Yeah, it's a problem if you don't. A guy in the local club that "rolls his own" did a test burn, motor burried in a pit - nozzle up. Cores were NOT aligned. Spectacular Roman Candle!
 
I cou see it be a problem aligning all the cores[/QUOTE said:
Actually Cesaroni 75 & 98 mm moonburners are not hard to get lined up at all. As indicated in the motor assembly instructions (not quoted). A piece of pipe longer than the stacked grains, such as a copper water pipe or cpvc water pipe that will fit in the core is used to line up the offset core when gluing the grains together in the liner, once all the grains are together the pipe is pulled out leaving a perfectly aligned core. Very simple really. I believe that some of the moonburners even come with the alignment pipe included.

Greg
 
I had the cores a little misaligned (probably around 1/8") on the M685W I flew at XPRS. I asked Karl from Aerotech about it before I flew it and he said they don't need to be perfect. Karl said they misaligned motors on purpose and test fired them (the cores weren't totally blocked) and they burned fine.
 
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