Cesaroni M3700 White Thunder.... 5.3Grain Case?

Kinda random question, but I couldn't help but notice that CTI has a reload for a 5.3Grain Case. The M3700 White Thunder.

It turns out they make a certified .7 grain spacer for the 6G case and they also make a 5.3Grain case.

Just curious about what do you think about it?

Has anyone ever seen it?

Own the case? Spacer? Reload?


Why?

that's a bit...funky



Braden

Ya exactly what I was thinking.



I kinda want one...


Or maybe a 6G Case...

I've got the spacer, and I've flown it in the 6g case. It's one hell of a load. It took my Ultimate Wildman to 8,200ft, pulling 20G's throughout the burn.

It uses 4 long grains with an interesting core. It has a standard round core, with small slots on each end.

The flight video is on this page: https://www.mdra-archive.org/photos/ESL151/
It's titled "Ultimate Wildman."

From what I understand, the motor was originally for a military contract. CTI liked it so much that they decided to certify it for hobby use.

Rocketman248 said:

The flight video is on this page: https://www.mdra-archive.org/photos/ESL151/
It's titled "Ultimate Wildman."

Click to expand...

Flights like that make me appreciate White Thunder propellant even more. Great propellant, great load, and nice flight! That's awesome that CTI is willing to do such a unique geometry in a smaller motor. When you built it, were there any notes about lining up the slots, or just load it 'n light it?

bandman444 said:

Why?

Click to expand...

I'm betting that they had to shorten it up from a more "normal" 6g variant because that propellant was getting a little ignorant in the longer case. The fact that they had to go to four longer grains with that unique geometry indicates that things were getting a little crowded in the core; it's hard to burn 7000 N-sec worth of propellant that quickly.

Rocketman248 said:

I've got the spacer, and I've flown it in the 6g case. It's one hell of a load. It took my Ultimate Wildman to 8,200ft, pulling 20G's throughout the burn.

It uses 4 long grains with an interesting core. It has a standard round core, with small slots on each end.

The flight video is on this page: https://www.mdra-archive.org/photos/ESL151/
It's titled "Ultimate Wildman."

Click to expand...

finocyl core


Braden

daveyfire said:

Flights like that make me appreciate White Thunder propellant even more. Great propellant, great load, and nice flight! That's awesome that CTI is willing to do such a unique geometry in a smaller motor. When you built it, were there any notes about lining up the slots, or just load it 'n light it?

Click to expand...

I wondered the same thing, so I asked Jeroen. Just load it and light it. The o-rings kept everything spaced properly.

UPscaler said:

finocyl core

Click to expand...

It wasn't a true finocyl. The slots only extended about an inch into the grain.

Rocketman248 said:

I wondered the same thing, so I asked Jeroen. Just load it and light it. The o-rings kept everything spaced properly.

Click to expand...

Oh yeah - that makes sense. Especially since...

Rocketman248 said:

It wasn't a true finocyl. The slots only extended about an inch into the grain.

Click to expand...

I was ready to jump on this one and back you up, but on closer inspection, it actually is - a Finocyl is a 3D geometry, varying in r, θ, and z - it's a "finned cylinder", with the fin depth going to zero as the z coordinate goes from the nozzle end forward. Slots that go all the way through are "cruciform" or something lame like that, I think Nakka calls it a pseudofinocyl but there's too many soft consonants in that word to make it easily pronounceable. It's an awesome geometry (very tailorable thrust profile, very controllable mass flux, very high propellant loading fraction) and it's ADORABLE in a grain that size!

What about slot-to-solid configuration, Rocketman248?

Agent titan: assuming I understand what you mean properly, it doesn't matter.

This is what I mean:

Say the slotted side of the grain = A , and the unslotted side = B.

Would it matter if the grains were put in in different ways:

A
B

A
B
(etc.)

OR


B
A

A
B
(etc.)

Ohh...

I think they're slotted on both sides. I'm not positive though.

Yup. They're slotted on both sides. As stated above, you don't have to worry about lining up the slots or anything. Just put the O-rings between the grains. Like the N10,000 and a lot of the bigger CTI motors, you need to glue the grains in.

Ohhhhh, kay........

That makes more sense, because I would think it could cause some weird pressure/performance differences if they were slotted on one side, and you aligned them to make un-even "pockets" that could mess it up.

Instead of cupping the grains on both ends they slot them. It also helps with a little more kick off of the pad.


JD

Actually, there's no real initial kick. The thrust curve is almost perfectly flat.

https://www.thrustcurve.org/simfilesearch.jsp?id=1773

The reason that it's flat is that the propellant burning area remains constant during the burn time.

Contrast this to a single propellant grain with a central bore. If the grain length is many times its diameter so the 2 end areas are insignificant, the circular central bore geometry is progressive, since the bore increase with time and so does the burning area and the thrust. If the outer diameter is 3 times the central bore diameter, near the end of the burn you have 3 times the mass flow rate, thrust and chamber pressure, none of which is desirable. In practice, you can reduce the progressivity by breaking a single long grain into n bates grains with specific length to diameter ratios so the the burning area remains relatively constant during the burn.

Another advantage of a finocyl or a star bore geometry is that there is more surface area so for a given casing size you get more thrust as thrust is proportional the burning area, all without changing propellant formulation, eliminating the need to add catalysts to increase the burn rate.

Bob