24mm Sugar EndBurners ?

After flying a two stage 24mm sorbitol rocket I was curious about trying an endburner for the sustainer.
A longer/lower avg. thrust burn should squeeze out some more altitude.
It seemed like some 1 atm burn tests could give a rough idea of some possible formula variations to try.
Curious about a couple of catalysts, and perhaps using some Maltitol with the Sorbitol I did a table matrix to cover these rambling ingredient questions:
Sulfur was one catalyst and the other ...well....let's call it catalyst "V". :-P
(Don't worry what "V" stands for ... the sulfur won, in the statics, anyway. :-)

Here is the table of the one atmosphere strand burn tests of the various formula combinations. The results are in seconds per inch.

KN/Sorb  65/35
KN/Sorb/Malt  65/18/17
0% Sulfur
1% Sulfur
5% Sulfur
0% Sulfur
1% Sulfur
5% Sulfur
0% "V"
10 sec.
10 sec.
9 sec.
8 sec.
7 sec.
6.5 sec.
1% "V"
7 sec.
7 sec.
5 sec.
5 sec.
5 sec.
4 sec.
5% "V"
5 sec.
5 sec.
5 sec.
4 sec.
3.5 sec.
4 sec.

The underlined results above represent the formulas that were chosen for static motor testing.

A fellow rocketeer had asked if I'd ever heard of using a conical core to get an endburner off to a faster start....
... I hadn't heard of such thing so out of curiousity the grains were poured with a short concave conical core at the nozzle end.

The depth of the cone can be adjusted to adjust the initial thrust spike....

Back to the formulas:

Motor #126 was 65/18/17/5/1 KN/Sorb/Malt/S/"V"
Motor #127 was 65/18/17/5 KN/Sorb/Malt/"V"
Motor #128 was 65/18/17/5 KN/Sorb/Malt/S

Static testing gave the following thrust curves:

The area under the curves is greatest with the motor 128. So that one was chosen for motor comparison purposes.
The data was plugged into Engedit and showed motor 128 to be a C-3 with a 2.9 second burn.
Avg thrust 2.7 N
Total Impulse 7.87 NS
Peak thrust 8.45 N

I always like to compare to a standard Bates motor so:
I filled that same case dimension (ID 17mm L 37mm)
with a plain 65/35 KN/sorbitol Bates grain having a 5mm core.
Then I static tested it and got the results of:
C9 with a 0.83 second burn
Avg thrust 9.6 N
Total Impulse 7.93 NS
Peak thrust 16 N

I was pleased to see the total impulse about the same using the same case dimensions.

How will the motors compare sim-flying in RocSim ?
Here is the two stage 24mm rocket design for RocSim flying these motors:

But first flying as a single stage along with some Estes motors for comparison:

Altitudes in feet:
Estes A8: 437
Estes B6: 768
Estes C6: 1188
Endburner motor128: 1146
Bates Sorbitol: 944

So the Estes C6 wins in single stage. It has the kick to get it going faster with a max acceleration almost three times the leisurely endburner.
But the reason I was looking at endburners was for a Two Stage Sustainer motor where a Bates Booster will get the rocket up to speed.
My hunch is the Motor128 will have the edge now...??

So I simmed the motors above as sustainers on top of a sorbitol booster (Boost) motor:
The booster motor is a 2 grain sorbitol motor / schematic below:
Altitudes in feet:
Boost + Estes A8: 1309
Boost + Estes B6: 1490
Boost + Estes C6: 1855
Boost + Endburner motor128: 2043
Boost + Bates Sorbitol: 1840

Ha! Long slow burn wins out in sustainer.

To get more altitude a two second delay between booster burnout and sustainer ignition will help so resimmed with the 2 sec delay between motors.

Altitudes in feet:
Boost +2+ Estes A8: 1566
Boost +2+ Estes B6: 1838
Boost +2+ Estes C6: 2286
Boost +2+ Endburner motor128: 2454
Boost +2+ Bates Sorbitol: 2257

Similar pattern with overall higher altitudes.

RocSim screen captures:

(The plain sorbitol Bates grain is called "Ti-sponge 0" in the following tables)

Single stage Sim-flights:

Two stage Sim-flights:

So what's next?
Try some different catalysts
Also a longer motor to see if the case will survive a 5 or 6 second end-burn.

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