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24mm Sorbitol motors:
Drysophila Project: with construction ideas
About
This page is about the 24mm single use Sorbitol propellant motors that I make for flight and for testing propellant variations.
The standard motor static tests as a D16 and can be made with varying motor ejection delay times.
Numbers of grains can be varied yielding C's thru E's:
I have had good results with staging this system
Staying at 24 mm has several advantages over HPR Ex:
1. Increased Safety
2. Decreased cost
3. Can make static test equipment with minimum cost.
4. More locations are acceptable for this size static testing
5. Staying under 62.5 grams simplifies meeting legal requirements by not needing a LEUP
6. Can fly at more sites without the need for FAA notification or waivers.
7. Making, Testing, and Flying all can be accomplished faster, Don't have to wait for a few big remote launches per year to try things out.
That is why this page is called "Drysophila" Project. When biologists want to study generational genetics they often go with Drysophila.
Fruit Flies are small, inexpensive to feed, and reproduce rapidly. There are not many scientists that study generational genetics with elephants.
There are disadvantages staying small:
1. Static data yields less info partly due to the short burn times.
2. There are issues in large motors that can't be reproduced in small short burn time motors
3. LPR Ex Doesn't get much respect from the Ex crowd that often sees E motors as just good for an ignitor pyrogen.
4. Can't lift as much payload nor large rockets
4. Not as much WOW factor
Safety
The propellant is KNO3/Sorbitol as described at Richard Nakka's site
Note:
Read every thing you can find on safety first.
Here are a few safety sites: Follow every applicable item
Richard Nakka's safety page
Jimmy Yawn's safety page
NAR safety page
Tripoli EX safety page
United Nuclear's formula safety page
There are more..find them, read them, and follow them.
If you dont read and follow safety first or you don't think you need to make it a first priority then CLICK here
For safety I use an oil-bath/double boiler. The heat source must be shielded and cooler than the ignition temp of the propellant. Keep the oil (or paraffin) covered/contained so propellant can not fall into it. Some sites describe other heating methods but I feel safer with the double boiler method.
Legality
It is each persons responsibility to determine the legality of this hobby in their area and any needed permits and paperwork. In the U.S. staying under 62.5grams per motor removes the requirement for some permits and storage requirements.
There are sites that can help with determining this. This site does not get into those details. One of the best sources is to visit a local Tripoli Section and talking to local members who have figured out the local requirements.
Construction
For sites that explain the KN03/Sorbitol propellant used in these motors see the links at the bottom of this page.
Construction uses paper casings and pressed clay nozzles.
To avoid problems with paper case bonding the propellant is poured into cylindrical autoclavable plastic caps (heat resistant).
The motors are assembled using concepts borrowed from reloadable motor systems. The end cap is made of Epoxy with a touch hole drilled through, for ejection.
Basic Construction Pages:
1. Standard 24mm D16 Construction sequence
.........and D16 design schematic with static thrust curve
.........Comparing D16 static results to SRM.xls simulated results
.........Early attempts had failures, and inconsistencies, due to poor paper case bonding;
..................then success pouring in plastic liners: See Autopsy Page
.........The system is now reasonably consistent from motor to motor
2. Two stage booster motor Construction
.........and booster design schematic with static thrust curve (vs SRM.xls simulated curve)
3. More grains/motor? Three grain motor static tests as E43 (SRM-Sims as E49)
Flight.
Have had many successful flights including a nice two stager flight. Lost a few minimum diameter rockets due to parachute drift out of the launch area, into the rocket eating blackberries
I only have video of the fatter rocket I use to keep altitude low. Unfortunately this one's ejection delay took too long and the rocket, with squealer, tangled 20 feet up an oak tree :-( YES the parachute did come out at the last second! sigh.
This is D16 motor construction #78 and had been stored a couple years before flight.
Not sure if that was the reason for the slow ignition startup and overlong delay?
Static Tests and other Projects
1. Static Test Stand Thrust vs Time Accuracy ??
.........So far my static tests have been by video capture frame analysis.
.........I had a hydraulic scale and a spring scale available.
.........I needed to know if they were accurate, so I tested both systems with Estes C6 motors
.........and compared results to the Estes published thrust curve data:
......... Red curve is measured data. Black curve is Estes published curve.
.........(Blue is a hydraulic system that didn't do well for low power).
.........
For these small motors the spring scale was the way to go.
.........It's disadvantage is if a motor starts up very fast one can get spring oscillations overlapping the actual data :-(
2. Comparing Test Stand Accuracy to SRM.xls simulations
.........1. Background discussion: Applying SRM to these Non-Standard "Bates" Grains
.........2. The Standard "Two" Grain D16 Motor
.........3. "Two" Grain Booster D25 Motor
.........4. Two Full Grains E26 Motor
.........5. Three Full Grains E43 Motor
3. Using Static Tests for Formula Variations
.........These are preliminary "peeks" at different formula questions.
.........I'm fickle on my questions, I tend to take a peek and move on to the next question
.........1. Lithium Nitrate; Possible sugar oxidizer? 03/2006
.........2. Titanium fine sponge: Fuel Rich: Thrust Curves. 04/2006
.........3. Titanium fine sponge: Fuel Balanced: Thrust Curves. 06/2006
.........4. Opacifiers: Willow, Graphite, Carbospheres; Thrust Curves 04/2006
.........5. Dextrose/Sorbitol Alloys; Static Tests in low KN motors 04/2006
.........6. Possible Sugar Enburners 1/2007
.........7. Carbosphere Opacifier: Varying the % added This page will die when Geocities is dropped by Yahoo
.........8. Early attempts at Maltitol and Glycerin additive This page will die when Geocities is dropped by Yahoo
..................NEW 3/2009
.........9. TiO2 : Possible Reflective Opacifier; Preliminary Light Transmission Measurements.
..................NEW 7/2009
........10. TiO2 Statics :Preliminary Static tests with TiO2 opacifier
4. Other Projects
.........1. For learning HPR flight the best way is to commercial cert with NAR or TRA.
............. My sugars may be tiny, but I like J350s for commercial
.........2. PDT-5a: Melting Temperature and Slurry Characteristics of Sugar Alloy Formulas
.........Small scale experiments can sometimes contribute to larger projects;
.........Check out projects #4:2 and 4:3 and then the Sugar Shot to Space site.
.........3. PDT-5c: Cure Rates for Sugar Alloy Formulas
.............NEW 3/2009
.........4. TiO2 : Possible Reflective Opacifier; Preliminary Light Transmission Measurements.
.........5. PPP :Preliminary Peak @ Pectin
Links:
Richard Nakka's site A must read sugar site. Don't even start without reading this one.
I would add: buy McCreary's Experimental Composite Propellant It's focus is AP but it has essential motor theory info that is easy to read yet thorough.
Jimmy Yawn's page Recrystallized sucrose and many other great innovative ideas
Nakka's SRM.xls sim software. An Excel file that allows one to sim sorbitol or dextrose motors with Bates grains. (Excellent for sorbitol with it's varied "n" value.)
Inverse Engineering Dan Pollino's site with great projects.
Some of Dan's work with glycerin
McCreary's Book:
Was available at Binder Design, not finding it there now, but do Check out Mike's main page for rocket kits etc.
Binder rocket kits are what I like for my commercial motor HPR flights
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