Ideas, Theory & Experimentation

[stix]

"Rocketry" is perhaps not the best category to put this under, but there was nowhere else - "Ideas, Theory & Experimentation" could almost be a category all by itself?

 

But this is to do with sugar rocket fuel, so best be here. My question can be applied to pyrotechnics or almost anything else - it's about the correlation & analysis of data. I don't want to sign up to a math forum, hopefully someone on here may have studied statistics or along those lines.

 

-

 

Over the last six weeks I've been experimenting with Sorbitol as an alternative sugar to my standard Dextrose/Glucose powder (KNDX - 65/35). From what I've read in the past, I've always considered Sorbitol as a great sugar because it melts at a much lower temp (around 110C/230F) than sucrose (around 185C/365F). It has always been too expensive, but now I've come across some at a good price and hence, the experiments begin...

 

I'm not that happy with Sobitol - It's too brittle in the small 19mm/3/4 inch ID size that I'm making. So I'm mixing in Dextrose for strength. I've done about 15 tests with varying ratios and some positive results - it's looking good. Now I need to get the data together properly so I can have and "overall" view.

 

I've recorded in a database the formulas, with the method and results - but not as good as I should have. What I'm faced with is 15 tests. I've printed out the results on paper, and flicking through them is doing my head in - it's too much info to take in. I do have a feel for the direction I need to take, but I would like to refine it.

 

Yes, graphs will be the way to go for the final "visual", but what is the best way to extract the data from my notes to make that graph or graphs? You know, what processes are involved to correlate my data into something meaningful that I can understand and then take a calculated and informative direction?. I've got ideas like making categories and weightings for certain variables etc. but It's beyond me.

 

This is by no means an amazing piece of work in the pursuit of Sugar Rockets, but to me it's worthwhile. I'm near the end of this and need to refine things further and come to a result.

 

Cheers.

Edited August 4, 2015 by stix

[schroedinger]

Maybe you can post an example of the data you've collected, that would help.

[stix]

Thanks Schroed's - This is indicative of the data for one experiment.

 

 

25/7/15: Composition Formula & Specifications.

FUEL: KNDXSB16+C

KNO3: 62
Dextrose/Glucose Powder: 22
Sorbitol Powder: 16
+ .3 Carbon Black

----

Production Method:

MELTED METHOD - USING THE NEW OIL PAN.

The purpose of this mix is to make the mix more pliable for casting. Also no Dextrin with this as it's looking like Dextrin may contribute to the faster burn rate.

1. Melting Stage: 150C (302F) works well - nice slurry, and much more "liquid" than previous tests.

2. Drop back to 107C (225F) - ????? Nice putty but still a bit hot to handle - but will have to stick with that.

Even though it's hotter - 120C (250F) may ensure that the putty is nice and pliable. TRY ON THIS MIX?

-

 

Results:

25/7/15: Overall this seems the best mix so far (maybe try more SB - KNDXSB18+C ?)

250F seems ok but a bit hot - I managed to roll a couple of strands - seems a nice "putty" but I noticed that there was some slight crumbling when the mix touch my (colder) hands - it was also very hot and stuck to my fingers - not good.

I've dropped the temp back to the standard 225F (107C). The mix is still good to roll - better than 250F.

Overall, this mix is looking good. It's not too hot, therefore "snakes" can be rolled easily. The mix doesn't "set-up" too quick. After 1-2 hrs, the smaller strands (2-3mm) can still be carefully bent.

BURN TEST: Doesn't burn too fast - this is good.

After about 4hrs, some of the thinner strands are still flexible (slow bend). It will be interesting to see if it has completely cured over 24hrs.

It seems quite strong but will have to check again when fully cured.

27/7/15:

Most of the thinner strands (3-4mm) have cured and snap relatively easy but not too weak. The larger 5-6mm strands are obviously much stronger and a few are still slightly pliable. It will be interesting to compare with the next mix KNDXSB18+C.

Also I will be making a standard KNDX+C mix as a "base-line" comparison, ie. test for burn rate and strength - I never did really do this mix properly with the new oil pan.

 

 

 

Most of this was written "as it happened" with evaluations made after days (even after many days) and still a work in progress. I should have been more diligent with the recorded events but I think I have enough to gather an overall picture.

 

Cheers and thanks for your interest - Like I said, there must be some structure or procedure to make sense of the ramblings.

 

Cheers.

 

[EDIT] Probably too much "observational" than actual measured - hopefully enough info to make a reasonable analysis.

Edited August 4, 2015 by stix

[mikeee]

You should try some Erythritol there are several R-Candy guys that use it for big motors.

Scott has some good tutorials and information on making motors from this compound.

 

http://www.thefintels.com/aer/rocketindex.htm

[stix]

Thanks for the info Mike, but I think you must be looking at this differently than I am. I'm not looking for a new sugar to use - I'm looking for some ideas as to how I can collate and review my data (pretty slack data that it is). The question I was asking isn't particular or exclusive to sugar rockets or pyrotechnics, but about data analysis.

 

I'm familiar with Scott Fintell's site and many other good ones which I have gathered great info from many times. I've tried Erythritol and Xylitol in the past but they're expensive so I didn't go too far into it.

 

I should have taken better notes but I was being lazy - I've made enough sugar rockets over the years that I'm getting a bit bored with it, but would like to finalise a formula and easier method for "my use" - using Sorbitol.

 

So, back to my data analysis conundrum. The reality is that there is no short-cuts - I sort of hoped there was but it will take some work.

 

Cheers.

Edited August 6, 2015 by stix

[schroedinger]

From your notes i would make the categorys.

Castability

Curing time

Burn speed

Coocking temp.

 

Much more isn't there from your notes.

 

For erythritol, it is a reallyy nice sugar for rockets, but not really suited for those small rockets. It has really good power but needs some time to build up (prob. Pressure related). In a 3/4 it kicks in at the momment right before end of burn time. Better use sorbitol on these small rockets.

[stix]

From your notes i would make the categorys.

Castability

Curing time

Burn speed

Coocking temp.

 

Much more isn't there from your notes.

 

For erythritol, it is a reallyy nice sugar for rockets, but not really suited for those small rockets. It has really good power but needs some time to build up (prob. Pressure related). In a 3/4 it kicks in at the momment right before end of burn time. Better use sorbitol on these small rockets.

 

Thanks for that Schroed's, much appreciated.

 

I sort of figured that properties/categories would need to be defined, I just needed a little push and confirmation from someone else - it all seems so obvious to me now! One other category would be strength - there may be more so I'll need to look over what I have, then define them.

 

I imagine then I'll need to give those categories a number for graphing purposes. Then finally decide which properties or characteristics are beneficial to compare - then graph that. I can't think of anything else at this point but there's likely going to be some other issue along the way - or maybe not.

 

The good thing is (and quite pathetic), is that the database program I'm using was written by myself in FileMaker Pro. It's easy to create drop down lists and input boxes for numeric data, then export the data as a csv file. Like I said, pathetic that I didn't foresee this in the first place, but just went headfirst into it. I didn't think I was going to do that many tests.

 

I've got plenty of samples for testing, which is good. Burn rate can be measured via video and a gauge, strength will just have to be measured by "feel" because I'm certainly not going to be making some contraption to measure it, although I probably could, but a tangent too far.

 

You are right about casting sugar rockets for small 3/4 inch (1lb size?) It's fiddly and sets up too quick, hence my standard "putty" method with dextrose which has worked well for me in the past. The introduction of Sorbitol was to improve pliability and extend setup time, hence my latest testing saga.

 

Typically I would make 2 motors at once using 70-80 grams of fuel. Not easily pourable, but 500grams for a larger motor may well pour. I don't have a scientific term for what I mean, ie. the viscosity is the same, but in a large amount (larger the better), it can be poured easier because its own mass helps drag the rest with it. You know that makes sense.

 

Thanks again Schroed's, you've helped me "focus" on what needs to be done.

 

Cheers.

[schroedinger]

Yes i think i now what you mean ( gravity is assisting).

I don't know what your program does but as long as you are fine with it, it ok.

For strenght you can make an engine, put it upside down onto a scale and video the scale.

Also i would take notes an how much the fuel weighted.

[Differential]

I prefer MS Excel to database software, since it's great for creating charts. Your data sounds useful, but too subjective for statistical analysis - "nice putty", "quite strong", etc. But you could graph the workable temp or the thrust as dependent variables versus your independent variable - ratio of dextrose to glucose, or sorbitol to glucose, assuming you keep the total weight of fuel the same each time.

 

When you have some hard data, you might want to make a trendline/"R-squared" analysis on it. Once you have a scatterplot, Excel has an option to draw a best fit line, polynomial, or exponential through the data. It can tell you the equation of the curve, and the strength of the correlation. R^2 = 1 is a perfect correlation, R^2 = 0.9 is strong correlation, R^2 = 0.5 is a fairly decent correlation, and R^2 of 0.2 or less is basically no correlation.

 

Have you tried Lithium nitrate? It's expensive, but I've played around with a LiNO3:sucrose mix and I think it would make a great rocket. If you have a way of making your own nitric acid, you can combine it with Lithium carbonate (which you can get it in bulk from ceramic supply stores) and it's a bit cheaper.

[stix]

. . . For strenght you can make an engine, put it upside down onto a scale and video the scale.

Also i would take notes an how much the fuel weighted.

 

Thanks schroed's - the "strength" I was referring to was the "physical strength" of the fuel, not the strength of the thrust on a thrust stand - that part is already sorted and I have a good measuring device.

 

Motor tests that I do are usually done with a bit more care, ie. fuel weight, nozzle diam. etc.

 

I prefer MS Excel to database software, since it's great for creating charts. Your data sounds useful, but too subjective for statistical analysis - "nice putty", "quite strong", etc. But you could graph the workable temp or the thrust as dependent variables versus your independent variable - ratio of dextrose to glucose, or sorbitol to glucose, assuming you keep the total weight of fuel the same each time.

 

When you have some hard data, you might want to make a trendline/"R-squared" analysis on it. Once you have a scatterplot, Excel has an option to draw a best fit line, polynomial, or exponential through the data. It can tell you the equation of the curve, and the strength of the correlation. R^2 = 1 is a perfect correlation, R^2 = 0.9 is strong correlation, R^2 = 0.5 is a fairly decent correlation, and R^2 of 0.2 or less is basically no correlation.

 

Have you tried Lithium nitrate? It's expensive, but I've played around with a LiNO3:sucrose mix and I think it would make a great rocket. If you have a way of making your own nitric acid, you can combine it with Lithium carbonate (which you can get it in bulk from ceramic supply stores) and it's a bit cheaper.

 

Agreed about the data being too subjective - I may as well have thrown in "smells nice".

 

Hopefully I have enough to work on - Like I pointed out to schroed's, this is not about motor performance, but fuel formula experimentation, which is not too far off my standard workable fuel, that I have used successfully before in motors.

 

I need to work out what is important - ie. strength, pliability, dextrose/sorbitol ratio etc. first before I can graph anything.

 

"trendline/"R-squared" analysis" is beyond my comprehension, but may well be the way to go.

 

cheers.

 

[edit] thanks for the info on LiNO3 but I just want to stick with what I already have.

Edited August 10, 2015 by stix

[Differential]

In this case, an R^2 analysis is just telling you how much the mix affects your parameters (temp, thrust, etc) and letting you know if any perceived correlation could just be measurement error. You can tell a lot from just a graph. A steep line means that changing the mix has a big effect. Having all the data points close to a best fit line means you did a good job of measuring. You can "eyeball" a best fit line, and get pretty close to a mathematically perfect line.