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Candy rocket experiments

Fluburtur

Cardboard Boy
#1
About 6 months ago I had the idea to make a rocket propelled rc plane (and rocket too) so I started building some candy rocket motors. I dont really like how commercial rocket engines burn, very hard for half a second so I wanted one that could burn for a longer time but providing lower thrust, more like a real rocket.

Of all my testing not a single one worked correctly. Either that had like no thrust, blew the nozzle off or started spitting out excess potassium nitrate. I stopped doing those while I was working because I had no time but built one again yesterday, here is the result.

As you can see the burn is rather unstable, it looks like it is increasing in presure gradually until a presure burst appears then it cycles again. During the burst it actually produces a ton of thrust so I want to have it in that state all the time. My nozzle in that test was 8mm and the core around 10, I will try later today with a 5mm nozzle and 10mm core hopefully.

I wanted to keep this little project secret until I had a working rocket plane but I didnt think it would take that long so I will gladly accept any help.
 
#2
gaffe a pas te faire peter la gueule avec ce genre de truc ^^ je pense qu'il faut faire en sorte d'avoir un canal centrale le plus degagé possible
 

Fluburtur

Cardboard Boy
#4
Well, i think I have fixed my issue. Using a smaller nozzle made th burn much more stable and it looks like it had good thrust.
The divergent part of the exhaust probably had a angle that is too big causing some flow separation but that will be easy to mix, also it was spitting some plastic because I used a plastic pencil to core it and the tip got stuck in there.

I guess I will try to launch one maybe this weekend then.
 

Berekiah

Active member
#5
Interesting building your own engines/motors. I would be concerned of burning up your plane/rocket especially with how the burn ended in your first video. I am working on a similar project creating my own version of a RC Rocket Glider while standing upon what others have done. Mine will be a smaller scale version of the Orion Starliner you can find at https://dynasoarrocketry.com.

You can also find motors/reloads on this site which have a long burn (7s) with not too much thrust. I'm using the reloadable E-6RC in my version. Depending on how much yours cost to make this may be about the same price and possibly safer :)

Good luck.
 

Fluburtur

Cardboard Boy
#6
My point was to make my own motors, im not too concerned about burning the plane because I will probably have the motor in some sort of receptacle to swap them out quickly so that will isolate it from the plane and probably provide some airflow to cool the outside of the case, I have yet to have one catch fire on the outside but I guess it would look cool.

I am not yet to the point of strapping one on a plane anyways.
 

Fluburtur

Cardboard Boy
#7
I did some more test and tried to launch rockets this time but I ran into the same issue of pulsing combustion, I guess the combustion presure is too high since several of those started to rupture the casing of the rocket.
I dont know when the next test will be but I think I will make several identical rockets with different nozzles and one without nozzle to compare.
 

CarolineTyler

Well-known member
#8
I did some more test and tried to launch rockets this time but I ran into the same issue of pulsing combustion, I guess the combustion presure is too high since several of those started to rupture the casing of the rocket.
I dont know when the next test will be but I think I will make several identical rockets with different nozzles and one without nozzle to compare.
Check YouTube channel 'king of random', they did a couple of episodes on making sugar rockets. Sadly even making sugar rockets is illegal in the UK without an explosives permit.
 

JTarmstr

Well-known member
#10
Estes rockets have several nozzles and you could match one of the rockets with a similar impulse and copy its nozzle (E12 maybe?). Also Petersripol did some sugar rockets, I didnt see a formal guide to build them but I think his build process might help.