Rocket engine problems

[Nytro]

Hi i’m making some small rockets: engine is about 10cm long and1,6cm Wide, after having tested a lot of them They keep failing, the engine keeps exploding  (100% rate when i make  the inside nozzle with the tool and abt 70% when it have no internal nozzle)and when it goes properly it doesn’t have a lot of pressure going out from the nozzle to push very powerfully.the rocket composition i’m using is the standard 75/15/10  ball Milled and  granulated, (unconfined is quite  Fast )Idk what  to do  thanks if someone can help me 

[Zumber]

For core burner try slow burning bp mixture like 60/30/10 KNO3/Charcoal/Sulphur you can replace few percent charcoal with coarse charcoal for nice tail.

Try to slow down 75/15/10 mixture by varing ratio of ingredients or lowering milling time.

Try search tool over here and you may end up with lots of topice that already has been discussed on this thread many times.

[Arthur]

SLOW DOWN! Read some reference books, NO-ONE makes a fully satisfying rocket at their first attempt.

Lancaster's book "Fireworks Principles and Practice" offers a selection of formulae, all slower than standard BP and the powder speed is reduced by limiting the milling or not milling the powder. He also offers guidance on fuel for rockets with and without cores. Small bore rockets need faster fuel than large bore rockets.

Start with one tube size. Make a rocket with 20 mesh mixed ingredients (NOT milled). Fire it as a fountain -in the ground. If it's too fast add more charcoal, if it's too slow then add a tiny % of milled meal. 

ADDED;

Remember that a good rocket burns for 1 - 5 seconds, a fountain burns for about 30 seconds but a lift charge burns in about 50 milliseconds. Control of the burn rate is 90% of the effect.

 

 

Edited December 29, 2024 by Arthur
added

[Almostparadise]

15 hours ago, Nytro said:

Hi i’m making some small rockets: engine is about 10cm long and1,6cm Wide, after having tested a lot of them They keep failing, the engine keeps exploding  (100% rate when i make  the inside nozzle with the tool and abt 70% when it have no internal nozzle)and when it goes properly it doesn’t have a lot of pressure going out from the nozzle to push very powerfully.the rocket composition i’m using is the standard 75/15/10  ball Milled and  granulated, (unconfined is quite  Fast )Idk what  to do  thanks if someone can help 

Granulated with no binder right? I just had to ask. Milled 75/15/10 is generally meant for nozzless rockets. In my experience, even slowish milled 75/15/10 with a nozzle will cato (blow up) about every time.

Edited December 30, 2024 by Almostparadise