# How to find the correct size and angle for a conical nozzle on a rocket engine? [closed]

So I need to know the equations for finding the size and angle for a conical nozzle. I am making a rocket engine and I decided the conical nozzle would be the easiest to build. The rocket is going to be used at ground level(a stable altitude), so you don't need to worry about finding the best nozzle shape for a range of altitudes.

Overall, I need an equation that gives me specifically the nozzle length and the nozzle wall angle, and this equation needs to find those two things based on a stable altitude not a range of altitudes.

If there is a generally good nozzle angle online, then please send me that too.

Thank you.

• What's the propellant combination? Mixing ratio? Combustion chamber dimensions? Throat shape? Performance constraints? Jun 22 at 8:14
• All you need to design a passable nozzle is throat area and expansion ratio. Cone half angles are typically 10-30 degrees. You should design it for underexpanded operation, this way crude expansion contours are less likely to cause flow separation. Jun 22 at 14:36
• "...so you don't need to worry about finding the best nozzle shape for a range of altitudes." BUT WE DO have to worry about a "rocket (that) is going to be used at ground level (a stable altitude)"!!! Voting to close for "Questions about dangerous amateur experiments, such as constructing your own engine or propellants are off-topic."
– uhoh
Jun 23 at 3:21
• – uhoh
Jun 23 at 3:26
• Sorry about this question. I have been offline for a while. This question is pretty badly put together with not a lot of context. I just wanted to know if there was a equation to find the dimensions needed for a conical nozzle or if there was a good link to find this stuff. Also what I meant by it was going to be used at ground level is that I wasnt going to put it on a rocket and only fire it on the ground. I did try to research, but it is pretty difficult to find anything. I now realize how vague this is. The first comment outlines something I should've clarified before asking this question. Sep 2 at 21:53