# Are there any calculations involved for designing pulse jets? [closed]

Are there any requirements for calculations to determine things like exhaust length, combustion chamber size, etc? Also, does the end of the combustion chamber need to be a semi-sphere, or can it be flat?

• Do you think it is remotely possible that the answer to the question is, "No, there are no calculations involved in designing pulse jets; they just guess at everything"? Of course the answer is: "Yes, Aeronautical design is a math-intensive, rigorous subject" – abelenky Dec 22 '17 at 13:18
• Do you think it is possible to answer a question, no matter how dumb it may seem to you, politely? Or is this beyond your scope of ability? – S.Stevens Dec 22 '17 at 13:34
• Here you have something of interest: aardvark.co.nz/pjet/inside_pj.pdf – xxavier Dec 22 '17 at 15:36
• Thanks- I did find this calculator excel spreadsheet, which seems to answer my question. Now it's just finding the materials. :) – S.Stevens Dec 22 '17 at 16:49
• You can adjust the resonance frequency with the length of the jet using this formula. For the simplest pulse jets check out Colin Furze. This guy is not completely serious, but a genius nonetheless. – Peter Kämpf Dec 22 '17 at 20:58

YES

There are calculations involved in the design of a pulse jet. (title question)

YES

There are requirements for calculations... (first body question)

NO

The end of the combustion chamber does not need to be a hemi-sphere. (second body question)

• This may not actually be correct - chances are that if you had a fair sense of what a pulse jet should be, you could put together something via the "that looks about right" method which would sustain operation and produce thrust. It wouldn't be ideal, but there's a fair chance it would work, or could be refined to by experiment without any calculation at all. However, that is not the usual approach. You can design airplanes by similar methods - they often fly, but you might not want to be on board when they do so. – Chris Stratton Dec 22 '17 at 20:39