[AR] Re: Nozzle shapes
- From: Carlo Vaccari <airplaniac2002@xxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Tue, 12 Nov 2013 14:45:08 -0500
I have far less experience in motor design than most people on the list,
but I remember reading somewhere: a chamberless engine can be created
inside of a cone. Perhaps the Russian engines use this principle to gain
energy from combustion that occurs in the bell.
This speculation of mine could all be based on imagined evidence, of
course, so take my word with a giant cave full of salt crystals:
http://en.wikipedia.org/wiki/File:Cristales_cueva_de_Naica.JPG
On Tue, Nov 12, 2013 at 2:35 PM, Ben Brockert <wikkit@xxxxxxxxx> wrote:
> Anyone have further info to back this up, or Russian nozzle design
> logic translated into English?
>
> From a powerpoint on nozzles by D. R. Kirk of FIT:
>
> Q: Why do U.S. nozzles look more like a polynomial contour and Soviet
> nozzles look more conical?
>
> A: (Jim Glass, Rocketdyne)
>
> Interestingly, Soviet nozzle designs have a 'different' look to them
> than typical US designs. US designs are ‘truncated Rao optimum’
> bells, usually designed by method-of-characteristics methods. Soviet
> nozzles, to US eyes, look more conical than ours. Ours have that nice
> ‘parabolic’ look to them - less conical. One would suppose the
> Russians are fully capable of running M-O-C and CFD codes and thus
> their nozzles, if optimum, should look ‘just like’ ours. Since they
> don't, I've always wondered if they know something we do not. In my
> experience, the US is better at combustion engineering (minimal C-star
> losses) but has fairly substantial losses in the nozzle (aerodynamic
> losses). The Russians tend to reverse this, throwing away huge gobs
> of energy due to incomplete combustion and then using a very efficient
> expansion process to get some of it back. The bottom line is both
> design approaches appear to yield roughly the same Isp efficiency...
> One wonders what would happen if one were to mate a US combustor to a
> Russian nozzle…
>
>
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