[AR] Re: Nozzle shapes
- From: Ian Garcia <ianmga@xxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Tue, 12 Nov 2013 14:39:15 -0800
Also the "newer" engines? The RD-170 derivatives and RD-0120 look
comparable to the US bell shapes. The RD-107 is a very old engine.
On Tue, Nov 12, 2013 at 11:35 AM, 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…
>
--
Ian M Garcia
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