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