Experimental comparison of Dual Bell and Expansion Deection Nozzles

Replacing conventional bell nozzles with altitude compensating forms represents an attractive proposition for launch vehicle design, as both eciency across the altitude range and altitude performance. through the use of larger area ratios. may be increased. This paper compares the performance of two such compensating nozzle types, the Expansion Deection and Dual Bell, through a series of cold ow tests conducted at nozzle pressure ratios encompassing the entirety of the compensating regime. Nozzle eciencies are shown to vary signicantly across the pressure ratio range. Furthermore, relatively small changes in some design parameters associated with the ED nozzle type are shown to have an eect on overall performance. Despite this, the compensating behaviour of the type is shown to have similar potential to that of the Dual Bell. Combined with its other advantages of shorter length and potentially more adaptable design principles, it appears to show promise for application to future launchers.