Experimental study of conical aerospike nozzles

This document reports the experimental results of the flow development processes in conical aerospike nozzles in the base flow facility at NAL. Two configurations, namely full-length and 60% truncated spike, were chosen. Further the effect of cowl-length on each case was studied for different freestream conditions. The performance of teh various nozzle configuration was estimated using wall pressure measurements on the spike. Under static tests, the performance of the nozzle is found to be very sensitive to cowl-length variation, especially at higher NPR. However, under free stream conditions, the effect of cowl-length variation is not seen to be significant. Truncating the full-length spike does not change the performance of the nozzle under "open-wake" condition. But under "closed-wake" conditions, the performance is significantly affected. Adding base bleed is suggested to improve the nozzle performance. Real-time pressure measurements suggest the flow separation to be dominated with high-amplitude and low-frequency (1.5kHz) fluctuations that are seen to persist in separated region also. BOS measurements correlated well with the conventional schlleren pictures. The benefits of such a study can go in improving the payload capacity of the launch vehicle or RLV