Experimental and numerical assessment of regression rate and propulsive performance of 10N-class hybrid rockets for nanosatellite maneuvering

This work presents the results of a test campaign carried out on a 10N-scale hybrid rocket, using catalytically decomposed High Test Peroxide (HTP, 87.5 wt%) as oxidizer and different polymeric fuels (PolyVinyl Chloride, PVC; High-Density PolyEthylene, HDPE; Acrylonitrile Butadiene Styrene, ABS). Fuel regression rate behaviour was studied and compared with literature, also obtaining power-fitting laws of regression rate as function of oxidizer mass flux for PVC and HDPE. Regression rates were higher when compared to larger scale motors studied in literature, but coherent with literature on the same scale, even though at higher oxidizer mass fluxes. An increase in combustion chamber pressure appeared to increase HDPE and ABS regression rate. ABS and HDPE had a very high characteristic velocity, with efficiency close to unity, while PVC performed worse in most cases. A ballistic reconstruction code was used to calculate the instantaneous regression rate of PVC, whose values fit well with the space-time-averaged experimental ones, at least at low oxidizer mass flux. Computational Fluid Dynamic (CFD) simulations were carried out to investigate the internal ballistics of the rocket, when fuelled with HDPE, and get more insights on the regression rate behaviour. The model tends to underestimate the regression rate with respect to experiments, and does not appear to catch the increase due to pressure. However, a better fit was achieved between simulations and experiments when taking into account grain heating, which is supposed to be relevant in such a small-scale thruster.