M. Keith Hudson, Ann M. Wright, Chris Luchini, Paul C. Wynne, and Sterling Rooke
ABSTRACT: The purpose of this investigation was to find a high regression rate fuel suitable for use as a mixture with hydroxyl-terminated polybutadiene (HTPB). Guanidinium azo-tetrazolate (GAT) is the compound that was the focus of our research. GAT is a salt containing a high percentage of nitrogen. It has two conjugated nitrogen rings, which are negatively charged, and a positively charged component consisting of nitrogen, carbon, and hydrogen. In addition to the highenergy content of this compound, as a salt, it has a lower heat of degradation due to the ease of breaking its ionic bonds. GAT was found to react with N100, a common curative for HTPB. An alternative isocyanate curative was found, polyisocyanate (PAPI), with which it did not react. This polymer matrix was found to be suitable for GAT. The resulting fuel grains were difficult to cast due to the rapid polymerization of the HTPB/PAPI. Once grains were cast, they required no special care in storage or firing.
The fuel grains with the GAT additive were fired for 3-second runs with oxygen flows of 0.04, 0.06, 0.08, 0.10 and 0.12 lbm/s. The regression rate of each GAT concentration was computed and plotted vs. the oxidizer mass flux on a log/log scale. The resultant curve is fit to the equation, br=aGo , and the quantities a and b were recorded for each curve.
GAT was found to increase the regression rate of HTPB when it was used as an additive. The resultant pressure and thrust from firing even the highest GAT concentrations at high oxygen flows still remained within safe operating parameters of the UALR hybrid rocket motor facility.
Keywords: GAT, guanidinium azo-tetrazolate, GZT, HTPB, hybrid rocket fuel, ground testing, regression rate
Ref: JPyro, Issue 19, 2004, pp37-42
(J19_37)
© Journal of Pyrotechnics and CarnDu Ltd
