Performance Analysis of Short Takeoff and Vertical Landing Aircraft Nozzle in Hover

Figure 1 shows the ballistic results for propellants 1, A, and B. The burning rates show no signiŽ cant alteration among the three propellants. The differential scanning calorimetry plots for these three propellants shown in Fig. 2 tell a different story, however. Compared with the baseline, both the carbon and the fullerene soot appear to eliminate the secondaryexothermicpeak at approximately 275±C. Both also seem to have exothermic activity centered around the BTTN/TMETN exothermat 200±C. The existenceof the double exotherms for the soot propellant B (-071) as opposed to the single exothermfor the carbonblack propellantA (-028) can be accounted for by recalling that the fullerene soot contains a variety of carbon molecular forms, with different structures and volatilities. Examination of the optical microscope photographs of the extinguished surfaces of the two modiŽ ed propellants also revealed a substantialchange from the baseline.The surfaces for propellantsA (-028) and B (-071)were dry, with no evidenceof the ANmelt layer noted in propellant1 (baseline).Based on the absence of the second exotherm for propellantsA and B, it is evident that the exotherm is due to a reaction between BTTN/TMETN decompositionproducts and the ANmelt layer.This is supportedby the fact that, in the baseline propellant, which has a thick melt layer, the second exotherm shows a sharp drop at »270±C, corresponding to the rapid drop of the vaporization endotherm for the AN melt. If the melt layer is eliminated, then so is the exotherm. From a purely qualitative standpoint, the trade of carbon and fullerene soot for the nitrate esters has a substantial effect on the condensed-phasebehavior and surface morphology of the AN propellant compared to the baseline.However, no measurable effect is evident in terms of burning rate behavior,or dominanceof the  ame kineticsover diffusionmechanisms. There are two possible reasons for this behavior: 1) The gas-phase energy release dominates any condensed-phasecontributionto theoverall chemicalenergyrelease or 2) any beneŽ t gained from carbon or fullerene enhancement of AN combustion is masked by elimination of the second exotherm when the BTTN/TMETN is reduced. What is clear is that for this propellant/binder system,eliminationof themelt layeror changesin thecondensedphasereactionsdonot signiŽ cantlyalter theballistics. Additionally, although the fullerene soot has a different effect than carbonon the condensed-phasebehaviorof the AN/BTTN/TMETN propellant when exchanged for the plasticizer, its effect is not substantially different from carbon on the propellant ballistics.