Effects of counterflow jet on the performance of a generic rocket at Mach 4 to 9

Effects of a jet emanating from the nose of a generic rocket in the opposite direction of the incoming freestream in reducing the drag and the heat loading of the rocket for flight Mach numbers 4 to 9 are reported. Computations to determine the counterflow jet total pressures that would result in most drag reduction are made for 40,000 ft (12,192 m) atmospheric conditions using an ideally expanded Mach 1.5 jet flow as the counterflow jet. In comparison to the baseline case, counterflow jet results in ∼20% reduction in drag at every Mach number studied. The area-weighted average surface temperature is also reduced by 30–70% with increasing flight Mach number. Additional computations were made using the jet total pressure that resulted in most drag reduction for the Mach 6 case to determine the effects of the jet total temperature on the area-weighted average surface temperature. For this purpose, the jet total temperature was varied between 300 and 1000 K. Results indicate that the area-weighted average surface temperature is reduced by 500 K even for jet total temperature of 1000 K. Computations were also made using the jet total pressure that resulted in most drag reduction for the Mach 6 case but for flight Mach numbers ranging from 4 to 9, while jet total temperature was kept as a constant at 500 K. Results indicate that use of a constant jet total pressure value results in 14–22% drag reduction with the peak reduction observed at Mach 6. Results also indicate that area-weighted average surface temperature is decreased by 33–50% with peak reduction observed at Mach 6.