Conceptual Design for a Dual-Bell Rocket Nozzle System Using a NASA F-15 Airplane as the Flight Testbed

Abstract

The dual-bell rocket nozzle was first proposed in 1949, offering a potential improvement in rocket nozzle performance over the conventional-bell nozzle. Despite the performance advantages that have been predicted, both analytically and through static test data, the dual-bell nozzle has still not been adequately tested in a relevant flight environment. In 2013 a proposal was constructed that offered a National Aeronautics and Space Administration (NASA) F-15 airplane as the flight testbed, with the plan to operate a dual-bell rocket nozzle during captive-carried flight. If implemented, this capability will permit nozzle operation into an external flow field similar to that of a launch vehicle, and facilitate an improved understanding of dual-bell nozzle plume sensitivity to external flow-field effects. More importantly, this flight testbed can be utilized to help quantify the performance benefit with the dual-bell nozzle, as well as to advance its technology readiness level. Toward this ultimate goal, this paper provides plans for future flights to quantify the external flow field of the airplane near the nozzle experiment, as well as details on the conceptual design for the dual-bell nozzle cold-flow propellant feed system integration within the NASA F-15 Propulsion Flight Test Fixture. The current study shows that this concept of flight research is feasible, and could result in valuable flight data for the dual-bell nozzle. NomenclatureACN = altitude-compensating nozzle AFRC = Armstrong Flight Research Center (Edwards, California) AoA = angle of attack CB = conventional-bell CCIE = Channeled Centerbody Inlet Experiment CDE = Cone Drag Experiment CFD = computational fluid dynamics COPV = composite overwrapped pressure vessel DOF = degrees-of-freedom GN 2 = gaseous nitrogen I sp = specific impulse LEO = low-Earth orbit LMI = Local Mach Investigation MEOP = maximum expected operating pressure MSFC = Marshall Space Flight Center (Huntsville, Alabama) 2 NASA = National Aeronautics and Space Administration NNPR = normalized nozzle pressure ratio NPR = nozzle pressure ratio (P c /P amb ) NTF = Nozzle Test Facility OML = outer mold line P amb = ambient pressure P c = nozzle chamber pressure PFTF = Propulsion Flight Test Fixture PRA = pressure reducing assembly RAGE = Rake Airflow Gage Experiment RFS = rocket forebody simulator SSME = Space Shuttle Main Engine STS = Space Transportation System TRL = technology readiness level