Improvements in payload performance for the Air Force's EELV are advantageous to mission needs, since payloads typically increase. A third or "kick" stage is one potential solution to provide an incremental improvement in payload mass as well as to provide additional mission flexibility. A classical configuration stage design is very difficult to implement into the EELV architecture due to significant architecture impact. This could translate to vehicle structural changes and or payload volume reduction. Therefore, a stage that has minimal impact on the launch vehicle architecture by accommodating the vehicles's current characteristics is advantageous. A conceptual study addressed these limitations by examining a toroidal shaped stage solution that fits within the current envelope of the respective EELV's payload fairing interface section. This location imposes several kick stage size and shape limitations, but affords minimal changes to the overall existing launch vehicle. The analysis reviewed the overall vehicle architecture, identifying locations for modification or stage shape.Trade studies of various propellant types (LOX/LH2, LOX/RP, LOX/methane, hydrazine monopropellant) were included in the analysis. The effort generated a propellant tank and engine conceptual layout design. The analysis matured the stage design to a sufficient level and quantified the stage's payload payoff for different ΔV missions.
NomenclatureEELV = Evolved expendable launch vehicle GLOW = Gross lift off weight GTO = Geostationary transfer orbit Isp = Specific impulse LEO = Low Earth Orbit LOX = Liquid oxygen LH 2 = Liquid hydrogen POST = Program to Optimize Simulated Trajectories P c = Chamber Pressure RP = Rocket propellant (kerosene) ULA = United launch alliance USAF = United States Air Force ΔV = Change in orbital velocity
