Green gelled propellant highly throtteable rocket motor and gas generator technology: status and application

Work on gel propulsion began in Germany in 1999. The German Gel Propulsion Technology (GGPT) Program started in 2001 from a white sheet of paper, proposed by the DLR Institute of Space Propulsion, Bayern-Chemie (BC), and the Fraunhofer Institute of Chemical Technology. Aim of the first phase was to develop the technology needed to build a rocket motor burning gelled propellants and to demonstrate its operability by a free flight within significantly less than a decade. The research and development activities were guided by a suitable principal concept for a gelled propellant rocket motor (GRM). Based on theoretical considerations (regarding functional aspects) and experimental pre-tests (propellant development, gelation, rheology, spraying, ignition, and combustion), a motor concept was pre-selected and the motor developed. The identified requirements were proven in December 2009 by two successful demonstration flights. The achieved know-how from basic research and technology (R+T) development has been consolidated in an application-oriented way on component level up to motor development. Within this scope, also, the goal of an effective control of the thrust by throttling the propellant mass flow rate (PMFR) while maintaining an optimum combustion chamber (CC) pressure could be achieved. This publication describes briefly several major advances in the development of the gel propulsion technology in Germany from rheology to combustor development to the thrust and pressure controller of a GRM.

Spatially Resolved Gelled Propellant Spray Characteristics of Impinging Jets

The spatially resolved spray characteristics created by the like-on-like impingement of two gelled propellant simulants was experimentally investigated using Phase Doppler Anemometry (PDA). Water based gels of 1.0 wt.-% agar and 1.0 wt.-% kappa carrageenan, which were characterized using the Herschel-Bulkley rheological model, were used as the gel propellant simulants. Spatially resolved measurements for drop size and drop velocity were obtained up to 10 mm away from the centerline along the transverse axis in the plane of the sheet and up to 20 mm away from the centerline along the transverse axis in the plane normal to the sheet. All measurements were obtained at an axial plane 5 cm downstream of the impingement point. Larger D10 and D32 mean diameters and lower mean axial drop velocity Uz-mean were observed for transverse distances away from the centerline of the spray along both the axis in the plane of the sheet and in the plane normal to the sheet.