Progress in Study on Gel Propellants and Their Rheological Properties

The rheological properties are one of crucial factors limiting the injection, atomization, mixing and combustion efficiencies of gel propellants. This paper reviews the gelation of the fuel, oxidant and additive in liquid propellants by using energetic powder, polymeric gelling agent, inorganic SiO2 particles and novel low molecular weight gel (LMWG) as the gelling agent. The gel propellant prepared by energetic powder has good thixotropy and ignition and combustion efficiencies but high powder consumption, undesirable sedimentation effect and poor stability for long-term storage. The gel propellant prepared by polymeric gelling agents featuring stable molecular structures has high stability and combustibility but high viscosity and low injection, ignition and combustion efficiencies, and its rheological properties can be improved by using the polymeric and metallic gelling agents together. The SiO2 particles also show excellent gelation ability and wide adaptability to different components, but thixotropy and combustion characteristics are still not ideal. By contrast, novel LMWG brings gel propellant with excellent thixotropic characteristics by constructing a non-covalent interaction-driven self-assembly network. The physical network of the LMWG based gel propellant is beneficial to reduce the yield point, reduce the liquid propellant viscosity, and improve the thixotropic properties. In addition, LMWG is combustible and does not cause a serious energy loss. Therefore, LMWG can fine-regulate the rheological properties of gel propellant with excellent thixotropic properties, low viscosity, and small additive amount, and could be considered a potential candidate for future gel propellant optimization. © 2022, Editorial Office of Journal of Xi'an Jiaotong University. All right reserved.