Evaluation of Marine Plastic Combustion Characteristics and Its Application as Solid Fuel for Hybrid Rockets

Growing demand for small satellite launches has increased the need for low-cost and environmentally sustainable propulsion systems. Hybrid rockets have garnered attention as a promising alternative, but most solid fuels are petroleum-derived, contributing to resource depletion and greenhouse gas emissions. This study evaluated the potential of polyethylene recovered from marine plastic waste (Marine Plastics) as a solid fuel for hybrid rockets. For thermal and elemental analyses, commercial high-density polyethylene pellets (Standard HDPEs) were used as a reference, while commercial HDPE cylindrical material (Combustion-grade HDPE) was used for combustion tests. Differential scanning calorimetry and thermogravimetric analyses revealed that Marine Plastics exhibited a melting point of approximately 403 K, comparable to Standard HDPE, with slightly lower thermal stability. Elemental analysis indicated the absence of oxygen atoms, suggesting minimal UV-induced degradation. Combustion tests demonstrated that both Marine Plastics and Combustion-grade HDPE achieved about 60% of the theoretical characteristic velocity, with Marine Plastics exhibiting a slightly higher regression rate. Furthermore, Marine Plastics contained a small amount of sodium chloride, suggesting the potential formation of hydrogen chloride during combustion. These results experimentally confirm that Marine Plastics possess thermal and combustion properties comparable to commercial HDPE, indicating their potential as an alternative solid fuel for hybrid rockets.