Low-cost academic test bench for preliminary development of solid fuel ramjet engines

The Solid Fuel Ramjet (SFRJ) is an airbreathing propulsion system widely employed in missiles and aerospace applications due to its mechanical simplicity, high thermal efficiency, and relatively low development and production costs. Unlike traditional rocket engines, the SFRJ relies on atmospheric oxygen, eliminating the need for an onboard oxidizer, which significantly enhances its operational efficiency. This study presents the design and implementation of a low-cost experimental test rig specifically developed for SFRJ testing. A key feature of this setup is the incorporation of a packed bed heat regenerator, which enables controlled air heating. Additionally, a dedicated computational code was developed to assist in test planning by optimizing key engine parameters, such as equivalence ratio, air inlet temperature, and chamber pressure, to enhance stable operation. The effectiveness of both the test rig and computational tool was successfully demonstrated through experimental validation, where a polymethyl methacrylate (PMMA)-fueled ramjet engine of the 50 N thrust class achieved stable and sustained operation.