Within the research area of sCO2 power cycles, the direct-fired oxy-combustion cycle is of great interest because the inherent carbon capture makes it a desirable option for clean power generation. In order to better understand the combustion kinetics of the direct-fired cycle in sCO2, a laboratory-scale combustion test rig was designed. The design and thermal-mechanical analysis of the combustor test rig for steady-state open-loop combustion testing is presented. The test rig is designed for operating conditions of 265 bar and full-scale oxy-combustion temperatures. The test rig incorporates a laser igniter and modular fully premixed injector to enable testing with step- or swirl-style flame holders. The rig also employs an existing dense-phase sCO2 pump to provide a closed-loop high-flow cooling circuit to enable cost-effective short-lead manufacturing of liner and pressure casing components. Finally, the test rig’s multi-zone copper alloy C18150 liner design minimizes thermal stresses and allows for independent control of dilution flow in each zone to vary combustion temperatures. Planned measurements include exit temperature profile and chamber dynamic pressures. The sensitivity of CO oxidation and other reaction rates to temperature will be indirectly evaluated using post-combustion gas sampling for comparison with combustion simulations.