In stealth aircraft, precise characterization and mitigation of infrared (IR) signatures are essential for enhancing stealth and survivability. Major IR signature sources from aircraft include surface radiation, exhaust plumes, and hot engine parts. The exhaust plumes primarily emit in the 3–5 µm band spectrum. Cold air mixing and the use of high aspect ratio (elliptical) nozzles can dramatically reduce exhaust gas temperatures and IR emissions. Serpentine nozzles, with their curved centerlines, help shield hot engine parts from IR seekers but introduce pressure losses leading to performance decrement. To address and solve this issue, the reacting flow nozzle test rig was developed to enable fine control over flow parameters and allow for the investigation of IR emissions. This facility uses a vitiation heater or combustor that can simulate gas turbine engine nozzle inlet conditions across the aircraft flight envelope (take-off, cruise). This test rig helps validate theoretical models, predict lock-on range, and progress in stealth technologies, providing crucial insights for optimizing designs and minimizing IR detectability in future advanced aircraft propulsion systems. It contributes to the design of the nozzle for improved performance and reduced detectability in operational environments.