Background
The project was undertaken to address a critical gap in the field of hypersonic vehicle development, particularly for air- breathing propulsion systems such as scramjets. As the defense industry shifts focus towards developing reusable and long-duration hypersonic vehicles, there has been a growing need for advanced thermal management and onboard power generation solutions. Current systems are limited by fuel-based cooling approaches that either risk overheating due to hydrogen boiling or suffer from coking issues associated with liquid hydrocarbons. Moreover, in the absence of gas turbine engines these vehicles are heavily reliant on batteries for onboard power, which is not viable for long-term missions. The project is investigating the feasibility of employing a supercritical CO2 (sCO2) heat exchanger for both cooling scramjet walls and concomitant power generation. By leveraging sCO2's unique thermophysical properties, the project seeks to advance the state of the art in regenerative cooling, thereby meeting a pressing demand identified by the Department of Defense and facilitating the development of more robust and efficient hypersonic technologies.
Approach
The objective of the project is to design, build, and test a proof-of-concept supercritical CO2 (sCO2) heat exchanger for onboard cooling and power generation in scramjet systems. Currently, the design and fabrication of a bespoke ejector system for the test facility is being undertaken to create a low-pressure environment downstream of the test section to simulate high-altitude conditions. Concurrently, the project team is designing the sCO2 heat exchanger. The approach includes involving analytical and numerical modeling to optimize heat transfer efficiency while minimizing weight and size constraints. A key challenge is balancing the need for efficient heat transfer while keeping wall thicknesses large enough to contain the high-pressure sCO2. Once the ejector and heat exchanger are finalized and fabricated, the commissioning phase will involve installing the bypass piping and ejector, updating control software, and conducting a series of tests to ensure proper ejector performance and flow uniformity. The final phase integrates the heat exchanger into the test facility, followed by comprehensive testing to characterize its performance across a range of operating conditions, simulating a scramjet flight trajectory. The anticipated results are expected to establish the feasibility of using sCO2 technology for scramjet cooling and onboard power generation.
Accomplishments
Analytical models of the ejector operation and heat exchanger operation were developed based on known methodologies. Over 60 iterations of numerical simulations were attempted to design by analysis. Numerical simulations were also performed on the test section nozzle geometry to validate proper conditions will be generated. The results will be validated via upcoming testing. Mechanical design of the heat exchanger is nearing completion. Purchased components are expected to arrive sometime in late December with test build up and commissioning taking place thereafter.
Presentations
Anguiano, M., Jones, A., Di Sabatino, F., Connolly, B., “Analytical and Numerical Supersonic Ejector Design for a Propulsion Ground Test Facility.” AIAA SciTech 2026, 13 January 2026.
Resulting Project Work
Project work is still ongoing and thus has not been published. The analytical model was accepted for a presentation at AIAA SciTech 2026. Analytical and Numerical Supersonic Ejector Design for a Propulsion Ground Test Facility