SerpApi.Org
The U.S. has recently expanded one of its most advanced propulsion testing sites to speed up the development of hypersonic and supersonic technologies without the cost and risk of full-scale flight tests.
The Southwest Research Institute (SwRI), located in San Antonio, Texas, upgraded its High Energy Annex Test (HEAT) facility. With its new capabilities, engineers can now simulate the extreme temperatures, pressures, and airflow of supersonic and hypersonic flight.
SwRI said that the site currently supports testing of scramjets, ramjets, small gas turbines, and rocket thrusters in a controlled lab environment. This addresses a key challenge in hypersonic vehicle development by testing propulsion systems before flight.
“Testing in actual high-speed flight is expensive and risky, which is why accurate simulated testing is important,” Austin Jones, SwRI research engineer and project leader, pointed out.
Mimicking flight conditions
Hypersonic vehicles travel at speeds of Mach 5 (five times the speed of sound, or roughly 3,806 miles per hour at sea level). And they are exposed to temperatures of more than 1,400 degrees Fahrenheit (760 degrees Celsius) while operating in thin, low-pressure air at high altitudes.
Recreating these conditions on the ground has long been a challenge. It requires stable, high-velocity airflow and precise control of pressure and temperature. Due to the upgrade, the HEAT facility can now simulate these harsh environments.
For the project, SwRI engineers installed an ejector system that can generate the low-pressure conditions needed for realistic engine testing. The system relies on high-pressure air to produce a fast-moving jet that pulls surrounding air through a nozzle. This lowers downstream pressure and creates a vacuum.
“Simulating a scramjet isolator system requires very hot supersonic flow through a duct,” Jones said. “To achieve that, we added the ejector and used an existing high-pressure, electrically heated upstream air system.”
It closely mimics the atmosphere affecting hypersonic propulsion systems, which operate at high altitude. “The ejector creates a vacuum downstream in the duct, allowing for a significant pressure differential across a nozzle to produce the high-temperature supersonic flow,” Jones continued.
Controlled flight testing
The HEAT facility can now recreate high-altitude conditions with pressures as low as 2.5 pounds per square inch (psi). This means it can now support a wide range of supersonic propulsion tests.
“The new facility capabilities allow us to simulate these extreme conditions in a lab setting while allowing for adjustments and improvements to be incorporated before real-world testing,” Jones explained in a press statement.
The research team has already demonstrated temperatures up to 1,400 degrees Fahrenheit, while successfully generating scramjet isolator conditions equivalent to flight speeds of approximately Mach 4.
SwRI said the project remains ongoing as the engineers continue expanding the facility’s capabilities to support future hypersonic research. The institute aims to slash development time, lower costs, and improve the performance of advanced high-speed propulsion systems before they advance to flight demonstrations.
“The work supports a project that seeks to address a critical gap in hypersonic vehicle development,” SwRI added. The upgrades enable controlled testing of scramjets, ramjets, small gas turbines, and rocket thrusters.
