Notre Dame’s New Boundary Breaking Mach 10 Quiet Wind Tunnel

February 1, 2025

The University of Notre Dame (UND) opened its new Large Mach 10 Quiet Wind Tunnel — the first and only hypersonic research facility of its kind — in November 2024.

Notre Dame researchers describe the new facility as serving several immediate purposes, including to help address hypersonic testing backlogs at Department of Defense (DoD) facilities. It can also be used to help aerospace companies move from hypersonic vehicle concepts to prototypes, and will support a planned graduate program in hypersonic systems for the university.

The Large Mach 10 Quiet Wind Tunnel is the latest aerospace research facility to join Notre Dame’s campus, which also includes the Hessert Laboratory for Aerospace Research and Hessert at White Field, the Institute for Flow Physics and Control (FlowPAC), and NDTL Propulsion & Power. The tunnel is also the latest expansion of Notre Dame’s Hypersonic Systems Initiative that the university describes as an effort to engage its broad engineering and science expertise while also addressing “the technical challenges of developing efficient, hypersonic flight vehicles.”

The Large Mach 10 Quiet Wind Tunnel was designed by Thomas Corke, Notre Dame’s Clark Equipment Professor of Aerospace and Mechanical Engineering, pictured here. (Image: University of Notre Dame)

Notre Dame’s Hypersonic Systems Initiative includes research focused on hypersonic aerodynamics, energy storage, flight control, manufacturing and materials among others. Hypersonic research and development, along with developing the future hypersonic workforce, has remained a priority for the university’s Hypersonic Systems Initiative and its various research facilities and capabilities on campus as well. As an example, in a December 2022 article written by the university’s media team, it was noted that Atlanta-based startup Hermeus used their turbo machinery laboratory to test the ability of their Chimera hypersonic prototype engine to transition from turbojet to ramjet mode.

The opening of the new facility occurs amid an ongoing push by the U.S. military to develop hypersonic weapons and technologies. In December, for example, DoD published an update highlighting the completion of an end-to-end flight test of a conventional hypersonic missile from Cape Canaveral Space Force Station, Florida. The test was part of an ongoing collaboration between the U.S. Army and Navy to develop and field hypersonic missiles, known as the Common Hypersonic Glide Body (C-HGB). In November, the Joint Hypersonics Transition Office (JHTO) concluded its “Hypersonic Accelerated Manufactured Prototype Demonstration” challenge by issuing awards to Castelion Corporation and Specter Aerospace to produce novel new hypersonic prototypes.

The new Large Mach 10 Quiet Wind Tunnel was designed by Thomas Corke, Notre Dame’s Clark Equipment Professor of Aerospace and Mechanical Engineering, along with doctoral students Joseph Heston and Jacob Caldwell.

Check out our question and answer session with Corke below, where he provides Aerospace & Defense Technology (A&DT) with an understanding of some of the unique design, manufacturing and materials related challenges that the new facility could help the industry resolve in the quest to develop hypersonic flight vehicles of the future.

Aerospace & Defense Technology (A&DT): What are some of the main elements of the facility that allows it to function as a “quiet” wind tunnel?

The facility held an opening day ceremony, with university researchers and members of Congress in attendance. Pictured: Front (left to right): Congressman-elect Tony Wied, Congressman Pat Fallon, Chairman Mike Rogers, Dean Patricia Culligan, Vice President for Research Jeff Rhoads, Professor Tom Corke, Admiral Christopher Grady, Major General Michael McCurry, Ambassador Joe Donnelly, and Mayor James Mueller. Back (left to right): Doctoral Students Jacob Caldwell, Alec Jobbins, Will Jordan, Nicholas Hawley, Joseph Heston, Tim Moren, and Alyssa Spencer. (Image: Angelic Rose Hubert)

Thomas Corke: The concept of “quiet” tunnels comes from the observations in the 1980s at NASA Langley that there were differences in the location of turbulence onset in the boundary layers at supersonic Mach numbers over test articles between wind tunnel tests and flight tests. These differences were attributed to disturbances in the wind tunnel that were not present in flight. This led NASA Langley to design a Mach 3.5 (proposed Mach number of the Supersonic Transport) nozzle that suppressed instabilities of the boundary layers that would develop over the nozzle wall surfaces that would lead to the disturbances (pressure fluctuations) that were not present in flight and would affect turbulence onset on the test article. This has motivated all of the quiet tunnel development that followed to the present.

NASA Langley also developed a Mach 6 quiet nozzle in the late ‘90s that was eventually put in storage but later given to Texas A&M university. Purdue built a Mach 6 quiet tunnel that has been in operation for the past 15 years. Both of these facilities are small in scale and cannot reach Reynolds numbers where transition to turbulence will occur. This is a serious limitation as the object of these facilities is to predict turbulence onset.

At hypersonic Mach numbers, the onset of turbulence results in from 3 to 5 times higher surface heating. Failing to predict if and where this occurs is critical to hypersonic aircraft design. This limitation motivated the development of the quiet tunnels at Notre Dame, namely, to develop quiet hypersonic wind tunnels of a scale that can produce conditions that would result in turbulence onset on test articles. Regarding quiet tunnel design, Mach 6 is a relative “sweet spot” where requirements such as air temperature and pressure are not excessive. NASA Langley attempted to build a Mach 8 quiet tunnel that failed because of degradation of the nozzle metal that resulted from the required higher air temperatures. Before our design, no one has attempted or possibly considered a Mach 10 quiet tunnel.

A&DT: Why Mach 10?

Corke: Regarding powered (scramjet) hypersonic vehicles, at a given Mach number there is a maximum altitude at which combustion can occur. At Mach 6, this is about 31km. To fly at higher altitudes, the vehicle needs to travel at a higher Mach number. This generally motivates the development of higher Mach number facilities.

The other reason for developing a Mach 10 quiet tunnel, whereas Mach 8 would have been easier, is that there are fundamentally different boundary layer transition physics that affect turbulent onset at Mach 10 that does not exist at Mach 6 or 8.

In 2022, Atlanta-based hypersonic startup Hermeus used Notre Dame’s Turbomachinery Lab (NDTL) to test its Chimera engine, pictured here at the facility. (Image: University of Notre Dame)

The Notre Dame Mach 10 Quiet Tunnel has a large test section that can accommodate large test articles. This allows a scale of test articles over which turbulence onset can occur. This also allows large test articles used in large conventional (noisy) government hypersonic tunnels to be similarly tested in the Notre Dame quite wind tunnel. This provides a significant cost reduction to a program that can evaluate on the same test article, if the disturbance levels are important to the turbulence onset predictions.

Another design element of the Mach 10 quiet tunnel is that it does not use a “burst plate” to initiate the flow. This has a number of advantages including allowing a large test section, thin optical windows, and a rapid tempo (order of minutes) tunnel operation. Rather than typical 2-3 runs per day with burst plates, the ND design allows hundreds of runs per day.

A&DT: How can the research at this facility help to advance hypersonic technology for the aerospace and defense industry?

Corke: The wind tunnel is designed for both fundamental research as well as test and evaluation. Fundamental research generally involves somewhat generic test articles. These experiments are also generally coupled with numerical flow simulations. Test and evaluation will generally involve proprietary and classified geometries. In that case, the large scale of the facility allows can accommodate full-scale designs. The rapid tunnel operation tempo makes test and evaluation highly efficient.

Hypersonic flight within the atmosphere involves a large number of technologies. These include high-speed aerodynamics, flight control, high temperature materials, heat mitigation and transport, structures, manufacturing, propulsion, communications, energy conversion and storage, and systems monitoring and diagnostics. Experiments in the Mach 10 facility can be designed to directly address a number of these including high-speed aerodynamics, flight control, heat mitigation and transport, and propulsion.

A&DT: Over the last year, Department of Defense officials have repeatedly stated their need for more cost effective methods for developing and testing hypersonic weapons and vehicles. How can the new Mach 10 Quiet Wind Tunnel help the industry overcome some of the costs associated with development?

In December 2024, the U.S. Army’s Rapid Capabilities and Critical Technologies Office, in collaboration with the U.S. Navy Strategic Systems Programs, completed a conventional hypersonic missile test from Cape Canaveral Space Force Station, Florida. (Image: Department of Defense)

Corke: The tunnel follows a Ludwieg tube concept. By eliminating the burst plate, very little air is discharged during a run. This air can be recharged in 1-2 minutes allowing the rapid tempo previously discussed. Eliminating the burst plate is not only a time saving, but also a cost savings. For the operating conditions and scale of the Mach 10 tunnel, the burst plates would cost many thousands of dollars and are not reusable after a single run.

Another cost-saving feature of the design is that the large test section will allow multiple test articles to be tested simultaneously.

A&DT: How can the facility aid in the development of the new types of materials that would be necessary to withstand the type of heat transfer rates that exist for vehicles that are performing hypersonic flight at Mach 10?

Corke: The Mach 10 tunnel is a so-called “cold tunnel”. Although it has a high stagnation temperature, the static temperature at Mach 10 is quite low static temperature. Therefore, it is not the right facility for high-temperature material testing. Facilities that are designed for such high-temperatures are “Arc-heated Jet” facilities. Notre Dame has a smaller scale variable Mach number Arc-Jet Facility where such research can be performed.

Where the Mach 10 facility can impact the surface heat flux on hypersonic vehicles is on developing methods for delaying or preventing turbulence onset on the vehicle acreage and flight control surfaces. This is an area of research where Professor Corke’s Group at Notre Dame is well known.

A&DT: The Hypersonic Systems Initiative section of Notre Dame’s website notes that producing hypersonic systems is a challenge because of “the greater degree of thermal protection and inherent complications produced by hypersonic flight.” How could the research conducted at the new wind tunnel help design and manufacturing engineers overcome this thermal protection challenge?

Corke: There are a number of thermal protection approaches, both passive and active. The Mach 10 tunnel is best suited to active approaches in which the flow field has a role. One such approach involves “transpiration cooling” in which a cooled fluid ranging from water to supercritical CO₂, are injected through a porous surface at the leading edge. This has proved to be highly effective in reducing the high surface temperatures making it possible to use conventional leading-edge materials.

Transpiration cooling can also be coupled with thermal-electric conversion approaches where the cooling fluid plays a double role by using it to establish the “cold junction”. The lower temperature maintenance of the cold junction determines the thermal-electric conversion efficiency.

This article was written by Woodrow Bellamy III, Senior Editor, SAE Media Group (New York, NY).