Artist’s conception of the Raytheon-Northrop Grumman scramjet-powered Hypersonic Air-breathing Weapon Concept (HAWC) that successfully completed its first flight test in September.

Artist’s conception of the Raytheon-Northrop Grumman scramjet-powered Hypersonic Air-breathing Weapon Concept (HAWC) that successfully completed its first flight test in September.

Raytheon Missiles & Defense was selected by the Missile Defense Agency as one of the companies to develop and test the Glide Phase Interceptor, the first system specifically designed to defeat hypersonic threats. (Image courtesy of Raytheon)

Two recent developments in hypersonics portend the arrival of affordable, long-range hypersonic systems to strengthen national security.

In September, Raytheon Missiles & Defense, in partnership with Northrop Grumman, successfully completed the first flight test of a scramjet-powered Hypersonic Air-breathing Weapon Concept, or HAWC (pronounced “hawk”), for the Defense Advanced Research Projects Agency and the US Air Force. The HAWC flight test data will help validate affordable system designs and manufacturing approaches that will field air-breathing hypersonic missiles to our warfighters in the near future, according to DARPA.

And in February, Defense Secretary Lloyd Austin met with more than a dozen defense-company CEOs to discuss the need to accelerate development of hypersonics to counter Chinese and Russian advances in this area.

In this Q&A with Wes Kremer, president of Raytheon Missiles & Defense, we discuss the HAWC program, the difference between air-breathing and boost-glide hypersonics, and how the organization is using digital engineering for design and test validation.

Breaking Defense: Last year, your team at Raytheon Missiles & Defense, in partnership with DARPA, successfully completed the first-ever flight test of a scramjet-powered Hypersonic Air-breathing Weapon Concept, or HAWC. Tell us about that event.

Wes Kremer, President of Raytheon Missiles & Defense.

Wes Kremer, President of Raytheon Missiles & Defense.

Kremer: Hypersonics are a focus area not only for the U.S. Department of Defense but also for China and Russia. By definition we’re talking about things that travel faster than five times the speed of sound.

For us, the HAWC success last fall was a significant milestone and a history-making moment to be able to demonstrate the capability. There were many steps that went into HAWC. It has a scramjet engine so there are no moving parts. The scramjet essentially compresses and heats the air flow while fuel is injected into it to produce thrust.

HAWC was launched from a plane, a booster got it up to speed, the booster fell away, and the scramjet engine was ignited. It accelerated and climbed to its cruise conditions where it sustained powered flight.

That was the ground-breaking success — the real-world demonstration of a hypersonic air-breathing weapon.

Breaking Defense: Many times, but not always, these sort of DARPA demonstration programs lead to a procurement program. Is there a program on the horizon that HAWC was specifically developed for?

Kremer: You’re right, taking a success out of a DARPA program and converting that into a program of record for one of the services is always the goal. For HAWC, that program of record will be the Air Force’s Hypersonic Attack Cruise Missile, or HACM. It is part of the FY22 budget.

Last year, we received a contract from the Air Force for the Southern Cross Integrated Flight Research Experiment, or SCIFiRE. This program is the bridge between HAWC and HACM, resulting in the design and technology demonstration for a hypersonic cruise missile. It’s a bilateral effort between the U.S DoD and the Australian Department of Defense to advance air-breathing hypersonic technologies.

Breaking Defense: When we talk about hypersonics, we’re talking about two different solutions: air-breathing and boost-glide. What’s the difference?

Kremer: The hypersonics that have been demonstrated to date are most associated with the Chinese. The Air Force has been working to flight test a boost-glide system.

These use rocket motors to launch the weapon above the atmosphere where the glide vehicle is released and then gains speed — sometimes bouncing off the atmosphere to get range extension — eventually gliding down to its intended target. It travels at an incredibly high rate of speed and is maneuverable.

What we’ve demonstrated and what we’ll touch on in this conversation is the air-breathing cruise-missile concept. Air-breathing weapons fly in the upper reaches of the atmosphere, but don’t go outside the atmosphere, using scramjet technology, as I mentioned.

As the names suggest, there are big differences between these two types of hypersonic systems.

Air-breathing propulsion is lower risk because it is a less complex system. The single, solid-rocket booster and scramjet engine with no moving parts result in a more cost-effective solution than a boost-glide system. Air-breathers are smaller and can be carried in larger numbers on both fighters and bombers.

From a loadout and affordability perspective, air-breathing weapons are likely where we’ll see greater numbers in terms of procurement quantities. Our successful HAWC flight test went a long way toward demonstrating how far and fast we’ve been able to mature affordable scramjet technology that will meet warfighter requirements.

Breaking Defense: Is Raytheon Missiles & Defense working on a boost-glide solution or are you fully dedicated to air-breathing concepts?

Kremer: Our Advanced Technology team has been focused on developing both technologies from the beginning because both are needed to address the threats presented by our adversaries.

Boost-glide weapons, however, tend to be a lot larger because you have to boost them out of the atmosphere. Think of something more like a long-range ballistic missile. These are launched from platforms that can accommodate their size, such as a large bomber-size aircraft. Hypersonic boost-glide vehicles will also be capable of deploying from the land and sea.

Cruise missiles are smaller and, yes, they have a booster, but if you’re already at altitude, it’s much easier to boost something into that flight regime and then have it carry on as a cruise missile. Air-breathers don’t fly as high or as fast as boost-glide systems. Therefore they generate less heat and can rely on more conventional materials such as metals for their airframe.

Air-breathers tend to be more tactical than strategic. That’s important because it means they can be manufactured using lower-cost, higher-yield methods. Customers can get several air-breathers for the price of one boost-glide.

Breaking Defense: What are the challenges of developing hypersonic solutions, and then the specific challenges you faced in developing the HAWC air-breathing weapon.

Kremer: The challenge with all hypersonic systems is how you manage the heat associated with things traveling at speeds greater than Mach 5. Typically, boost-glide systems reach speeds in excess of that as they’re re-entering the atmosphere. That means you’re talking about temperatures that would melt conventional steel.

So you need more exotic materials for their thermal-protection systems to handle the thermal environments. And when we say “exotic materials,” think expensive and longer to fabricate.

Heat is less of a factor for air-breathing systems because they fly at lower speeds. Consequently, there are more subsystem material options, creating the opportunity for more tailorable and affordable solutions. It really comes down to the materials and the thermal management, which are the biggest drivers of cost in these vehicles.

Breaking Defense: What are some of the takeaways that came out of the HAWC test in September?

Kremer: The HAWC flight test validated our digital design and digital engineering concepts where everything was done in a digital model. What amazed me most about the test is that our model performance and our actual performance were almost exact overlays on top of each other.

When you think about having the power to model an environment — in this case the hypersonic flight regime where we as a nation have very little experience — and to be able to have that kind of accuracy really speaks to the power of digital engineering from several aspects.

One is the ability to do cycles of learning in a digital environment instead of building and flying hardware. Two is being able to streamline testing during validation. Digital design and engineering have the ability to cut 30 percent or more out of the development timeline and even potentially more out of the testing timeline.

As the fidelity of our models improves across all of industry, and the government gets more confident that we can show that correlation, the quicker we will see programs of record established to keep our warfighters, citizens and allies safe.

As our models continue to evolve and mature, we’ll get to a point where we will validate certain aspects of the design versus validating the entire system. Instead of a point solution, our models allow us to find a zone solution. That’s very helpful when it comes time for production because it gives you a producible solution where you can accept some variation and still meet the mission requirements.

This is about the future. This is how we move faster.


Raytheon Missiles & Defense was selected by the Missile Defense Agency as one of the companies to develop and test the Glide Phase Interceptor, the first system specifically designed to defeat hypersonic threats.

Breaking Defense: By, in essence, reducing risk through digital engineering.

Kremer: Yes, let me give you an example. In a typical design environment, you will have your mechanical model that’s done in Pro/ENGINEER or something similar to create a three-dimensional drawing of the structure so you can do things like computational fluid dynamics to see what that structure looks like in an airflow.

Then there’s the thermal model. Where will the heating occur? What temperatures can we expect on the leading edges of the intakes, wings, and fins? What kind of materials will that necessitate? You’ll also have performance models to understand how far it’s going to fly, how much maneuverability it might have, and even how survivable it is in a threat environment.

Typically, we take the results from one model and feed it into another. The issue with this dated approach is that its serial nature drives you to a series of iterations because you are continuing to update models after you’ve passed them to the next step in the analysis. This is time consuming. In our digital engineering environment, all of those models are brought together.

Historically when working these models independently, we’d get to a point solution that works, whether it’s for a rocket motor or a hypersonic weapon, and then we’d go build it. What we didn’t understand prior to the introduction of digital engineering was the margin around that point solution. When you start to build something and manufacture it, you’re going to have variability in all your pieces, all your materials, and all of your components. Through the use of a true digital thread, we can now get to a more robust part of the design envelope faster.

That’s one of the ways you drive a lot of the risk out too, because you understand the design margins you have, as opposed to, in some cases with new technology, just coming up with a point solution.

Breaking Defense: The point you made on understanding the margin is interesting as it relates to producibility.

Kremer: I’ll give you another example of what we learned as we have been developing hypersonic systems. Our Advanced Technology team was at a high speed wind tunnel to test a scale model to validate the results of our digital analysis and models.

While the team was running through the initial workups, they noticed that the actual data we were capturing out of the wind tunnel wasn’t matching anywhere near our model data. It turned out that our modeling was so accurate that a few test results showed a disturbance in the air flow, which indicated an anomaly in the wind tunnel that the engineers were able to correct. Our models were of such high fidelity that we were actually detecting imperfections in the test environment.

Breaking Defense: Final thoughts?

Kremer: There’s a lot of talk around hypersonics in terms of technology advancements and challenges, but infrastructure and workforce development in the mission area is equally important. We need the proper infrastructure and more people with the right skill sets, such as high-speed flight engineering and digital technologies to effectively deliver this capability at the speed of relevance.

We’re investing in training to ensure our workforce is at the cutting-edge of R&D and innovation. We partner with the DoD’s Joint Hypersonics Transition Office, the JHTO, and academia to inspire innovation and interest in this mission area to cultivate more hypersonic engineers for our nation. All of this is good, but we need more. Accelerating the development of hypersonic weapons requires digital engineering technologies, a robust supply chain, highly skilled human resources, and a stable DoD budget. This is what will help us innovate our way toward regaining a competitive edge.

We are committed and invested to help our nation in the hypersonics domain. We will continue to lead industry with our decades of missile experience and manufacturing capabilities. This is important for strengthening our nation’s deterrence posture and ensuring our warfighters have the capabilities they need to do their jobs. I was once one of them and know how much they rely on us — and we’ll be there for them.

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