The vision of hypersonic flight—flying at five or more times the speed of sound—has long been a dizzying combination of hope, cutting-edge science, and unbridled engineering skill. Now, that vision is moving steadily closer to fruition. With renewed worldwide interest and large-scale investments, the competition to build reusable hypersonic planes is hot again. Leading the charge is Boeing’s Valkyrie II, a concept that demonstrates how far the technology has developed—and how much more there is to develop.
The Evolution of the Valkyrie
Boeing has been interested in hypersonics for some time. But the debut of its latest Valkyrie II at the AIAA SciTech Forum in San Diego was a big leap forward. This new design enhances the 2018 model with a streamlined, more aerodynamically pleasing shape: a flatter center fuselage, shorter wings, dual tails, and relocated engines now contained in distinct fairings instead of side-by-side beneath the fuselage.
As Aviation Week’s Guy Norris summed it up, the Valkyrie II is a “refined, more realistic Mach 5 reusable air-breathing design aimed at military and space launch applications.” In hypersonic terms, Mach 5 is the starting line, and Boeing is looking at a design that’s not only quick but viable.
Engineering the Future of Hypersonic Flight
Within any hypersonic aircraft is its propulsion system. Boeing’s Valkyrie II, similar to Lockheed Martin’s SR-72, uses a combined-cycle engine. The system combines conventional jet engines—perfect for takeoff and subsonic flight—with ramjets or scramjets, which take over at hypersonic speed.
But at a cost: it’s not so simple to switch between these modes of propulsion. There’s an awkward speed range in which neither the scramjet nor the turbine operates well. As Mark J. Lewis, executive director of the National Defense Industrial Association’s Emerging Technologies Institute, describes, it is still one of the biggest engineering challenges in the field to design a flow path from Mach 0 to Mach 6.
Boeing’s latest design is drawn heavily from older hypersonic projects such as NASA’s X-43 and the X-51 WaveRider, the first air-breathing hypersonic vehicle to achieve sustained flight. A notable tweak: the Valkyrie II features rounded, extended air intakes—a departure from previous designs. Previously regarded as less efficient, these intakes are now favored due to advances in computational modeling and greater knowledge of airflow dynamics.
Materials That Can Weather the Heat
Flying at Mach 5 is about more than being fast; it’s also about enduring tremendous heat. At those rates, the airframe’s skin can become hotter than 1,000 degrees Celsius. Previous high-speed planes, such as the SR-71 Blackbird, employed titanium to resist heat at Mach 3. The Space Shuttle used ceramic tiles. Modern engineers are working on high-temperature alloys and hot-structure airframes, which render the whole structure heat-resistant, allowing them to do without the heavy insulation.
The Valkyrie II’s shape also plays a critical role. Its waverider configuration helps it generate lift from its shockwaves—an aerodynamic advantage that becomes even more effective at hypersonic speeds. Features like the cranked-arrow wing design and its smooth step-blended fuselage aren’t just for show—they help the aircraft perform more efficiently across a wide range of speeds, from takeoff to full-on hypersonic flight.
Strategic Potential and Commercial Promise
Reusable hypersonic aircraft would be a game-breaker. To the military, they provide possibilities of lightning-speed reconnaissance, worldwide strike missions, and quick-response options. Boeing has publicly disclosed that its hypersonic projects align with U.S. Department of Defense interests, such as Air Force programs like Project Mayhem.
On the business side, the opportunities are equally compelling. Ideas such as Valkyrie II can be used to launch satellites, making it cheaper and less complicated to go to space. And while it’s still conjecture, hypersonic travel for passengers is in the pipeline, crossing the Atlantic in two hours. Boeing’s investment in Hypersonix Launch Systems in Australia is just one indication that industry players are setting the stage for this future.
Of course, Boeing isn’t alone. Lockheed Martin’s SR-72, sometimes dubbed the “Son of Blackbird,” is also in development. Startups like Hermeus are innovating fast with compact, single-engine Mach 5-capable aircraft. Meanwhile, China’s growing lead in hypersonic missile technology has sparked urgency in the U.S. and allied nations.
Challenges That Remain
With promising developments, hypersonic flight remains one of the most challenging issues in aerospace. From designing smooth engine transitions to addressing thermal protection challenges and providing trustworthy structures at high velocities, the obstacles are daunting. And don’t forget the expense—building and maintaining these planes costs a fortune. Commercial viability remains in development.
There are even safety and regulatory issues. The prospect of seating civilians in what is a “guided missile” moving at Mach 5 is enough to raise some eyebrows, even among the enthusiast crowd. Aviation officials will have to witness safety systems that have been vetted, tried designs, and sound emergency procedures in place before approving such a plane.
By unveiling Valkyrie II, Boeing has given the world a straightforward message: hypersonic times are not science fiction—they are near at hand. Though much work still lies ahead, the pace is unmistakable. Progress in propulsion, materials, and aerodynamics is finally coming together to render sustained, reusable hypersonic flight more than a mere pipe dream. The sky is no longer the limit—it’s only the beginning.
