Key insights:
- The speed of air travel hasn’t kept pace with overall technological advancement. Today’s commercial planes travel slower than they did 70 years ago.
- A handful of startup companies are making the technological leap to hypersonic travel — at least five times the speed of sound. These advancements are solving key problems that have plagued high-speed travel, picking up where the supersonic Concorde (which traveled twice the speed of sound) left off.
- Increasingly affordable and available, hydrogen holds promise as a fuel source for hypersonic aircraft, offering a solution to the problem of hefty fuel costs that doomed the Concorde. The higher speeds and elevations of hypersonic aircraft, as well as advances in aerodynamic design, avoid problematic sonic booms.
- It’s a matter of when, not if, hypersonic travel will have wide implications and benefits, making the world a more connected and accessible place.
Although much about airplane travel has changed since the inception of the turbojet seven decades ago — think smoking sections, the emergence of bag fees, planes that now mostly fly themselves — the speed of planes hasn’t budged. In fact, despite leaps and bounds in overall technology advancement, commercial airplanes now travel slower than they did in the 1950s, due to airline efforts to improve fuel efficiency and trim fuel costs. This stands in stark contrast to the rail transport sector, where trains travel at least five times faster than they did in the ’50s.
Previous attempts at faster air travel have been saddled with technological challenges and cost barriers. The Concorde, with supersonic cruising speeds at twice the speed of sound (or Mach 2), only flew between Europe and New York because its loud sonic booms were a nuisance over populous areas. In 2003, the planes were permanently grounded largely because their heavy fuel consumption (seven times the rate of an Airbus A320) made them too expensive to operate. An average round trip transatlantic flight on the Concorde (adjusted for inflation) set passengers back about $12,000.
“In fact, despite leaps and bounds in overall technology advancement, commercial airplanes now travel slower than they did in the 1950s, due to airline efforts to improve fuel efficiency and trim fuel costs.”
Today, a combination of innovations is reviving the possibility of ultra-fast air travel — not just supersonic, but hypersonic, which is traveling faster than Mach 5, or about 6,000 km per hour. In the private sector, a handful of startup companies, including ours, have completed successful proof-of-concept tests of supersonic or hypersonic aircraft systems. None of these have involved human pilots or passengers, but they represent milestones in the development of larger aircraft that will one day ferry people or goods across the globe. In the defense arena, Russia and China have advanced their capabilities in hypersonic missiles, which, unlike ballistic missiles, are highly maneuverable. Russia has deployed them in Ukraine, and China has conducted tests. The US military is also developing ultra-high-speed weapons.
Why faster is better
Moving to higher speeds can actually circumvent some of the problems that have plagued supersonic aviation. With fuel consumption a major culprit in the demise of the Concorde, we believe that hypersonic flight and hydrogen represent a next-generation alternative. Hydrogen’s growing availability and declining costs raise the prospects of a clean energy source that can help solve high-speed aviation’s dual problems of affordability and carbon emissions. Although air transport contributes only 2.5 percent of global carbon emissions today, that contribution is predicted to grow (see Exhibit 1) and the industry is struggling to find ways to reduce it. Hydrogen offers a solution because burning it produces zero carbon emissions. This energy source also becomes attractive when flying at higher altitudes and speeds than the Concorde. It contains more energy than typical kerosene-based jet fuel, increasing the aircraft travel range without increasing the fuel weight. In addition, it is the most powerful coolant for managing the high temperatures of hypersonic engines and aircraft. Although hydrogen fuel can also be used on slower aircraft, it shines most at high speeds.
Somewhat paradoxically, hypersonic travel could also alleviate challenges associated with sonic booms, the sound created when an object travels through the air faster than the speed of sound. Since hypersonic aircraft will fly at altitudes between 30 km and 50 km above sea level — up to twice that of supersonic planes and three to five times higher than today’s passenger planes — the booms will sound more like the low rumble of a highway than explosions. Advances in aerodynamic design are also helping to soften these sonic booms. Additionally, the high speed and long range of hypersonic planes allow them to circumvent large populated areas.
Overcoming technological hurdles
Yet before hypersonic, or even supersonic, travel can become a reality, a variety of technological hurdles have to be overcome. Much of this is not pie-in-the-sky development, and instead has to do with weight and cost. Aerospace engineers already know how to get an aircraft to move at five or more times the speed of sound. The history of this technology is almost as old as aerospace itself. The US military’s SR-71 spy plane, the Space Shuttle, experimental NASA aircraft, and the aforementioned missiles are all hypersonic. The bigger challenge is getting aircraft to move at these speeds without breaking the bank. Whether it’s for cargo, private passengers, or commercial aviation, hypersonic travel needs to be affordable for it to work.
“Being able to reach Shanghai from Memphis in 3.5 hours, for instance, could shrink supply chains from weeks to days.”
Promising advances are already happening. Rapid prototyping and additive manufacturing allow hypersonic engines to be built one layer at a time and then quickly tested and improved upon. This is helping companies like ours create plane and engine designs that are both lower weight and lower cost. It’s also enabling us to find better ways to combine the two primary parts of a hypersonic engine: the conventional, kerosene-powered jet engine that propels the plane during takeoff and landing, and the powerful hydrogen-fueled afterburner and ramjet that kick in once hypersonic speeds are achieved. These two technologies aren’t new, but engineers are working on finding ways to combine them so they fit inside the aircraft and transition smoothly between the engines while in flight. Much of this comes down to carefully designing the air intakes that are needed to help generate thrust and finding ways to keep the engines cool. Two major technologies driving these development efforts are supercomputers for computational fluid dynamics and the 3D printing of compact and integrated heat exchangers. In addition, AI control systems and improved sensor electronics are making it easier to control hypersonic engines and vehicles during flight.
In a departure from the past, much of this innovation is being driven by private companies. Aerospace development has traditionally been a government-led endeavor, with private companies primarily serving as contractors. Today, work on hypersonic travel mirrors that of the space industry, where the contribution of private companies, such as Jeff Bezos’ Blue Origin and Elon Musk’s SpaceX, is growing. Nonetheless, the role of governments in the development of hypersonic aircraft remains critical for setting national objectives, providing funding, and modernizing regulations.
A smaller and more connected world
We believe that the availability of hypersonic jets is a matter of when, not if, with the first commercial flights taking place possibly in the 2030s. The implications will be far-reaching. After all, the world is only as big as the distance between two places. For starters, the ability to get to the other side of the world in just a few hours will shift the parameters of global travel. With a flight from New York to Paris lasting 90 minutes, a business traveler could arrive for dinner with a client in Paris and be back home in bed in New York that same day, all without jet lag. Hypersonic travel could also serve as a boost to economic activity, allowing businesses to quickly ship goods across continents. Being able to reach Shanghai from Memphis in 3.5 hours, for instance, could shrink supply chains from weeks to days. Hypersonic flights could also enable new services. Imagine receiving fresh croissants first thing in the morning that were baked in Paris just a few hours prior. Or wild sea bass caught off the Chilean coast earlier in the day.
Shorter haul hypersonic travel could also be a game changer for medical emergencies and rescue operations, allowing people in remote or rural areas to be transported quickly to top medical facilities. In military applications, hypersonic vehicles could enable the rapid deployment of troops and equipment into conflict areas, rendering certain current defense systems obsolete and pushing others to improve. Finally, developments in hypersonic technology would likely help advance space travel capabilities, reducing the cost and increasing the frequency of space missions, including satellite launches.
To make all this happen, companies will need to continue investing in more efficient hypersonic engines and lighter plane designs. Broader efforts are needed as well, since a key linchpin for hypersonic travel is the wide availability of hydrogen as an affordable fuel source. This will mean the continued development of something that doesn’t currently exist: a global hydrogen fueling infrastructure. Although costs have declined faster than previously expected and more than 1,000 hydrogen projects requiring $320 billion have been announced globally, this fuel source is not yet anywhere near mainstream. Realizing the enormous potential of hydrogen, not just for hypersonic flight but for energy-intensive sectors, like steel, chemical manufacturing, and shipping, will require the creation of value chains for equipment, a scale up in manufacturing, and the attraction of more talent.
Given the relative stagnation of modern aviation technologies, hypersonics are long overdue. Taking this next step would not only fulfill the desire of most passengers to spend less time on airplanes, but offer a range of ground-breaking benefits.
