The future starts at Mach 5 and beyond
Raytheon engineers are exploring the promise of hypersonic flight, addressing the hard problems that must be solved to master it.
WHAT IT WILL BE
The ability to fly planes, drones and missiles faster than Mach 5 – a little more than a mile, or 1.6 kilometers, a second.
WHY WE NEED IT
The U.S. is developing its hypersonics programs “with a particular sense of urgency, due to the rising pace of related research by peer adversaries,” said Dr. Steven Walker, director of the Defense Advanced Research Projects Agency, in a statement to a House subcommittee.
For military forces, the allure of hypersonic flight is clear: It lets them strike from much longer distances in much less time. Many of the advances are resulting from the development of missiles, but the underlying technology could apply to essentially anything that flies. That means hypersonics might have a future in fields like intelligence, shipping, passenger flight and space missions.
WHY IT’S A MOONSHOT
To be clear, there are already vessels that travel at hypersonic speeds, including ballistic missiles and re-entry spacecraft. The problem engineers and scientists are trying to solve now is to create maneuverable hypersonic vehicles that can hold such high speeds for an extended period of time.
There are two main challenges with hypersonic flight. First is the heat. An ordinary aluminum plane flying at hypersonic speeds would melt from the friction with the air around it, thanks to a phenomenon called aerodynamic heating. Heavier materials can withstand the heat (and the plasma it creates), but the problem with heavy materials is that it takes more power to get them up to speed. Any electronics, such as a guidance system, would also need heat shields, meaning even more weight to propel.
That leads to the second problem: the propulsion itself. Rockets are powerful enough to do the trick, but they're also big, bulky and much too expensive to use in large numbers.
WHAT IT TAKES
Finding materials that are simultaneously light enough to propel, but strong enough to take the heat, means engineers have to get creative. As in actually creating new materials.
“We’ve developed new materials to allow us to survive these conditions,” said Dr. Thomas Bussing, Raytheon's vice president for Advanced Missile Systems. “The materials are no longer exotic. They are things we can manufacture today.”
Tools for tasks like thermal analysis have also matured, he said, and additive manufacturing, also known as 3-D printing, has given engineers ready access to lighter, cheaper and more capable parts.
On the propulsion problem, one possible solution is improving upon the supersonic combustion ramjet, also called the scramjet. Rather than carrying its own large and hefty supply of oxygen, it "breathes," pushing the surrounding air into the engine to create combustion and keep things moving.
In all, Raytheon has invested $100 million in the development of hypersonic systems, Bussing said, and an additional $100 million in related technologies.
HOW IT WILL CHANGE THE WORLD
The effects hypersonic flight would have on the world depend on what's possible versus what's practical.
While hypersonic flight would most likely be too expensive for positively everything that flies, the potential applications are intriguing. Surveillance systems flying that fast could dispatch quickly and avoid detection, as radars would have a hard time tracking them. Drones could drop supplies to troops and emergency humanitarian aid to civilians.
Then there's the possibility of passenger flight; a hypersonic plane could get from New York to Paris in less than an hour – or it could deploy elite troops quickly to the other side of the world. As for spaceflight, hypersonic planes could even step in as a reusable alternative to the venerable liftoff rocket.
"Imagine a vehicle that can take off from a runway, accelerate to a high Mach number and high altitude, then launch a rocket," Bussing said. "The speed with which you can launch things is reduced, and the cost is dramatically decreased."