In development by the Air Force Research Laboratory is the next generation in high-speed flight. Air speeds of more than Mach 5, or hypersonic flight, are being researched for a new bomber capable of achieving up to Mach 10 at least partially to counteract the recent tests of hypersonic missiles by both China and Russia. However, an advantage of this vehicle would be the ability to use it again and again rather than launching a single-use missile at the cost of around $100 million.
This hypersonic effort known as Project Mayhem is to develop a “hypersonic multi-mission ISR [intelligence, surveillance, and reconnaissance] and strike platform,” as reported by Popular Mechanics. The challenges inherent to hypersonic flight will require highly advanced engineering to overcome. For example, conventional jet engines produce thrust with a spinning compressor with fan blades that limits the maximum thrust possible. This could be overcome with scramjets that produce boost from fuel pressure alone, but lack sufficient thrust at lower speeds. Furthermore, the extreme heat produced at this speed requires advanced materials that are expensive to produce and often difficult to work with.
It will be some time before this is produced if it ever happens in the first place. Many engineering barriers must be overcome as well as wrangling funding from an oft-dysfunctional Congress. Regardless, the U.S. Air Force is not an institution that tends to let its adversaries have an upper hand in anything, so it is almost guaranteed the research will continue.