Here’s an Air Force video report on one of the projects I cover in my book The Department of Mad Scientists.

The X-51 project seeks to break new ground in the field of hypersonic (mach 5+) air breathing flight. If all goes well, an unmanned aircraft will drop from a B-52 bomber off the California coast, fire a solid fuel booster rocket to get up to operating speed, and then light up a scramjet engine to get up to mach 6.
This will be the first time that a scramjet stays lit for as long as its fuel supply holds out. Previous tests have achieved powered flight for only a few seconds at a time. Staying lit for over a minute will be a first, and has tremendous implications for the future of aviation. See, for example, program manager Charlie Brink’s discussion of using scramjets for spaceflight in the second half of the video.
Thanks to Nancy Colaguori of the X-51’s propulsion contractor, Pratt & Whitney Rocketdyne, for the link.