The Hypersonic Age is Near

The Real Race Begins

The first true reusable, free-flying scramjet could be Darpa's HTV-3X. Also known as Blackswift, the unmanned vehicle looks like an alien spaceship, with black curves, a rapier-like prow and oval exhaust ports. It's still only in the planning stages as part of Darpa's Falcon program, but it could represent the biggest breakthrough in aeronautics since the jet engine itself. It will demonstrate for the first time all the technologies needed for a practical scramjet-powered aircraft by taking off and landing under its own power and running on scramjets as long as needed to complete its mission.

The HTV-3x could make its inaugural flight as early as 2012. Here's how a perfect mission would go: The unmanned craft taxis out of a hangar at Edwards Air Force Base. Its twin conventional turbine engines throttle up before it accelerates down the runway and climbs into the desert sky, followed closely by a chase plane. The chase plane keeps pace until shortly after the unmanned craft hits the speed of sound. At Mach 2, doors just within the jets' inlets close off the turbines and open the airflow to the scramjet engines, which fire out of the same nozzles used by the turbine jets. On the ground, engineers watch their bird hit Mach 6, twice as fast as any turbine- jet-powered craft ever built. The test completed, the craft slows to subsonic speed, switches to turbine jets, and lands back at Edwards, mission accomplished.

Darpa officials are keeping quiet about Blackswift for now. Spokesperson Jan Walker says no project engineers could give interviews for this article because "it's a very busy time for the program." But Pratt & Whitney Rocketdyne is already at work on the engine that HTV-3X will use—a combined-cycle turbine-scramjet engine—and although Lockheed Martin won't confirm it, the company's famously secretive Skunk Works division is widely believed to be building the vehicle itself.

Meanwhile, there's competition. Last July, engineers from China showed up at the American Institute of Aeronautics and Astronautics Joint Propulsion Conference in Cincinnati and revealed a growing scramjet research program of their own, including a new hypersonic wind tunnel in Beijing and work on rocket-powered combined-cycle scramjets. None of the American scramjet experts we talked to would discuss their reactions to the Chinese revelations. But Craig Covault, an editor at Aviation Week & Space Technology who reported on the conference, believes one of the main reasons the Chinese attended was to glean all available intel on Western scramjet research. "I would bet that they have a serious research program under way that has a lot more going on than just the few papers that they issued at this forum," Covault says. "The reason that they issued them was just kind of a message to the rest of the world that they are engaged in these high-tech things. It also allowed them to get the 500 or more other papers in propulsion technology of all kinds delivered at the conference."

Scramjet projects have failed before, and some of the initiatives under way today could fail too. But many researchers say that this time around, scramjets are for real. "Advanced propulsion technology has a development timescale that appears to be on the order of decades," says Johns Hopkins's Van Wie. "The first scientific paper on rockets was published in 1903, and rockets became practical during World War II, 40-some years later." He points to a seminal conference in 1960 during which researchers first hashed out the major challenges to building practical scramjets. "So if you look at that—1960 to now, 47 years or so—it's kind of on the same timescale to see this roll out." In other words, that two-hour flight to Tokyo just might be leaving sooner than you think.

See more pictures of the test program in action, launch the gallery here.

Michael Belfiore's book Rocketeers chronicles the private space industry.