Imagine taking off from any U.S. airport and landing on any other runway in the world in less than two hours. Or making a quick hop from that same airport to the International Space Station and back - a trip that normally takes days or weeks - to drop off science experiments, provisions and new equipment.

Sound far-fetched?

Not anymore. Technology now being developed by NASA and its partners could - within two decades - achieve such rapid trip times, yielding limitless possibilities for international travel, commerce and access to space.

An artist's rendering of the air-breathing, hypersonic X-43B -- the third and largest of NASA's Hyper-X series flight demonstrators. Credit: Media Fusion, Inc./NASA

And this week, they're going public with the hypersonic shape of things to come.

Visitors to the 50th annual Experimental Aircraft Association's AirVenture Air Show, opening July 23 in Oshkosh, Wis., will be among the first to see mockups of NASA's proposed "Hyper-X" series. These technology demonstrators, intended for flight testing by decade's end, are expected to yield a new generation of vehicles that routinely fly about 100,000 feet above Earth's surface and reach sustained travel speeds in excess of Mach 5, or about 3,750 mph - the point at which "supersonic" flight becomes "hypersonic" flight.

It also may be the point at which traditional air transportation becomes as outmoded as the covered wagon.

Revolutionizing the way we gain access to space is NASA's primary goal for the Hypersonics Investment Area, managed for NASA by the Advanced Space Transportation Program at NASA's Marshall Space Flight Center in Huntsville, Ala.

The Hypersonics Investment Area - which includes leading-edge partners in industry and academia - will support future-generation reusable launch vehicles and improved access to space. Over the next 20 years, the U.S. will develop and test a series of ground and flight demonstrators. The flight demonstrators - the Hyper-X series - will be powered by air-breathing rocket- or turbine-based engines and ram/scramjets.

Air-breathing engines for hypersonic applications are known as "combined cycle" systems because they use a graduating series of propulsion systems in flight to reach an optimum travel speed, or to leave the atmosphere altogether. Air-breathing engines achieve their efficiency gains over rocket systems by getting their oxygen for combustion from the atmosphere, as opposed to a rocket which must carry its oxygen. These systems capture air from the atmosphere during flight - an arrangement that improves efficiency up to 5-10 times greater than that of conventional chemical rockets.

Once a hypersonic vehicle has accelerated to more than twice the speed of sound, the turbine or rockets are turned off, and the engine relies solely on oxygen in the atmosphere to burn fuel. When the vehicle has accelerated to more than 10 to 15 times the speed of sound, the engine converts to a conventional rocket-powered system to propel the craft into orbit or sustain its top suborbital flight speed.

An artist's concept of the X-43B craft and a B-52 mothership. Credit: Media Fusion, Inc./NASA

Despite the astounding paradigm shift it promises for suborbital and orbital flight, the concept of hypersonic flight is not a new one. NASA's hypersonics program is built on research dating back to the 1950s.

But the new effort - leveraging technology resources and manufacturing capabilities unavailable 30 years ago - is intended to yield practical results before mid-century: a future fleet of government and commercial hypersonic vehicles, traveling between dozens or even hundreds of "skyports" around the world. And beyond it.

NASA's series of hypersonic flight demonstrators includes three air-breathing vehicles: the X-43A, X-43B and X-43C.

The X-43A, an unpiloted research craft mounted atop a modified Pegasus booster rocket, was first flown in June 2001. During the flight, an in-flight incident forced the mission to be aborted. NASA has planned three X-43A flights; two more X-43A flight demonstrators, built in early 2002, are being prepared for flight testing at NASA's Dryden Flight Research Center in Edwards, Calif. Fueled by hydrogen, the X-43A is intended to achieve Mach 7 and possibly Mach 10, or speeds of approximately 5,000 and 7,500 mph, respectively.

The X-43C demonstrator, powered by a scramjet engine developed by the U.S. Air Force, is now in development. The X-43C is expected to accelerate from Mach 5 to Mach 7, reaching a maximum potential speed of about 5,000 mph. NASA will begin flight-testing the X-43C in 2008.

The largest of the Hyper-X test vehicles, the X-43B, could be developed - and would fly - later this decade. Successful ground- and flight-testing of various engine configurations aboard the X-43A and X-43C will determine whether a rocket- or turbine-based combined-cycle engine powers the X-43B.

All three X-43 flight demonstrator projects are managed by NASA's Langley Research Center in Hampton, Va.

An artist's rendering of the air-breathing, hypersonic X-43C, part of NASA's Hyper-X series of flight demonstrators. Now in development, the X-43C is expected to accelerate to a maximum potential speed of about 5,000 mph, and could undergo flight-testing as early as 2008. Credit: Media Fusion, Inc./NASA

NASA expects to spend about $700 million on hypersonics research and development over the next five years, according to Steve Cook, deputy manager of Marshall's Advanced Space Transportation Program. Cook anticipates the investment will yield unprecedented results, opening up new commercial markets for industry, furthering human and robotic exploration of the solar system and significantly improving national security.

"Testing conducted over the last four years proves that air-breathing propulsion is the most promising technology we've seen to date for accomplishing NASA's third-generation space transportation goals," Cook said.

Those goals - focusing on radically safer, more reliable and less expensive access to space - permeate not just the Hypersonics Technology Program, but all NASA's space transportation and propulsion systems programs.

NASA's Space Launch Initiative, managed by the Marshall Center, is working to develop the technology for a second-generation vehicle that could lead to a replacement for the first-generation Space Shuttle by 2012 - providing a vastly safer, more cost efficient and more reliable fleet of vehicles. The third-generation program seeks, by the year 2025, to develop advanced reusable launch vehicles and associated flight and transportation technologies that will allow for even more significant reductions in payload costs, and even greater improvements in safety and reliability.

NASA is leading national research into hypersonics systems development, analysis and integration. Spearheaded by the Marshall Center, the program includes researchers at Ames Research Center in Moffett Field, Calif.; Dryden Flight Research Center in Edwards, Calif.; Glenn Research Center in Cleveland, Ohio; Kennedy Space Center, Fla.; Langley Research Center in Hampton, Va.; and the Air Force Research Laboratory, which encompasses research and development facilities at nine U.S. Air Force bases. NASA is also partnering with leading academic institutions and industry partners around the nation.