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Hallion: Hypersonic Future 'Not Wishful Thinking'
Richard Hallion really does believe that the U.S. has a need for speed.

And by speed, he's not just talking a paltry few hundred miles an hour. No, he's talking in terms of hypersonics — roughly Mach 5 and above.

That's how fast Hallion says America's aircraft need to fly in order to maintain the edge in what he refers to as "a global hypersonic race."

Richard Hallion talks about the history of hypersonics.
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At a "Hypersonics: A Review of its History and Application" talk at NASA Langley, Dick Hallion, former chief Air Force historian, reviewed the main developments in hypersonic research, highlighting lessons learned and challenges yet to be resolved. Credit: NASA/Sean Smith

X43 testing at NASA Langley.
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Mach 7 wind tunnel test of the full-scale X-43A model with spare flight engine in NASA Langley's 8-Foot High Temperature Tunnel. Credit: NASA

Space Shuttle Columbia landing.
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The first Space Shuttle landing was Mission 41-B on Feb. 11, 1984. Credit: NASA

Hallion, former chief Air Force historian, made his case at NASA’s Langley Research Center on Wednesday during an American Institute of Aeronautics and Astronautics (AIAA) lecture, "Hypersonics: A Review of its History and Application."

Though Mach 5 is exceptionally fast, Hallion believes the ability of the U.S. to fortify its defenses with hypersonic aircraft is not only necessary, but well within reach.

"This is a subject field that's practical," he said. "It's not wishful thinking."

Hallion then turned back the clock for a history lesson, going all the way back to Nazi Germany and the Silbervogel (silver bird). Designed by Eugen Sanger and Irene Bredt in the late 1930s, the rocket-powered Silbervogel, conceived as a long-range bomber, never went into production. It was too complex and expensive.

But with elements like a flat bottom and low-aspect-ratio wings, the aircraft's sleek, advanced design did foreshadow what we would later see with hypersonic craft.

Back in the U.S., by the early 1950s, scientists had developed a good grasp of supersonic flight, with manned aircraft traveling at speeds of Mach 2 and beyond.

"People were thinking, 'where do we go from here?' " Hallion said.

The answer was higher. And faster.

The space race was an important part of that equation. But just a little closer to Earth, pilots like Neil Armstrong and Robert Rushworth were reaching hypersonic speeds in the X-15, which still holds the world record for the fastest speed ever achieved by a manned aircraft. That record was broken on Oct. 3, 1967, when a flight piloted by William "Pete" Knight reached Mach 6.7.

Then there were the ideas that never got off the ground, including one called the Aerospaceplane. Meant to take off from a runway, fly into orbit and return to Earth, the Aerospaceplane, like the Silbervogel, was too complex to be built. In 1963, a U.S. Air Force Scientific Advisory Board panned the project as having an "erratic history" and being subject to "so much ridicule."

"This thing was really kind of wacko," Hallion said.

Much more successful was NASA's Space Shuttle program. But because the cost of launching a flight test into space would've been prohibitively expensive, the shuttle program differed from previous programs in a key way.

"The shuttle is dependent to an extraordinary degree on basically ground research methodologies," he said.

And that ground research wasn't entirely accurate. Still, the first shuttle mission, STS-1, was a success. When the Space Shuttle Columbia reentered the atmosphere, it marked the first winged hypersonic reentry of a manned spacecraft.

Meanwhile, in the shadow of the shuttle program, hypersonic programs sporting names like HySET (Hypersonic Scramjet Engine Technology), IHPRPT (Integrated High Payoff Rocket Propulsion Technology), Blackswift and HyperSoar — an "alphabet soup," as Hallion refers to them — continued to come and go.

But it's only been the in the last few years that Hallion has really started to feel reinvigorated by some of the developments in hypersonics, especially the advancements he's seeing in unmanned scramjet aircraft like the X-43 and X-51. He was particularly encouraged by the first flight of the X-51, which reached Mach 4.87.

"I'm inclined to say it was the Kitty Hawk moment for air-breathing supersonic combustion," he said.

Given the advancements in our understanding of hypersonics, Hallion feels like we'd be remiss not to make the technology a key part of our national security — especially considering that countries like China, Russia and Iran are developing hypersonic technology as well.

"Hypersonics is a huge game changer if used against us," he said.

The way Hallion sees it, hypersonics would give the U.S. some key advantages. It would help us reach distant targets quickly. It would also give us an edge over evolving defenses and offer a much-needed facelift to our military's aging force structure.

A self-described optimist, Hallion believes the U.S. is on a path to a hypersonic future. He points out hat we entered the 19th century traveling 6 miles per hour on horse-drawn carriages, the 20th century traveling 60 miles per hour on steam locomotives, and the 21st century traveling 600 miles per hour on intercontinental jetliners.

"If you run that line out there, you find a very interesting thing," he said. "You may enter that next century above 6,000 miles per hour."

By: Joe Atkinson

The Researcher News
NASA Langley Research Center
Editor & Curator: Denise Lineberry
Executive Editor & Responsible NASA Official: Rob Wyman