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A computational fluid dynamics image shows how air would behave when Rocketplane XP flies at 2.74 times the speed of sound; red is high pressure, blue is low. (NASA)

The O Prize

Will Rocketplane launch spacecraft from Oklahoma?

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(Continued from page 3)

Once settled at Rocketplane’s new headquarters, a single-story building at Oklahoma City’s Will Rogers Airport, Urie set about hiring a team of engineers composed of equal parts seasoned veterans and young engineers right out of school. One of Urie’s prime hires was engineer Bob Seto, who took over the day-to-day operation of building Rocketplane XP. Talking to him made the whole enterprise sound almost reasonable to me.

Seto explained that at a maximum velocity of three to four times the speed of sound, Rocketplane XP wouldn’t experience anywhere near the heating from atmospheric friction that the space shuttle, traveling at 25 times the speed of sound, encounters returning from orbit. Nevertheless, reentry heat would pose a problem for an ordinary Learjet’s aluminum structure. Aluminum, used for airframes because of its light weight, melts at a lower temperature than a heavier metal like steel.

So Rocketplane’s engineers and machinists would replace the areas subjected to the greatest heat—the engine inlets, the nose, and the leading edges of the delta wing—with steel or titanium. The rest of the ship would get a coating of a heat-dissipating paint that had been developed at NASA for next-generation spaceships and that had then been released for commercial use. Even though the bulk of the ship would still be of lightweight aluminum, all those modifications, plus the rocket engine and its fuel, added up to a much heftier craft. At takeoff, Rocketplane XP would top out at 19,500 pounds, compared with the unmodified Learjet 25’s 15,000 pounds. The spaceship would need a hell of a long runway to get airborne. Fortunately, the state of Oklahoma had one.

Burns Flat, Oklahoma, is 80 miles from Will Rogers Airport. Bob Seto flew me there, along with Reda Anderson and Misuzu Onuki, in his Cessna 182. He banked on approach so that we could get the best view of the 13,503-foot runway at Burns Flat’s former Strategic Air Command base. It had been built during the cold war for heavily laden B-52 bombers ready to scramble at a moment’s notice to rain nuclear death on the Soviet Union. Seto remarked that he could take off sideways on it. The place was all but deserted. These days the only traffic the place saw was Air Force pilots practicing takeoffs and landings.

In June 2006, the Federal Aviation Administration certified the place as a commercial spaceport, and it officially became known as the Oklahoma Spaceport. This is where Rocketplane chief pilot John “Bone” Herrington will fly from and land if the spacecraft becomes operational.

Herrington had left the NASA astronaut corps early and taken a pay cut to join Rocketplane. He’d flown in space once, on the last space shuttle mission before the shuttle Columbia disintegrated in 2003. He knew he’d likely have a long wait before his next ride on the shuttle, and he just could not pass up a chance to be part of what he thought would be a historic event—the first suborbital flight to carry paying passengers into space.

Anderson grilled Herrington about the Rocketplane XP’s flight profile, about every aspect of the experience of flying in space, about all the potential dangers. And about whether she’d get a good view out the window. “I’m not wild about getting out of the seat and floating around,” Anderson told the pilot. “I’m more interested in the view.” Fortunately, there just wasn’t time to get up and float around and get used to the sensations of weightlessness and take in the sights. The cramped interior of the Rocketplane XP would prevent much floating anyway.

But would Rocketplane XP even get off the ground? Dan Erwin, associate professor of aeronautics at the University of Southern California, thought it had an excellent chance. “The performance numbers given by the company are reasonable, based on their estimate for vehicle mass at launch,” he told me. The team’s greatest challenge would be the ship’s rocket engine.

The AR-36, built by Polaris Propulsion, will run on kerosene and liquid oxygen and deliver 36,000 pounds of thrust. Its regeneratively cooled design (in which kerosene circulates along the combustion chamber’s outer wall before flowing inside to be burned) would allow the engine to be fired many times without much maintenance, just like a jet engine. This design had an advantage over rocket engines with ablative coatings, which char and flake away to take heat with them; ablatives have to be replaced after every firing of the engines.

ROCKETPLANE AND RICHARD BRANSON’S Virgin Galactic, which is buying space tourism craft from Scaled Composites, seem to be vying for the honor of flying the first suborbital space passengers. But theirs are by no means the only ventures gearing up for suborbital flights. Scaled Composites’ neighbor at the Mojave Airport, XCOR Aerospace, has been working on a two-seat rocketplane design that, like Rocketplane XP, would launch under its own power from a runway but without the encumbrance of jet engines; Xerus would be rocket-powered all the way.

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