Can aviation's newest spectator sport lead to routine space travel?
- By Larry Lowe
- Air & Space magazine, September 2007
(Page 2 of 4)
The league, formed in October 2005 by X-Prize creator Peter Diamandis and financier and Indy car team owner Granger Whitelaw, is looking forward to the first flight of its X-racer this fall. Three independent teams—and two more owned by the League—have each paid the $100,000 ante to race, a down payment on the $1.2 million rocketplane, which the league has named Thunderhawk. Annual operating costs and racing fees could run each team owner another $500,000. The league expects to offer a purse starting at $1 million.
There had been four independent teams: Leading Edge Rocket Racing, the first to sign on, withdrew last May because it and the league had “incompatible business practices and communication standards.” Team owners Don Grantham Jr. and Robert Rickard, business partners in Phoenix, Arizona, and F-16 pilots with the Air Force Reserve, had expected a handsome return on their investment. “We looked at the closest comparison we could, which is NASCAR,” Grantham said last November, “and compared it to the potential we have with RRL. It took 40 years to progress from racing on the sand in Florida to the spectacle it is today. Title sponsorship is worth about $20 million to top teams, and the NASCAR merchandising business as a whole generates $1.5 billion annually.” That earning potential, though, depends on the development of a racing airplane.
THE AIRFRAME THAT proved the concept for a viable racing rocket, no one will be surprised to learn, is a design by X-Prize winner and aeronautical magician Burt Rutan. XCOR took Rutan’s famous canard kitplane, the Long-EZ, and replaced the pusher propeller with two 400-pound-thrust rocket engines. The EZ-Rocket, as it was called, flew in 2002 at the Experimental Aircraft Association’s Oshkosh, Wisconsin airshow and again in October 2005, at the X-Prize Cup, an annual demo and trade show in Las Cruces, New Mexico, held to encourage private space ventures. The prototype racer is based on the Velocity SE FG kitplane, manufactured in Sebastian, Florida, a four-seat, composite derivation of the Long-EZ, which offers a cabin large enough to house the 39-inch-diameter liquid-oxygen tank in the aft section.
Before XCOR began modifying the Velocity, Searfoss put 25 hours of flight tests on the airplane—mostly sawtooth climb-and-descent patterns. He had written a computer program to analyze the rocket engine thrust and aircraft drag. From the data he collected, he could project what would happen when the piston engine is replaced with a rocket.
“You are going to have amazing climb rates and angles,” says Searfoss.
The calculations are not straightforward, but the league’s director of technology, Michael D’Angelo, says the 1,500 pounds of thrust from XCOR’s XR-4K14 rocket engine is—at around 220 mph—roughly equivalent to 1,000 horsepower. This is five times the power the SE FG airframe was designed to handle.
XCOR spokesman Doug Graham explains that the company is strengthening the airframe, which has a 200-knot indicated-airspeed limit, to handle the stresses of racing and also to handle the greater weight of the aircraft with a rocket engine—3,000 pounds instead of the 2,400-pound prop-driven Velocity. Because the rocket could easily push the aircraft past its rated speed, XCOR has also incorporated a governor that stops the engine from firing if a certain speed is exceeded.
Flying the EZ-Rocket gave Searfoss a good idea of what to expect in the operational vehicles. “The first thing you notice is how much smoother it is,” he says. “You turn that engine on and it’s just a great feeling to have that kick in the pants and not feel that shaking and vibration. It’s a whole heck of a lot easier than flying a Cub. You take the recip engine and the big swinging prop out of the equation and all those gyroscopic effects are gone.”
The rockets are simple: off or on. Power off, the Thunderhawk is a docile glider that offers a lot of leeway to a pilot who masters speed control. Power on, it’s a different animal.