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• Flight Today

X-Racers

Can aviation's newest spectator sport lead to routine space travel?

• By Larry Lowe
• Air & Space Magazine, September 01, 2007

THIS IS WHAT THE FANS IN THE BLEACHERS WILL SEE.

At one end of the track, two racing aircraft are poised less than 50 feet apart at a starting line. They silently exhale mist from vents in the fuselage liquid-oxygen tanks. When the gun sounds, their 1,500-pound-thrust rocket engines ignite, hurling the racers down the runway past the fans and throwing back brilliant 10-foot kerosene flames: 0 to 200 in 15 seconds. At the end of the straightaway, the rocketplanes pull vertical and shoot straight up on pillars of fire. At about 3,000 feet, they pitch over inverted, roll, and, engines now off, dive through an invisible gate to follow a course that twists and turns like a roller-coaster track.

The pilots see the course superimposed on the sky around them by helmet-mounted displays. As the first pair dive silently into the first roller-coaster drop, two more rocketplanes launch. Eventually six pairs of racers are weaving around the serpentine, five-mile course.
At several points the undulating tunnel will sharply ascend, forcing the pilots to re-ignite their engines for the power to get uphill. At least one climb will be designed at a point where the racers are facing away from the spectators, treating them to the full concussive power of rocket thrust, which they will feel in their chests as well as hear. Intermittently lighting the rocket engines, the racers will dash and glide, competing in a four-lap heat lasting about 14 minutes.

On jumbo TV screens set up near the runway, a computer-augmented display will show the rocketplanes and the courses they’re flying. No two racers will be following exactly the same course. Instead, each racer will follow its own predetermined path, generated by computer, based on GPS-provided coordinates, and painted on the jumbotrons like the yellow line on television screens that shows football fans where the ball must reach for a first down.

Because the individual race courses all differ, they considerably reduce the potential for a mid-air collision, a scenario that the Reno Air Racing Association in Nevada spends a great deal of time training pilots who race around ground pylons to avoid. In a rocket racing event, each aircraft flies its own private proficiency race: The pilot strives to make the most efficient use of the racer’s fuel, which will produce thrust for no more than 200 seconds. And therein lies the real contest.

“This is really going to be a thinking man’s game,” says former space shuttle commander Rick Searfoss, who is the chief test pilot for XCOR Aerospace, the Mojave, California company building the rocketplanes. “It’s very much a matter of flying parameters, managing energy.” It will be of considerable importance, for example, how the pilots manage speed during dives and how much energy they use during each following climb to the next set of gates. The fender-bumping, paint-trading competition of NASCAR will be replaced with something closer to a three-dimensional chess match at 200 mph. The proximity of other racers in the sky is more a strategy to generate excitement among the spectators than a factor affecting the competition.
Because rocket racing will rely on a course defined by data, not by pylons or oval tracks, it has two advantages over the motorsports of Reno and the Indianapolis Motor Speedway. First, a computer-designed course allows for experimentation and refinement without costly surveying and marking. Second, a much larger audience than the fans in the grandstands can watch—and play. While 12 racers will be alternately roaring and gliding in the real sky, the viewer at home will be looking at 13 rocketplanes. The extra competitor will be the fan’s own entry, controlled by a joystick on a game console: He or she will fly a virtual racer, create a strategy, and experience everything in the race except the G forces and the smell of the cockpit.

That’s what the Rocket Racing League hopes to bring to race venues and the fans at home.

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.
At full fuel weight for takeoff the racer has a 0.6 thrust-to-weight ratio, which is comparable to that of an F/A-18 going to full power without afterburner. The feel of an afterburner comes later in the race, when the fuel load is lighter and the thrust-to-weight rises. The rate at which things will happen during takeoff is also comparable to what pilots face in an F/A-18.

XCOR DIRECTOR OF BUSINESS development Rich Pournelle is too young to have seen the Apollo missions on TV, but he is part of a movement—New Space—to replace big, government-funded space programs like Apollo with nimble, energetic space businesses that respond to a market. New Space entrepreneurs look with a mixture of disappointment and disgust at the broken promise of the complex, expensive space shuttle to provide routine access to space. Their goal is to make space travel airline-like, and XCOR’s Pournelle goes them one better: The ultimate goal of XCOR engine technology, he says, “is to power the Southwest Airlines of space.” Like Richard Branson’s Virgin Galactic, which has licensed Burt Rutan’s SpaceShipOne technology to produce rocketships for carrying tourists into space, XCOR is developing a reusable rocket vehicle, Xerus, that will travel to an altitude of 60 miles and back. The Rocket Racing League contract, says Pournelle, is “a perfect fit in our critical path.”
To solve the problems the Rocket Racing League requirements present, XCOR has turned the process of designing rocket engines on its head. Traditionally, rocket engine designers aimed for maximum performance whatever the cost. XCOR designs for safety and economy: The engines must be reliable and easy to maintain. In a race, crews must be able to load them with fuel quickly. And, with 200 seconds’ worth of fuel in a 14-minute race, the engines must be capable of reliable restarts—lots of them. “The requirements of racing can drive the technology in a sort of way that will have spinoffs for the suborbitals,” says Searfoss. Flying tourists on airline-like schedules will also require safe, reliable restarts, ease of maintenance and production, and fast fueling.

In the X-Racer engine, ignition begins with a a tiny spark plug, designed to ignite the fuel-air charge in model airplane engines. XCOR engineers repurposed the hobby shop item to ignite an equally tiny burner inside the XR-4K14. Once sensors confirm that this igniter rocket, essentially a blowtorch, is up and running, the engine control computer opens a sequence of valves to force a mist of liquid oxygen and kerosene into the combustion chamber through a proprietary pattern of spray nozzles. When the mist hits the igniter blowtorch, it ignites immediately and reliably, going from 0 to 1,500 pounds of thrust in less than a half a second. Because the blowtorch ensures that the LOX/kerosene mist cannot accumulate without ignition, the XR-4K14 cannot suffer what’s known as a hard start, an explosion in the combustion chamber instead of a controlled ignition. “Our engines don’t come apart without a wrench,” says Rich Pournelle. Even so, the engine installation includes a blast shield to keep shrapnel inside the cowling, just in case.

XCOR met the design goal of a 10-minute time to refuel the X-Racer in 2005, a vast improvement over the three hours it took to refuel the EZ-Racer. It’s a remarkable achievement to pump a half a ton of LOX—which boils at –300 degrees Fahrenheit—into a tank that has to be pressurized with helium to force its contents into the combustion chamber. The design of the 39-inch-diameter LOX tank and support was a surprising engineering challenge. The mounting had to be flexible enough to allow for expansion and contractions due to thermal shock and at the same time provide rigid structural support for the inertial loads created by the LOX mass sloshing around due to G and power changes.

On race day, there will be three, maybe four bracketed races. Qualifying rounds held in the days before will determine the racers’ positions for the first race. The fastest racers from the field of 12 in the first race will move forward in position until in the fourth, or final, race, the two fastest vehicles of the day will launch from the front two spaces on the starting grid to vie for first place. The remaining pairings will be of equally matched racers.

Granger Whitelaw envisions the oldest scenario in sport—the underdog comes from behind—as possible if a great pilot/plane combination has a bad day qualifying and ends up in the back row for the first bracket race of the day. If the pilot wins his pairing for that bracket, he will move up a row for the next round and may conceivably be sitting in the front row for the final, deciding race.

THE RACE PILOTS WHO HAVE signed on bring to the sport a vast range of experiences. Dave Morss, chief pilot for the Santa Fe racing team owned by New Mexico land developer Marc Cumbow, has 27,000 hours in more than 30 types of aircraft and has competed in more air races (170) than anyone else since the national races restarted in Reno in 1960. “Basically, I am going to take my 34 years of experience and apply it as need be to get the job done,” he says, already perfecting the sound bite for the sports announcer. On the other end of the experience spectrum, league racer Nick Mowery has about a tenth the hours Morss has—2,500 of them as an instructor in Cessna 172s. Among his students: league founder Granger Whitelaw. “I’m just the average guy, I guess,” says Mowery, who is currently learning aerobatics and getting a glider rating because gliding “is going to be a big part of the race.”
Independent team owner and race pilot Jim Bridenstine is a former Navy E-2 Hawkeye pilot who now flies the F/A-18 Hornet at Naval Air Station Fallon in Nevada. Nearing the end of his Navy career, Bridenstine sees team ownership as a way to make money while flying something that will be as much fun to fly as the Hornet. “Think of the number of people who went to all the NFL football games in 2006,” he says. “Now double that and you have the number of people who went to an airshow in 2006.” Bridenstine sees huge sponsorship potential in the combination of the largest on-site audience with the large television audience for motor sports. (According to Nielsen ratings, NASCAR is second only to the National Football League in television sports viewership.) “This could be the most viewed sporting event in history,” says Bridenstine, “once it gets going.”
It’s not too difficult to imagine the Olympics-style video profiles of the racers, interspersed with segments in which announcers describe the mood of the crowd on race day…once there is a race day. The first Thunderhawk was to have flown in 2006; racing was supposed to have begun this year.

The Rocket Racing League now plans to begin with demonstrations this year and races in 2008. Plans include piping data over the Internet to home systems that will re-create what is happening on the course and selling video games and home gaming consoles. Finally the plans require the not-so-minor detail of producing operational rocket-powered racing craft. Can they do it?
The fact that the Rocket Racing League has missed a series of deadlines doesn’t mean its plans won’t be fully realized. Projects of greater complexity—the U.S. space program, for instance—have foundered in their initial stages only to come from behind and win.