Can aviation's newest spectator sport lead to routine space travel?
- By Larry Lowe
- Air & Space magazine, September 2007
(Page 3 of 4)
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.”