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Gentlemen,start your rocketsComments>>

发表于 2008-01-07 12:03 | Tags 标签:

 

What combines the romance of

space travel with the visceral thrill of road racing? Welcome to the new era of motor sport, says Greg Klerkx

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~THE skies above Oshkosh,Wisconsin, are usually assleepy as the town below, butin August they come alive with the howlof jet engines and whirr of propellers.

Oshkosh is home to the worlds largest annual air show, properly called the EEA AirVenture Oshkosh but affectionately known as Oshkosh by the nearly 1 million fans who flock to it every year.

Over the years Oshkosh has seen it all, from elegant second-world-war Mustangs and Spitfires to cutting-edge 21st-century planes such as the stealthy F-22 Raptors. In 2005, it hosted the first and only public appearance of Burt Rutans SpaceShipOne after it had won the X Prize for being the first privately funded spacecraft to make it into space twice within two weeks.

This years show will feature another first: the throaty roar of rocket-powered planes going head-to-head in a race of speed and agility. After nearly three years of rumours, false starts and setbacks, the Rocket Racing League (RRL) will take to the air at Oshkosh 2008. RRL has exhibition races scheduled for 1 and 2 August, and while these will be a mere taster for a full-blown event involving at least six teams (see table, page 31), the RRLs founders hope the exhibition will light a fire under an idea that marries the other-worldly fascination of space tourism with the visceral excitement of big-time motor sport. The organisers also hope the RRL will boost the private space industry, both in terms of popular appeal and technological progress. Rocket-powered planes have been around for more than 60 years, though as a commercial proposition they have never really got off the ground. In the second world war, the Germans and the British added rockets to propeller or jet aircraft to give them extra oomph on short runways or to lift heavy payloads. In the early days of the space race, rocket-powered planes clocked up some important aviation milestones.

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One of the RRLs test planes takes off on a flight last October

“You are miles high and alone. The words ‘you got a clean shutdown’ are most agreeable”

In 1947, a US air force plane called the Bell X-1 became the first plane to break the sound barrier – around 1225 kilometres per hour, depending on air temperature and pressure – while in the 1960s the mighty North American X-15 set a speed record that still stands, 7274 kilometres per hour (Mach 6.7). The X-15 was also the first plane to reach the edge of space and held the altitude record until 2004 when it was beaten by SpaceShipOne – also rocket-powered.

The rocket planes lined up for Oshkosh cant climb as high as the X-15 and with a top speed of around 480 kilometres per hour they wont break the sound barrier. But the crowd should still be treated to a thrilling spectacle.

At the start of the race two planes will blast along the runway and take off steeply, engines aflame and roaring, then climb sharply to a height of about 400 metres where they will navigate several laps of an 8-kilometre virtual circuit, roughly 3.2 kilometres long and 800 metres wide. The route will keep the planes within view of the crowd at all times, with several close passes so spectators can see the flames and hear the howl of the engines. The winner will be the pilot who successfully completes the course in the fastest time. (The number of laps hasnt been specified yet, though the RRL says it expects the real races to be four laps.)

clip_image011[4] Record-breaking rocket planes Bell X-1 (top) and the North American X-15

Each plane will be powered by a single rocket engine capable of 6700 newtons of thrust, giving it similar acceleration to a state­of-the-art fighter plane. The engines will carry enough fuel to burn for about 4 minutes, meaning that the pilots will have to pursue a burn-and-glide strategy to stay in the air for the 12 minutes or so it will take to complete the course. The initial take-off burn will last about 45 to 60 seconds; after that the duration of the burns will depend on the course and the pilots strategy.

In a real RRL race, pilots will see the course as a series of fly-through hoops on displays inside their helmets. The RRL hasnt released the details of the exhibition races, but they wont be quite as sophisticated as that. Each plane will have its own track to reduce the risks of a catastrophic collision – though of course no one can guarantee the contest will be completely safe.

More lift, less drag

The planes themselves are an unusual design. Both employ a canard configuration in which the horizontal tailplane is mounted at the front of the fuselage rather than at the back. Because it offers greater lift and less drag, this design is particularly well suited to rocket planes and other pusher aircraft, where the propulsion system is at the rear.

The planes will be built by Velocity Aircraft of Sebastian, Florida, which was recently bought by RRL for this purpose. Both are off-the-shelf models from Velocitys range of propeller-powered planes, one a Velocity SE and the other a Velocity XL, with the

propellers replaced by a rocket engine. RRL will eventually choose one of the planes as the prototype for a standard RRL plane, which will be called the Rocket Racer.

For the engine, the RRL initially had

a contract with just one company, XCOR Aerospace of Mojave, California, which has been experimenting with rocket planes since the late 1990s. In May,

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however, the RRL announced a second deal with Armadillo Aerospace of Rockwall, Texas, to design and build a competing engine. The idea is to give the RRL teams a choice of engine much as Formula 1 teams used to be able to choose between Bridgestone and Michelin tyres.

XCOR’s engine will use a mixture of liquid oxygen (LOX) and kerosene, a departure from the company’s traditional LOX-alcohol mix. The decision, says XCOR spokesman Douglas Graham, is largely aesthetic: alcohol gives a colourless burn, but the RRL wants to wow spectators with bright, colourful flames. Armadillo is likely to stick with a LOX-alcohol mix, but may seed the flame with sodium or another chemical to produce colour.

A key difference between XCOR and Armadillo’s engines is control. Most rocket engines have no throttle: they’re either on or off. XCOR’s engine will stick with this design, but Armadillo’s will have a throttle, allowing pilots greater flexibility with their burn-and¬glide strategy.

Flying a rocket plane isn’t for novices. Veteran test pilot Dick Rutan, brother of SpaceShipOne’s Burt Rutan, is one of only

a handful of experienced rocket-plane pilots, whose exploits include a stint in an XCOR

powered experimental EZ-Rocket plane

at Oshkosh in 2002. He told New Scientist

that the feel of a rocket plane in flight is very different from propeller or jet-powered aircraft. “Since the rocket motors consume a copious amount of fuel, the take-off and initial climb gross weight is very heavy,” he says. “Once the take-off, initial climb angle and airspeed are obtained the ride gets better and better, steeper and faster. The thrust on your back lets you know you are getting with the programme.”

Another veteran military and test pilot with rocket-plane experience is Rick Searfoss, who has also flown three shuttle missions. He compares rocket-plane performance to that of the T-38, a popular training jet used by the US military. “It’s definitely more challenging than a light aircraft,” he says. “But it’s less challenging than performing a full-up mission in a fighter-type aircraft.” However, he adds that because the RRL vehicles are still very much prototypes, “we haven’t yet seen anything close to best performance”.

Searfoss has long-standing links with XCOR and has been hired by RRL to fly in the exhibition race, where he will be piloting the Velocity SE with an XCOR engine. The other pilot, Len Fox, will fly the Velocity XL, which is slightly wider and longer than the SE, powered by an Armadillo engine. Theres not much difference between the aircraft, says RRL chief executive Granger Whitelaw. Were just testing some safety and performance parameters.”

Whitelaw, an entrepreneur who was part of the Indianapolis 500 winning teams of 1996 and 1998, co-founded the RRL in 1995 with X Prize impresario Peter Diamandis. The idea was to combine the pioneering spirit of the X Prize with the more down-to-earth world of motor racing, with its blend of high technology and crowd-pleasing thrills.

One important parallel between the RRL and motor racing, says Whitelaw, is that the competition will stimulate technological advancement. Formula 1, IndyCar and NASCAR all serve as test beds for a variety of technologies, from rubber compounds to valves, brakes and safety harnesses. So many things that go into a race vehicle end up in your car, says Whitelaw. Thats why Indy and other races are heavily supported by manufacturers.

Much as motor racing teams generate intellectual property in the form of engines, materials and parts, so the RRL will end up owning new aerospace technologies. Velocity Aircraft will design a standard airframe and avionics for all teams in the league, although the teams will be allowed to make small adjustments; XCOR and Armadillo will do the same for the engines. In this way the RRL and its affiliates will create intellectual property they can sell or license to the aviation and private space industries.

Big money

Whitelaw also hopes that the RRL will stimulate competition and cooperation in private space-flight, much as the X Prize did. If you get Virgin and Bigelow and Blue Origin [the space company created by Amazon.com founder Jeff Bezos] and others to work together, youll have more success, he says. The league is a place they can do that.

Potentially, there is big money to be made from ticket sales and merchandise. Whitelaw points out that the two existing plane-racing events, the Reno and Red Bull air races, attract millions of people. Its huge, he says.

Spectators at a real RRL race will see something quite different from the Oshkosh exhibitions. The real league has six teams so far, and races will feature multiple aircraft – possibly as many as 10 – with several in the air at any one time. Since the races are not head­to-head contests but a set of individual time trials, there is no equivalent of pole position and no obvious race leader. Each race will have several heats and require at least one pit stop for refuelling, says Whitelaw.

He says that one of the more nerve-racking aspects of an RRL race will be the process of landing, refuelling and getting airborne again as quickly as possible. The big events in rocketry are start and shut down, says Rutan. Each has its own unique set of sequences that must go just right. If not, real bad things can happen.

Its not hard to work out what those real bad things might be: since rocket engines rely on the controlled combustion of highly volatile chemicals, fires and explosions are not infrequent. Last year three people were killed at Burt Rutans Scaled Composites in Mojave, California, when an experimental propellent system for SpaceShipTwo exploded. Dick Rutan recalls one test flight where he had to get out and run from a rocket plane while it was still on the ground – not an option when you’re shutting the engine down in flight during a burn-and-glide race. You are miles high and all alone, he says. The words you got a clean shutdown are most agreeable.

As an added complication, the rocket planes will land only after they have burned through all their fuel, meaning theyre essentially gliders performing a deadstick landing, at the mercy of gravity and what little aerodynamic performance the pilot can coax out of them. No second chance with that,” Rutan says dryly.

On top of the flying challenges, the RRL teams will need smart strategy and effective teamwork. Its definitely a thinking mans game,” says Searfoss. As in Formula 1 or NASCAR, successful RRL teams will need to employ detailed planning, clever engineering and meticulous operation before and during the race. It aint gonna be just turn-and­burn, says Searfoss.

Even if all goes well at Oshkosh, Searfoss isnt yet convinced that the RRL will be ready to take off in earnest. Conceptualising this rocket-plane racing operation is one thing and its a very exciting prospect, he says. But actually designing, building, testing and flying these systems is orders of magnitude more difficult than I believe virtually anyone recognises. The league also has to decide how many races to hold in a season, and where.

Right now, RRLs leadership are happy just to be getting the exhibition races off the ground. After the league formed in October 2005, several teams joined up only to drop out or fold. The first exhibition race was

lined up for the 2006 Wirefly X Prize Cup, but didnt happen. Along with Oshkosh though, the RRL is scheduled to fly three more exhibition races before the end of this year, and the first full RRL race could happen as early as next year.

I really want to get through one or

two exhibition races, to see how the tech looks and feels, how fans react, says Whitelaw. Theres a lot to consider. We have to produce multiple planes, train multiple teams, make sure the Federal Aviation Authority is comfortable with everything were doing. I just think youve got to do things right. Get it right, though, and the NASCAR of the skies can start dreaming of soaraway success. ~

Greg Klerkx is a writer based in London

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3 Responses to “Gentlemen,start your rockets”

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