Jet motorbike: Record breaking Attempt

RICHARD BROWN is a man with unfinished business.

In 1999, he smashed the one-way speed record for a motorbike by hitting 584 kilometres per hour on the salt flats of Bonneville in northern Utah. But his claim on the outright world record - which is based on the average of two runs in opposite directions - was thwarted by technical problems.

Now he is trying again. He hopes to be the first person to exceed 720 km/h on a motorbike while achieving an average two-way speed of at least 640 km/h. Any old bike will not do: he will be using one that is jet-propelled.

While cars used in land-speed-record attempts, like the Bloodhound jet car that will attempt the challenge in 2012, and certain types of boat have taken advantage of jet thrust since the 1950s, all record-breaking motorbikes have used a conventional engine that drives the rear wheel.

This is because it is difficult to pack a jet engine into a two-wheeled frame capable of enormous speed with any degree of safety. Fast cars can be built around old jet fighter engines, but these are far too heavy to fit into a bike that must be balanced by the driver making tiny steering adjustments to the front wheel.

So for his new bike, called Jet Reaction, Brown has redesigned a 930-kilowatt helicopter engine to produce thrust instead of turning a rotor. It was "quite difficult", he says.

"One is working with very fine tolerances in very difficult materials. If you get it wrong, destroying the engine is the most likely result."

Brown has also added his own reheat unit, or afterburner. It sprays fuel into the hot exhaust gases, causing it to ignite and generate yet more thrust. The idea sounds simple enough, though he says that getting it to work at something approaching its theoretical potential "requires much more development". The reheat burner sits above two canisters that deploy braking parachutes when needed.

Brown has a track record in ambitious jet engine projects. Following his 1999 record attempt he built a sub-orbital rocket, but the launch in South Africa had to be cancelled. He is also working on a gas-turbine-powered jet pack, similar to one developed by the US military, that he hopes will allow the wearer to remain airborne for 10 minutes.

Brown's 1999 record attempt involved his own Gillette Mach 3 Challenger bike, which featured a custom-built hybrid rocket engine. The attempt failed because soft ground forced the team to use tyres rather than the usual aluminium wheels. The tyres were only designed to withstand speeds of 380 km/h or so. Eventually the massive centrifugal forces on the rear tyre caused it to deflate.

The current motorbike land-speed record, 606 km/h, was set in 2010 by Rocky Robinson on a bike called the Ack Attack Streamliner. Such record-breakers feature elongated metal bodies - as does Jet Reaction - making them look more like giant bullets than motorcycles. They are also fitted with retractable stabilisers for balance when moving slowly or stationary.

Brown expects to carry out trials with Jet Reaction at a UK airfield in March next year, with an attempt on the world record back at the Bonneville salt flats pencilled in for 2013.

It won't be easy, says Mark Chapman, Bloodhound's chief engineer. "The biggest issue is air intake," he says. "You have to be sure the air flow through the jet is stable or the engine could surge, which could be dangerous."