Page last updated at 15:07 GMT, Tuesday, 16 March 2010

Bloodhound supersonic car's lift problem fixed

By Jonathan Amos
Science correspondent, BBC News

Bloodhound SSC (Curventa)
The aero solution is a major milestone in Bloodhound's design

Engineers designing the world's fastest car believe they now have a solution to keep the vehicle flat on the ground.

Bloodhound SSC is being built to smash the world land speed record by topping 1,000mph (1,610km/h).

Initial iterations of the car's aerodynamic shape produced dangerous amounts of lift at the vehicle's rear.

But the latest modelling work indicates the team has finally found a stable configuration, allowing the project to push ahead with other design areas.

"At Mach 1.3, we've close to zero lift which is where we wanted to be," said John Piper, Bloodhound's technical director.

"Up until this point, we've had some big issues. We've had lift as high as 12 tonnes, and when you consider the car is six-and-a-half tonnes at its heaviest - that amount of lift is enough to make the car fly," he told BBC News.

"We're very close now to fixing the exterior aero surface, which really opens the floodgates to the rest of the design work to really get going."

Computing power

By playing with the position and shape of key elements of the car's rear end, the design team has now found the best way to manage the shockwave passing around and under the vehicle as it goes supersonic.

The solution is a major milestone in Bloodhound's design.

The effort has been assisted greatly by project sponsor Intel. It brought immense computing power to bear on the lift problem.

Before Intel's intervention, the design team had worked through 11 different "architectures" in 18 months. The latest modelling work run on Intel's network investigated 55 configurations in just eight weeks.

To claim the world land speed record, Bloodhound will have to better the mark of 763mph (1,228km/h) set by the Thrust SuperSonic Car in 1997.

It will be powered by a combination of a hybrid rocket and a jet engine from a Eurofighter-Typhoon.

Three who worked on Thrust are also engaged in the Bloodhound project, including driver Wing Cmdr Andy Green, project director Richard Noble and chief aerodynamicist Ron Ayers.

They plan to mount their assault on the record in late 2011, driving across a dried up lakebed known as Hakskeen Pan, in the Northern Cape of South Africa.

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The power of imagination: Bloodhound's race with a Eurofighter

Bloodhound's aero shape is not completely fixed. Further work is still required on the jet intake ducts, the winglets that control lift, the air brakes (deployable structures that slow the car), and the large rear fin. The team also needs to model the air flow into the car.

But settling on the principal exterior surface means the team can now push forward on the main chassis structure and interior packaging of all the components that go into the vehicle.

John Piper intends to produce a master model of the car in late August, early September.

This will be followed by about five to six months of detailed drawing to direct the manufacture of components.

The aim is to have the car built and ready to begin testing in the second half of 2011.

Work is progressing on the wheels which will have to endure tremendous forces as Bloodhound races across the pan.

The 900mm-diameter, 120mm-thick aluminium discs will rotate at 10,300 rpm. The radial acceleration will be equivalent to about 50,000 g at the rims. Under those conditions, the alloy actually begins to stretch.

Lockheed Martin is working on the design. It will shortly run an experiment in which earth from Hakskeen Pan is fired out of an air gun at a sample of aluminium that has been pre-stretched to simulate the loads that will be experienced by the real wheels.

"A piece of dirt at Mach 1.4 is faster than a bullet so we've got to make sure we're not overstretching the material," said John Piper.

World land speed records by Britons

Jonathan.Amos- INTERNET@bbc.co.uk



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SEE ALSO
Bloodhound diary: Number crunching
04 Jan 10 |  Science & Environment
Bloodhound diary: South Africa is the place
26 Nov 09 |  Science & Environment
Design fixed for 1,000mph car
23 Nov 09 |  Science & Environment
Bloodhound diary: On a roll
04 Nov 09 |  Science & Environment
Bloodhound diary: Rockets firing
16 Sep 09 |  Science & Environment
Bloodhound diary: Pressure builds
23 Aug 09 |  Science & Environment
Bloodhound diary: Speed record
30 Jul 09 |  Science & Environment
Supersonic car targets 1,000mph
22 Oct 08 |  Science & Environment

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