Rocket, gas turbine, and V12 to power speed bid

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  • Image: Bloodhound Tri_Side_(480x270).jpg
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Image: Bloodhound_ssc_by_Curventa_Press_-_Image_2.jpg

Not the usual land vehicle tailpipe image, but this is Project Bloodhound with a targeted 1000-mph maximum speed. (curventa)

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The target is to a­chieve 1000 mph, or Mach 1.4, and establish a new world land speed record—and that, said Richard Noble­, leader of the newly revealed Project Bloodhound, "is as much an engineering adventure as the ultimate speed record challenge."

The aim is to take the rocket/gas turbine/gasoline engined Bloodhound to a new world record in 2011 driven by British Royal Air Force fighter pilot, Wing Commander Andy Green, who holds the current record of 763 mph that saw the Thrust SSC exceed Mach 1.

Project Bloodhound involves the detail design and development of a carbon-fiber composite car that is scheduled to reach 1000 mph in carefully paced gradations, beginning with an 800-mph run in 2009, followed by 900 mph in 2010, and 1000 mph in 2011. The Black Rock Desert, where Green took Thrust SSC to the current land speed record 11 years ago, is a possible site for the attempts. Richard Noble also achieved a world land speed record in October 1983 at 633 mph with Thrust2.

The Bloodhound project is being sponsored by the fuel additive brand STP. The company sponsored Athol Graham in a land speed record bid almost half a century ago and backed Art Arfons for world land speed record attempts in the 1960s, including his success in 1965 at a speed of 576 mph.

A stated aim of the project is "to re-ignite interest in science, technology, engineering, and mathematics amongst youth, and raise the numbers entering technology careers."

Achieving 1000 mph is an enormous engineering challenge, with involved disciplines including aerodynamics, computational fluid dynamics (CFD), and materials technology—notably carbon composites.

The car will be 12.8 m (42.0 ft) long, 6.4 m (21.0 ft) wide, with an all-up weight (fueled) of 6422 kg (14,160 lb). The capability of its wheels and tires will be central of the Bloodhound’s success. Its 900-mm (35-in) wheels will rotate at more than 10,000 rpm, generating 50,000 g radially at the rim.

Target performance figures include 0 to 1050 mph (1689 km/h) acceleration in 40 s. Aerodynamic downforce at maximum speed is put at more than 12 t/m² (1.2 ton/ft²).

Although the project is a private venture, the UK Government is part funding a three-year associated education program but not the build and running costs of the car. Together with STP, founding sponsors are Swansea University (Wales), the Engineering and Physical Sciences Research Council, Serco, and the University of the West of England.

The engine combination is necessary not only to provide required thrust, but also because pure rocket propulsion—a 27,500-lb (122,000-N) maximum thrust unthrottled hybrid produced by The Falcon Project, positioned above the gas turbine—would not provide the required small steps in Mach numbers necessary for the project’s aerodynamicists to acquire essential development data.

The gas turbine chosen is a 20,000-lb (89,000-N) thrust, afterburning Eurojet EJ200, as used by the multinational Eurofighter Typhoon, and provides power controllability. The car also has an Menard Competition Technologies (MCT) 4.4-L V12 race engine for multirole uses including APU, engine start for the gas turbine, and to pump the rocket engines’ HTP (high test peroxide). It is necessary to pump a tonne of HTP to the rocket’s catalyst in 22 s at 1200 psi (8.27 MPa).

"The beauty of the hybrid rocket is that it uses a safe and green oxidizer in the shape of HTP and only burns its solid fuel as long as the HTP is flowing," Noble explained. "Shut off the HTP flow and the rocket shuts down in safety, with no emergency problems of having mechanically to jettison a burning solid fuel rocket or running the risk of an explosion from shutting down a bi-propellant rocket with horizontal combustion chambers."

Daniel Jubb, who heads The Falcon Project, said: "The hybrid Falcon rocket is based around an 18-in combustion chamber, which contains a solid fuel in the form of a synthetic rubber, HTPB (hydroxyl terminated pulybutadiene). The liquid HTP is supplied to the chamber by a high speed (12,000 rpm) pump driven by the MCT engine. The HTP is decomposed by a catalyst pack (comprising 80 silver-plated nickel mesh discs) producing steam and oxygen (at 600°C), which enters the fuel grain. The fuel then burns in the hot oxygen."

The heat transfer from the combustion back into the surface of the fuel grain governs the amount of fuel liberated to sustain combustion. Perfecting this while maintaining the correct mixture ratio is the primary design challenge of a hybrid rocket, explained Jubb. The chamber can be shut down by simply turning off the supply of HTP. This facility, together with the hybrid rocket having a far less complex technology than a liquid bi-propellant system, is the salient advantage over a solid propellant rocket.

The cockpit of the Bloodhound is positioned under the EJ200’s intake, its external configuration part of the intake aerodynamic shock management structure.

Noble said that aerodynamic challenges include the need for Bloodhound to have a small cross section to minimize drag but a supersonic intake. Because of the rocket’s position above the jet engine, the car’s rear wheels and "smart" suspension are on drag-inducing struts. With state-of-the-art CFD, it is possible to compute the drag of wheels and struts at Mach 1.4 and so optimize the shape to reduce drag and shock effects, he explained.

Because the car has been designed to have good directional stability, it has a relatively small vertical stabilizer (fin), which reduces any crosswind effects.

The UK National Physical Laboratory (NPL) has worked with the Atomic Weapons Establishment (AWE) and Fluid Gravity Engineering (FGE) to advise the Bloodhound team on wheel design and materials as well as rocket design details. The effect of shockwaves on the wheels was considered and advice given on manufacturing processes.

NPL and FGE developed a modeling tool to simulate the internal motor ballistics of the rocket motor, providing data for the design team to compare with its own test firings completed with a 6-in (150-mm) chamber. The work will help to optimize the injector design, oxidizer streams into the fuel grain, radiation transfer, regression rates, and rocket motor exhaust.­

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