The latest attempt at the land speed record is set to take place next year at Hakskeen Pan in the Northern Cape. However, the goal of the Bloodhound project is not simply to exceed the current benchmark of 763 mph (1228 km/h) achieved in 1997 by Royal Air Force wing commander, Andy Green, but to smash it in a car designed to travel at over 1000 mph (1609 km/h). Put into perspective, to achieve this Bloodhound will need to cover the measured mile (1,6 km) course in a blinding 3,6 seconds, or 4,5 football fields laid end to end per second.
The propulsion system consists of three power plants, a Rolls-Royce EJ200 jet from a Eurofighter Typhoon, a cluster of Nammo hybrid rockets and a 550 bhp Supercharged V8 Jaguar engine that drives the rocket oxidiser pump. Between them they generate 135 000 thrust hp, equivalent to 180 F1 cars. According to the official website, at the end of its run Bloodhound will be travelling faster than a bullet fired from a .357 Magnum.
But how does one stop an 8000 kg projectile like this from its terminal velocity of over 1600 km/h? Apparently conventional wheel braking systems would simply catch fire and parachutes would tear themselves to shreds.
Enter project sponsor and leading designer of motion control solutions, Parker Hannifin. The answer is to achieve the initial deceleration required through the use of airbrakes that are mounted in the bulkheads on either side towards the rear of the craft. Parachutes are then deployed to increase the drag once the speed has dropped to around 600 mph, and finally, the conventional wheel brakes are deployed below 250 mph.
The problem with airbrakes is that to stop Bloodhound in the required distance, they must virtually double the cross-sectional area (and therefore the drag) of the car. Developing a system that can slow a six and a half ton car by 60 mph per second is one of the key areas on which Bloodhound and Parker Hannifin engineers have been working together.
Simplistically, a system of two independent hydraulic linear actuators coupled through drive bars force the airbrake doors open into the supersonic jet stream blasting over the vehicle’s low-drag aerodynamic bodywork. The problem the Parker engineers had to overcome was the design of a compact lightweight cylinder that could withstand the loads that the airbrake doors would exert on them – approximately seven tonnes per door.
Parker found the solution through tweaking and customisation of its regular products. Standard cylinders had their port fittings modified in order not to encroach on the jet engine, while at the same time being able to withstand the enormous loads experienced when the braking system is deployed. In addition, a bespoke hydraulic accumulator was developed using the latest composite material technology. The accumulator is the all-important backup system. If a loss of hydraulic pressure occurs for any reason, the energy stored in the two piston accumulators will be released to deploy the airbrakes at the controlled design speed.
Parker has made a big investment in the design of these hydraulic accumulators and it sees commercial uses for the technology, particularly in offshore applications where corrosion is a serious problem. For Bloodhound, the benefit is a failsafe hydraulic system that stays below the weight limit required in order not to upset the car’s centre of gravity. For more on the design of the braking system that will slow this supersonic vehicle at G forces that driver Andy Green describes as ‘a controlled crash’, see the Parker press release in 'A closer look at Bloodhound's airbrake system' or watch the official project video at http://tinyurl.com/kb8jlbs
X-Change 2014
One of the landmark annual events on the local automation calendar is the hugely successful Wonderware X-Change conference. This year’s event promises to be the biggest and best yet, with a focus on improved operator effectiveness, mobile operations, cloud-based solutions, actionable intelligence and the virtues of virtualisation.
Combine all of this with four keynote presentations, over 70 breakout sessions and 20 international presenters, and the Champagne Sports Resort looks well worth a visit from 19-22 April. We hope to see you all there.
Steven Meyer
Editor: SA Instrumentation & Control
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