Bloodhound SSC project – success depends on NDT and condition monitoring
09/06/2014
The Bloodhound Project is a global education initiative focused on a 1000 mph land speed record attempt. It aims to inspire young people to pursue careers in science, technology, engineering and mathematics and its centrepiece is the Bloodhound SSC (SuperSonic Car), a 135,000 horsepower rocket- and jet-powered racing car being built in the UK by a team of Formula 1 and aerospace experts. NDT News editor David Gilbert was invited to the Bloodhound Technical Centre in Bristol to witness some testing of the carbon composite air intake that will funnel air into the jet engine…
Bloodhound SSC will be driven by Royal Air Force fighter pilot Andy Green and powered by a Eurofighter Typhoon EJ200 jet engine and a NAMMO hybrid rocket, with a pump driven by a 750 bhp racing car engine. The car will be 13.5 m long, weigh 6.5 tonnes empty (7.5 tonnes fully-fuelled) and will accelerate from rest to 1000 mph and back to rest again in 120 s, covering 12 miles across the South African desert. With the current world land speed record at 763 mph, set by Thrust SSC in 1997, also driven by Wing Commander Andy Green, this exceptional challenge is being led by former world land speed record holder Richard Noble.The project has attracted a world-class team of experts, with companies and individuals contributing their time and expertise to play a part in this extraordinary test of engineering.
Bloodhound SSC is also a significant educational initiative to showcase engineering and science, which currently involves more than 5,600 schools, nearly 50 universities and more than 250 further educational colleges. 2 million primary and secondary students have access to Bloodhound SSC in their classrooms to learn about science, technology, engineering and maths.
The vehicle is a mix of car and aircraft technology, with the front half being a carbon fibre monocoque, like a racing car, and the back half being a metallic framework and panels, like an aircraft.
The carbon composite air intake will funnel huge volumes of high-pressure air into the EJ200 jet engine. In the very unlikely event that the engine were to experience a surge, it would force air back up the intake, which, if not robust enough, could rupture. This is a safety-critical part of the car, as it will be subject to a pressure of around 1.5 bar (22 psi) at 1000 mph, which will exert a ‘bursting load’ on the intake of around 29 tonnes. If the intake bursts, it may take the upper bodywork with it. To make sure that the intake is up to the job, it is to be pressure-tested. For the testing, engineers have fitted strain gauges to the air intake to see how much it deforms when pressurised to 30 psi (about 2 bar).
A large air bag inside the intake is inflated and the strain gauges measure the movement (or ‘strain’) in the carbon fibre structure. This will confirm (hopefully!) that it can cope with the full 1000 mph load, and more. The strain gauges (and a huge number of others) will remain in place for the life of the car, so that its structural health can be monitored at every stage of its life.
As the air is pumped in and the bag inflates inside the intake, members of the engineering team watch the gauges intently and Roland Dennison, Engineering Lead – Stress Analysis, and the test engineers read and analyse the data being generated, giving a running commentary on how the test is progressing. At 6 psi the deflection is higher than expected. The trend continues as the pressure increases, so the strain is higher than that predicted by modelling and analysis. More investigation is required and further testing will be carried out later.
Every key part of the car has been tested, is being tested, or will be tested, and every run of Bloodhound SSC will be to validate the test results. Huge amounts of data are being generated. “There’s a data mountain to build, and then to climb, over the next 2 years,” said Engineering Lead Conor La Grue. “It’s a huge effort, but it’s what will keep the car safe, so it’s what we’re going to do.”The plan for the whole car involves around 400 high-speed sensors, measuring everything from air pressure (in over 100 places, to validate computational fluid dynamic modelling), through to structural loads, and even Andy Green’s heart rate while he is driving at 1000 mph. Each one of these sensors will be recorded at 500 Hz, so the data can be analysed in incredible detail.
The wheels are, of course, also safety-critical items. Each 95 kg disk will spin at around 10,300 times a minute (170 times/second) at 1000 mph, subjecting it to loads of 50,000 times the force of gravity. Maker Castle Precision has already made one, which will be thoroughly tested before the rest are finished. Rolls-Royce is going to spin the wheel on its engine test-rig and it will be tested ultrasonically. This should validate all computer modelling and prove that the wheel will cope at over 1000 mph.
“When the wheels are fitted and we start running the car, we’ll be monitoring them on every run,” said Conor La Grue. “This will allow us to build up a picture of the normal ‘noise’ that they generate running on the desert. By filtering this out, we can then listen for any changes or unusual ‘events’ that might indicate a problem.”
Roland Dennison thinks of the Bloodhound Project as a sort of ‘rolling laboratory’, involving continuous NDT exercises over its existence. “The whole car is an active NDT experience,” he said. “NDT is carried out as part of the manufacturing process and on materials and components by suppliers. Each component is tested using the most advanced and appropriate technology available. Every test run of the car will be continuously monitored and the condition of each critical part checked, over and over again.”As driver Andy Green puts it: “This phase of Bloodhound’s engineering is all about details. Any mistakes we make now will cost us dear when we get to the desert in South Africa next year and things don’t work as they should. If we’re going to have a world-class engineering adventure, and push the boundaries of physics at 1000 mph, and do it all safely, then we need to get the details right first time. It’s a fascinating process to watch as it all comes together.”
Watch NDT News for news and updates on the progress of the Bloodhound SSC project and the role of NDT and CM within it.
