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Calculating the velocity of Bloodhound is setting the aerodynamics team some unprecedented challenges. Standard methods, and findings from Thrust SSC, do not provide sufficient accuracy when faced with the extreme conditions of this record-breaking attempt.
Ron Ayers began his engineering career with an apprenticeship at Handley Page Ltd, and went on to study for a degree in aeronautical engineering at the College of Aeronautics at Cranfield (now Cranfield University).
As Chief Aerodynamicist at the Guided Weapons division of the Bristol Aeroplane Company, one of the principal projects Ron worked on was the Bloodhound surface-to-air anti-aircraft missile. As Richard Noble notes in his blog, today’s record-breaking attempt was originally code-named after Ron’s missile, and the project never looked back.
After a distinguished career, Ron entered retirement. He volunteered at the Brooklands Museum in Weybridge, and his interest in record-breaking was ignited when he discovered wind tunnel reports relating to pre-World War Two cars, such as Golden Arrow, Bluebird and the Railton Special.
In 1992, a chance meeting with Richard Noble changed Ron’s future. He says,
“Richard was already planning to repeat his Thrust 2 successes, but this time he had ambitions to exceed the speed of sound. When he found out that I had, in an earlier career, specialised in high speed aerodynamics, his powers of persuasion ensured that my retirement was over. With Thrust SSC we set the supersonic record in October 1997, and that record still stands.”
Following that achievement, Ron went on to become the aerodynamicist on the JCB Dieselmax project, which achieved an International Land Speed for diesel cars of 350mph in 2006.
As Chief Aerodynamicist on Bloodhound SSC, Ron outlines some of the challenges of measuring velocity on the car. He is calling on engineers who have specialist knowledge in this field to put forward their suggestions to the team.
“On most cars, determining the velocity of the vehicle is carried out simply by measuring the wheel rotation. At high velocities, this is not possible for Bloodhound. At velocities above about 600 mph the shockwaves and vibration fluidise the desert so there is no solid surface for the wheels to grip, and experience with Thrust SSC showed that they under-speed by some 5% to 10%.
“There are other possible methods, but they all have their weaknesses. For instance, we can integrate the output from a longitudinal accelerometer, but experience with Thrust SSC showed that small errors can accumulate so the results from this method are never better than approximate.
“We can also measure airspeed using a pitot-static tube, but this gives air speed, and is at best an approximation for ground speed.
“Bloodhound is fitted with a GPS receiver. Although this clearly works well enough at road speeds, I am unclear whether possible lags in the system will introduce errors at 1000 mph. If such lags exist, can they be quantified and a correction applied? Will the fact that Bloodhound can accelerate at up to 2g, and decelerate at up to 3g, further complicate the matter?”
Ron concluded: “I have a lot to find out, so would welcome contact with anyone with specialist knowledge of the subject.”
If you can offer advice or insight to support the Bloodhound aerodynamics team, please contact:
engineering@bloodhoundssc.com. Or find out how to volunteer to be a
Bloodhound SSC ambassador.