(ThrustSSC at the Goodwood Festival of Speed. Photo: Laurence Baker)

I am standing in front of ThrustSSC and studying its shape. My reaction is one of sheer disbelief. Why disbelief? Well, it is a long story that started in 1992 when I met Richard Noble. It was a purely chance meeting in Ken Norris’ office. Ken, you may know, was the designer of Donald Campbell’s Bluebird.

Richard told me of his ambition to build a car that would not only create a new land speed record, but would also travel at supersonic speed. He asked for my opinion, as an aerodynamicist with experience of high speed vehicles, what should be the best shape for such a car.

My immediate reaction was to distance myself from the project. To drive at supersonic speeds would clearly be extremely dangerous, and indeed, it could well be impossible. I pointed out to Richard that even keeping the car on the ground would be extraordinarily difficult. The aerodynamic forces would be simply enormous - quite enough to lift the car and throw it around like an autumn leaf in a gale. Because they would be so large, these forces would need to be determined with great accuracy. This seemed out of the question, as there was no obvious method - experimental, theoretical or empirical - for determining the aerodynamic forces even approximately. The crux of the problem is knowing how the flow would behave underneath the car at sonic speeds - and what would happen to to shockwaves in that region. No-one could tell me, but everyone I consulted viewed the prospects with pessimism and foreboding. As one highly respected authority warned me, ThrustSSC was just an expensive way of killing someone and I certainly did not want to do that.

So why did I continue sketching shapes and doing calculations? Purely out of curiosity, and as an academic exercise: "If someone should ever be daft enough to make a supersonic car then what shape should it have?" Here was a nice little problem that no-one seems to have tackled, and one which could occupy many hours of my retirement with enjoyable cogitation. And who knows? By re-energising my few remaining brain cells and rubbing them together they may even produce a spark. In any case, contemplating a supersonic car was much more interesting than doing the gardening so I continued to design.

(Rolls-Royce Spey on maximum reheat. Photo: Jeremy Davey. Digital camera courtesy of Canon (UK) Ltd)

My first thought was that stability would be the crucial problem. A twin engined configuration would be more stable than a single engined one, so two engines it had to be. The Rolls-Royce Spey, used in the British version of the Phantom, looked the best engine for the purpose. It gives plenty of performance, and is a simple and robust workhorse with an enviable record of reliability in service. Its one problem is that, being of venerable design it is very heavy, so using two Speys would result in a very large and heavy car. With advice from Richard, and from Glynne Bowsher, who also worked on the Thrust2 Project, I produced a shape. It looked rather like a twin-jet fighter with the wings removed. It seemed like a feasible solution, but as all of my initial objections remained unanswered I still did not seriously think it would ever be built. And there were even more fundamental objections - the project had no design team, no research facilities and no money!

(CFD airflow)

So what happened to change my views? Three things occurred in quick succession. First, I was persuaded that the flow under and over the vehicle could be studied by computational fluid dynamics (CFD), and CDR Ltd volunteered to carry out this study. Secondly, we found that rocket sledge testing at the DTEO at Pendine could provide experimental evidence to compare with the CFD. Thirdly, Castrol made the courageous decision to fund a feasibility study. This enabled us to carry out both the computational and sledge test research and compare their results. Amazingly, the comparison showed close agreement between the two methods. Eureka! Even more satisfying was the fact that the design I had produced purely by gut feeling was shown to be satisfactory and the car could be made to stay on the ground. So perhaps a supersonic car was possible after all.

But those were just the initial hurdles. There were many occasions, particularly in the early stages, when I doubted our ability to complete the car. Always we have somehow managed to overcome the difficulties, invariably as a result of Richard Noble's drive and determination or Glynne Bowsher’s ingenious solutions to the numerous engineering problems.<.p>

That is why I am looking at the completed car in disbelief. The shape I started drawing four years ago has actually materialised in solid form. All 10 tons of it. In a sense it is a dream come true. Its creation is the result of dedicated effort by a small but highly skilled team, assisted by many expert consultants, and backed by some 200 sponsoring organisations. Incredible!

The shape of the car has certainly aroused much comment. Everyone agrees it is impressive. Many people have said it is beautiful. One young lady disagreed. She told me in accusing tones that the shape I had designed was the ultimate male sex symbol. Lamely I shrank from asking her what geometric modifications would be required to turn it into a female sex symbol. I contented myself by telling her that the shape had been designed by mathematics, and that I would check the equations to see which one contained the gender information.

My own views on the shape? I will answer that when I see how well it performs at high speed. I am quietly confident, but on a project like this one can never afford to be complacent.

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