You might think, as I did, that Green is the UK’s go-to land speed record pilot simply because of his background flying Phantom and Tornado jets for the RAF and his experience with Thrust SSC. However, he is bringing more than just a fundamental understanding of the physics of the challenge.
Green is also making a huge contribution to the design and engineering of Bloodhound, because he happens to be a maths whizz – the sort of whizz who got a first in his mathematics degree at Worcester College, Oxford.
I like to dig into a vehicle’s engineering, but talking to Green about the design of the Bloodhound is wholly different from the average automotive technical briefing. Judging by our conversation, trying to run a wheeled vehicle – powered by both a jet engine and a three-bore rocket – up to 1000mph and stopping it again requires a significant grasp of higher-level physics and maths.
Safety-critical areas, such as steering stability, the ability of the suspension to cope with dips in the desert surface (which could translate into 30-tonne loadings) and how to keep the rear wheels on the ground (the rear of Thrust SSC famously lifted off), have all benefited massively from Green’s input.
I also run into Mark Chapman, chief engineer of the Bloodhound project, and it is clear he’s a bloke who’s interested only in the most challenging tasks in engineering.
He’s just clocked up seven years with the Bloodhound project, and before that he worked on an immensely complex jet engine ‘lift system’ for the Lockheed Martin F-35 Lightning II, said to be the most expensive aeroplane programme of all time.
As we stand next the Bloodhound mock-up, Chapman points out the forged and turned aluminium alloy rear wheels and explains that they will be rotating at 10,500rpm during the record run. To that end, they have to be in perfect balance.
Chapman says the production wheels were tested by Rolls-Royce in Derby and given the thumbs up. The aero engine maker has to balance the compressor fans that run at similar speeds inside jet engines, so it is pretty experienced in this area.
It’s also surprising to hear that the Bloodhound team has just two operational jet engines for the 1000mph attempt. The pair of EJ200 turbofans come from a Eurofighter Typhoon and are good for nearly 21,000lb of thrust on reheat.
Chapman says they have about 15 to 20 hours’ life left in each of them. “We can start them about 60 or 70 times each,” he says. The engines are aged by ‘hot-cold’ cycles and can self-diagnose their remaining life.
However, generating the power to propel Bloodhound to 1000mph isn’t nearly as complicated as getting the vehicle to cut cleanly through the air and across the surface of Hakskeen Pan, where the record attempt will take place.
Perhaps Green’s key experience in Thrust SSC was what he described as “hitting a wall” as the vehicle reached its 763mph maximum speed. The engineers named the phenomenon ‘spray friction’. As Thrust SSC accelerated, a huge shock wave was created that ‘exploded’ the surface of the desert under the vehicle. The resultant plume of debris caused huge drag, preventing it from gaining more speed.
It is why the 13.5-metre-long Bloodhound is a svelte machine with a relatively small footprint, outboard rear wheels and an upright rear end. This design should prevent the car from sucking up the desert and ejecting the debris in its wake.
That can only be a good thing, because Green needs as little to worry about as possible. Once the jet engine gets him up to around 350mph, Green will light up the rocket, which should run Bloodhound to 1000mph in just20 seconds. Then he has to slow back to a standstill without losing control or running out of track.
Green has designed the cockpit’s layout himself. The days of radial dials are long gone, with Green opting instead for a pair of flat-panel displays. In basic terms, he says, “the right-hand panel deals with power and acceleration and the left-hand panel with stopping”.
The right-hand readouts include information on fuel loads, tank pressures, the state of the Jaguar V8-powered pump used to drive hydrogen peroxide into the rocket booster, and oil temperatures. “Visually,” he says, “the view is right to left.”
The left-hand readout covers the braking system in all three of its forms: air brakes, parachute and wheel braking. The central display – which Green thinks he will be looking at for 90 per cent of his high-speed run – is a dial, but that makes it easy to read off the Bloodhound’s speed and Mach number.
If you look closely, you can see a small triangle on the edge of the central dial. This moves around in real time, helping Green to calculate when the parachute can be safely deployed. This is at around 600mph, after the air brakes (800mph), but before the wheel brakes (200mph).
And the two big, rather traditional-looking Rolex dials? They’re not just branded jewellery, says Green. The one on the left is a GPS-governed speedo, which has its own power supply. Should the cockpit lose power and the other instruments die, he will be able to use the Rolex – combined with his huge command of mathematics – to calculate his complex deceleration routine.
The next step is a test-firing of Bloodhound’s rocket, in Norway. Green, meanwhile, is focusing on his own preparations, which involves taking to the skies in an aeroplane.
It’s the only way he can simulate the g-forces he’ll experience when he gets up to speed in South Africa.