Date:24 March 2014
Part car, part aeroplane and part spaceship, Bloodhound SSC aims to shatter the land speed record set in 1997 by Thrust SSC. Here’s how to build the world’s fastest car in 12 tortuous steps:
1. Break the sound barrier first. On 15 October 1997, high in Nevada’s Black Rock Desert, a sonic boom cracked the air as Royal Air Force pilot Andy Green raced past 1 200 km/h, the speed of sound, at the location’s 1 200-metre elevation and ambient temperature. The Thrust SSC jet car’s twin Rolls-Royce Spey turbofans – also used in the F-4 Phantom fighter – produced 180 000 newtons of thrust, pushing the car to 1 227,896 km/h in a run that averaged 1 217,895 km/h. After 12 years of design, development, fabrication and testing, meeting the land speed record criteria of the Fédération Internationale de l’Automobile came down to turning around and making a second run within an hour. On the return trip, the Thrust SSC broke the sound barrier again, traversing the measured mile at 1 233,704 km/h, for a two-way record of 1 227,9858 km/h and proving that, when man battles Nature, technology is a mighty weapon. As Green said before the historic run: “Just because it hasn’t been done doesn’t mean we can’t do it.”
2. Call back your key players. Fast-talking and irrepressible, the Thrust SSC team’s leader, Scottish aviation entrepreneur Richard Noble, has a history in the sport. He himself had set the record in 1983, piloting the jet-powered Thrust 2 to 1 019,47 km/h. (He told the press he had done it “for Britain and for the hell of it”.) After breaking his own record 14 years later with the Thrust SSC, he retired. But when celebrity adventurer Steve Fossett announced in 2006 that he would pursue a new record, Noble rose to the challenge.
Like an impresario reassembling a veteran rock band for one last tour, Noble began recruiting key members from the Thrust SSC team, including Andy Green. He also brought back aerodynamicist and engineer Ron Ayers, now 81, whose experience dates back to his work on Britain’s Cold War bomber, the Handley Page Victor. (Another previous Ayers project, the Bristol Bloodhound surface-to-air missile, gives the current jet car its name.) Today, Ayers toils away at a desk strewn with laptops, half-drunk cups of tea, and a computational tool most young engineers know as a relic: a slide rule.
Chief engineer Mark Chapman is another longtime associate. He helped design the single-engined aircraft now known as the Kestrel JP10 for Noble’s somewhat rocky venture, Farnborough Aircraft. The Bloodhound project requires a diverse range of talents, Chapman says. “The vehicle is part plane, part car and part spaceship. We need people with a huge breadth of experience.”
Fossett was killed during a solo flight over California’s Sierra Nevada range in late 2007, and his speed-record team disbanded soon after. But by then Noble was committed, fostering his resources and his talent. Now he has them, and some key technologies – namely, CAD and computational fluid dynamics, or CFD – fully deployed. “Thanks to CFD, designers and engineers can take charge,” Noble told The Telegraph. “Land speed record attempts are no longer about some maniac with an enormous engine and a tiny car disappearing off into the blue.”
3. Learn from your mistakes. During Thrust SSC’s run, video taken from a distance makes the car look as if it’s riding on rails. But cockpit audio and video contain an expletive-laden outburst as Green struggles to maintain control, turning hard right and left to counteract dangerous oscillations as the vehicle nears the speed of sound. In this trans-sonic period the airflow over the car is supersonic in some places, and subsonic in others, which makes the car unstable. “It got a lot calmer after it broke the sound barrier,” Green says, betraying no sense of concern. In fact, he was one twitch away from catastrophe. The culprit: unwieldy rear-wheel steering, a design compromise required by Thrust SSC’s tight front end.
4. Embrace failure, then correct for it. Frontwheel steering for Bloodhound was an easy call (Green insisted), but other configurations require painstaking trial and error. After the project kicked off, in October 2008, the team burned through 13 design iterations in three years. Initially, the heavier jet sat beneath the rocket.
But the rocket’s thrust from a high position would have pushed down the car’s nose; then, after the rocket fuel was spent, eliminating weight and thrust, the possibility of the front end getting airborne would increase. “A nose-up moment at speed would not be good,” Noble says.
To improve stability and maintain ground force, the team repositioned the rocket below the jet and made the rear fin bigger. In front, winglets help keep the nose level. At present they’re movable, to address the changing forces during the run. But computer-aided movement of the wings introduces a big risk.
“What would happen if Andy got the blue screen of death at high speed?” Chapman asks, referring to the visual result when an old Windows operating system freezes. For Green, the analogy would be literal.
The goal is to make the winglets static. “With experience, as we begin practice runs, we hope to fix them into place,” Chapman says. The fewer things Green deals with while driving, the better.
5. Build it like a fighter jet. Bloodhound project headquarters is a boxy industrial building on the outskirts of Bristol (fittingly, a hub for England’s tech and aviation industries) flanked by builders’ supply warehouses and a tile depot. A food truck serves hamburgers in the parking lot. The hangar-style structure is the site of the monthly team meeting as well as where the car’s pieces come together. The rear two-thirds of the vehicle resembles a plane, with an aluminium and titanium frame, and an aluminium floor to deflect debris.
The rocket engine mounts on the lower fuselage, and even the titanium and steel skins are load-bearing. Like the F-4 Phantom that Green flew for the RAF, Bloodhound has an internal air-supply system and ‑ re extinguishers.
Unlike that jet, the car has no ejector seat, because ground impact after ejection would be inevitable. “We’d be talking about a near-sea-level Mach 1,4 ejection, so the forces are huge,” Chapman says.
6. Get indestructible wheels. Bloodhound doesn’t have tyres; it runs on precisely fabricated aluminium discs. A forging process breaks down the crystalline structure of cast aluminium, making it denser and stronger. This requires heating the aluminium to more than 370 degrees, moulding the metal into discs with a 3 275-ton press and then milling the blanks to the finished specs: 90 kilograms, 90 cm diameter.
The wheels not only have to bear the car’s 7 700 kg, but also to hold together while experiencing 23 000 kg of radial g-forces at 10 200 r/min. That means their shape is as crucial as their strength.
Recent testing at Hakskeen Pan revealed that twin-keel-shaped rims like those on the Thrust SSC would break through the site’s soft surface. As a result, Bloodhound will use a rounded wheel profile.
7. Put a rocket on it. The Thrust SSC’s 1 228-km/h run provided valuable reference points for Bloodhound, but gaining an additional 250 mph (400 km/h) presents a disproportionately more difficult challenge. Aerodynamic drag increases with the square of speed, which means that there is 1,7 times more drag at 1 000 mph than at the existing speed record. Even though the speed increase is only 31 per cent, 2,3 times more power is required to make up the difference.
Ayers calculated that two jet engines wouldn’t work for Bloodhound – the air intakes would produce too much drag, and the engines would be too heavy. Instead, Bloodhound uses the steady power of a Rolls-Royce EJ200 turbofan producing 90 000 newtons of thrust, while a hybrid rocket provides a 20-second boost. Designed by the Norwegian firm Nammo, which makes stage-separation and acceleration boosters for the European Space Agency’s Ariane 5 launch vehicle, the rocket is an ingenious design that burns a solid synthetic rubber fuel, but uses liquid high-test peroxide, or HTP, as the oxidiser. The engine consumes a staggering 1 000 litres of HTP in about 20 seconds to achieve peak thrust of 120 000 newtons.
8. Find the right track. Both Thrust SSC and Thrust2 made their record runs on the flats of Black Rock Desert. But drought and other factors have roughed up that surface, so the team looked elsewhere.
Using custom software, the Bloodhound team identified 22 sites with a smooth, ‑ at surface 19 kilometres long and 5 kilometres wide. After narrowing the list and visiting 14 sites, South Africa’s Hakskeen Pan, a dry lakebed, was chosen.
But even this, in its natural state, was flawed. So, with the backing of local officials, workers moved about 6 000 tons of stones from the proposed track, largely by hand. The stones have been piled up beside the track; removing them is prohibited because the team lacks a mining licence. After the run, geologists will sift through the piles for meteorites.
9. Figure how to get from 1 700 to 0 km/h. If all goes as planned, Bloodhound will cover the measured mile in 3,6 seconds and reach a top speed of 1 050 mph (1 700 km/h). But, to claim the record, the car must turn around and make a second run within an hour. And space is an issue.
“You can just run out of desert,” Chapman says.
Bloodhound has three means of deceleration: At 1 280 km/h, perforated air brakes swing out from the fuselage, two parachutes can deploy at 1 000 km/h if extra slowing is needed, and at about 300 km/h Green will apply steel friction brakes.
But slowing down is just one concern. The idling jet engine will continue to produce heat at the end of the run, which Green must dissipate by steering in a huge arc while slowing to a stop. Whether that’s all possible, no one knows. “We can’t really test that until we get to South Africa,” Chapman says. “For a lot of things, the car is the testbed.”
10. Pay attention to the little stuff. Dust, for instance. “We’re looking at peak flows of over 600 metres per second of dusty air hitting the car – it’s worse than a shot blaster,” Chapman says. So, steel armours the undercarriage. Surprisingly, there’s no need to physically protect the engines from dust. “There isn’t enough time for the dust to travel the 1,5 metres to the intake,” he says.
11. Keep calm and speed on. Green’s experience makes him the obvious pick to pilot Bloodhound. But 20 years ago he wasn’t a shoo-in to drive the Thrust SSC. The final eight applicants, all pilots, went through fiendish psychological and co-ordination tests devised by Roger Green (no relation), professor at the Centre for Human Sciences in Farnborough, England.
“The most obvious thing to do was to give them all a sanity test and take the ones who failed,” Roger Green joked at the time. Andy Green was not the fastest driver of the bunch, but during trials he showed an almost out-of-body detachment, which allowed him to objectively analyse what was happening at high speed. He is also famously taciturn. Many journalists have tried and failed to goad Green into expressing any sense of excitement or nervousness about driving in excess of 1 000 mph. “And there’s the extreme vibration and noise and the stress of checking and rechecking the systems,” says Roger Green. “Apart from all those things, it should be fairly easy.”
12. Control what you can, but accept that you can’t control all that happens at 1 000 mph. One engineer confessed that, when the Thrust SSC ran, he felt physically ill for fear of the car failing – because he knew all of the “10 000 things” that could go wrong. When Bloodhound goes for the record, Chapman says, “We don’t really know what it will be like. We’re not [even] sure what a safe observation distance will be from a vehicle travelling at Mach 1,4, or how far the shock wave will spread out sideways from the car.”
Ron Ayers may share some of Chapman’s concern when Bloodhound makes its run. But as the most experienced member of the team, Ayers doesn’t see failure as an option, for one simple reason: “Andy Green is a good friend of mine.”
Specifications (see image above):
a. Fin: It gives the car straight-line stability, but to do so the fi n itself must be straight. The team aims for a maximum variance of 2 mm from top to bottom.
b. Upper chassis: To withstand the stress of supporting the fin and jet engine, the stringers and upper skins are made of titanium.
c. Jet: The EJ200 turbofan is also used in the Eurofighter Typhoon. The airplane is rated for only Mach 1,2 at sea level; Bloodhound will shoot for Mach 1,4 with a rocket-engine boost.
d. Rocket power: A rocket using solid fuel oxidised by liquid high-test peroxide (HTP) will provide 120 000 newtons of thrust.
e. Rear diffuser: The 1-square-metre section that protects the rocket engine from surface debris is machined from a single piece of aluminium and took 192 hours to make.
f. Air brakes: Deployed at 1 300 km/h, the carbon-composite plates have holes in them to reduce turbulent airflow that could otherwise cause instability.
g. Cockpit: The inside looks like a fighter jet, but driver Andy Green will use foot pedals to control the jet engine and engage the friction brakes.
h. Tank: A capsule-shaped steel tank holds HTP. Bloodhound’s rocket will use about 1 000 litres of the stuff in 20 seconds.
i. Wheels: No rubber can handle 1 600 km/h and 10 200 r/min. Bloodhound rides on aluminium discs, each 90 kilograms.
* 1 609 km/h
Video – Bloodhound Project: first hybrid rocket test