A British attempt to hit four-figure speeds on land has higher aims – to inspire a new generation of UK engineers and scientists
By Gordon Cruickshank
Acrazy target, 1000mph – but so was Mach 1 and they hit that. Because some of the supersonic ThrustSSC team are also steering BloodhoundSSC: Richard Noble directing, Andy Green driving, and Land Speed Record specialist Ron Ayers overseeing aerodynamics. They’ve been at it secretly for 18 months, and the car should be ready to run at a gentle 800mph late next year, hit the 900s in 2010 and go for the big one a year after. And if he makes 1000mph, Green will break the low-altitude aircraft record. Yet 1000mph is not top of the agenda: Noble emphasises his £10m project is about boosting UK engineering skills.
Knowing Steve Fosset, among others, was planning an LSR challenge before his death, ideas for defending ThrustSSC’s 763.035mph record were already buzzing around Noble’s head. But it was then-defence minister Lord Drayson, also known as ALMS racer Paul Drayson, who lit the fuse. Seeing a severe shortage of engineering skills in UK industry in general, he met Noble and Green to suggest that an iconic project could excite young people and tempt them towards technical subjects. It’s this educational angle which makes BloodhoundSSC different.
Noble talks knowledgeably about how major projects have excited the public in the past, back to the Schneider Trophy and even the building of Brooklands. He points out that racing had to introduce formulas to control speeds, which restricts development and fosters secrecy.
“We’re doing the opposite. We’re going to put everything up on the web as it happens, including problems, and we’ll read all the feedback. And if a student hits on a good idea, we’ll follow it up.” He hopes that schools and technical colleges will factor the project in to coursework. It is already part of the engineering course at the University of Western England in Bristol, whose engineers are working on the project. There is a supporters’ organisation, the 1k Club, whose members get to watch the build, or even a test run, while the vehicle itself will be built in a ‘visitor centre’ at Filton, near Bristol, with continuous public access. Openness is Bloodhound’s middle name.
Boosting interest in engineering is the primary aim, says Noble. “If we hit 1000mph but don’t achieve the other aims, we’ll have failed.” Andy Green is equally eager: “We know we can build the car, but getting the project into schools is something no one has done before. If we can point to the simulator readouts and say to the kids ‘this tank is at 1.7bar’ and then explain that, they’re studying maths without realising it.”
When I bring up the green question, Noble chuckles. “There’s a great answer to that. Bloodhound’s CO² output is equal to 4.1 lactating cows! Yes, we’ll be producing a little CO², but we’re also producing the generation of engineers who will face the challenge of climate change.”
Choosing Wing Commander Green, the RAF pilot who steered ThrustSSC through the sound barrier, as the driver was not automatic. “The team approached me to devise a driver selection process,” he says. “Which I did, but I realised that my process pointed directly to me. There are other speed record drivers, but none who have gone supersonic. There are other fast jet pilots, but none who have driven a record car. I’m the only one. So I said ‘how about it?’ and the team were delighted.”
He’s already familiar with one part of Bloodhound – the Eurojet EJ200 turbofan engine from the Typhoon fighter. But the car also packs a specially designed rocket motor riding piggy-back. Why both? Engineering director John Piper, ex-Williams F1, who also worked on Dieselmax, explains that while the EJ200 can push a Typhoon to Mach 1.4 at 40,000ft, drag on the ground is much higher.
A pure jet car would probably plateau at some 800mph, so the rocket is vital to boost speed. But a rocket is not easy to throttle; it’s all or nothing, making it hard to hit and hold the incremental speed targets the team needs for development. Variable-throttle rockets exist but are more complex and riskier, as they use liquid fuel. The jet brings controllability and reduces the amount of volatile rocket fuel to be carried to foreign parts; and as Piper points out, it comes fully developed. Of course, it helps to know people: Green tells me the MoD, his employer, is loaning test engines which conveniently have no flight time left.
Perched above this, the hybrid rocket engine is the biggest ever built in Britain. When Green hits 350mph he will press the red button and 25,000lb of thrust will erupt behind him, doubling Bloodhound’s power for 17 brutal seconds to push it to 1050mph – Mach 1.4. Hybrids are inherently safer as they use solid fuel triggered by an oxidiser, and until ignition the two are kept separate: the solid fuel inside the motor only burns while the oxidiser – hydrogen peroxide, or HTP – flows. The rocket will be constructed by Falcon Project, which builds military rockets in the UK and US.
But Bloodhound packs a third engine too. In those few seconds the rocket consumes one tonne of liquid HTP, which has to be pumped from a tank behind the pilot. This is done by an 800bhp petrol V12 built by MCT (similar to Superleague series engines) via a pump developed for Blue Streak, Britain’s advanced ballistic missile of the 1950s. Very appropriate, as that was a period of technological surge when Britain seemed about to grab a world lead. The V12, buried inside the machine and cooled by ice, also provides hydraulic systems power and fires up the jet – the most powerful starter motor ever.
With this double-deck power layout raising the centre of gravity the rear wheels have to be out-rigged for stability – a drag-raising choice, but cleaner than doing it with the fronts. To minimise shock wave formation they run in close-fitting needle-nosed shrouds, mounted to faired double-wishbone suspension arms with pull-rods to internal coil springs. And before you say “aren’t salt lakes flat?”, the team reckons that wherever they run they need a good 100mm of suspension travel. Running out of wheel movement could have a catastrophic effect on the car’s stability. Currently the 36in wheels are likely to be forged titanium, though Piper says they are investigating a composite centre with aluminium ‘tyres’.
The crucial aero design is handled at Swansea University’s School of Engineering, where Ben Evans runs the Computational Fluid Dynamics programme. There will be no wind tunnel models, says Evans; this will be the first LSR car shaped entirely inside a computer. Even with a hugely powerful supercomputer it takes a day to run a full test at a single speed, he says. Nevertheless this slashes development times and removes the need for tunnel testing over the critical step from Mach 0.99 to 1.0, when trans-sonic shock waves cause enormous drag.
Even more crucial is the car’s balance. It’s vital to maintain constant loading on the wheels at all times, despite the huge pressure shocks of piercing the sound barrier and the fact that the car’s weight alters radically during the run. “We burn one tonne of HTP and half a tonne of jet fuel,” says Piper, “so our 6.5-tonne car drops to five tonnes in 80 seconds.” Wheel loads and the critical pitch angles are controlled by moveable winglets above the wheels. It’s not a fully active system, Piper explains; instead the adjustments are pre-mapped against speed, and will be optimised after each test run. As for that dainty vertical fin, it may look small, but Piper says the car is highly stable directionally and this is enough to give control. Green amplifies this, pointing to the window from 3-500mph where the wheels lose influence and the aero hasn’t built up. “That’s fine,” he says coolly. “It doesn’t have to be stable as long as it’s controllable…”
Feeding the jet engine is another problem: it can’t swallow supersonic air, so Evans’ team has spent hours shaping the intake trunk above Green’s head. Supersonic air is first slowed by hitting the cockpit canopy, then again inside the trunk as the cross-section expands. Once it’s subsonic, it sweeps downwards over the fuel tanks and the V12 to the engine’s compressor stages. The huge intake trunk makes a big hole just where the 43ft vehicle needs strength, so it will be a structural element made of composites, sharing loads with the tubular steel framework which forms the car’s rear section, clad in composite panels.
Up front, Green sits in a composite monocoque between the HTP tank and the front wheels on their double wishbones. This safety cell protects both him and the highly explosive liquid. Unlike ThrustSSC Bloodhound steers from the front, though maximum deflection is five degrees so opposite lock is off the menu. And no one has even worked out the turning circle… Between its two runs the car will be turned by trolley. Because the forces from a 300lb wheel turning at 10,000rpm are enormous, explains Piper, Bloodhound uses a 30:1 worm and wheel system which obviates kickback but gives little feel. So a servo motor will give Green artificial feedback as he strains to follow a thin black line at a mile every four seconds, peering between the front wheel arches – his position has been lowered to clear the air intake.
LSR rules have not altered much since Donald Campbell’s day, so despite the radical speed jump (the biggest in LSR history) Bloodhound still only has 11 miles to play with – five to run up, the measured mile, and five to stop in. And like an F1 pitstop, Green must halt on the mark to get the car readied for its return run. “We only have one hour for the turn-round,” says Piper. “There is no time to move the car.” Stopping from 1050mph happens in stages: simple aero drag after shutting off the engines will haul the car back to 800 at a fearsome 3g. Then Green releases an air-brake; at 650 he pulls ’chute one, and ’chute two pops at 400. From 200mph down it’s over to a set of carbon discs.
Where will all this happen? Not on Black Rock Desert, scene of ThrustSSC’s record. The surface has deteriorated too much. Instead, through a global satellite search, the team has identified some 14 possible sites, in the US, South Africa, Turkey and Australia. Visits to narrow the options follow soon.
Meanwhile Noble’s job ramps up: with £1m already under his belt he needs to find the next tranche of that £10m from commercial sponsors to begin the build. The government may be behind him, but it’s not offering cash. This time, though, he has something fresh to offer: not just media exposure and national flag-waving, but a chance to influence this country’s technological future.