Material Marvels: The chase

Materials World magazine
,
1 Aug 2018

In 1997, the current land speed record was set following a race to Mach 1. Ines Nastali reports. 

In 1990, land speed record holder Richard Noble met fellow racing enthusiast and 1960s lane speed record setter Craig Breedlove. He was in possession of two GE J-79 turbojets with which he was planning on challenging Noble’s then record of 633.47mph. 

By the time Breedlove and Noble parted ways, they were both planning to attack the record with newbuilds. Breedlove went on to develop his Spirit of America, Noble the so-called ThrustSSC, which, in the end, would win the competition to reach Mach 1 on land. 

But, in the meantime, a third racing fan was undertaking research into breaking the sound barrier. Aerodynamicist Ron Ayers worked at the Brooklands racing museum, UK, where he had access to the archive. He scanned the museum to look at the design of previous record attempting cars to find out why reaching Mach 1 had failed.

His work led to a potential design for a supersonic car. ‘Twin engines to get the weight up front, with a long thin fuselage behind to provide dart-like aerodynamic stability, and the driver at the centre of gravity,’ writes Jeremy Davey, ThrustSSC’s online reporter on the project’s archived website, describing Ayers’ idea.

However, Ayers also came to the conclusion that it wasn’t possible to set a supersonic land speed record. Instead, the shockwaves under the car would lift it into the air and send it to destruction, he said. Nevertheless, he got in touch with Noble’s manager to discuss his findings. 

When asked why he continued sketching and doing calculations, he said, ‘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 that could occupy many hours of my retirement with enjoyable cogitation.’ He added, ‘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.’

Unbeknown to him, Ayers was just the man Noble was looking for, and so they agreed to work together. The first challenge was to design a test bed. While there was data available on how a car reacts at Mach 0.83 from Noble’s record Thrust2 ride, there was no supersonic wind tunnel with rolling roads. 

Unknown territory

If there is no real test bed available, a computer simulation helps. Nowadays, computational fluid dynamic tests are standard in research, but they weren’t in the early 1990s. Help came from the University of Swansea, UK. The aircraft engineering faculty had a Cray 92 – a supercomputer with a maximum working memory capacity of a now underwhelming 8GB. The team ran the Flite software that was normally used to test plane designs for their calculations. 

Ayers hadn’t worked with software before and was therefore uneasy about the calculations. For him, there was no way around real life experiments to test the car design and ensure its safety for the driver. 

Establishing the design

The team stayed in Wales for these tests. At Pendine Sands, they were able to use a rocket-sled track used to test missile heads at speeds of up to Mach 3.2. A 1:25.4th scale model of the car equipped with sensors to measure the pressures around the vehicle was built for this. ‘With each run, the model was lowered closer to the road, until finally, it was leaving witness marks in the wooden surface,’ Davey states. ‘The runs passed without major incident – provided one excludes a supersonic bird strike from consideration.’

This test data was then compared to the computer analytics and as it matched on a high level, the design was approved and named Thrust supersonic car – ThrustSSC.

When determining the design for a super fast car, the engine is of utmost importance. The team had to decide between rocket and jet propulsion. While the latter is a lightweight method, it also uses a lot more fuel and that changes the weight of the car when the fuel is burned within a few seconds of the engine starting. The team therefore decided to go with heavier jet engines, two Rolls-Royce Spey engines, which were also used to propel the RAF Phantom jets, making the car more stable when running on high speeds. 

‘Our two Spey engines provide a total thrust of more than 20 tons. At full speed, this is equivalent to over 100,000 horsepower, making it by far the most powerful car ever built. Acceleration figures are quite impressive – from zero to 600mph in 16 seconds,’ Ayers states. 

Noble asked the designer of the Thrust2 car brakes and aluminium wheels, Glynne Bowsher, if he was interested in working on the mechanical design for the new car. Bowsher said yes and the first challenge to overcome was how to balance the weight of the vehicle to enable steering. 60% of the car’s 10t weight was on the front wheels, giving ‘enormous gyroscopic forces when the driver turned the steering wheel at the maximum design speed of 850mph – forces large enough to risk overturning the car,’ Davey explains. 

It was therefore decided to steer the car from the rear wheels. Tests on an old Mini showed that it was possible to steer it with an accuracy of 1 inch at 100mph. The wheels were asymmetrically arranged due to space constraints. 

To ensure the car runs straight on the ground, the team followed the logic of a dart by using ‘a tailplane assembly mounted right at the rear to exert enough aerodynamic drag to pull the car straight if it strays off line’. Davey continues, ‘The combined effects of the centre of gravity towards the front of the vehicle and the aerodynamic drag exerted on the tailplane assembly at the rear, gives the design the same sort of basic stability that ensures that a dart hits the dartboard pointy bit first. The principle is exactly the same.’

One of the things,the engineers worked on was improving the car’s adhesion to the ground. Noble’s Thrust2 ‘skated around like it was being driven on ice, and the jarring in the cockpit was almost insufferable. To this day, Richard Noble talks of having the car sideways at speeds of up to 300mph,’ writes Davey on the project website. 

The metal wheels didn’t perform well on the concrete surface of the Bonneville Salt Flats in Utah, USA. Rubber tyres wouldn’t have had this problem as rubber grips the salt better than asphalt, but the ones available at the time had reached their performance limit and there was no money to develop Mach 1 rubber tyres. 

The Thrust2 team found an alternative test bed in the Black Rock in Nevada, USA, which comprises of dried alluvium – essentially alkaline mud. Learning from this, the ThrustSSC team targeted their aluminium wheels again to run on alluvium. ‘Initial performance computations show that the vehicle should comfortably achieve a supersonic record, and well within the 13-mile space available at Black Rock Desert. Indeed, it can travel from zero to 800pmh and back to zero again in only seven miles. That journey will take approximately one minute,’ Ayers states. 

Testing the vehicle

The car was taking shape. UK racecar builder G-Force Engineering was commissioned to deliver the spaceframe of the car made of welded steel tubes. ‘The front third of ThrustSSC’s bodywork is constructed from carbon fibre while the middle third is manufactured from rolled aluminium. The rear third, however, is designed differently as it must cope with the exhaust of the engines. Temperatures at the rear body skin can reach more than 300oC. The panels adjacent to the exhausts are therefore constructed from titanium rather than aluminium,’ said Ayers.

By Autumn 1995, the vehicle’s shape had progressed enough to exhibit it at the London Motor Show, UK, and announce that it would be completed by April 1996. Noble also met with Breedlove and they agreed that a race between the Spirit of America and ThrustSSC to the sound barrier would take place in the well-known Black Rock Desert.

The team wasn’t able to make it in time as by September, test runs were still taking place at the UK Defence Research Agency’s base in Farnborough and at Boscombe Down. 

‘The tests began by dry running the engines – spinning the turbines on the starters with the fuel and ignition off to ensure that all is well. Next, the fuel system was brought into action, but with the ignition still off. Finally, the ignition was used to light the engines, and they will turn under their own power in the car for the first time. As the engines are run up to speed, all the complex systems to control and monitor the car’s performance were tested,’ writes Davey.

He adds, ’Finally, with ThrustSSC firmly secured against the force of the two engines, the power from the Speys will be gradually increased until they are running on full reheat and developing their maximum power of up to 50,000lbs of thrust. The noise levels from each Spey alone will be a literally deafening 120 decibels as the cones of the
re-heat flames extend from the rear of the engines.’

Going off-road

The time came to travel to the Al Jafr Desert, Jordan, for initial desert tests. Testing on a desert piste meant some preparation for the team. ‘As the technicians got into action to prepare the car for the first runs, the remainder of the team headed out onto the playa to begin the fodding – picking up the stones. The number of stones on the Jafr would prove a huge handicap – and thousands of manhours would be expended in picking them up,’ Davey remembers. In the end, it took two weeks to clear the course of stones. 

Meanwhile, the technicians struggled to get the car off and on its trailer due to the solid desert wheels, resulting in the use of an inflatable hangar on the playa. 

In the end, the team managed to get the car to 331mph, battling problems with the steering system, partly due to the dusty desert. The issue remained unsolved as the team had to evacuate their desert settlement as rain flooded the area and ended test runs for the year – at least by that time, dust wasn’t a problem anymore.

Collect yourself

While this meant another delay in the project, the break during the winter months was used to solve another problem – generating more funds. ThrustSSC was a privately funded project, which cost £2.5m in the end, and continuously needed more money to be raised. 

Alone the fuel costs for the heavy lift air-freighter Volga-Dnepr Antonov 124 that was used to ship car and team to Nevada were enormous. The plane needed 1m litres of fuel.  

The team set to the internet for a crowdfunding bid. One of the sponsors had suggested early to build a website that would document the project – which today exists in its archived version – and serve as an online project newspaper with regular articles. This website is still available in its archived version.

It helped promote raising funds and selling merchandise – an established process nowadays, but not so common in the 1990s.

When they came back to Jordan in spring 1997, the team managed to get the car to 550mph. During summer, the team prepared for the big show run in Black Rock where the ThrustSSC finally met the Sprit of America to determine which car would break the sound barrier. 

Setting the record

October came and, when seeing the desert conditions for the first time, Andy Green, RAF pilot and designated driver of the world record attempt, said, ‘The surface itself is incredibly smooth – we drove from one end of the course to the other without seeing a single ripple or bump. The surface is slightly cracked, like all such playas.’ He added, ‘Another major difference from Jordan are the stones. We picked up literally tonnes of stones from the Jafr desert. In the Black Rock, we drove for 25 miles and saw just one stone – and yes, we did pick it up.’

For a few days, the team went out to trial the car and to get it to Mach 1. After final checks and adjustments to the bottom structure where a cracked bottom panel stringer had to be repaired, on 15 October 1997, ThrustSSC reached a two way average of Mach 1.01, which was agreed with the Federation Internationale de l’Automobile to be the minimum speed to make an official record. In the end, ThrustSSC reached, Mach 1.020, 763.035mph, and the land speed record was set for years to come.

Rocket start

Both Green and Ayers now work on BloodhoundSSC, the current car under development to attack ThrustSSC’s record. The team decided to use a rocket to propel the vehicle and work on this has resumed this month after the team announced in May this year that they intend to attempt the record during the last quarter of 2019, looking to write another chapter in the history of land speed records.