Supersonic car prepares for high-speed runs in SA
NEED FOR SPEED
The Bloodhound supersonic car is back, under new management and preparing to renew its pursuit of the land speed record.
The project went into administration in 2018, unable to secure the financing needed to go racing even though the vehicle was all but built. But with the purchase of the car by UK entrepreneur Ian Warhurst, Bloodhound is on a new footing.
The team expects to start high-speed trials at Hakskeen Pan in the Northern Cape as early as October, with reigning world land speed record holder Andy Green behind the wheel.
A British team is developing a car capable of breaking the world land speed record of 1,228km/h. Powered by a rocket bolted to a jet engine, the vehicle aims to go progressively faster with the ultimate goal of reaching 1,000mph (1,610km/h).
ANDY GREEN’S DIARY
The Bloodhound Land Speed Record site is a hive of activity as we prepare the car for its first high-speed test runs. These will give us some key data to confirm the aerodynamics. In the age of supercomputers and artificial intelligence, it may seem oldfashioned to do test runs surely computers can predict everything nowadays? The simple answer is no, they can’t.
US statistics expert George Box is credited with the saying: “All models are wrong, but some are useful.” That’s all very well for statistics, but slightly worryingly, Bloodhound’s chief engineer Mark Chapman has also started quoting it.
Mark and his team are building the car, based on computer models, that I’m going to drive it at supersonic speeds. Should I be worried at this point?
No, I’m not worried, for the very reason that we are going to be doing high-speed test runs.
We’ll explore how accurate our models are during our stepby-step testing, correcting the models as we go.
Cutting edge projects from Formula One to spaceflight do a lot of modelling and a lot of testing. We’re no different.
In advance of the test runs, a lot of background work is still going on to understand what the computer models can tell us, and how we can check them against the test result. This is the bit where the models will prove “useful”, even if they are not perfectly accurate.
Another fascinating area is understanding how the highspeed solid metal wheels will behave on our desert track. Hakskeen Pan is a firm, smooth, dry mud surface, which (we believe) is the ideal surface for supersonic record breaking.
Before we get to supersonic speeds, though, we want to know more about the way the wheels interact with the surface. At slow speeds the wheels will simply make shallow ruts, perhaps 7mm-8mm deep, due to mass of the car (about 5.5 tons for our initial tests).
However, at high speeds the wheels will start to “plane” on the surface like high speed boat hulls, reducing the depth of the wheel ruts to around 3mm.
All these figures are based on models, and so are probably wrong (see above!), but they are useful in understanding how the car will behave.
One of the side-effects of planing like a high-speed boat is that the wheels will throw up “spray” from the surface. What Ron Ayers, our legendary aerodynamics and performance expert, has termed “spray drag” is the first problem.
Measuring the effect of this spray drag will give us a more accurate indication of how much power Bloodhound needs to get to 1,000mph.
The second problem with the dust spraying up from the wheels is that the rotating storm of supersonic air around the wheels will suck a lot of the dust up into the bodywork. We saw exactly the same with Thrust SSC back in 1997, when the car generated big supersonic dust storms inside the bodywork.
This didn’t matter very much for Thrust SSC, as the structure around the wheels was all metallic. But Bloodhound’s front end is composite, raising the prospect of rapid erosion of the carbon fibre structure and (to quote our chief engineer again) the front end of the car “suddenly going all floppy“…
To counter any possible erosion, we are putting aluminium liners inside the composite wheel arches. This will also allow us to monitor the erosion effects (if any) of the desert dust, without any risk to the bits of the car that stop the nose from becoming unexpectedly floppy.
It’s exciting to see Bloodhound sitting in its new workshop at Berkeley Green University Technology College in Berkeley, UK, gradually being modified from its “runway” test configuration (rubber tyres, partial bodywork, no brake parachutes) to its desert test spec.
This includes fitting the brake chutes, all the bodywork panels, and the desert wheels and fairings (complete with aluminium liners, of course), as we get the car ready for some high-speed tests in SA.
Won’t be long now.