One of the important things to understand was how the high-speed solid metal wheels would behave on the desert track.
BLOODHOUND Land Speed Record (LSR) is a hive of activity as the team prepares the car for its first high-speed test runs in South Africa.
According to Andy Green, all the technical bits are coming on well, so the test dates will be decided by the paperwork.
“This includes the import/export licences for classified military jet engines, rocket systems, etc, which take a bit of time,” Green said on Bloodhound LSR’s internet page.
“We’re still aiming to go as soon as we can, hopefully late this year – we’ll confirm as soon as we know.”
Green pointed out that the high-speed test runs would provide key data regarding the aerodynamics of the car. “In the age of supercomputers and artificial intelligence, it may seem old-fashioned to go out and do test runs but computers cannot predict everything.”
He stated that one of the important things to understand was how the high-speed solid metal wheels would behave on the desert track.
“Hakskeen Pan in South Africa is a very 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 how the wheels will interact with the surface.”
According to Green, at slow speeds the wheels will simply make shallow ruts in the desert surface, perhaps 7-8mm deep, due to the mass of the car (about 5.5 tons for the 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.”
He pointed out, however, that all these figures were based on models.
“One of the side-effects of ‘planing’ like a high-speed boat is that the wheels will throw up ‘spray’ from the surface. As the mud particles of the track surface are pulverised by the passage of a solid wheel doing several hundred miles per hour, the resulting dust will spray out like a fluid – hence the boat hull comparison.”
This presents a number of problems, he stated.
“The first problem with the ‘spray’ from the wheels is what is termed ‘spray drag’. Just as high-speed boats encounter drag from water spray, Bloodhound will see ‘spray drag’ from the huge clouds of dust that it is throwing up. 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, according to Green, 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.
“Bloodhound’s front end is composite, raising the prospect of rapid erosion of the carbon fibre structure and the front end of the car suddenly going all floppy.”
To counter any possible erosion, the team is 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.
Green stated that it was exciting to see Bloodhound sitting in its new workshop at Berkley UTC, 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 to do some high-speed tests in South Africa. It won’t be long now.”