Racecar Engineering – September 2019

SEPTEMBER 2019 http://www.racecar-engineering.com 75

Bloodhound, the project that aims to break the

1000mph barrier and is due to undergo high

speed testing at Hakseen Pan, South Africa,

this autumn, where 500mph is being targeted.

The project has been relaunched recently after

being saved by businessman Ian Warhurst.

Dieselmax is included here because at its

top speed of 350mph the fl ow around the

wheel-to-ground contact points locally

exceeded the velocity of sound. Thus, Dieselmax

genuinely qualifi es as ‘transonic’, since this is

actually defi ned as ‘locally experiencing both

subsonic and supersonic fl ows’.

We’ll start this examination by looking at

wheel loads. As a vehicle running by itself on a

smooth surface without obstacles, there is only

one object with which the LSR car can have a

collision, and that is the track surface – there is

nothing else to crash into. Therefore, to avoid

such a collision, the primary safety of the vehicle

comes down to keeping all of the wheels on the

ground, all of the time. You can’t have a crash

with something you’re already resting on.

In the case of Bloodhound we aim to

ensure that the download (due to gravity plus

aerodynamic up/downloads) is predicted to

be never less than 10kN (kilonewtons) on each

wheel. Thus, there is a margin to ensure that

unexpected and transient loads (for example,

due to crosswind gusts, or steering inputs,

irregularities on the track surface, etc.) will

never result in a wheel leaving the ground.

I

s it a high-speed car? Or is it a very low

fl ying aeroplane? When considering the

stability and control of very high velocity

cars, the answer is: neither. These vehicles

have unique characteristics and their stability

must be analysed from fi rst principles.

Much has changed since the early jet cars

of the 1960s. Access to computational fl uid

dynamics (CFD), CAD systems and low-cost

instrumentation has transformed the fi eld

of Land Speed Record (LSR) attempts, and it

is now feasible to design record cars that will

exceed the velocity of sound.

This piece is a summary of lessons learned

from Thrust SSC and the JCB Dieselmax,

which are being employed in the design of

The dynamic yaw response of Bloodhound will probably feel like

that of a supersonic hovercraft or hydrofoil, if such things existed