IEEE Spectrum August, 2015 - 55

building bloodhound

fin on a supersonic aircraft that
flies at 45,000 feet, it's being
pushed through treacle."
Elvin and his colleagues are
the engineers put wheels onto a trailer carusing a combination of finiterying 3.5 metric tons of water to mimic the
element analysis and compuweight of the fully fueled car. The team then
tational fluid dynamics (CFD),
pulled the trailer across the desert where the
which models airflow and prerecord attempt will take place: Hakskeen Pan,
dicts the stresses it will create
in the northwestern corner of South Africa.
on the component. The results
Using a small truck as a tow vehicle, they
hand In gloVe: the steering wheel was
have given the team confiwere able to get the trailer going up to about
formed of hollow titanium to fit andy
green's hands. It is light, yet tough enough
dence that this aluminum tail
60 km/h-good enough for a low-speed test
to take wild handling should the planned
fin
can stay the course.
of the wheels' ability to bear weight.
straight-arrow course go awry.
Bloodhound's entire strucThe engineers also put the wheels into a
ture-the titanium skin of the
rig that Rolls-Royce uses to test compressor
discs for its jet engines. "Metal is a very uniform material, and it upper chassis, which is supported on aluminum ribs; the steel
can be modeled quite well," says Holdsworth. "We were moni- under chassis, designed to withstand a supersonic spray of
toring the stretch at the rim and the changes at the hub with a desert gravel and sand; the carbon-fiber monocoque that surlaser sensor rig, and the stretch that the [finite-element analysis] rounds the driver and forms the air intake for the EJ200-is perpredicted matched up with what we saw, including the effects forated with hundreds of millimeter-wide holes. These tiny
openings lead to pressure sensors fixed to the inner surface
of the temperature rise from air friction."
That agreement between measurements and modeling gave of the skin. Other sensors include a network of strain gauges
Bloodhound's designers greater confidence in their computers, placed at strategic points on the car's structure.
These sensors will, in all, collect 197 channels of data as
which they've used to design all of the structural features of
the car, including its tail fin. "This is the hardest-working tail Bloodhound runs, measuring the air pressure and the flex
fin in history," says the engineering lead for mechanical design, of the body as the car skims over the desert. "The pressure
Mark Elvin. "Not the fastest necessarily, but relative to a tail sensors are placed at zones of high transition, where the air-

stefan MarjoraM

co nti n u e d f ro m pag e 35

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Table of Contents for the Digital Edition of IEEE Spectrum August, 2015