Bloodhound SSC's designers flip their car upside down

The designers of Bloodhound SSC, the British-based team planning an assault on the world land speed record, have turned their vehicle upside down, it will be announced tomorrow.

At a meeting at the team's HQ in Bristol to reveal which desert will be the venue for Bloodhound's record-breaking attempts, which are scheduled to start next summer, the team will show off a redesign for the car which places its ex-Eurofighter Typhoon EJ200 jet engine up top, in place of its hybrid rocket engine.

The most obvious design configuration - and the one in all the images so far - was to put the main jet engine behind the driver and then strap the rocket booster on top. This had the advantage of keeping the centre of gravity low, as the jet is heavier than the rocket.

The problem was that it put the rocket off-centre. Its huge thrust of 122kN would have acted like a lever, pushing the nose of the car down and lifting the tail up - an extremely dangerous combination.

Then - according to Bloodhound driver Andy Green, speaking at the NIDays conference at the IET in London - an engineer asked the question: why don’t we swap the two engines around? After all, as the car accelerates towards the sound barrier it is the rocket that becomes the primary engine, not the jet with its "mere" 90kN of thrust.

It was one of those questions that seems so obvious - but only once someone has thought to ask it. Putting the rocket below the jet means its line of thrust can be angled below the centre of gravity and slightly downwards, giving the car extra down-force to hold it on the track.

It also means the jet engine can sit directly in line with its air intake above the driver’s head, instead of needing a duct running down through the car, and it makes it easier to load a new rocket for the return run - it will just slide in like a torpedo into its tube.

On the down side, having the heavier engine up top will raise the centre of gravity by several centimetres, and that means the rear wheels must be further apart to maintain stability. Given that the wheels and their struts are responsible for about 40 per cent of the car’s drag, that is not ideal, but Andy Green said it is preferable to having the car try to dig its nose into the ground when the rocket fires up.  

Although the Bloodhound SSC (super-sonic car) team aims to break the land speed record of 763mph, currently held by ThrustSSC - also driven by Andy Green - and then have the first car to exceed 1000mph, Green added that this is only its secondary motivation.

He said that its primary motivation is actually to inspire the next generation of engineers to "join the adventure".  To realise that, the team is running the Bloodhound education programme which now has over 2500 primary and secondary schools using its materials to help teach and promote science, technology, engineering and maths (STEM), and is seeking volunteers to work as education ambassadors.

Related stories:
Noble's Bloodhound scents new land speed record 
British team claims world steam speed record 
World land speed attempt car to be built in Bristol 
Bloodhound – the 1000 mph super sonic car (The IET Wheatstone and London Network Christmas Lecture 2009)

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