We have a wonderful opportunity with BLOODHOUND: an opportunity to create the ultimate Land Speed Record car. When we designed and built Thrust2 we had the objective of achieving a peak speed of 650 mph, just beyond the existing record of 622.407 mph held by Gary Gabelich in Blue Flame.
Then came ThrustSSC, which raised the Thrust2 record by a whopping 130 mph – that’s 20%. But BLOODHOUND is different - so different. The target is 1,000mph - that’s a 31% jump and there is no way that the BLOODHOUND SSC is going to look like anything we have seen before.First, the all-important powerplants. We have chosen a jet and hybrid rocket. The reasoning is that we need the rocket for its raw power and lack of draggy air intake, but the downside is that the rocket is an on/off device and with rocket power alone we would have real difficulty hitting and holding selected Mach numbers for the aerodynamicists to gain their data. And at these speeds we have to tread very carefully, increasing the Mach numbers in small, careful steps.
So we need power controllability and this is where the beautiful Eurojet EJ200 comes in. The Typhoon engine is incredibly small and light for its power and of course is a fully developed engine, enabling us therefore to control the output of the combination of rocket and jet by throttling the jet alone.
The car has to run through a wide speed range and keep the same loads on all four wheels - much as ThrustSSC did. The little winglets above the wheels are fully dynamic trimmers making small adjustments in microseconds. They are not there to develop massive download as needed for a wheeldriven circuit-racing car, but simply to maintain constant wheel load up to Mach 1.4.
In the middle of the BLOODHOUND SSC is the MCT V12 800 bhp race engine which doubles as our APU delivering hydraulic power as needed, starting the EJ200 and of course pumping the High Test Peroxide (HTP) through to the Falcon rocket. The pump has to move a ton of HTP through to the rocket catalyst in 22 seconds and at 1200 psi. The beauty of the hybrid rocket is that it uses a safe and green oxidiser in the shape of HTP and only burns its solid fuel as long as the HTP is flowing. Shut the HTP flow off and the rocket shuts down in safety. No emergency problems of having mechanically to jettison a burning solid fuel rocket or running the risk of an explosion from shutting down a bi-propellant rocket with horizontal combustion chambers.
The BLOODHOUND SSC shape is completely different to anything seen before. We need to minimise the cross-sectional area to minimise drag, but we also need a supersonic intake and a smart suspension system which will enable the car to run smoothly over the rough salt surfaces. Because the rocket is positioned above the EJ200 and thus raises the centre of gravity, we will need to position the rear wheels on suspension outrigged on draggy struts. In the past this was always seen as a huge aerodynamic disadvantage - one that made the famed Budweiser Rocket wheelbarrow at times - but today running computational fluid dynamics (CFD) with multi-million elements we can compute the drag of the wheels and struts at Mach 1.4 and optimise the shape to minimise drag and shock effects.
In ThrustSSC Andy’s cockpit was positioned comfortably between the two Spey 202 afterburning turbofan engines but in the BLOODHOUND SSC design packaging of all the components including Andy has been a difficult issue. He and his cockpit have ended up just under the EJ200 intake, with the cockpit external shape being a part of the all important intake shock management structure. Andy has lost out on comfort value there, but that’s one of the compromises that have been necessary in developing a Mach 1.4 car.
The rear wheel covers are going to attract considerable attention as they look like something from a sci-fi movie. We have to reduce supersonic drag -hence the pointed parts front and rear - and also protect the upper surface of the wheel from the oncoming airflow where, if unprotected, it would reach Mach 2.8. Inside the wheelarches there are also problems – the 900 mm (35.8 in) wheels are wasting energy winding up and whirling the airflow in the wheel bays, so we have to ventilate the bays to reduce power losses.
The fin is also very small – traditionally these Land Speed Record cars have had big fins to ensure good stability in yaw. But too much fin means a car which will severely be affected by crosswind and not enough fin means that the car will be directionally unstable. One of the key design issues is whether we have enough fin area to control the car directionally when we bring in the afterburner and the rocket at low Mach numbers. The designers believe that BLOODHOUND SSC has very good directional stability and will probably only need that small fin.
So when BLOODHOUND SSC finally emerged in Config 3 status, I was very pleased – like I said earlier, it looks like nothing we have ever seen before. And that’s just how it should be…
Richard Noble Oct 5 2008
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