Tuesday/ how to build a 1,000mph car

 .. which is of course not really a car : it’s a rocket on wheels.   

This recent article on the Bloodhound Supersonic Car project appeared in last week’s Economist (see text below).   I found the diagram of the other British landspeed records elsewhere.  And where exactly is the proposed Hakskeen Pan test site?  I wanted to know.   Well, it’s in the north-west of South Africa, right in that wedge between Botswana and Namibia, in the Kalahari desert.     Could that place ever be the same after that insatiable need-for-speed Hound had thundered across its flats?


From May 5 issue of The Economist :

How to build a 1,000mph car

THIS summer Daniel Jubb will perform the equivalent of lighting the blue touch paper and standing clear. The 27-year-old will undertake the first full test firing of a hybrid rocket which he has designed to help a British team set a new land-speed record by driving at 1,000mph (1,609kph). Mr Jubb’s rocket, however, will also need the assistance of a powerful EJ200 jet engine from a Typhoon fighter aircraft and a Cosworth Formula 1 racing engine if Bloodhound SSC (supersonic car) is to become the fastest thing on wheels.

Combining a rocket, a jet and a racing-car engine into one vehicle is engineering of an extreme sort, but record-breaking often demands that new problems be solved. Mr Jubb’s task was to build a rocket that could be used safely in a car, but was also controllable and could be switched off quickly in the event of an emergency.

A rocket works by burning fuel with an oxidiser, which provides a source of oxygen for combustion. The hot exhaust gases are then blasted through a nozzle to produce thrust. Rockets using liquid propellants can be shut down reasonably easily by turning off the pumps delivering the fuel and oxidiser, but they tend to be complex and their propellants, such as liquid hydrogen and liquid oxygen, difficult and hazardous to handle.

Solid-fuel rockets, in which the fuel and oxidiser are pre-mixed into a stable, solid propellant and then packed inside the case of the rocket, are simpler, lighter and relatively safer. But once a solid-fuel rocket is ignited, it is off like a firework and keeps going until all the fuel is burned up. About the only way to stop it is to blow it apart. In a car, that would not do.

The hybrid design which Mr Jubb has come up with uses a solid fuel called hydroxyl-terminated polybutadiene, a form of synthetic rubber used to make things like aircraft tyres. It is contained within the case of the rocket, into which is pumped a liquid oxidiser called high-test peroxide (HTP), a concentrated form of hydrogen peroxide which is relatively safe to handle. When the HTP comes into contact with a catalyst contained within the rocket, it turns into steam and oxygen. And it does so at a high enough temperature to ignite the solid fuel. This provides the added advantage of not having to build an ignition system into the rocket.

If the hybrid rocket needs to be shut down in a hurry all you need do is turn off the pump delivering the oxidiser. That is where the Cosworth engine comes in. Apart from generating auxiliary power for Bloodhound SSC’s electrical and hydraulic systems, it also drives a high-speed pump capable of delivering all 800 litres of HTP in the tank to the rocket in 20 seconds.

The rocket gives the car plenty of power, but it is either on or off. To provide some form of throttle to allow acceleration and deceleration, the vehicle’s designers added the EJ200 jet engine. This will be used by Andy Green, a Royal Air Force pilot who will drive the car, to get the vehicle moving. At about 200mph he will start the pump to deliver the HTP into the rocket.

At first there will be a stream of steam coming from the rocket. But then ignition gets going and at full blast the jet and the rocket will each provide about half of the 210,000 newtons (47,000 pounds) of thrust needed to break the record. At about 750mph the car will go through the sound barrier. Wing Commander Green has been there before—and not only in a fighter plane. In 1997 at Black Rock Desert, Nevada, he drove Thrust SSC to become the first person to break the sound barrier in a car and set the existing land-speed record of 763mph. This time the Nevada desert will not be big enough, so the attempt will take place over an even larger expanse of flat ground at Hakskeen Pan in the Northern Cape in South Africa, perhaps next year.

Bloodhound SSC could reach up to 1,050mph. Wing Commander Green then has to slam on the brakes. After turning off the jet and rocket he will deploy an air brake at 800mph, parachutes at 600mph and finally put his foot on a car-type friction brake at 250mph—any faster and the brakes could explode.

Then the car is serviced and refuelled to do it all over again. This is because the Fédération Internationale de l’Automobile, which keeps the land-speed records, takes as its measure the average of two runs over one mile in opposite directions completed within one hour.

The attempt is being organised by Richard Noble, a veteran British record-breaker, and is sponsored by a number of companies. Mr Jubb’s firm, The Falcon Project, was one of the first to step forward—and into the limelight. He usually designs and manufactures secretive military rockets in Britain and the United States. Construction of Bloodhound SSC has begun at an apt location: a borrowed warehouse on the dockside in Bristol next to Isambard Kingdom Brunel’s SS Great Britain, which in 1845 crossed the Atlantic in a record 14 days.

Unusually for such an enterprise, all the technical details, including computer-aided design files, are available online (bloodhoundssc.com). Mr Noble is involving schools in the project to encourage interest in engineering as a career. So far, more than 4,000 schools are taking part. This was part of a deal with Britain’s defence ministry in order to borrow the EJ200. It is to be hoped, though, that none of the children will try to build one of these cars at home.

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