Almost exactly 15 years since the Thrust supersonic car broke the sound barrier and the land speed record, last week the team behind Bloodhound SSC tested the rocket system that they hope will break that record.

The Bloodhound engine roars into life © Stefan Marjoram

Based at RAF St Mawgan in Newquay, UK, the test brought together hundreds of engineers, sponsors, media and schoolchildren. The RAF base was chosen because of its hardened air shelters (HAS), bomb-proof hangars originally designed to protect fighter planes during the cold war. This meant that those of us gathered to watch would be well-protected if the rocket exploded.

The rocket system consisted of a Cosworth Formula One engine, a pump from a 1960s Blue Steel cruise missile, 400 litres of ultra-pure hydrogen peroxide and 180kg of solid rubber rocket fuel (HTPB). You might think that a Formula One engine would be used to power the wheels, but then Bloodhound isn’t one of the ‘small, slow cars that goes round in circles’, as its driver Andy Green describes F1 cars. In Bloodhound, that powerful engine is needed just to push the peroxide into the rocket chamber at a high enough pressure.

That peroxide is fed through a silver-plated grating to break it down into oxygen and water, releasing energy and raising the temperature to 600°C. The combination of high pressure oxygen and heat ignites the rubber fuel, burning at 3000°C and unleashing up to 27,000 pounds of thrust.

There were a lot of unknowns before the test: would the pump withstand the high pressure, would the fuel burn evenly, would the chamber withstand the high temperature? In a year’s time, Andy Green will be sitting directly in front of that rocket system and the team need to be certain that the answer to those questions is a resounding ‘yes’.

We assembled 200 metres from the rocket in a neighbouring HAS to watch the test streamed live. The atmosphere was tense as we sat in complete silence while the engineers went through the final checks and the bombproof doors closed behind us. On the screen we could see the rocket chamber pointing slightly downwards, held in place by a large concrete rig. As the engine roared into life and started pumping the peroxide, we could see the flame leaving the back of the chamber as the fuel rod ignited. The engineers then unleashed the full power of the engine, pumping the peroxide at 820psi – the equivalent pressure of four family cars sitting on your palm. At this point, for a split-second, the screen turned white as the camera tried to adjust for the brightness. This was just long enough for it to appear as if the rocket had exploded. That was always a possibility and the engineers had even said beforehand that an explosion would be better than nothing happening. Happily, the camera quickly adjusted to reveal the incredibly smooth shape of the flame bursting out of the chamber. But we didn’t need the camera to know that the rocket was burning steadily, we could feel it in the ground. The quaking of the earth and deafening roar were clear signs that the engineers had got it right.

After 10 seconds, when the fuel was exhausted, the hangar erupted in applause. We had just witnessed the largest rocket test in the UK for 20 years and it was a great success. The rocket will be tested four more times over the next year, before the first record attempt in South Africa in late 2013. But the team don’t just want to break the 763mph record; they want to smash it. In 2014 they will return to South Africa and push the car to 1000mph. Keep an eye on http://www.bloodhoundssc.com to follow them every step of the way.

Ian Le Guillou

                  

Source:
http://prospect.rsc.org/blogs/cw/2012/10/10/bloodhound-rocket-test-whoosh-or-bang/