Before the ThrustSSC team can consider taking the car to Jordan for high-speed tests two things must happen: the engines need to be taken to maximum reheated thrust in the Boscombe Down test cell to check the systems and integrity of the rear fuselage, and the car must be proven in ‘low-speed’ tests (maximum 200mph) on the runway at the Defence Research Agency, Farnborough.
The former started in August (please see "Tie Down Engine Tests Continue" for details), while runway tests began with a single run on Monday ("ThrustSSC Runs At Farnborough!"). Two more runs were achieved on Wednesday ("Farnborough Runs Continue Successfully").
Thursday was not a pleasant day outside the dry shelter of Q Shed - although Farnborough did not wake to the patchy mists of earlier in the week, a gusty wind was blowing dark clouds over Hampshire. It did not bode well for the team, although they were determined to run the car if a suitable break in the drizzle arrived.
The plan for the first run called for brake efficiency tests, calibrating the performance of the carbon-fibre brakes at different operating temperatures, and calibrating the Air Speed Indicator (or ASI). The accuracy of the ASI in particular is safety-critical - the team could not risk running ThrustSSC faster then the length of the runway permitted. Towards the end of the afternoon a suitable break in the weather finally came and at 1600hrs local time the jet-car forged once more down Runway Two-Five. A peak of 70mph was quickly reached. Andy Green braked to walking pace before accelerating again to 70. Another brake application brought the car to walking pace again, followed by another sprint to 70. As the car approached the end of the runway, Andy brought it to a stand opposite the waiting recovery team.
The team was pleased with the test - the necessary brake and ASI calibration information had been collected and the car had performed well. The weather had other ideas about more runs, however, and the car was returned to the shelter of Q Shed to be prepared for more tests the next day.
Dawn on Friday was cold and damp - but at least it wasn’t raining! Some good windows in Farnborough’s flight schedule were available for tests, and the team set to work with their spirits high.
The first run - ThrustSSC’s fifth to date - had two objectives: to confirm smooth deceleration from 100mph to zero at ¼g without any tyre problems after adjustments had been made to the brake system, and to check the calibration of the ASI’s pitot tube. By half-past ten the car was in position and the engines started, but as Andy Green drove the car under its own power off the ‘Alpha link’ onto the end of the runway he found - to his embarrassment - that he had insufficient lock in the steering to take his intended line, and was forced to shut-down the twin Rolls-Royce Spey jet engines and call for assistance!
The start team quickly lined the car up and restarted the engines, and at 1055hrs Andy brought the engines to 80% of maximum revolutions before releasing the brakes as the Jaguar fire-chase accelerated alongside. ThrustSSC accelerated swiftly to 100mph as Ron Ayers called out speeds from the Jaguar for checking against the ASI. At 90mph even the supercharged Jaguar could not keep up with ThrustSSC which was only developing some 12% of its maximum thrust - the fire-chase only caught up as the jet-car braked slowly, and once more speed readings in the two cars could be compared as they decelerated together.
The calibration of the ASI was confirmed, as was the capability of the brakes in their last check - the ‘profile’ of the next run called for 80% of rpms up to 120mph before selecting idle and deploying the parachutes for the first time. The run could not have gone better - the parachutes deployed well, flying just clear of the ground and slowing the car down well. Run 7 required a similar start, but with an increase in power to 90% at 50mph, reaching a peak of 140mph. After waiting until mid-afternoon for a suitable opportunity to run, ThrustSSC performed impeccably for the team once again.
Both team and car were getting into the swing of it by now - procedures were being refined and the strength of the teamwork was really beginning to show. The day’s fourth run saw another increase in both power - 95% - and speed: the peak of 155mph was achieved in a much shorter distance than before. Only when the in-car video was re-played after the run was Andy caught uttering a mild expletive….
Both sets of static tests at Boscombe Down had experienced problems with engine surges above 95%, due to insufficient air being able to reach the engines when vortices formed in front of the intakes. The team were confident that all that was needed to cure the problem was forward speed to ram a little more air into the intakes: Run 9 would be the acid test that proved the theory. ‘Max Mil’, or full unreheated power, was called for. Would the engines surge, or would the day’s amazing run of progress continue?
At 1810hrs ThrustSSC once more rolled forward onto Two-Five and took up position. Permission to run was received from Jayne Milligton in the Air Traffic Control Tower and Andy brought the engines to 80% before releasing the brakes. At 50mph the throttles were opened to full power - without reheat - and ThrustSSC accelerated to 160mph in just 5 seconds and without a hitch! Barely 2000ft into the run the ‘squibs’ were fired and the ‘chutes deployed, slowing the car to a stand over the remaining length of the runway.
The day could hardly have gone better for the team - after months of unrelenting hard work they had seen their creation power itself again and again down Farnborough’s main runway. The car and the team had all performed impeccably. Andy Green was delighted with the ThrustSSC’s performance: "Excellent! The engine performance was perfect, the brakes worked superbly, and the ‘chutes deployed perfectly every time. All we need to do now is run with reheat and we can tick-off the runway tests!"
Engineering Manager Pete Ross was delighted, too: "It looked absolutely fabulous!" he said, while Aerodynamicist Ron Ayers described the day as: "The best the Project has ever had."
Tonight there was no need to ask in Q Shed how the five runs had gone - it was obvious from the smiles on everyone’s faces. It just gets better and better.
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