This page contains a Flash digital edition of a book.

fly at Mach 1. They can do up to about 0.97 but then the drag falls and they accelerate right through Mach 1 and do not slow down until they get to Mach 1.05 or faster. ‘There are two ways of dealing with the shock waves on different parts of the car. One is to design a vehicle that is very sensitive to them, to be hyper critical about every point in the design and eliminate all of the problem areas. That’s the way Ron Ayers does things. Breedlove, on the other hand, went in a different direction and decided to develop a vehicle benign to these forces and not worry too much about them. The guys I work with from Boeing and from Stanford feel that this is the best approach. I think there are areas on Thrust SSC that could have been re-shaped so that they would not have had these problems.’

The sheer speeds involved

in this record attempt make the mind boggle, but so do the other forces the vehicles have to contend with. When the Bell X1 broke the sound barrier it just had to contend with the aerodynamic forces. A supersonic car, on the other hand, has to contend with the planet itself, so that part of the Fossett LSR had to be made

bulletproof, and other parts must push materials beyond their natural limits. ‘When you consider this car

weighs 9700lb (4409kg), when driving across the desert at over 700mph the loads on the wheels are enormous, and critical. At 1000mph, a 900mm diameter wheel runs at about 9500rpm and has around 45,000g of hoop stress. There is not a natural material on the planet that can take those loads, only man-made composites. Including significant stress contribution from the

special carbon fibre tyre around the edge. Our analysis showed they are probably good for between 1300-1400mph.’

BULLETS FROM A GUN Foreign object damage (FOD for short) stopped Sonic Arrow first time around and it was a critical consideration in the wheel design on the Fossett LSR. ‘We are travelling faster than a bullet, so it’s very important to think about impact resistance. If the vehicle is hit by anything at this speed it is essentially being hit by a bullet.

“there is not a single

aerodynamically stable vehicle on the road today”

wheel disc, aluminium is only good for 800mph, titanium maybe1100mph, when we count its sensitivity to notch stress and fatigue. I don’t know what all of the other teams are smoking, but you can’t do this with a metal, the load, the mass and the damage requirements are just too high. Breedlove saw this a long time ago and they came up with a great solution – a hybrid wheel with an aluminium centre and a

Even with the whole course having been ‘fodded’ (when teams on foot remove potential FOD- inducing rocks from the course by hand) there are still a lot of small rocks under the surface at a depth of 1-10mm. It is likely that the wheels will hit them from time to time. With metal you’re literally cutting a notch in it, and that can cause a stress concentration, which leads to a crack and may end up causing catastrophic

failure. Breedlove had used woven fibreglass as a sacrificial surface layer in his tyre design, and the first set held up beautifully for nearly 20 runs between 1996 and ’97, including two at over 600mph. We have reinforced anything that may take a direct hit from a rock with stainless steel, but overall the car does not need a lot of armour plating. Most of it only takes glancing blows, but the wheel wells take horrible impacts so we planned on those sections to be easily replaceable. They’re sitting there essentially with bullet-proof vests on!’ Once a car has achieved such high speeds, of course it also has to stop again before it runs out of space, as Breedlove once did in the 1960s at over 500mph (in sequence: parachute failure; brake failure; telephone pole; dyke; brine-filled ditch; swim away). Initial braking for the Fossett LSR from 800mph+ is, in fact, achieved by parachutes adapted from Cold War-era ‘lob-toss’ nuclear bomb drogues. At lower speeds, you would expect to turn to the experts in stopping vehicles at high speed when facing such a challenge, but Breedlove did something quite unlikely – he turned to a company that makes medical implants. Sonic Arrow’s unusual braking system is a big piece of serrated metal that is hydraulically shoved into the desert floor at 300mph. ‘It’s a remarkably good idea and is one of the best features of the car. It is made of cobalt-chromium, a particular alloy that is used in medical implants. ‘Avoiding the use of wheel

brakes has the advantage that the skid brake works at any speed. The best point about it, though, is that we have no chance of locking a wheel and flat spotting it as we brake from 300mph down to zero. There were rumours saying it didn’t work, but I’ve got the telemetry printouts that show it worked perfectly and, in fact, is far better than any wheel braking system on these cars.’

The data from the 1996 run showing acceleration at ~90% throttle, wobble, roll, parachute deployment, and skid braking. The performance projection was added by Thrust 2 designer John Ackroyd

12 • January 2012

FURTHER UPGRADES Ahlstrom went on to explain that he had been thinking about further upgrades to the car that could help it reach even higher speeds, and a three-year plan,

Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92  |  Page 93  |  Page 94  |  Page 95  |  Page 96  |  Page 97  |  Page 98  |  Page 99  |  Page 100