The Budweiser Rocket Car
It has been 35 years since the Budweiser Rocket car ran and tried to “Break the sound barrier on land”. It was never meant to take the Land Speed Record, as it could not to maintain speed over a measured mile.
The Budweiser Rocket Car - 35 Years On
The compromise meant that much less fuel for the main rocket was required and a very short duration “one shot” sidewinder boost rocket was used for a final burst to try and hit Mach 1.
Whether the Budweiser Rocket car broke the sound barrier in 1979 at Edwards Air Force Base all those years ago, has always been controversial and a discussion for another day, but it sure got pretty damn close. At around Mach 0.95 both back wheels lifted off the ground about 9-12 inches (seen in attached pic, sorry for poor quality) and wheel tracks proved it went about 800ft with both rear wheels in the air, scary stuff. With all rocket power and no engine torque, the car ran dead straight on its single front wheel.
The transonic shock wave pattern was seen in the dust storm generated by the front wheel. Subsequent investigation and CFD analysis has indicated transonic shock wave pressure under the rear struts and body in ground proximity as the cause. The shockwave impact varies with speed, ground proximity, body and rear strut area and profile.
Firing the boost rocket to overcome the drag build up would have increased the rear end lift, as the rocket was located above the centre line of drag. Stan Barrett reported that when the sidewinder fired at about 600mph, it was like being hit in the back with a sledgehammer, he was a very brave man to press that button!
Aussie Invader 5R is a different beast, a lot heavier and a lot more powerful, but the same rules apply and that is why we have designed it with a “V” shaped underbelly to reduce the surface area for the shock wave to get hold of. The “V” shape underbelly will also deflect the shock wave either side of the car. We also have a solid rear axle and no supporting struts, only testing and high speed runs will tell if this approach is right, but we think it is the way to go.
Thanks to John Ackroyd for his analysis also on the Budweiser Rocket Car.