Budweiser Rocket
See updates shown in bold. These may help to clarify and correct some of the initially provided info.
The Budweiser Rocket was a 3-wheeled land vehicle powered by a hybrid liquid and solid-fuel rocket engine that has been claimed as being the first vehicle to have broken the sound barrier on land, driven by Stan Barrett and designed and built by William Fredrick. Neither the Fédération Internationale de Motocyclisme nor the Fédération Internationale de l'Automobile, the official speed record certifying bodies, recognise the record attempt, the speed purported to have been reached or that the vehicle ever attained supersonic speeds.
Despite an unauthorized written speed certification by the U.S. Air Force, there is much debate over the validity of the claim. The USAF states it "never intended to give official sanction to test results, nor to give the appearance of expressing an official view as to the speed attained by the test vehicle. Any such opinion was that of individual Air Force personnel, not of the Air Force".This was in a letter from Lt. Col. Michael Alba to Wisconsin Senator William Proxmire on December 17, 1981 verifying the USAF non-involvement in the actual timing of the car. None of the land speed record sanctioning groups was present for the run, nor was the run duplicated within any particular time frame as required by most sanctioning bodies for official recognition of a new land speed record. No accurate measurement was taken of the car's speed, which was announced as having been calculated from accelerometer data which has not been made public. The prior statement is not entirely true. The data used to determine the speed of the vehicle was based on the azmith, elevation, timing, and overlaid range data from the AN/TPQ-39 Instrumentation Radar DIR)used to track test aircraft and missiles. As a result the Budweiser Rocket is not officially considered as the first vehicle to have broken the sound barrier on land, and few people believe the car to have actually done so[citation needed].
The claim of breaking the sound barrier on land was made on December 17, 1979 after a run on Rogers Dry Lake at Edwards AFB. While it has been claimed that the Budweiser Rocket did briefly break the sound barrier, it could not gain any official titles because standard ground speed record regulations measure an average speed over a measured distance (either one kilometer or one mile (1.6 km), depending on the particular sanctioning body's rules). The measurement of the vehicle's top speed during the run has been disputed primarily because of the methods used to calculate the speed, and its extremely small margin of success.
The first run of the car at Bonneville Salt Flats showed that the propulsion system was unable to develop enough power to sustain a speed high enough to establish a new official World Land Speed Record. The team decided then that their goal would be to exceed the speed of sound on land, if only briefly, although no official authority would recognize this achievement as a record.
The speed of sound is a function of the air temperature. In other words sound barrier is not an absolute speed value, but dependent on air conditions. The speed of sound during Barrett's speed run was 731.9 miles per hour (1,177.9 km/h).
No independent authority sanctioned the performance, although United States Air Force radar tracked the vehicle and recorded the speed at 38 mph. I am not sure where the author came up with the 38 mph. It is true that the radar lost the range tracking information during the record run due to ground clutter, but the azimuth, elevation, and timing data used in the final calculations was from the actual run. The range data was recreated after the run based on a truck (The beacon lab van) that drove over the same track the Rocket Car used and then overlaid with the actual azimuth, elevation, and timing data to provide the final speed number. The azimuth and elevation data was provided, not by the auto tracking of the vehicle, but rather manual tracking via the camera that was mounted to the radar. That is why the range (which was set for auto tracking) was able to lose the vehicle and still allow for correct azimuth, elevation and timing data. With the overlaid range data from the van, the actual track was recreated. There were error coefficients that could be included; however all but one are so small there would be no meaningful effect on overall accuracy. The only error coefficient that could cause an incorrect measurement was the ability of the operator to keep the camera cross hairs on the target (the Rocket Car) as the vehicle passed through its top speed. This was obviously an error, and is generally considered to represent the movement of a truck in the vicinity. The report on the speed achieved was confused, but eventually a figure was produced nearly eight hours after the run. This figure was based on in-car accelerometer data, which were affected by vibration. I believe the accelerometer data was used to help validate the data from the radar, but the final numbers were derived from the radar data and not the accelerameter data. These data were interpreted by the team as indicating a high degree of probability that the car exceeded the speed of sound at one point in its path by achieving a peak speed of 739.666 miles per hour, or Mach 1.01. This data, however, has never been publicly released and one expert claimed that the vibration interference was so great that almost any speed could be claimed.[1]
According to witnesses no sonic boom was heard. It is claimed that this was because of the short distance between the observers and the deafening sonic waves from the combined liquid and solid-fuel rockets used to propel the vehicle.[citation needed] Standing shock waves in the rocket exhaust produce continuous supersonic shock waves (a continuous "sonic boom"). The auditory dynamics of two screaming rocket exhausts, combined with the pounding physical effects of such intense sound waves over the short distance to the observers, made it questionable whether close observers could have differentiated the vehicle's sonic boom from the general cacophony of background noise. No boom was heard at greater distances either, in marked contrast to the runs of Thrust SSC, which generated extensive and well attested sonic booms over a wide area.
The "Budweiser Rocket" is in the Talladega Superspeedway Museum, Alabama, USA. (circa 2004)
The British Thrust SSC is officially recognized by the FIA as breaking the land speed record - and the sound barrier as well - in 1997, with an average speed of 763.035 mph (1227.99 km/h) on a measured mile in both directions.
