| A
Review of Chuck Yeager's Letter of Testimony on the Budweiser
Rocket Car by Don
Baumea The purpose of this review is to encourage the reader to reevaluate a document that has been used to support the Project S.O.S. (Speed Of Sound) claim that Stan Barrett drove the Budweiser rocket car to a speed exceeding Mach 1. Hal Needham and the team must have reckoned
that the rules for land speed racing were in fact obsolete
and did not apply to their project. In the team's estimation
the general public would not be able to distinguish a peak
speed run from an official World Land Speed Record. If the
general public accepted their logic and claim of being the
first to exceed the sound barrier on land, it could be expected
that corporate sponsors would pay a great deal of money for
the chance to ride with history. The team in fact, claims
a World Land Speed Record, while the Mach 1 event is a purely
aerodynamic or atmospheric related phenomenon. Their approach
has generated arguments that may rage for quite some time
and it is not the author's desire to debate it here. The only
issues of critical importance are: did this car reach and
exceed Mach 1; and is there evidence that can support such
a claim?
On that cool December morning, Stan Barrett
and the Budweiser rocket car were ready to answer the skeptics.
With the aid of an additional rocket engine, Stan blasted
away on his bid for a place in automotive history.
The final determination 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. Although there were spectators and
members of the press present for the run, it was up to the
Project S.O.S. team to provide the final judgment as to the
outcome of the run.
This verification process was unique to this
project in that at no time previously has any team ever been
allowed to determine whether or not they were successful.
Only impartial officials should make the final determination
of speed.
In the final analysis, it is important to note
that even after further evaluation of the data, which proposed
three new and different projected velocities, all of which
were rejected and the original preliminary estimate 739.666
miles per hour was proclaimed as the final speed.
Equally unprecedented was the wait for the
report on the speed, which came nearly eight hours after the
run. Then came the team's verdict. A preliminary investigation
of the run data was interpreted, indicating a high degree
of probability that the car exceeded the speed of sound by
achieving a velocity of 739.666 miles per hour, or Mach 1.01.
No sonic boom was heard however. This speed was estimated
from data supplied by a radar system that had initially reported
the speed at 38 miles per hour, as it had tracked a large
truck off in the distance, away from the track that the rocket
car had used.
The press received the team's verdict with
mixed enthusiasm. Some chose to accept the claim while others
rejected it. To this day, virtually all further published
references to this event which claim the sound barrier had
been broken can be traced to these few initial reports.
Credibility is very much like a line of credit:
if someone extends it to a person, then it is quite likely
that others will follow suit. It is most interesting to note
that even the press, at times, believes that what it reads
must be true.
About one month after the run, the Project
S.O.S. began distributing a letter written by Brigadier General
Charles Yeager, enclosed in this review, to further lend support
to their claim. The release of this document has been universally
regarded as a public relations maneuver on the part of the
team to further lend his credibility to their assertion of
a Mach 1 run.
The original interpretation of the run data
was not producing the result the team had expected, since
the results were ultimately ambiguous. Records of all kinds
often generate controversy as a byproduct. This dispute of
the Project S.O.S. claim is important because it represents
a very unique event. Once it has been done, it will be recorded
in history forever.
The author of this review has the opinion that
the Budweiser rocket car did not achieve the velocity that
is claimed by the team.
Mr. Yeager's singular proof of evidence is
the fact that the vehicle's rear wheels came off of the ground
at the rocket car's terminal velocity. It is the author's
opinion that the car did achieve a very high velocity, while
Stan Barrett drove most skillfully and fearlessly. In a 1987
telephone interview, Stan Barrett vividly recalled that the
car was beginning to go divergent (turn off-course) as the
rear wheels touched down, slightly off the center line track
created by the front wheel, and that, in his estimation, the
margin of time remaining until total loss of control of the
vehicle resulted could be measured in milliseconds. The author
honestly wishes that this fearless man had achieved the claimed
speed. Yet the records that are available clearly indicate
that the speed that the car reached is unknown in terms specific
enough to grant a claim of Mach 1.
This review will focus on this aforementioned
letter, and will pinpoint problems that the author has with
various assertions within it.
The following is a direct transcript of that
document.
Gentlemen:
It is quite obvious that the Hal Needham,
Budweiser rocket car exceeded the speed of sound because
of the rear wheels leaving the ground as the car achieved
top speed.
As the car approaches .9 to .94 Mach number,
very strong shockwaves will form on the nose, the tail and
the wheel struts. When the car goes supersonic, the shockwaves
which formed on the nose at lower speeds will move to the
rear of the car. Evidentially the chocking effect of the
shockwaves under the car, as they moved to the rear, lifted
the rear of the car off the ground. I observed the track
of the rear wheels on the supersonic run and the rear wheels
were off the ground for 650-700 feet. A photo taken at the
trap shows the rear wheels off the ground about 10 inches.
Since the rear wheels weigh about 100 lbs. each and were
rotating between 7-8000 RPM, they acted as gyros to keep
the car from turning, directionally or laterally.
Having been involved in supersonic research
since the days of the XS -1 rocket plane, which I flew on
the first supersonic flight on October 14, 1947, there is
no doubt in my mind that the rocket car exceeded the speed
of sound on its run on December 17, 1979.
(Signature of Charles E. Yeager)
Charles E. Yeager Overall, Mr. Yeager asserts that the car achieved
Mach 1 because the rear wheels lifted. He adds several seemingly-reasonable
conclusions that he makes based on his extensive experience,
which was afforded to him through the exclusive privilege
of piloting the world's first supersonic aircraft. His experiences
certainly must have opened many doors for him, and it would
seem to be a fair assessment that he must have also had a
great deal of exposure to an entire range of supersonic research
material, facilities, and personnel. When his letter is read
with this preceding assumption it is easy to accept the conclusions
he makes. The author does not make these assumptions at all
because his personal experience in aerospace, as well as the
automotive racing field, has demonstrated to him that, although
an individual may posses great knowledge or experience in
one general area, it is almost always the case that an individual
is not as informed or experienced in other fields of endeavor.
Clearly, the activities associated to aerospace research and
the pursuit of a land speed record are vastly different endeavors,
not only in objective, but also in methodology.
Mr. Yeager says it (the Mach 1 claim) is quite
obvious because the rear wheels left the ground. Many people
are not aware of research that was conducted by Jim Reisbeck
at Boeing Aircraft who developed a principle and application
in aerospace where a symmetrical airfoil with a given weight
and a specified velocity demonstrated buoyant lift, which
is to say, the airfoil reached a stabilized height above the
ground plane relative to its physical properties as opposed
to the normal aerodynamic lift associated to this type of
airfoil. The exposed portion of the rocket car's wheels do
in fact represent the essential elements of that shape. The
result of this research was the definition of a type of height
stabilized flight which is the result of pressure lift that
is generated because of the interaction of the ground and
the airfoil. The rear wheel assembly has an aerodynamic fairing
that left exposed a substantial portion of the wheel to the
high velocity air during its final run. The wheels have a
machined knurled surface which would have contributed to higher
air pressures which would have had force vectors applied predominantly
upward.
Many people who have studied this project miss
one unique detail of the three-wheel design. The two rear
wheels present more potential lift due to the combined area
of both wheels which are, in the case of the Budweiser rocket
car, individually the same width as the front wheel. As an
analogy, imagine three water skis that support a vehicle which
is balanced at its middle. The rear skis would rise up on
plane before the front due to the unequalized lift, front
to rear. With the car, moving the center of gravity toward
the rear would help equalize this effect but it would reach
a practical limit eventually because aerodynamic forces constantly
build as the vehicle accelerates toward the transonic speed
range. Also, the vehicle was liquid-fueled, and had demonstrated
an aft center of gravity which would have shifted forward
slightly while the overall weight was dropping incredibly
quickly. Between both propellant sources, solid and liquid,
the vehicle lost 1,560 pounds of weight, which represents
a 28.8% loss in a span of 19 seconds. As the lift forces climbed
higher, the car got lighter. Now the front wheel did not levitate
because a small set of wings, mounted far forward of the center
of gravity, were used to push down with sufficient force,
while no such device was used to provide any down-force at
the rear of the car. The wing provided much leverage, as revealed
in the front suspension load cell data.
Another detail that bears noting is the location
of the solid-propellant JATO booster rocket. Its location
was above the center of gravity, and its line of force contributed
lift above the center line of the vehicle, in the vertical
plane. The auxiliary booster was ignited and burned for only
5.5 seconds before all thrust ceased at the vehicle's top
speed.
Another lifting source was very likely caused
by the cockpit canopy due to its shape and location far aft
of the center of gravity. Normally, a windshield profile,
as found on most cars, will generate a definite high pressure
region at the lower base of the windshield and a very low
pressure area at the forward roof line. The author has demonstrated
in a wind tunnel to his satisfaction that this condition also
existed on the rocket car. But of major difference is the
feature of the rocket car's half-conical windshield design,
which has a very small surface area at the front for the high
pressure air to act upon, whereas the upper portion of the
canopy does in fact have a sufficiently large area to allow
the low pressure air to act upon. In this case, the overall
airflow results in a slightly forward lifting force, however
not enough to lift the rear wheels alone.
Over the course of many interviews with on-site
witnesses, the author believes that the rear struts, which
were fabricated from round tubing and faired with sheet metal
trailing edges, were also a significant source of lift at
the rear of the vehicle. Witnesses claim that these fairings
were installed with their trailing edges noticeably lowered
which would have clearly met the requirement for generating
significant lifting force. These witnesses were very specific
in their descriptions of this particular detail. In his final
report (AIAA Paper 81-0219, dated January 12-15,1981) Ray
Van Akin also states, "This configuration was thought to reduce
drag while not likely to generate much lift. As mentioned
before, however, the rear wheels experienced a period of being
airborne." If he was able to eliminate this as a source of
lift, he would have stated it. The author therefore believes
that the true reason the rear wheels lifted is because several
events converged at the same time to create a combined total
lifting force which acted upon the rear of the vehicle. These
forces, by themselves, probably would not have been enough
independently to cause the rear wheels to lift. As Mr. Van
Akin alludes, these forces were overlooked in the design phase
because they were not deemed large enough to calculate.
It is highly unlikely that the wheels lifted
for the reasons Mr. Yeager claims. No portion of his letter
provides reasonable explanation of the cause of the lifting
rear wheels at the vehicle's terminal velocity. The many converging
events which occurred, as documented by onboard data acquisition
systems, clearly record maximum thrust levels being reached
at the point of lowest vehicle weight. It is worth noting
that the rear wheels settled abruptly upon the termination
of thrust of the booster rocket without any momentum effects
observable, as would be generally expected given the rate
of deceleration the car exhibited.
Mr. Yeager states that, "as the car goes supersonic
the shockwaves which formed on the nose at lower speeds will
move to the rear of the car." In reality, a shockwave should
attach to the nose, but only when the vehicle actually achieves
Mach 1, not at lower speeds as he indicates. The bow shock
would then remain attached to the nose thereafter while other
shocks of different types may migrate to some degree. In reference
to his claim that it will move to the rear, perhaps it is
time for him to go back to flight test school to brush up
on the basics. When an aircraft reaches a higher Mach number,
the shock will lay back (become a more acute conical or wedge
shape) around the nose and other locations. For certain types
of shockwaves there is slight rearward movement, but nowhere
near as much as he suggests. And certainly, shockwave migration
or geometry sweep increases do not happen significantly at
Mach 1.01. The shockwave on the nose is very much like a slightly
conical dish, approximately 170 degrees (at the velocity that
is claimed) which would emanate away from the vehicle in all
directions. The sweep geometry can vary slightly, but not
even close to what Mr. Yeager proposes.
Jim Reisbeck's research did not account for,
nor did it fully investigate, transonic effects, which can
be present at speeds substantially lower than Mach 1. In the
case of the final run, which occurred early in the morning
when the air temperature measured a brisk 20 degrees F., the
conditions did exist which would further encourage the formation
of very localized shock fronts directly ahead of the exposed
portions of the wheels, front and rear. In fact, published
photographs clearly show the formation of these local shocks
which finally stabilized approximately five to eight inches
away from the tread surface, as would be entirely expected
for this type of physical arrangement. At no time (in the
very clear photos) did the shock front emanate away from the
local flow field of the wheel or the car. Mr. Yeager speculates
(note his use of the word, evidentially) how the shockwave
will have developed and choked causing the rear wheels to
lift. Five-time world land speed record holder Craig Breedlove
truly experienced transonic chocking effects in his Spirit
of America Sonic 1 jet car at slightly under 600 miles per
hour, which caused the front wheels to lift and then stabilize
at a specific height. He was not supersonic at the time. It
is worth drawing attention to Mr. Yeager's conjecture, which
is what it most definitely must be, because there has never
been any mention of wind tunnel testing by the designer, Bill
Fredricks. In fact it is widely known that the Budweiser rocket
car is in fact a repainted version of his prior LSR project,
The SMI Motivator and not a new vehicle specifically built
for an assault on the sound barrier. The SMI Motivator was
essentially an eyeball-engineered vehicle and no documentation
exists suggesting otherwise.
How can he know the precise shockwave formation
characteristics of an untested and unverified design other
than by pure speculation? Perhaps Mr. Yeager is referring
to a well known research paper which studied the supersonic
viability of an other vehicle named The Blue Flame, which
was the official world land speed record holder in 1979. Though
a model was fully tested in a wind tunnel by qualified personnel,
it did not precisely represent every detail of its successful
full-scale counterpart. Their widely-published research photographs
clearly depict the formation of a shockwave strongly present
and attached to the nose of the model, with the specific geometry
that is typical for the velocity tested. No shockwave has
ever been seen on the Budweiser rocket car at the expected
locations in any published photographs, further evidence that
the vehicle did not achieve Mach 1. At no time, in any currently
available photographs, is there any evidence that a shockwave
is present or forming at the nose of the car. The author believes
that the reason for this is because the car did not even achieve
Mach .9, because that is the only explanation that can create
a local shock in front of the wheels but not at the nose of
the vehicle. A disturbance on the surface of the lake bed
would have betrayed the presence of the bow shock.
The author has never seen nor heard of any
type of vehicle or aircraft that does not demonstrate a shockwave
either ahead of or attached to the nose when at a velocity
equal to or greater than Mach 1. Critics are curious how Mr.
Yeager would propose to explain this amazing violation of
transonic/supersonic aerodynamics. A transonic shock condition
is the only explanation. It is a situation where local airflow
conditions meet sonic requirements. Though away from this
local environment where the conditions are dramatically different,
the conditions that cause the formation of a shock do not
exist. Blunt objects are great shapes for demonstrating shock
up conditions. The wheel/ground plane environment does fit
the general requirements.
The rear wheels have long been argued to have
stabilized the car after they lifted off the surface of the
dry lake bed. Who would dare dispute Mr. Yeager's assumption
in the face of his observed opinion? The gyroscopic forces
are substantial indeed. It bears noting that this explanation
went completely unchallenged, that is until recently when
famed speed king Craig Breedlove returned to the world of
officially sanctioned high speed record racing with his third
and final Spirit of America jet powered racer. To the horror
of all who witnessed, Craig lost control of his car when he
ran into a 15 mile per hour crosswind at a speed nearing 675
miles per hour. He was attempting to set a new officially
sanctioned world land speed record. Evidence exist that Craig
would have reached nearly 800 miles per hour within the measured
mile if the run had been uninterrupted. During the crash,
Spirit rolled onto its left side and continued on, making
a 90-degree right turn. The gyroscopic effects of his wheels,
which were very close in weight and size to the Budweiser
rocket car's wheels, were no match to the forces that act
upon the vehicle's body at those high speeds. These two vehicles
are very different in design, yet the gyroscopic forces are
nearly identical. Such is the power of aerodynamic forces
at speeds approaching the speed of sound. Craig has been quoted
in several interviews after the crash that the rear wheels
were beginning to get very light and in fact had began to
lift slightly. Certain questions concerning Mr. Yeager's understanding
outside the realm of aerospace come to bear with some relevance
in the light of these and many other facts regarding the entire
Budweiser Project S.O.S. effort. Again, the author provides
the possible explanation that Mr. Yeager was provided information
which appeared to be correct without personal analysis and
confirmation. He may have been regurgitating information that
he believed was true then.
An interesting item is the nose mounted pitot
tube for measuring the vehicle's air speed. Other than one
minor mention of its data in published reports, this sensor
is left out of the whole picture. The reason for this can
only be guessed at by the author. It may be noted that given
all of the other areas that the team neglected to calculate
for it is quite possible that they did not anticipate the
extreme vibrations that would be transmitted to the pitot
tube from the vehicle's interaction with the bumpy track.
In aircraft applications these devices work predictably and
are quite reliably. On the car, its readings may have been
too erratic to have provided reliable data. Yet the Mach 1
event is an aerodynamic event and this device was the only
instrument on board that could have captured the dramatic
pressure shifts at the nose of the vehicle as they occurred.
Instead the team resorted to accelerometer data to verify
the final speed.
What then is the value of having a celebrity
who provides testimony which should provide approval and validation
of a claim if he is out of his element? One interesting point
that has been made by critics is that, although everyone accepts
that Mr. Yeager was the first man to pilot an airplane in
excess of Mach 1, there is never any mention of what documentation
exists that proves he achieved this great feat. The author
does not doubt the claim that he is the first. He does make
this point to demonstrate how easy it is to claim something
without ever having to provide the evidence or documented
proof, nor require it to become convinced. This does not apply
to Mr. Yeager as it does to all of us who have perpetuated
his incredible story without any evidence other than the Air
Force says he did. Something to think about. It was the Military
who told the world that Mr. Yeager broke the sound barrier
first. I wonder if Mr. Yeager would be able to look at the
Bell X-1 data, perform the apparently complex calculations,
and arrive independently at the conclusion that he broke the
sound barrier? Would Stan Barrett be able to verify the claim
similarly? I do hope the Military was able to solve these
calculations in less than eight hours back then. The author
speculates that Mr. Yeager was quite comfortable in his endorsement
because in essence the Military did the same for him. That
may be the way it gets done in the Military, but here in the
civilian world we rely upon independent verification which
is provided by a sanctioning organization. His argument might
incorporate the idea that nowhere in automotive racing and
sanctioning organizations is there a qualified group capable
of setting up, recording and rendering an accurate finding
of the results because of the extremely technical nature of
supersonic aerodynamics. The Budweiser team paid their people
to perform this vital function, though it appears they may
have overpaid if the results are any measure. Any organization
can hire qualified experts. The issue is impartiality and
accuracy.
The author acknowledges that Mr. Yeager acted
in good faith without any intent to deceive the public. It
is very difficult to imagine anyone endorsing this claim which
rightfully should stand on its own merit without celebrity
endorsement. Any record is exactly that, a matter of record.
It reflects that there is specific qualified evidence that
proves the claim and this evidence is recorded in a format
by regulated officials for the express purpose of proving
that the claim is based on fact and not speculation. Any record
that requires an endorsement by a celebrity is doomed, because
this type of endorsement is in direct opposition the whole
record process.
On a final note, let us again be reminded that
the goal of exceeding Mach 1 on land is in fact an aerodynamic
event, one that is transient in response to subtle changes
in atmospheric conditions. It is not so precise an event that
anyone should expect to easily claim victory while attempting
to do so at a speed so close to its mathematical demarcation
line, as the Budweiser team had tried to do. Any competent
aerodynamicist would have been able to establish a network
of sound recording devices appropriate for the conditions
that would have captured not only the signature of the passing
shockwave, but the velocity as it passed from station to station.
The results would then be easily viewed on an oscilloscope
so that it could be compared to the expected pattern the Budweiser
rocket car would generate, based on wind tunnel evaluations.
Microphones could have been placed above the track by being
suspended on a wire, should there be any ground attenuation
effects which may not have been foreseen.
The Mach 1 event was to be recorded over a
distance of 52.8 feet. At the speed the car is reported to
have achieved, so many critical measurement errors potentially
exist that literally only a slight rise in air temperature
alone could invalidate the claim, in addition to the problems
of using radar over such ridiculous distances.
It has been claimed on the basis of a preliminary
analysis of radar and accelerometer readings that the car
exceeded Mach 1. Yet in a published report on the reported
Supersonic Run, author Ray Van Akin states throughout that
other detailed and exhaustive studies have been performed
on the data and that extensive analysis were required to arrive
at a conclusion. One such conclusion was that "For all intents
and purposes, we have achieved a probability or confidence
level of one that the vehicle exceeded the referenced speed
of sound." If the event should happen very close to the limiting
boundary between subsonic and transonic regimes where no absolute
determination can realistically be made with certainty, it
would be fair to expect that the Mach 1 event should not rely
upon probabilities. The language of probabilities and data
smoothing techniques, confidence testing and so on permeate
the report's text. In an event such as the Mach 1 event, the
reader should understand that it can and does exist outside
of the realm of probabilities and data interpretations. So
fragile is their proof, that after many years of research,
the author is unable to find any evidence whatsoever that
can establish the validity of the Project S.O.S. claim.
It may be quite obvious to Mr. Yeager, and
he may have had no doubts in his mind at the time of his endorsement.
Still, it is a shame that his endorsement did nothing to quiet
the critics. He should have realized that the Mach 1 event
will always require that the documentation be the final endorsement,
not a poorly-written letter by a figure from aviation's pioneering
past. It is also quite obvious to the author, and he has absolutely
no doubt in his mind, that Mr. Yeager knows considerably less
than he should about supersonic aerodynamics and endorsements.
(However, the author really liked him in the movie The Right
Stuff. That was a great cameo scene at Pancho's.)
Finally then, we come to the one piece of evidence
that is for critics, a critical blow to the Project S.O.S.
claim. The speed and all of the previous claims are based
on the accelerometer data. The author has reviewed the strip
chart recording of the actual run and it clearly records several
major spikes in the data, which indicate a very erratic thrust
output. There is a great deal of noise present as well.
All of the accelerometer readings from other
sources in the vehicle have substantial noise, but the Mach
1 claim is built on the forward vehicle acceleration data,
and it is quite a mess. The author and other critics do not
support the Mach 1 claim because the data does not clearly
support such a claim, and this is consistent with the assessment
of Mr. Van Akin, who, in the author's opinion, does not truly
know if Mach 1 was exceeded, though he believes it did.
A final indictment comes from the curious fact
that Mr. Needham has not consistently challenged publications
when articles contrary to the Project S.O.S. claims are printed.
What we do have is a few individuals who have discovered that
editors of various non-automotive publications will gladly
print their letters of rebuttal when the Mach 1 claim is challenged
in the course of other articles on the subject of land speed
record racing. After all this time and energy, their best
defense is now played out in the editorial comments section
by obscure individuals, who without any documentation or proof,
try to convince others to believe as they do purely because
they say the Mach 1 event happened. Sometimes they succeed.
If it were my project, I would not let it be defended in this
way, unless I knew I could not prove my claim and I felt that
these individuals could do a better job than I could. Defending
is not proving.
One final point that must be addressed is the
fact that several
major land speed record programs exist currently, and
it was the stated goal of the Thrust SSC team to exceed Mach
1 for the first time ever. How would a Project S.O.S. supporter
explain how so many millions of dollars could be raised and
many major corporations be enlisted if a definitive answer
on the subject of the Budweiser rocket car were not reached?
Their verdict exceeds opinion by the widest margin: it just
did not happen, period. And by the way, they have bet millions
on it. Would Mr. Yeager be so inclined to gamble with his
own money? It is an interesting idea, their millions versus
his opinion. One man versus many corporations.
The "Budweiser Rocket Car Episode", as it has
come to be known, will be an important chapter in the history
of land speed record racing. It is a terrible shame that the
Budweiser team did not achieve Mach 1, not only for Stan Barrett,
but for everyone that loves the world of speed.
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