Breaking the Sound Barrier on Land - and What it Took To Do it
The aerodynamic stability of a jet-engined Land Speed Record car is directly proportional to its "plume", the long column of fire and heated air exiting its tail as it streaks across the desert. By design, the air flowing over the car's surface is fooled into thinking the plume is an extension of the body. Like an arrow with its heavy center of gravity close to the nose and its center of pressure aft near the almost weightless "feathers" of heat, the already long wheelbase is effectively extended, leading to an ideal balance of power, weight and stability.
With this invisible extra length, the car is relatively easy to drive under full power at speeds up to 500 mph. however, serious control problems arise as the car approaches the trans-sonic region near 600, and at the end of the run when the throttle is cut.
At that point, several alarming and dangerous phenomena occur simultaneously. The instant the plume disappears, the car's stabilizing center of pressure leaps forward, moving much closer to its center of gravity. At the same time, the air which had been flowing smoothly into the engine's carefully designed intakes suddenly has no place to go. It dams up and tumbles uncontrolled down the body, increasing the frontal area while reducing the effectiveness of any aero aids protruding from the body to impart a measure of stability. And inside the fuselage, the huge spinning mass of the turbine slows rapidly, markedly altering the torque effect acting on the chassis and pitching the car to one side.
That's just for starters. If the machine has gone supersonic, it gets even worse.
Making it Official
Because of a jet's constant acceleration, record speeds are largely determined by the distance the car travels before entering the speed trap-like a slingshot, the force of the projectile depends on how far back the elastic is pulled. And, since an official LSR record is the average of two runs made in opposite directions within the FIAs onehour time limit, the course is essentially the same on both ends. Early test runs usually start fewer than two miles from the traps; as confidence builds, both the distance and speeds increase.
Before the advent of jet cars and electronic data acquisition, trying to determine just where friction, drag, and tire slip (on a wheel-driven car) would begin affecting the speed was pure trial and error. Now, budget permitting, every influencing factor can be plotted and analyzed right after-or even during-a run, and corrections can be taken quickly through the active-suspension settings and aero devices.
Still, events occur so rapidly in an LSR car approaching the speed of sound that each potentially dangerous situation must be predicted in advance. The compounding speed of events makes it impossible for the driver to react on the fly, so every possible pitfall must be anticipated before it happens.
The trouble is, before Englishman Andy Green began assaulting the sound barrier in Richard Noble's Thrust SSC (Super Sonic Car), no one knew what to plan for. The interactions between aerodynamics, shockwaves, and ground speed were simply too complex and theoretical to be known with any certainty. No rolling-road wind tunnel exists that can model the speeds of an LSR run, and even the best supercomputer and CFD (computational fluid dynamics) software are no more accurate than the assumptions entered in. The only way to know for sure is to build a car and run it very carefully; even then, it's hard to be positive that the causes of those data are fully understood.
Now that Thrust has broken the sound barrier, a few of the unknown questions have been answered. Thrust aerodynamicist Ron Ayers and his team proved that trans-sonic airflow is essentially predictable, provided that test speeds rise in small increments and careful records are kept. Still, much of what they learned applies only to Thrust, a decidedly unusual design. What will happen to other record cars-most notably Craig Breedlove's Spirit of America-as they approach the trans-sonic region remains unknown. The only thing that gives Breedlove the confidence to climb into the cockpit is what he thinks will occur.
Indeed, it may be that the emotional issues involved in the LSR are even more dauntinthan the technical ones. Since seat time at 500+ is acquired in precious multisecond increments, most drivers must fire up their untested missiles with less total seat time than it takes to do a single lap of most racing circuits. Since the engine often has only two settings (off and on), and the steering's only true function is corrective (less than 5' at full lock), and even the best predictions of trans-sonic behavior are only theoretical, the real skill in driving a record car may be understanding what it might do and still having enough courage to fire the engine.
Long Time Coming
Public interest in the LSR seems to run in long cycles, so there are usually large gaps between serious attempts. During these periods, advances in technology, instrumentation, and data acquisition may completely change the accepted notion of how an LSR car should be designed. Thrust SSC is a completely unconventional machine compared to previous record holders. It's a perfect example of the new, scientific, aerospace approach to record-car design.
In 1997, Noble's own LSR of 633 mph had stood for over 14 years, and it had been 32 years since two LSR teams met on the same spot to challenge each other for the record. This made the current round of racing a major media event. This time, Californian Craig Breedlove-who battled Art Arfons' Green Monster in the last heads-up duel, at Bonneville '65-would face Englishman Richard Noble at the desolate but beautiful Black Rock Desert in northwestern Nevada.
To some observers, it seemed a lopsided duel. Noble, his driver Andy Green, and their team of some 40 RAF volunteers arrived at Reno's International Airport in the world's second-largest airplane, a Russian Antanov 124 heavy-lift Volga Dnieper containing what appeared to be a significant slice of the British aerospace industry. In addition to the imposing, professionally-designed Thrust, the team brought 100 tons of support equipment including food, housing, computers, machine tools, and telemetry gear. In addition to the two standard 202 engines, they brought two uprated Rolls-Royce Spey 205 engines, just in case, Nobel revealed, the standard 55,000-horse Spey 202s already fit to the car "didn't meet the design team's expectations." It took six hours just to unload the spares.
Compared to the Spirit's small, finely polished, but essentially amateur effort, it looked like the Brits had staged a full military assault on a group of relaxed California hotrodders. But Breedlove-the first racer to break 400, 500, and 600 mph in 40+ years of LSR experience-remained unflappable. When Noble's huge, black, 10ton Thrust rumbled through tiny Gerlach, Nevada atop its even larger transporter on the way out to Black Rock, Craig watched from his tiny HQ. "Man," he said with a laugh, "if that thing's as fast as it is ugly, we're in real trouble!".
It wasn't so much a disparaging remark as a cogent reflection on a difference in philosophies. Breedlove's lithe, white Spirit was tiny by comparison. Craig had personally penned almost every line of its 44-foot body himself-an artistic distillation of decades of experience. Noble's twin-engined juggernaut was a I 10,000-horsepower sledgehammer with which to crush the sound barrier; the slim, almost delicate Spirit was an arrow designed to pierce it.
An unrivaled aesthetic beauty, Spirit of America took a minimalist's approach to speed. Every unneeded piece of its ex-military jet engine had been removed, including the variable-nozzle exhaust that would have allowed Craig to modulate its power. "Once the afterburner kicks in," he explained with a laconic smile, "it won't matter; I only need full power for the record." Similarly pragmatic was Craig's decision to run simple unleaded gasoline supplied by prime sponsor Shell in place of aviation jet fuel. "We'll be up there several weeks-there's no point in having two fuel trucks." Down to the smallest detail, Breedlove relied on experience, simplicity, common sense, and the hotrodder's instinct for speed.
Noble's approach was diametrically opposed. With few exceptions, his eclectic team of designers, engineers, pilots, and electronics wizards had little previous experience with fast cars.
Noble Intentions
The Englishman knew just how difficult the sound barrier would be from piloting his own single-engined Thrust II to the existing LSR of 633 mph in 1983. Later, he quickly learned just how hard it would be to interest sponsors in this new project-a concept perceived to be so fraught with danger that most potential patrons could only envision a fiery, well-publicized, 600mph crash with their name emblazoned on the careening parts.
But Noble wasn't a man who quit lightly. In a chance meeting with Ron Ayers at the home of Ken Norris (designer of Donald Campbell's Bluebird record car) he finally found the person who could analytically determine if his dream was feasible. Ayers, a retired senior aerodynamicist with Bristol Aircraft, had designed the famous Bloodhound, an English air-to-air tactical missile. The 70-year-old engineer explained that he'd never done any subsonic research other than a little basic study of some early LSR cars, but he was intrigued and challenged by Noble's vision of breaking the sound barrier on land.
When they met again later, Ayers told Noble that he wanted to work on the project. Over dinner, Ayers went on to outline a program of pure mathematical research that might determine the ideal LSR shape. This, he explained, would have to be further proved with a three-dimensional test phase to confirm mathematical theories. It would take months of laborious calculations, explained Ayers, but he had the time and desire-provided the funds could be arranged for some very expensive supercomputer time. Noble went on to raise these with a rousing, visionary speech in Palm Springs to the sales directors of Castrol Oil.
With funding thus secured for Phase One, Ayers launched a CFD program on Cray 92 supercomputers to determine how air would perform over different shapes at high speed-and, even more importantly, what might be expected below these shapes at the speed of sound. That, both men knew, was the main question at hand.
While the concept of an unbreakable "sound barrier" seems quaint today, to the pilots and builders of early aircraft attempting to exceed it, the shockwaves generated at this speed had proved lethally real. There was every reason to expect they'd be deadlier still on terra firma, where the trans-sonic missile would travel through heavier air and had no luxury to pitch, roll, or vibrate. Additionally, while the flat, cone-shaped shockwave off the nose of a jet fighter can dissipate into the atmosphere with no more damage than the sound of its passing, the same shockwave off a landbound craft would inevitably rebound off the ground and bounce back onto the surface which had caused it. The exact forces and reflective actions were largely unknown: Would they be enough to knock the car out of control? No one could say.
As already described, Ayers planned to study the problem on two fronts: mathematically (with computers and CFD) and practically, with a 1:25-scale model driven at high speed with tiny rockets. To assist with this second task, Ayers recommended an enthusiastic Scotsman named Martyn Davidson. A ballistics expert at the Pendine Labs in Wales-England's equivalent to America's Aberdeen Proving Grounds Davidson had access to a 1000-meter test rail complete with a 45,000 frame/second camera and Kirilian imaging (a technology usually used to study the effect of shockwaves on artillery projectiles).
Slowly, the three men devised a plan for a vehicle that might be capable of diverting and controlling the shockwaves of Mach 1. After two years of comparative analysis, Ayers was certain that Davidson's model tests had corroborated his mathematical data enough to start laying plans for a car.
Singles Only
Ayers began his studies by examining single-engined layouts,. Every successful LSR jet to date-Arfons' Green Monster, Breedlove's various Spirit designs, Gary Gabelich's Blue Flame, and even Noble's own Thrust II - had used this approach, but Ayers came to believe that all had missed their full potential. One of the main reasons was that the accepted single-engine layouts required an increase in frontal area, either by putting the driver next to the engine (as Arfons and Noble had done) or on top, as in Breedlove's first Spirit.
The only other option was locating the driver ahead of the engine, as in the current Spirit of America. But the driver-first layout requires extremely sophisticated air intakes and compromises driver safety, two things that Noble and Ayers were unwilling to accept. So even though Ayers determined that a single-engined LSR could carry enough power to break the existing record, he proposed using two engines instead. In this form, his CFD calculations indicated a thrust-to-frontal area ratio improvement of some 30 percent!
Additionally, a twin-engined layout promised other, less obvious advantages. The wheelbase could be substantially longer than that of a single-engined design, for additional directional and pitch stability. It enabled the designers to put a higher percentage of the total vehicle weight on the front wheels. And by drawing a thin section of fuselage rearward from the space between the engines, Ayers believed he could create an ideal shape for controlling the airflow aft of the jet exhaust. This extended structure could also be used to mount a high tailplane far in the rear for good directional stability and pitch control.
What the layout couldn't provide, Ayers realized, was a simple steering mechanism. Trying to put the front wheels in the same area as the jet intakes was impossible without increasing the front track, which would in turn increase the frontal area. The logical alternative was rear-wheel steering-something that was traditionally regarded as hopelessly unstable.
Noble initially balked at the idea of RWS, but he trusted Ayers' instincts enough to repress these preconceived notions and commit to the concept. Noble called Glynne Bowsher, the design engineer who'd developed the brakes on Thrust 11. Bowsher accepted the challenge and ultimately formulated a plan for a staggered, narrow-track rear suspension whose wheels turned in slightly different arcs.
While the naysayers derided Glynne's "forklift" steering concept, Bowsher went ahead and constructed a full-sized working model and mounted it to the back of a Morris Mini sedan at the University of Leeds. It worked-so well, in fact, that the modified Mini wound up driving around campus and proving grounds for hours with a variety of grinning drivers at the wheel.
Ayers, meanwhile, progressed with his calculations to thwart the shockwaves that would occur under and around the various leading edges of Thrust SSC. At the same time, Noble located another vital new team member named Jeremy Bliss, a computer expert from Lotus Engineering who'd handle the car's complex electro-hydraulic active suspension.
Tests had proven Thrust's underbody would create tremendous downforce at subsonic speeds, but approaching the trans-sonic region two other phenomena would occur. First the downforce would move rearward, unloading the nose wheels; second, pressure waves off the front wheels and nose would create almost uncontrollable turbulence beneath the car. Ayers calculated that with Thrust's huge surface areas, even a tenth of a degree of nose-angle change at 600 mph could raise or lower the weight on the front wheels by more than two tons! If the car's attitude couldn't be adjusted quickly enough to compensate, it might bury its nose in the dirt or, worse still, launch into flight.
The now four-man design team determined that Thrust's pivot point for its angle of incidence should rotate around the front wheels. That way, by raising the rear ride height by some four inches as speeds reached the critical range, the car might be kept perfectly attuned to the ground.
Bliss's solution was a three-stage electro-hydraulic damper at each rear wheel. The lowest stage was a passive unit with two inches of travel to absorb minor imperfections in ride height as the car rolled across the desert floor. The active portion of the strut stack sat on top: A computercontrolled ram could raise or lower the chassis virtually instantaneously to keep the car trimmed to the correct angle. In between these two stages, an emergencyabort cylinder that would automatically raise the rear another four inches was used to kill any lift if the electronic suspension monitors detected excessive positive pitch. At the same time, the abort system would automatically kill the engines and fire the braking parachutes. Rough adjustment of the ride height would be made by manually adjusting the angle of incidence of the high-mounted rear tailplane.
Actual construction of Thrust SSC was assigned to G-Force, the race-car engineering firm best known in America for its IRL Indy cars. Some 35,000 man-hours were originally budgeted for the job, but in the end that swelled to over I 10,000-not including the uncounted hours donated by more than 230 partner companies culled from the British aerospace industry.
The American Way
Breedlove did things quite differently. The Spirit was built in his own workshop using the same materials and methods found in racecars and private planes. While some very sophisticated engineering was incorporated into the design-the complex intakes were created under the direction of Wait Sheehan, the aeronautical genius who designed the intakes for F104 Starfighter -in principle Spirit was a fiberglass-and-aluminum cigar designed to carry a driver, some fuel, a highly tweaked engine, and just enough aerodynamic skulduggery to keep everything on the ground.
In September 1997, Breedlove's first test runs at Black Rock were supposed to determine if the changes made over the winter were effective. Spirit of America had crashed the previous year and several significant mods had been performed during the rebuild, including a larger rear dorsal fin for greater directional stability and a relocation of the parachutes from the bottom of the chassis to the top-so they wouldn't yank the rear wheels off the ground at 600+! Almost everything, including the all-important PI data acquisition system on Spirit was new, so some sort of baseline was required before any serious record attempt could begin.
Craig's speeds were progressing smoothly until September 8th when a metallic object was sucked into the engine at 328 mph, causing catastrophic failure of the turbine blades. Noble had brought two spare Rolls-Royce turbofans and a complete cache of spares; Breedlove had only a military - salvage "junk motor" under a tarp back at his shop. He had no option but to load the car into its transporter and go home.
Back in Rio Vista, the Americans quickly set about rebuilding the surplus engine. Whatever funds the team had allocated for the record were now diverted into rebuilding the backup powerplant, and if not for a lastminute infusion from sponsors Shell Oil and Autozone, Breedlove wouldn't have had enough money to return to the desert. Thousands of dollars also came through spontaneous fan donations.
The team's low-buck rebuild didn't permit a run-up on a certified test stand, which would have provided exact power, thrust, and fuel-feed readings. Instead the crew installed the engine in the car, chained Spirit down in a run-up bay at the local airport, and spun the engine up to maximum rpm, pronouncing it a "screamer" before heading to Black Rock. No one trusted the chains enough to light the afterburner, so the final tests and adjustments would have to be done on the desert.
The British team started their own tests in Breedlove's absence. In spite of some 50 previous test runs on the Al Jafr desert in Jordan, Thrust's first few passes were plagued with minor computer malfunctions, and it took four days and before the test data had been sufficiently analyzed and reconformed to prevent an automatic shutdown. On September 20th, Green's first high-speed pass of 533 mph confirmed Noble's decision to return to Nevada. The surface proved so smooth and soft that the suspension and shocks could carry nearly-ideal settings.
On returning, Breedlove's first tests went no better than Noble's. Insufficient fuel flow to the "new" engine found Spirit unable to exceed 400 mph. Breedlove ordered a new fuel pump and waited.
Two days later Thrust SSC made runs of 618 and 653, only missing the official record because the turnaround wasn't made within the FIA's one-hour window. The next day Green saw 693 and 719, but again missed the mandatory turnaround time. During these tests, it was discovered that the long flame from Thrust's twin engines was burning away the hawsers of the parachutes, causing the car to overrun its predetermined stopping point. Two days were required to build protective fire shields and re-prepare the car for an official attempt on the record.
History Is Made
On September 25th, under skies still overcast from a light morning rain, which delayed the run two hours, Green arrowed silently across the Black Rock at just over 700 mph.
A couple of seconds past the timing stand, a loud thud and a deafening wash of jet-exhaust noise confirmed the first breaking of the sound barrier on land. The visual evidence was even more exciting; preceding the car's huge roostertail as it raced into the miraged mirror surface of the desert was a 300-foot-wide, six-inch-high dust cloud! At sub-sonic speeds, Thrust's distinctive fourline wheel tracks were pressed about an inch into the lakebed; where the car went supersonic, the soil between its front wheels had been pulverized to a fine powder.
Downrange, the boom had been even more distinct. Andy's turnaround crew greeted him in jubilation as the car rolled to a stop. They didn't have to wait for USAC's confirmation-they had clearly heard the sound barrier being broken. The car was quickly turned around, and Green made the return pass at 728, for a 714-mph average, the first car to officially exceed 700 mph.
The car was fast enough, but the turnaround still wasn't. Noble's dream of a supersonic car had finally been realized, but Thrust SSC couldn't make it official.
The Final Showdown
Now, success was denied by nature, the weather closing in and preventing any more attempts for almost three agonizing weeks. When it dried out on October 12, Breedlove, with a new fuel pump installed, ran 517 and 530 but due to unfamiliarity with the new engine, was unable to light the afterburner. Nevertheless, the American's spirit was high. With only 50 percent of their power and just 1.5 miles of runup, they comfortably exceeded 500 mph. In concept, at least, Spirit of America had just proven itself-by every conceivable calculation, it had more than enough power to break 750.
On October 13, Thrust broke the sound barrier twice, now from more than five miles back-but once more it couldn't make the return trip in time to be official. Still, the barrier had been broken and the concern surrounding this "barrier" evaporated. Noble announced that the team would take a day off to prepare the Thrust for another official attempt on Thursday.
In the euphoria of the moment, most of the world's press decamped to Reno to file their stories-and consequently missed Wednesday's activities on the desert, where Breedlove's team had finally found the key to adjust Spirit's afterburner.
On the third run of the day and starting just two miles from the traps, Craig lit the afterburner with a resounding crack a hundred yards off the line and disappeared toward the clocks so quickly that the jubilant crew could hardly believe their eyes. Finally, it was all falling into place.
When the team reached Craig at the other end of the course, he was already out of the car smiling. "Man," he told them jubilantly, "that thing came on so strong I could hardly breathe!"
"Yeah..." replied a member of the engine crew. "And that was only the first stage." The afterburner had three more stages, each representing a 25 percent increase in power. Spirit of America's fifth and last test of the day clocked 636 mph-just a few mph short of the standing world record.
The next morning, Thursday October 16, Noble's team rolled out for what would prove their final assault on the record. Making two passes within the necessary hour, Green averaged 763.053 mph, reaching Mach 1.02 and sending sonic booms rattling off the mountains surrounding the Black Rock Desert.
Afterward, RAF pilot Andy Green formally announced that his team had met its goal. "We're finished here. The car has broken the sound barrier, and we're going home." It was an incredible achievement.
Breedlove, though disappointed in not being first to 700 mph or the sound barrier, was decidedly upbeat. "I honestly didn't think they could do it," he said, "but they have and I congratulate them." Then he narrowed his eyes in the classic racer's glare. "But it ain't over!" The previous day's 636 mph runs had given the Americans the psychological boost they needed to continue.
Ron Ayers, for his part, seemed happy to leave them to it. "We failed to reach 850 mph, which was my goal, and I know that even if we switched engines we still couldn't run that speed. The car is totally maxed out; the transonic drag is above our calculations, like hitting an invisible wall. Still, I'm delighted with what we have done." To break the record, Thrust had to back an additional half-mile past its predicted starting point and required full throttle all the way. The car's stability was taxed, and Green had needed full lock correction to keep the car on course, his tracks in the desert running almost 100 feet wide of their intended path. Once through the sound barrier Thrust ran true again, but then it became difficult to handle as it slowed on the opposite end of the course.
Breedlove plans to refine Spirit's throttle control for next year, separating the afterburner control from the normal throttle settings to preserve the plume during shutdown, making the car easier to control.
Ever the can-do optimist, the most experienced LSR driver on the planet seemed both respectful of his rivals and unfazed by their approach. "The Brits did a great job," Craig said as he loaded Spirit's transporter, "but they left a lot on the table." Over the winter, Breedlove plans to fit new wheels to Spirit. These will be rated past 900 mph.
Because of a jet's constant acceleration, record speeds are largely determined by the distance the car travels before entering the speed trap-like a slingshot, the force of the projectile depends on how far back the elastic is pulled. And, since an official LSR record is the average of two runs made in opposite directions within the FIAs onehour time limit, the course is essentially the same on both ends. Early test runs usually start fewer than two miles from the traps; as confidence builds, both the distance and speeds increase. 
Now that Thrust has broken the sound barrier, a few of the unknown questions have been answered. Thrust aerodynamicist Ron Ayers and his team proved that trans-sonic airflow is essentially predictable, provided that test speeds rise in small increments and careful records are kept. Still, much of what they learned applies only to Thrust, a decidedly unusual design. What will happen to other record cars-most notably Craig Breedlove's Spirit of America-as they approach the trans-sonic region remains unknown. The only thing that gives Breedlove the confidence to climb into the cockpit is what he thinks will occur. 
To some observers, it seemed a lopsided duel. Noble, his driver Andy Green, and their team of some 40 RAF volunteers arrived at Reno's International Airport in the world's second-largest airplane, a Russian Antanov 124 heavy-lift Volga Dnieper containing what appeared to be a significant slice of the British aerospace industry. In addition to the imposing, professionally-designed Thrust, the team brought 100 tons of support equipment including food, housing, computers, machine tools, and telemetry gear. In addition to the two standard 202 engines, they brought two uprated Rolls-Royce Spey 205 engines, just in case, Nobel revealed, the standard 55,000-horse Spey 202s already fit to the car "didn't meet the design team's expectations." It took six hours just to unload the spares. 
Noble's approach was diametrically opposed. With few exceptions, his eclectic team of designers, engineers, pilots, and electronics wizards had little previous experience with fast cars.
As already described, Ayers planned to study the problem on two fronts: mathematically (with computers and CFD) and practically, with a 1:25-scale model driven at high speed with tiny rockets. To assist with this second task, Ayers recommended an enthusiastic Scotsman named Martyn Davidson. A ballistics expert at the Pendine Labs in Wales-England's equivalent to America's Aberdeen Proving Grounds Davidson had access to a 1000-meter test rail complete with a 45,000 frame/second camera and Kirilian imaging (a technology usually used to study the effect of shockwaves on artillery projectiles). 
Additionally, a twin-engined layout promised other, less obvious advantages. The wheelbase could be substantially longer than that of a single-engined design, for additional directional and pitch stability. It enabled the designers to put a higher percentage of the total vehicle weight on the front wheels. And by drawing a thin section of fuselage rearward from the space between the engines, Ayers believed he could create an ideal shape for controlling the airflow aft of the jet exhaust. This extended structure could also be used to mount a high tailplane far in the rear for good directional stability and pitch control. 
Tests had proven Thrust's underbody would create tremendous downforce at subsonic speeds, but approaching the trans-sonic region two other phenomena would occur. First the downforce would move rearward, unloading the nose wheels; second, pressure waves off the front wheels and nose would create almost uncontrollable turbulence beneath the car. Ayers calculated that with Thrust's huge surface areas, even a tenth of a degree of nose-angle change at 600 mph could raise or lower the weight on the front wheels by more than two tons! If the car's attitude couldn't be adjusted quickly enough to compensate, it might bury its nose in the dirt or, worse still, launch into flight. 
Actual construction of Thrust SSC was assigned to G-Force, the race-car engineering firm best known in America for its IRL Indy cars. Some 35,000 man-hours were originally budgeted for the job, but in the end that swelled to over I 10,000-not including the uncounted hours donated by more than 230 partner companies culled from the British aerospace industry.
Now, success was denied by nature, the weather closing in and preventing any more attempts for almost three agonizing weeks. When it dried out on October 12, Breedlove, with a new fuel pump installed, ran 517 and 530 but due to unfamiliarity with the new engine, was unable to light the afterburner. Nevertheless, the American's spirit was high. With only 50 percent of their power and just 1.5 miles of runup, they comfortably exceeded 500 mph. In concept, at least, Spirit of America had just proven itself-by every conceivable calculation, it had more than enough power to break 750.