How the North American Eagle Works

Photo courtesy of NASA
F-104 Starfighter in flight.

The North American Eagle is a car, but only in a strictly academic sense. It has wheels, an engine, instrumentation and a place for the driver to sit. That's where the comparisons end, however.

It's closer to the truth to call the North American Eagle a jet on wheels. In fact, the car's chassis is based on the fuselage of an airplane known as the F-104 Starfighter. Introduced by Lockheed Corporation in 1954, the Starfighter was the first operational military jet capable of sustained flight at Mach 2, or twice the speed of sound. It was phased out in 1967 in favor of newer planes, but even today the sleek, streamlined jet looks like it was built for speed. Shadle and Zanghi were clearly interested in the aerodynamic qualities of the Starfighter when they bought the decommissioned plane from a surplus aircraft dealer in Maine for $25,000. To convert it into a car, the North American Eagle team covered the wing roots (the wings had already been removed) and added a suspension system. The team also made modifications to a powerful turbojet engine, the same type that propelled the fighter jet to over twice the speed of sound in the air with wings, which the car uses as its source of power.

As you can imagine, the North American Eagle is not a vehicle someone would drive on the streets. Instead, it belongs to a group of cars known as land speed racers. In official competition, land speed racers must adhere to strict rules and regulations established by the Federation Internationale de L'Automobile (FIA), the main governing body of most types of automobile racing. The FIA recognizes several classes of land speed racers, based on their overall design and source of power, and acknowledges record-holders in each. The North American Eagle competes in the Special Construction class, which itself includes three categories: Unlimited Streamliners, Lakesters and Unlimiteds.

Photo courtesy of The U.S. Air Force/ Photographer Sue Sapp
A turbofan engine being tested at Robins Air Force Base, Georgia, USA.

The Unlimited category was developed specifically for vehicles that rely on jet or rocket propulsion to increase speed. Jet propulsion occurs when fuel is burned in the presence of oxygen from the atmosphere, creating a stream of expanding gases that, when expelled through a nozzle, generates thrust. Rocket propulsion is based on similar principles except the oxygen is transported along with the fuel. The North American Eagle, of course, is a jet-propelled vehicle that takes advantage of a General Electric LM-1500 turbojet engine. We'll talk more about the engine in the next section, but you should know that the LM-1500 can produce, in its fully enhanced form, 52,000 horsepower -- almost 375 times more power than the average Honda Civic.

Used under the Creative Commons Attribution ShareAlike 2.5 License.
The Spirit of America at the Chicago Museum of Science and Industry in Chicago, Illinois.

Although anything goes when it comes to thrust, Unlimiteds must meet other stringent design requirements. For example, they can't use any winged surfaces to control the vehicle and must have a minimum of four wheels. Vehicles with three wheels are not considered cars at all and must compete as motorcycles.

Unlimiteds have consistently stretched the limits of land speed since the FIA established the class in 1964. Cars such as the Green Monster, Spirit of America, Thrust II and Thrust SSC raced through the record books, surpassing the 500 mph milestone, the 600 mph milestone, the 700 mph milestone and, finally, the sound barrier, which is 760 mph at a temperature of 15ºC and sea-level pressure. The goal of the North American Eagle is to beat the current land speed record of 763 mph averaged speed — and to become the fastest car ever to race across the surface of the earth.

Although the North American Eagle is unlike any car you'll see on the interstate, it has many of the major automotive systems you would find on a production vehicle. Let's break the Eagle down and see what makes it move so fast.

Chassis
The North American Eagle chassis, which maintains all of the basic dimensions of the Starfighter fuselage, is 56 feet long, seven feet wide at the nose and nine feet wide at the tail. As you can imagine, transporting such a large vehicle poses quite a challenge. To move it from site to site, the team uses a Volvo diesel tractor pulling a full-sized semi-trailer.

Suspension
As a plane, the Starfighter didn't require a suspension system to help absorb the shocks and bumps that come from driving over a rough surface. As a car, the North American Eagle must be able to navigate imperfections in the road without losing speed or compromising vehicle stability. The car will only run on a dry mud lake bed that is completely free of imperfections for the entire run distance; no roads. This is why the Black Rock desert is a good venue for record attempts. The team solved the problem by using a gas shock system to suspend the front of the car. The rear suspension is based on a rectangular frame, constructed of rectangular steel tubing arranged in a delta, or triangular, configuration towards the rear. This frame is made of mild (or low carbon) steel, which is cheap, strong and easily shaped.

Photo courtesy of the Airplane Flying Handbook
The basic components of a gas turbine engine.

Engine
The turbojet engine that powers the North American Eagle is typical of most commercial and military aircraft. If you read How Gas Turbine Engines Work, you'll see that these engines consist of turbines, a combustion chamber, fuel injectors and a compressor. The compressor sucks air into the combustion chamber, where oxygen is used to burn fuel. As the fuel burns, exhaust gases are directed toward the turbines. One set of turbines directly drives the compressor via a shaft. The other turbines rotate freely and create a high-speed stream of air that is directed through a nozzle. This high-speed stream of air generates thrust based on Newton's third law of motion (for every action, there is an equal and opposite reaction).

The Eagle's LM-1500 engine is the civilian version of the J-79-15 engine used in military aircraft such as the F-4 Phantom. It measures three feet in diameter and weighs 3,840 pounds. The compressor is connected by a single shaft to the turbines and has 17 stages to feed super-oxygen-rich air to the fuel pumped in by the injectors. Both the fuel nozzles and the burn canisters are ceramic-coated, which helps reduce heat and produces 13 percent more power.

At idle, the engine consumes 18 gallons of jet fuel per minute. The team has two different models of the LM-1500; one produces a total of 42,500 horsepower for low speed testing, and a second one has ceramic coatings on the turbine blades and burn canisters, which will produce as much as 52,000 horsepower for high speed record runs.

Wheels
The North American Eagle rides on five wheels -- one in front to steer, two side-by-side on an offset mid-chassis axle and two in the rear. For low-speed runs (under 350 mph), the wheels come equipped with rubber tires. For high-speed runs (up to 800 mph), the standard aircraft wheels are removed and replaced with solid billet aluminum wheels with a titanium band on the outside running surface of the wheel for greater strength and stress retention, machined specifically for use on the Eagle. No tires are used in the high-speed configuration.

© 1996 - 2007 E&D Services, North American Eagle, Inc. All rights reserved.
The parachute deploys to slow the Eagle down on its way to stop.

Braking Systems
Slowing a vehicle down from supersonic speeds requires a phased approach using multiple technologies. Assuming the Eagle is traveling at its target speed of 800 mph, here's how braking works:

• The driver pulls back on the throttle. In doing so, he deploys speed-brake doors located on each side of the fuselage, just forward of the tail section. Hydraulically actuated, these speed brakes were part of the original aircraft design and function in the same way by creating drag to slow the vehicle down. With the speed brakes deployed, the car begins a gradual deceleration.
  
• At about 650 mph, a drogue parachute is deployed to assist the speed brakes. A drogue chute is more elongated and much thinner than a conventional parachute, which means it creates less drag and is less likely to get torn apart. A much larger main chute follows the drogue at about 500 mph, creating even more drag. This slows the car to approximately 125 mph.
• At 500 mph, the driver can activate the magnetic brakes on the rear wheels to scrub off kinetic energy built up in the massive 300 pound wheels, which tend to spin down slower than the car will decelerate. These are state-of-the-art components made of rare earth (neodymium iron boron, or NdFeB) magnets mounted in stainless steel brackets on the rear axle near each wheel. The brackets move close to, but do not touch, an aluminum rotor mounted on the inside of wheel's hub. The resulting magnetic resistance slows the car to 100 mph.
  
• Finally, with the car traveling less than 100 mph, a "Flintstone" break pad (currently in development) just off the cockpit, will hydraulically activate to drag along the ground at speeds below 100 mph.

© 1996 - 2007 E&D Services, North American Eagle, Inc. All rights reserved.
The North American Eagle cockpit

Cockpit
The cockpit of the North American Eagle houses a single driver who is strapped into place by an extra-wide seatbelt with a five-point attachment. Instead of a steering wheel, the driver will find the Starfighter’s original flight stick. A hydraulic system communicates input from the cockpit to the front wheels, allowing the driver to steer the car right or left. A very basic instrument panel, which includes temperature gauges, fuel and oil pressure gauges, air speed indicator and Mach meter, is visible just beyond the flight stick. And a radio enables the driver to communicate with ground crew members and other support personnel who help monitor the condition of the track and other variables that could affect the outcome of the race.

Photo courtesy of the Airplane Flying Handbook
Diagram of shock waves.

One of the biggest challenges the North American Eagle faces is overcoming issues related to traveling at supersonic speeds. At such speeds (i.e., greater than the speed of sound), the car will produce shock waves that can affect the stability of the vehicle and produce a sonic boom. Let's take a quick look at how these shock waves form and how the North American Eagle will compensate for them.

As an object moves through the air, it pushes air molecules out of the way, creating waves of compressed and uncompressed air. These air pressure waves move away from the object in all directions at the speed of sound. As long as the object travels slower than the speed of sound, it will not catch up to the pressure waves. But if the object travels at the speed of sound or faster, it catches up to the pressure waves and begins pushing on them, piling up the waves as they're created. These piled-up waves are called shock waves.

Photo courtesy of the United States Government
Illustration of where the canards are located (in blue).

When the shock waves reach the ground, they can be sensed as a sonic boom. The intensity of the sonic boom is determined by several factors: the distance between the object and the ground, the size and shape of the object, and atmospheric conditions, including air pressure, temperature and winds. Sonic booms have been well-studied in airplanes, but less so in vehicles traveling just a few inches above the ground.

One problem with land speed cars is that the shock waves building up at the nose can create an upward force that lifts the car off the ground. The North American Eagle team has installed canards -- small wing-like projections -- to provide extra stability and control. If you've ever stuck your hand out the window of a car traveling 60 mph, then you have a feel for how canards work. Their angle in the air stream can either create an upward force or a downward force. In the case of the North American Eagle, the system will be controlled independently of the driver by a computer. It will monitor a load sensor on the front axle. The project's testing program will be verifying that the software program on the computer will adequately adjust the canards down slightly to apply just enough, but not too much, down-force to keep the front wheel from leaving the ground and prevent a nose up attitude.

Photo courtesy of the Nevada Commission of Tourism
Black Rock Desert, Nevada

Going for the Record
Of course, having a car that will travel faster than the speed of sound is just part of the problem. You also have to find a place to race it safely -- and to have your results officially measured and recognized as a true world land speed record. In North America, there are only a few places suitable for land speed racing. That's because land speed racers require a long track (as much as 15 miles or more!) of extremely open, flat land. Daytona Beach was used until 1935. Then racers turned their attention to the Bonneville Salt Flats, a stretch of barren salt flats covering about 100 square miles in northwestern Utah. Bonneville was the favorite North American site for land speed racing until 1983. However, the thrust of the jet engine causes the metal wheels to fishtail on the hard salt when accelerating. Also, the distance which now exists is only a total of seven miles due to salt mining over the past several decades, making the track much too short to use. For those reasons Black Rock Desert in Nevada has been used since. Black Rock Desert offers more open space, and, because it used to be the bottom of a lake instead of a saltwater ocean, it causes less corrosion to the cars.

To go for the record, the North American Team will have to transport the car to Nevada and invite officials from the FIA. Then, over the course of several weeks, the team will prepare the vehicle and make a run for the record. An official run consists of two trials, each in opposite directions and averaged. The second run must enter the timed area within 60 minutes after leaving the timed mile area of the first runm to qualify under the existing rules.

The time for each trial is measured along a one-mile stretch called the measured mile. The official time is the average of the two trial times. For example, here is how the Thrust SSC team did it in 1997 when they set the world land speed record:

• First trial: 759 mph
• Second trial: 766 mph
• Average: 763 mph
• Speed of sound on that day, in that location: 748 mph
• Mach speed: 1.02

To break the record set by the Thrust SSC team, the North American Eagle must be at least one percent faster -- or roughly 770 mph (Mach 1.03). So far, the North American Eagle has reached a top speed of only 312 mph, recorded in March 2005, but that was on low-speed aircraft tires rated at 350 mph. With aluminum wheels and afterburners kicking in, the team expects that the car could reach 800 mph.

Photo courtesy of Mary Frances Howard
Steve Fossett

The Race to the Race
The North American Eagle's official run for the world land speed record will have to wait as the team raises more money and finishes tweaking the design of the car. In the meantime, one or two other teams are working on cars that might challenge the record. One such competitor is Steve Fossett; the record-setting millionaire who recently purchased Craig Breedlove's Spirit of America and is modifying the vehicle for an October 2007 record attempt. At a 2006 press conference, Fossett told reporters that he believes his modified Spirit of America can reach speeds of 800 mph.

The North American Eagle, of course, hopes to be first -- and faster. This goes to prove that in land speed racing, the race to the starting line is just as crucial as the race to the finish.