The fastest car on earth.
The record for fastest travel on the ground was set by Englishman Richard Noble in 1983. This "land-speed record" currently stands at 633.468 miles per hour (1,019.883 kph). That's about 10 miles (16 km) per minute--faster than most commercial airplanes fly!
Swenson isn't the only driver who dreams of "flying" on the ground. Record-holder Noble is supervising the construction of the Thrust Super-Sonic Car. He hopes to see it beat his record--and maybe even zoom past the speed of sound (about 750 mph or 1,200 kph). And at least three other teams are gearing up for record runs. One standout: Craig Breedlove, who broke the land-speed record five times between 1963 and 1970.
Going fast on the ground is exceedingly difficult. One reason is that when a car moves at high speed, air flowing underneath it creates an upward force, explains Mark Drela, a professor of aeronautics at the Massachusetts Institute of Technology.
To help keep Swenson grounded, the engines in American Eagle One are angled slightly toward the ground, says Keith Zanghi, a technical adviser on the car's team. So the engines not only push the car forward, but also slightly downward. Designers will also add small "wingless" over the car's front wheels and rear end just before the record run. Like the "spoiler" on a sports car, these wingless will force air rushing over the car to push the car down, Zanghi says.
While too much air may be Swenson's biggest problem, too little ground is a close second. Swenson still doesn't know where he'll be able to run his race. Even the longest open stretches of land in America--like Black Rock Desert in Arizona or the Bonneville Salt Flats in Utah--are "only" about 8 to 11 miles (13 to 17 km) long. And Swenson will need to use that distance to start, speed up, slow down, and stop.
Speeding up should be the easy part. American Eagle One has enormous jet engines. These should provide enough forward thrut, (push) to propel the car to 700 miles per hour (1,127 kph) in less than 15 seconds, the car's designers say. However, American Eagle One's stopping mechanism--brakes, plus two small parachutes--are not as efficient at slowing the vehicle, Zanghi says.
"We need about 2 miles [3.2 km] to get up to speed plus about 6 miles [9.6 km] to stop--if everything goes right," Swenson explains. Timing is the key.
The land-speed-record rules say the car's speed must be measured over an entire mile (about 1.6 km). Graham Light of the National Hot Rod Association, one of the organizations certified to time record runs, explains how they clock high-speed attempts:
Officials set up two light beams, one at either end of the middle mile of the course (see diagram, below). Each beam shines across the track and hits a sensor on the other side. When the car breaks through the first beam of light, the sensor starts a clock. The clock stops when the car runs through the second beam.
Officials use the time and a simple formula to calculate the car's velocity (speed in one direction):
velocity = distance/time
For example, let's say American Eagle One takes 5.538 seconds to run the mile. That would mean Swenson's speed would equal 1 mile [divided by] 5.538 seconds--or 0.18 miles per second. That's equal to 650 miles per hour (1,046 kph).
To prove that in the wind didn't help Swenson achieve record speed, he will have to refuel and make another run in the opposite direction within an hour. Officials will then average those two times to determine whether Swenson's name enters the record books.
But Swenson won't be satisfied with just the record. "I want to be the first human to go over 700 miles per hour [1,127 kph] on land," he says.
For competitors Noble and Breedlove even that isn't fast enough. They want to push their cars faster than the speed of sound. If any of the cars do go that fast, there will be no need for fancy timing devices. The spectators will be able to hear a sonic boom when the racers reach their goal.
When a car moves, explains aeronautics professor Drela, it presses against the air and forms compressional waves--alternating areas where air molecules are pushed together and spread apart. At low speeds, the waves race in front of the car. That's why you can usually hear a car coming. But when an object moves faster than the speed of sound, the waves "pile up," behind the car, Drela says.
At first, a car moving faster than the speed of sound seems to zip past spectators silently. But when all those piled-up sound waves arrive--KABOOM! Spectators would hear a thunderous noise--the sonic boom.
The weird thing is a supersonic driver wouldn't be able to hear the noise while moving away from the sound waves at such high speed. Too bad. That tremendous boom just might sound like applause for the fastest driver on Earth.
RELATED ARTICLE: HANDS-ON
What helps a car go fast? Try this race-y experiment!
WHAT YOU NEED:
* a partner * a small plastic take-out sandwich "box" * balloon * scissors * masking tape * meter stick * stopwatch * pencil and data sheet (in Teacher's Edition) * time needed: about 20 minutes
WHAT TO DO:
1. Cut a 1-centimeter hole in the side of the box.
2. Place balloon inside with open end sticking through hole. Tape box closed.
3. Using masking tape, make a "starting line" on the floor. Make a "finish line" exactly 50cm away.
4. Blow up balloon. Holding balloon closed, place "car", on starting line with balloon end facing you. Release balloon at the same time your partner says "go" and starts the stopwatch. Have her stop the watch when the box reaches the finish line. Record time on data sheet.
5. Repeat Step 4 four more times to get an average.
6. Try to make your car go faster by adding a nose, winglets, or wheels. Change one feature at a time, and test its effect on your car's speed with five trial races. Compare the average speeds of the different designs.
Which design changes made the car go faster? slower? Why?
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|Title Annotation:||includes related experiment|
|Date:||Sep 6, 1996|
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