A projectile on batteries / Gregory Moon

A group of students plans to break speed records using an electric vehicle

As he walked into a math class during his freshman year at Ohio State University, R.J. Cromer's eye caught an ad calling for students to join a team planning to build a car powered by fuel cells. He had never built anything more complex than Lego robotics kits, and yet he emailed the group and asked to join. To his surprise, the students managing the team responded immediately. "I thought there would be all kinds of demands," Cromer recalled, "but they said, 'No, just come and that's it.'"

Cromer therefore turned to the team's workspace, the Center for Automotive Research (CAR), and discovered that his friends were the ones who built the "Ohio Bullets,"* a series of cars powered by alternative fuel and breaking world speed records. He soon realized that this unique group of baby-faced engineers planned to test his devotion to purpose first and foremost. Cromer started his work in the equivalent position, in the world of engineers, to an errand boy. For several months he mainly swept the workshop and arranged various devices and spare parts. However, between one maintenance job and another, the older members of the team, who are in their last year of study, began to teach him about wiring, control systems, and more. Soon he was learning more in the workshop than he was in the classroom. The following year, two team members graduated, and Cromer was put in charge of electrical engineering. "It turns out that if you're willing to stop sleeping, you can get down to business pretty quickly," he says.

The Ohio Rockets team is full of similar stories. The head of the team, David Cook, joined by chance when he was in his first year. Senior engineer Ivan Miley joined when he was an innocent high school student who loved fast cars. Cook says that when the team evaluates the suitability of new volunteers, they are not specifically looking for the people who scored the highest on IQ tests, but those who are willing to work hard. Cromer's voluntary insomnia is the band's hallmark. Bullet engineers often watch the rising light of dawn creeping under the ten-foot-tall garage door slits at the end of their workshop. They sleep on the floor of lecture halls, and occasionally on test tracks. They scorn the beer-drenched weekends of the average student in favor of cutting metal, examining batteries and designing dedicated suspension systems.

These are not suspension systems for light go-kart style racing cars. This group has created some of the fastest alternative fuel powered vehicles in history. The right-handed fuel cell car that caught Cromer's attention reached an average top speed of 460 km/h in 2008. Two years later, the team built a revamped model of it, turning it into a battery-powered race car that crossed the 300 mph (482 km/h) line. Now the team says that in September 2013, in the Bonneville Salt Flats outside the Utah town of Wendover, its new vehicle will be the first electric race car to break the 400 mph (643 km/h) barrier.

No more than nine gasoline-powered wheeled cars managed to reach such a high speed. "The jump from 300 to 400 is huge," says Cook. As the car approaches 400 miles per hour, the aerodynamic drag force increases by an engineering column. The motors require more current, and this means more batteries, and in any case - additional weight for vehicles that should be as light as possible. Finally, the tires will spin so fast that the centrifugal forces threaten to tear them apart. These massive challenges can also tire the hands of a team of seasoned engineers, not to mention a bunch of research students and a few other guys studying for an undergraduate degree.

Fast planning

In 1993, Giorgio Rizzoni, now director of the CAR Center, assembled the first student team to compete in a short-lived college battery car racing series. The team's vehicle, the Smokin' Buckeye, won most of the races it participated in, but after a few years the race series was canceled, and Ritsoni assumed that would also be the end of the project. However, two of his students informed him that they had signed a sponsorship deal with a local company. They wanted to build the fastest electric car in history. "I looked at the students and said, 'You are completely out of your mind,'" Ritsoni recalled.

In the ten years that followed, the team built three world record-breaking vehicles. Now Ritzoni hardly doubts the high goals that the team members set for themselves, or their skills in engineering or signing deals. When Cook and the team decided they wanted to break the 400 mph barrier, they knew they had to deviate sharply from conventional funding channels. So they turned to Gildo Planca Pastor, the 45-year-old owner of Venturi Automobiles, an electric vehicle manufacturer based in Monaco. Pasteur, formerly an amateur racing driver, who headed a real estate powerhouse in Monaco and was also a restaurateur, had already started following the team a few years before. In 2010 he signed a sponsorship deal in which he pledged to provide financial support for the race to reach 400 miles per hour.

Two years later, on a humid Wednesday morning in August 2012, in CAR's headquarters, a two-story brick building with a brick facade in front and several cave-like hangars in the back, the bearded 26-year-old Cook explains that the overall design of the car is almost complete. . The length of the "Ohio-Venturi 3" (VBB3) will be 11.5 meters, and it will have a dual propulsion system (4×4). The power needed to accelerate the car to a speed of 400 miles per hour would be greater than the power of a single engine, so the team plans to divide the task between four engines. Each engine will produce 400 horsepower, and a total of 1,600.

Cook and several other people have been working for some time in collaboration with Venturi engineers on the design of a dedicated engine. The bullet's engineers established an outline for its ideal dimensions, its performance specialties and other details, and for a year now they have been passing the design to Venturi's team for inclusion, receiving it again and again, God forbid. Pastor has already begun conducting field tests for a scaled-down version of the bullet motor in the Venturi America electric sports car, whose top speed is 124 miles per hour (200 km/h). The four projectile engines will be slightly longer and more powerful, but their construction will be completed only a few weeks later.

However, at this stage the engines are not the main concern. All the VBB3 team members, the research students, the younger students as well as Cook, Miley and a prickly 23-year-old engineer named Ling Wang Shu share one small office at CAR. As Miley and Cook get in, Wang is turning a 300D computer model of the car's vertical tail fin from side to side on his computer monitor. Wang is the aerodynamics expert, and arguably aerodynamics is the biggest challenge in the jump from 400 to XNUMX mph. The power required to overcome the aerodynamic drag increases in direct proportion to the desired speed to the power of three. Thus, if you want to double your speed, you will need about eight times more power.

Kerry Burke, a former crew member who had just left for a job at Boeing, spent two years refining and fine-tuning the VBB3's aerodynamic shell, changing its shape and adding drag-reducing features, such as spoilers that cover the wheels. The projectile will have a steel chassis and a carbon fiber shell, with a strong but lightweight core made partly of Nomex, a fireproof fiber. But some big questions remain open. Today, Wang focuses on the tail fin.

Anything sticking out of the car adds drag, but the team has to add a tail to keep the test driver, a 62-year-old racing driver named Roger Schroer, safe. It is possible to reduce all the aerodynamic forces acting on vehicles to a single point, known as the center of pressure. With this point close to the rear of the vehicle and its center of mass closer to the front, the two points balance each other and allow the vehicle to continue traveling in a straight line even when there is a crosswind. The VBB3 will have a pair of parachutes, and a set of back-up jet brakes, but neither will help the roar if the car goes into a spin. "Ultimately," says Cook, "Roger's life is the most important thing."

The question is how to find the balance between aerodynamics and safety. With a few quick mouse clicks, Wang disassembles the tail and rotates it in virtual XNUMXD space. It changes a flat part that ends in a point and turns it into something that resembles the tip of a dolphin's tail: a flipper that is balanced on top of another flipper, perpendicular. Miley explains that the team is trying to figure out a way to add a GPS unit and two cameras, one facing the front and the other looking back, to capture data during the run. Wang added the horizontal fin to accommodate all three, then sent his revised version to Burke at Boeing.

The new addition, Wang reports to his friends, has just been "discovered". It's the verb the team came up with to describe a situation where Burke rejects a change because it would add too much drag. "He tells us, 'If you're going to make the car go slow, then don't do it,'" explains Cook.

Wang, slightly angry, clarifies: "I knew it was going to slow her down," he says, "but how slow?"

Wang returns to the model, and Cook approaches another challenge, the batteries. Earlier in the day he proudly displayed CAR's battery test cells. Inside these cells, a computer runs dedicated programs that repeatedly drain and recharge battery cells, while constantly changing the environmental conditions. This process provides CAR engineers with a clearer idea of ​​the battery's true performance, which does not always coincide with its published technical specifications. Over the past year, Cook and the group have been closely examining a prototype lithium iron phosphate battery, known as a "nanophosphate" from the maker of a now-defunct company, A123 Systems. On race day, the projectile will have to complete at least two runs to win an official world record, and at the end of each 60-second jump, Cook notes, the batteries must be completely empty. "We want all the energy to come out of the battery in one run," he says. "If there is some energy left in it, it means we carried an excess weight of batteries."

The A123 batteries, which were designed in part by two former projectile team members who worked for the company, not only hold more charge than any other product on the market, but they also do so in a slimmer package. Cook explains that the standard cylindrical cells, like the ones used in their latest race car, take up too much space. The round cross-section leaves gaps when the batteries are pressed together. The added space translates into a larger overall volume and a bigger car anyway. This means a thicker aerodynamic profile, and ultimately, less speed.

Cook takes down from a shelf next to his desk a black box that resembles a car battery, and together with it a square, silver, flat and thin package, which could be mistaken for an ice box from a cooler. These batteries, with the flexible casing (pouch cell), produce more current in a smaller volume. Each of these black units will contain 25 flexible cells, packed side by side without gaps, and the savings compared to cylindrical batteries will be enormous. The total number of units that will be there will be 80. "You cut a third of the weight and volume," says Cook. "This is above and beyond the best you can find."

The packaging challenge is not limited to batteries alone. The vehicle design process is, to a large extent, about trying to cram as much as possible into as narrow a space as possible. In front of Cook's computer station, for example, you can see a virtual version of the suspension system on Miley's monitor. Record-breaking race cars often forego suspension to save weight. However, since the driver would only have one mile to accelerate the vehicles, Miley and the team decided that they would need road grip for every inch of that mile. Any bump on the surface of the salt desert that would cause the wheels to spin freely, even for a small moment, could result in the loss of valuable power. Miley later explained that they initially planned to set the shock absorbers under the engine and transmission. It is now in the midst of rewriting the program. After factoring in the overall packaging, he saw that the shock absorbers would shift the vehicle's center of gravity upwards. "When you think about the weight of the engine and the transmission, it turns out that we are talking about several hundred kilograms," he says. "And you would want to keep that weight as low as possible to achieve stability."

Next, Cook turns to the workshop, a long, open warehouse that also houses a variety of other student-run CAR projects. At the bullet station, Cook grabs a rubber tire that is only one-sixth of an inch thick. He explains that when the vehicle crosses the 300 mph line, the tires will spin so fast that the centrifugal force causes them to expand. The more rubber there is, the more mass there will be and the greater the force that tries to tear this mass to pieces. A thinner tire means less mass and less chance of the tire coming apart at high speeds. The catch is that the vehicle is about to drive across a rather rough salt desert. "Will the tires hold up?" Cook asks loudly. "It's one of the things that keeps me awake at night."

The countdown to the launch

Three months later, in early November 2012, the team is only two months away from the start of the construction phase. Miley redesigned the suspension to lower the engines and the car's center of gravity, but the tail remained controversial. As a safety measure, the team is considering including three or even four brake parachutes. Because of these additions the rear of the vehicles may be too large and increase drag. "We haven't decided on the number of parachutes yet," admits Wang.

A month before, the battery supplier A123 went bankrupt, but fortunately the graduates of the bullet project who worked for the company managed to extract the batteries for the project from the "back door". "We got everything we needed from them, plus some to spare," says Cook.

The construction of the engines was also completed, albeit in a slightly modified version. After several more simulation tests, Venturi engineers claimed that the engines might not be able to develop the necessary power. But Cook's spirit did not fall like that. "We learned that you can't just accept 'no'," he says. "We have to ask why. Why can't we create more doubt? Is the problem that it is physically impossible to pass more current through the copper covers?" After digging further, it turned out that the problem was, in fact, temperature related. According to the simulations, the engines were supposed to overheat. So Cook, Miley, and another undergraduate student named Luke Kelm worked with Venturi to redesign the engine's cooling system. They changed the flow of the oil-based coolant so that it comes into contact with the engine at a greater number of points, allowing it to absorb more heat and keep the temperature from rising and staying low.

This is the legacy of Project Bullet: less reliance on a system of technological innovations, as impressive as they may seem, and more commitment to understanding the limitations of existing technology in order to overcome them. "It's a great exercise," says Pastori of the Venturi company. "When you have to squeeze the ingredients to the last drop, you can discover new things and promote your ideas in a different way."

In the end, these challenges provide an incomparable educational experience, and the team members leave the university with a unique experience. The projectile program has produced 50 engineers over the years, and most of them have received senior positions at car manufacturers, in the aerospace and battery technology fields. "They're better engineers because they've dealt with these complicated problems," Pastor says.

Cromer, the first-year student who joined on a whim, says he gained an educational experience far beyond what he learned in class. The boy who knew nothing about cars spent the last two years designing the vehicles' electronic brain, a system that monitors the performance of each and every component and coordinates them all with the driver's control. And yet, Cromer and the others don't do it just for the sake of studying. Inside, they're still young undergraduates, and the prospect of breaking the 400 mph barrier in September 2013 is a driving force very much in the air. "We can break an international speed record," he says. "How many people who have just graduated with a bachelor's degree can say such a thing?"

*Ohio bullets, Buckeye Bullets, named after the fruit of the chestnut tree, a symbol of the state of Ohio

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About the author

Gregory Moon (Mone) writes about science and technology for magazines including Atlantic, Discover and Popular Science. He also authored four books.

in brief

Members of the Ohio Projectile team at Ohio State University are building an electric vehicle that they hope will be the first of its kind to break the 400 mph barrier, a feat that only nine gas-powered cars have managed to achieve.

Earlier versions of the vehicles have already broken speed records for electric vehicles, but if the team wants to reach the 400 mph line, it must come up with solutions to a long series of engineering problems.

Among the challenges: developing enough power in the four electric motors, adjusting the aerodynamics to keep the car fast but stable, and making sure the tires don't explode.

If all goes according to plan, the team will attempt to break the 400 mph barrier during September 2013 test runs in the salt flats of Bonneville, Utah.

design

Electric rocket - an inside view

This third version of the Ohio Bullet is completely redesigned, with a carbon fiber shell and a steel driver chassis adapted from an IndyCar model. A protruding tail fin adds stability, especially in crosswinds, but it also adds aerodynamic drag. Power comes from 80 specially designed batteries and four electric motors, each producing 400 horsepower. After the run, a system of at least three parachutes will slow down the vehicles; Brakes from the aviation industry will provide backup in case of an emergency.

And more on the subject

Driving to Mach 1. Gary Stix in Scientific American magazine, Vol. 277, no. 4, pages 94-97; October 1997.

Ohio projectile:

Watch the previous version of the Ohio projectile crossing the 320 mph (515 km/h) line On the Scientific American Israel website