Photo: Hans-Peter van Velthoven

Stop and Go: Nuna 4 breaks down on the starting line and the team members inspect their motor controller; later, the solar car maneuvers through traffic in Darwin, on the first stretch of Stuart Highway.

A race official looks at his wristwatch—8:00—and waves Umicar Infinity off the starting line. It glides down the street and out of sight. Then comes Aurora 101, the local favorite, accompanied by exuberant hoots from the crowd. And then Nuna 4, the weight of its celebrated predecessors pressing down on it.

Inside the Nuna, a panicked Oliver van der Meer gestures furiously at his tiny dashboard. He taps the pedal, but the car doesn’t budge. After a quick consultation, a dozen Dutch students in the team’s blazing orange shirts strip off the tape that holds the top shell, with the solar array, to the car’s carbon-fiber body. Solar cars navigate around them, drift up to the starting line, and disappear into Darwin. Six Nunans heave the top over van der Meer’s head.

It’s that pesky motor controller, which regulates the motor’s rotational speed and direction. Its Hall-effect sensors are producing a bizarre reading—the lights for both “drive” and “reverse” are lit on the console. In a brushless dc electric motor, which is what most high-end solar cars use, these highly specialized sensors track the position of the motor’s permanent magnet rotor. The team has seen this glitch before, but only in hot weather. It’s cool this morning, so what the heck? Someone runs to a support vehicle to fetch a spare—and less efficient—controller. “Anyone have a small screwdriver?” yells Vincent de Geus, the race strategist, over the spirited bleats of a local brass band.

Out comes the troubled controller and in goes the replacement. Some crew members reattach the top shell and swiftly tape over the edges, while the rest of the crew, visibly shaken, scurry to their chase vehicles.

With 27 solar cars now in front of it, Nuna 4 plunges into the race—straight into the chaos on leafy Mitchell Street and out to the first few kilometers of Stuart Highway, which it will ride all the way to Adelaide. Here the highway’s shoulder is a site of solar carnage, as a dozen teams facing early emergencies have pulled to the side of the road and ripped off the tops of their vehicles to poke and prod at misfiring components. The worst off is Michigan’s solar car, whose driver had braked late in the bumper-to-bumper traffic and hit a team vehicle, crumpling the car’s nose and damaging the steering system. Two rows of solar cells have been destroyed, and the driver is in tears.

The rest of the pack navigates through heavy traffic down the busiest stretch of Stuart Highway. Nuna 4 weaves easily between vehicles, overtaking solar racers and chase cars alike. Within 3 hours it’s in second place, ahead of Aurora 101 but behind the leading Umicar Infinity.

By midday, the highway thins to one lane, and signs of civilization dwindle to the odd roadhouse amid spotty clumps of spinifex grass. On either side, spindly eucalyptus trees poke out of the hard red earth. Every 20 minutes or so, a road train pulling three trailers bombs past, blasting the cars with strong side winds.

One of those trucks’ blasts dislodges the latch on Nuna 4’s canopy. The bubble top flies open, and van der Meer barely manages to grab it and pull it down. With one hand on the wheel and the other holding the canopy down, he can’t reach the regenerative brake anymore (which is a hand-operated toggle, unlike the foot pedal for the mechanical brake). The next 200 km become a battle between not braking, so as to not waste energy, and not cracking up. A cold sliver of air cuts at his neck while he drives.

So it is that the Nuna team makes its entrance into the outback. Around its convoy, dirty tendrils of smoke rise from patches of iron-tinged earth singed by recent fires. Where earlier local residents had lined the road to cheer them on, now only statuesque termite mounds—man-size piles of orange dirt—stand like mute sentries. The crippled racer rattles down the highway, its hollow body amplifying the reverberations to a deafening clatter. As another Nuna driver later describes it, “It was like riding inside a giant guitar.”

Meanwhile, around midday, the Nuna team’s strategists realize they’ve got a problem. In their “mission control” vehicle, the three of them are monitoring the state of the racer’s lithium-polymer battery through the voltage and current readings sent over a wireless link from the solar car’s motor controller. They’ve tailored their strategy software to calculate speeds for a day that lasts from 8 a.m. to 5 p.m., but with the half-hour delay in the start and the corresponding shift in light conditions, their algorithm is off. De Geus, the chief strategist, manually calculates the speeds, scribbling on a pad of paper as the sun’s intensity wanes.

Short of crashing, the biggest disaster that can befall a solar team is draining the battery prematurely. The load on the battery is related to the drag on the car, and that drag increases with the square of the speed. Put another way, driving too fast for the conditions can do a team great harm. The strategists spend their time calculating, at 2‑minute intervals, the optimal speed, taking into account variables such as how much driving they anticipate for the rest of the day and the near-term weather forecast.

Luckily for the Nuna team, the race rules and the staggered start let them recoup the time they squandered replacing the motor controller. As other cars pull off the road to mark the end of the first racing day, Nuna’s scouts speed ahead to find a suitable campsite—one with unobstructed western exposure that will let them use the remaining sunlight to top off the battery for tomorrow’s start.

Soon the convoy turns into a little clearing surrounded by brittle grasses. The sun starts to set, and desert flies emerge in swarms. As day one ends, the Nunans are behind the Belgian Umicar Infinity team, which has set up a bare-bones campsite 13 km ahead, butted up against tall grass a few meters off the shoulder. A few kilometers behind Nuna, Aurora 101 is doing the same. Flies clinging to their faces and shirts, the racers pitch their tents on the red gravel, tilt their solar arrays to catch a last few photons, and set up lights to examine their cars before bedtime.