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Solar Challenge rally benefits from space technology 
The Dutch Nuna vehicle, which will participate in the 3010 km World Solar Challenge rally through Australia this November, is not just special because it is solar powered. This racing car also benefits from the most recent European space technology and expertise. The World Solar Challenge 2001 will be a tough race. Driving from Darwin to Adelaide at the end of November means traversing 3010 km of Australian desert during the hottest season. It will be a four-day battle against the elements and yet 40 racing cars are still keen to enter the competition. Among these is the Dutch vehicle ‘Nuna’ that will be driven by students. Place your bets on Nuna as the winner - it is much more than a ordinary solar powered racing car.
Nuna is partly fitted with solar cells which have actually been in outer space, as part of the Hubble Space Telescope. Other solar cells are so new that ESA has yet to use them in space. The Alpha Centauri Team, which built the Nuna, is supported by Dutch astronaut and Delft University of Technology (TUD) Professor Wubbo Ockels.
The solar cells are such a recent development that the European Space Agency (ESA) has yet to use them in space. Their first space application will be at the end of next year when the SMART-1 lunar mission is launched. One of the jobs of SMART-1 is to test a solar powered ion engine.
Martinez continued “Nuna will also occasionally be in the shade, which reduces the efficiency of solar cells. But the MPPTs will ensure that the solar cells supply a lot of power and will also stabilise the power. A chip measures the voltage supplied by a solar panel, compares it with the fixed battery voltage, and then determines the best voltage to charge the battery. In this way we can get an efficiency of no less than 97%. Of course, we also need a high-performance battery to operate effectively in poor weather conditions. Depending on the speed, we will be able to travel 250 to 500 km on a full battery.”
The batteries are also based on space technology. The 48 large Li-ion cells are connected in series and can supply the solar racing car with 5 kWh of electrical energy. They are specially developed for use in satellites, where high reliability is essential.
Kevlar is extremely strong and is used not only in bullet-proof vests but also in spacesuits, for protection against micrometeorites. Some walls of the International Space Station (ISS) are also reinforced with Kevlar to protect the astronauts. The Alpha Centauri Team even considered the use of real space suits. Air cooling would adversely affect the aerodynamics of the racing car. As the temperature in the cockpit can be as high as 70°C, a space suit might help. However, in the small cockpit it would be too restrictive. Instead, the pilot will wear a cooling vest with ice cubes.
“Will we win? With this car we stand a pretty good chance.” concluded Martinez. “In theory, we should be able to reach a speed of 190 km/h. In practice it will probably be around 160 km/h, which would still be a record for a solar powered racing car. However, we will only reach that speed on a special test circuit, before the race. During the race on public roads the normal Australian speed limits will apply. The Nuna will be followed by a support vehicle with Wubbo Ockels, captain of communications, and the rest of the team. The support vehicle will collect data about the temperature and current from the solar panels. This information will help the pilot to determine the strategy. Should you try to drive away quickly from under cloud cover? Or should you try to save energy in that situation? Selecting the best racing strategy should help us to gain on the other teams.”
For further information about ESA’s contribution to the Nuna, please contact ESA's Communications Office at ESTEC in Noordwijk, tel. + 31 (0) 71 5653006, fax: + 31 (0) 71 5655728.
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