Speaking of Voyager 1, it would be handy to drive 17.2 kilometres per second! The 5.5 hour drive I make to visit my family would take a mere 34.8 seconds. Then again, I’d be instantly vaporized by friction with the air, so maybe it’s not such a good idea.
And while we’re on about speed, I wrote some time ago about the Bugatti Veyron. Propelled by a 16 cylinder, eight litre, 1001 horsepower engine, this beauty’s top speed is governor-limited to 407.5 km/h (253 mph). I could make the trip to visit my family in just over 88 minutes, with no danger of being vaporized. But there is a small snag, even besides the €1 million price tag.
Despite the fuel economy rating of 33.6 l/100 km in the city and 23.5 l/100 km on the highway, air resistance takes a serious toll at the vehicle’s top speed. At 407.5 km/h, the fuel use rockets to a staggering 78 l/100 km. Why is this a problem? At speed, the 100 litre fuel tank is drained dry in 12 minutes. My trip would require almost eight tanks of fuel! Goodness, if it took ten minutes to stop, refuel, and get going, the trip would take nearly three hours, with only half the time spent at speed. I’m not sure what premium goes for right now but the cost of the required fuel would surely exceed $800. As enjoyable as it is to think about, I’ll just putter along at a quarter the speed, pay somewhere between $20 and $25 in diesel for the entire trip, and not have to stop until I get there, thanks.
This Wikipedia thing is handy! The entry on atmospheric drag explains that the power required to overcome drag is quadrupled when speed is doubled. And the work is done twice as fast, doubling the quadrupling, resulting in an eight-fold increase in the power requirement. They caution the reader against broad generalizations based on this formula because of a ridiculous number of variables. I can see this because driving 40 km/h does not require eight times the power of driving at 20 km/h, surely. Air resistance is much less of a factor at low speeds. At high speeds however, all bets are off. I noticed a 25% increase in fuel economy when I slowed down from 125 – 140 km/h to 110 km/h. It really does make a big difference. A more striking example again comes courtesy of the Veyron. Csaba Csere, in his ‘First Drive’ report for Car and Driver, wrote “When you lift off the throttle at 253 mph, the aerodynamic drag alone slows the Veyron at 0.3 g.” He didn’t press the brake. He simply removed his foot from the throttle and experienced a one-third g deceleration because of air resistance. Frig.
Veyron photos courtesy Bugatti Automobiles S.A.S.