题型:阅读理解 题类:常考题 难易度:普通
山东省潍坊市2018-2019学年高二下学期英语期末考试英语试卷
Like Marty McFly's banana-powered DeLorean (德罗宁时光机),a future generation of flying cars could tip over the idea that all flying is bad for the climate. Firms such as the Rolls Royce, Lilium and Vertical Aerospace have argued that flying cars could be a green mode of transport despite the large amounts of energy they need to get off the ground.
One study into the environmental impact of such vertical (垂直的)takeoff and landing ((VTOL)) vehicles suggests their backers could be right — at least in some circumstances. Gregory Keoleian at the University of Michigan and colleagues found that VTOLs, if they ever took to the skies, would produce 6 per cent less emissions than an electric car over a 100-kilometre journey. "The VTOL is particularly energy intensive (集中的)during takeoff and landing. The flight phase,however,is much more efficient,and over long distances,makes fully loaded VTOLs competitive with ground based vehicles," says Keoleian. Flying cars would also have the advantage of being able to fly in a straight line, bypassing meandering routes.
However , don't act immedialely . The difference was only very small and there are several big catches. Flying cars don't really exist yet — they are only at the prototype (蓝本)stage. The prototypes rely on electric power and act as a taxi, but another issue is that the study is a bit of an apples-for-oranges comparison.
The researchers assume that each electric car carries an average of 1.54 passengers while the passengers and drivers of the flying car are three and one. The reason for this assumption is that the flying car will provide a shared taxi service like UberPool, but in fact electric cars can do the same. In addition t due to the need for energy during take-off, the emissions from the flight below 35 km will be more than those of electric vehicles.
Keoleian and his team conclude flying cars could have a minor role in sustainable transport. But even if they do prove to be green, they have a lot of other hurdles to cross first.
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