托福official66综合写作科技类Integrated Writing范文+题目解析

An airship is a type of aircraft that flies using a very large balloon filled with a lighter-than-air gas. Airships were an important means of air transportation before the 1940s but are little used today, having been largely replaced by airplanes and helicopters. However, some aeronautical engineers believe that airships could become popular again because they offer a number of advantages over airplanes and helicopters. One advantage of airships is that for vertical lift (the force that keeps the ship airborne), they use a balloon that floats rather than an engine. Airplanes and helicopters use engines for both vertical lift and horizontal movement, but airships use engines solely for horizontal movement. So, airships use less fuel than a typical aircraft—thus making their fuel costs more economical. Another advantage of airships is that they can be used in hard-to-reach locations. Unlike airplanes, airships do not require a long runway for takeoff and landing because of their ability to lift off and land vertically. The only other aircraft capable of ascending into the sky by going straight up and descending straight down to the ground is the helicopter, which can carry only a small amount of weight. Airships, meanwhile, are able to carry very heavy loads. As a result, airships could do jobs that neither airplanes nor helicopters can do, such as carrying heavy logs from forests to distribution centers. Finally, airships could even be used to replace satellites. Currently, satellites are launched into Earth’s orbit carrying all kinds of equipment important in telecommunications or in surveying large areas of Earth’s surface for military purposes. Since airships can also rise high above the surface and stay there without refueling for a significant amount of time, they could provide services similar to those provided by satellites, and at a considerably cheaper cost.