科技 飞蛇 空中滑行

　　Fancy aerodynamics explain why some snakes are good gliders

　　奇特的气体力学解释了为什么一些蛇善于飞行

　　MANY animals have mastered the trick of gliding through the forest canopy. Flying frogs stretch the webbing between the toes of their enlarged feet. Some lizards spread elongated ribs covered in flaps of skin. And the colugo, a strange South-East Asian mammal, can travel as much as 70 metres (230 feet) between trees by spreading a membrane of skin that connects its limbs. Despite a lack of obvious body parts that can double up as a decent pair of wings, some snakes, too, can glide for remarkable distances.

　　许多动物掌握在林冠中滑行的技巧。青蛙在飞行时展开它的脚蹼;一些蜥蜴展开皮肤软组织下的细长肋骨；猴猫，一种生长在东南亚的哺乳动物，通过伸展连接四肢的薄膜在树中滑行多达70米（230英尺）。尽管身体明显缺少一部分，如一对能够拍打且适于滑行的翅膀，一些蛇也能飞行很远。

　　To discover how snakes manage it Jake Socha of Virginia Tech and his colleagues conducted a series of test flights with paradise tree snakes, a mildly venomous variety found in parts of Asia. They launched the snakes from the top of a 15-metre tower and used four video cameras to construct 3-D images of the animals' trajectories. The results, just published in Bioinspiration and Biomimetics, show not only that flying snakes are surprisingly good aviators but also that they employ some complex aerodynamic tricks.

　　为了查明蛇类如何成功的飞行很远，维吉尼亚理工学院的Jake Socha和其同事用一些天堂树蛇做了一系列的飞行试验，这是一种毒性适中的蛇，它生长在亚洲部分地区。研究人员使树蛇从15米高的塔顶端飞行，过程中使用了4个摄影机拍摄蛇滑行的轨迹，以拍摄成三维立体图像。不久前在生物灵感和仿生学上发布的结果显示：飞蛇的飞行不仅令人叹为观止，并且飞行过程中使用了一些在空气动力方面的很复杂的技巧。

　　A paradise tree snake flattens its body into an aerofoil-like shape that can provide a degree of lift before it takes off from a branch by jumping upwards. It then falls at a steep angle and starts undulating from side to side. As it gains speed its glide path becomes shallower, allowing it to cover a greater distance. The researchers found some snakes could glide for 24 metres.

　　天堂树蛇展平它的躯体，使其形成机翼般的形状，这可以使它在借助树干弹跳前产生一定的提升力。然后它急剧下降并且不停地摆动身体。随着下降速度的增加，下滑道变得越来越浅，这使树蛇滑翔很长一段路程。研究人员发现一些树蛇可滑翔24米。

　　The 3-D analysis showed the snakes take up a staggered posture when gliding, with their bodies angled upwards at about 25° to the oncoming air and their heads slightly higher than their tails. Dr Socha says this orientation seems to provide the creatures with an aerodynamic advantage. As a result of it, the wake of air forced backwards by one segment of the snake's undulating body may provide extra lift to the segment behind in the sidewinding glide. Flying fish rely on a similar flow of accelerated air from their pectoral fins to provide lift to their smaller pelvic fins. Indeed, it is possible that the effect works both ways, and that rearward segments provide lift to those in front.

　　对三维立体图像的分析表明：树蛇滑翔过程中摆动着身体，躯体向上抬，与迎面的空气呈25度角，头部稍微高于尾部。Socha博士表示在空气动力学角度上来讲，这样的身体趋向可能会对飞行的树蛇产生推助的作用。这样，摆动树蛇的身体的前半部分擦过的空气尾流可对侧风滑行的后半部分起到提升的作用。同样，飞鱼借助胸鳍所产生的加速气流，就可以对较小的腹鳍产生一定的提升作用。事实上，反过来也可能产生这种效果，即后半部分可为前半部分起到提升作用。

　　The snakes are also surprisingly manoeuverable and have been seen to turn in mid-air. To find out if this might be deliberate, Dr Socha limited their view from the tower so that they could see only straight ahead when they launched themselves. Once airborne, and thus able to observe trees to the side of their glide-paths, some of the snakes turned towards them.

　　树蛇的飞行技巧也也令人叹为观止。人研究人员观察到它们在飞行途中可以变向。为了探明树蛇是否故意发出这一行为，Socha博士限制了树蛇在飞行时的视野，目的是让他们在起飞时只能向前看。一起飞，这些树蛇就可以看到滑行路径两旁的树，一些就转变方向朝树木飞去。

　　Dr Socha, who studies the relationship between form and function in animals, was partly funded in his snake research by America's Defence Advanced Research Projects Agency, which said it was interested in the science but obviously wonders about military applications.

　　研究动物的构成和功能的Socha 博士在对蛇进行研究时得到了美国国防发展研究项目的资助，它称它对这部分科学很感兴趣，但也明显质疑是否可以将这部分科学应用到军事领域。

　　Dr Socha does not expect to see snakelike drones in the skies soon. However, the ability to slither through holes, to swim and to climb trees and rocks, as well as to glide between elevated features of the landscape, is an attractive mixture for designers of robotic vehicles. The staggered-wing effect, in which the front of the body helps to provide lift for the back, may also be of interest to aircraft engineers. In the long term, then, the world's battlefields may see machines that resemble some people's worst nightmares, slithering as they do towards the enemy both on the ground and through the air.

　　Socha博士并未预期蛇形般的遥控飞机即将腾空出世，然而，设计集各种功能于一身的交通工具-全部自动化，能够滑穿孔洞，穿行在水中，爬得大树和岩石，滑行在凹凸不平的风景中-对于设计师来说，很具吸引力。摆动的双翼所产生的效果-机身的前半部分可为后半部分增加提升力，对飞机工程师来说也可能颇感兴趣。从长远来看，在世界战场可以看到那些出现在一些人的噩梦里的飞机，在陆地和空中滑翔，攻打敌人。