首页
登录
职称英语
For centuries men dreamed of achieving vertical flight. In 400 AD Chinese ch
For centuries men dreamed of achieving vertical flight. In 400 AD Chinese ch
游客
2023-07-27
54
管理
问题
For centuries men dreamed of achieving vertical flight. In 400 AD Chinese children played with a fanlike toy that spun upwards and fell back to earth as rotation ceased. Leonardo da Vinci conceived the first mechanical apparatus, called a "Helix", which could carry a man straight up, but this was only a design and was never tested.
The ancient dream was finally realized in 1940 when a Russian engineer piloted a strange-looking craft of steel tubing with a rotating fan on top. It rose awkwardly and vertically into the air from a standing start, hovered a few feet above the ground, went sideways and backwards, and then settled back to earth. That vehicle was called a helicopter.
Imaginations were fired. Men dreamed of going to work in their own personal helicopters. People anticipated that vertical flight transports would carry millions of passengers as do the airlines of today. Such fantastic expectations were not fulfilled. The helicopter has now become an extremely useful machine. It excels in military missions, carrying troops, guns and strategic instruments where other aircraft cannot go. Corporations use them as airborne offices, many metropolitan areas use them in police work, construction and logging companies employ them in various advantageous ways, engineers use them for site selection and surveying, and oil companies use them as the best way to make offshore and remote work stations accessible to crews and supplies. Any urgent mission to a hard to-get-to place is a likely task for a helicopter. Among their other multitude of uses: deliver people across town, fly to and from airports, assist in rescue work, and aid in the search for missing or wanted persons. [br] What is a "Helix"?
选项
答案
"Helix" is an unrealized mechanical flying machine.
解析
从第一段最后一句可知。
转载请注明原文地址:https://tihaiku.com/zcyy/2873762.html
相关试题推荐
[originaltext]Mrs.RuthLi,aChinesewomanlivinginSingapore,namedher
[originaltext]Mrs.RuthLi,aChinesewomanlivinginSingapore,namedher
TheMid-AutumnFestivalisatraditionalChinesefestivityand______(崇拜月亮的风俗可以
Centuriesago,mandiscoveredthatremovingmoisturefromfoodhelpstopres
Centuriesago,mandiscoveredthatremovingmoisturefromfoodhelpstopres
Centuriesago,mandiscoveredthatremovingmoisturefromfoodhelpstopres
Forcenturiesmendreamedofachievingverticalflight.In400ADChinesech
Forcenturiesmendreamedofachievingverticalflight.In400ADChinesech
Centuriesago,duringtheMiddleAges,mostofthelandinEuropewasowned
Centuriesago,duringtheMiddleAges,mostofthelandinEuropewasowned
随机试题
Iboughta$600digitalcamerainMayof2003atFutureShopinKitchener,ON.I
Thetownisfamousforits______bridge.A、uniquegreyancientstoneB、greyuniq
下列关于智力的说法错误的有()。A.智力包括言语能力、数学能力、推理能力
A.9/2 B.6 C.13/2 D.7 E.8
使科学、技巧、艺术和人的属性在实现组织目标过程中有机结合起来的是()。A.指导
食物血糖的生成指数的意义和评估方法是什么?
患者,男,68岁。有胆结石病史,上腹部剧痛1天,大汗淋漓,烦躁不塞,口燥咽干,静
抑制需求拉动通货膨胀,可以采取的措施是( )。A.减税 B.降低工资 C.
在文献检索时,研究者不仅要搜集那些与自己观点一致的资料,也要搜集与自己观点不一致
A.脑血栓形成 B.脑栓塞 C.蛛网膜下腔出血 D.脑出血 E.急性脊髓
最新回复
(
0
)