缘来文化,知识视界,科教视频,国际教育视频,青少科教视频,视频教育资源库

Video Recommended——

简图

Submarine

Country: America
Added: 2006
Category: Military Warfare
Duration: 24 mins
Click to play>>
Abstract: Speed, strength, stealth and power, the submarine is a mean machine, it takes man into a hostile world. Submarine design has been evolving for centuries. The dream of travelling underwater existed long before it became a reality. Man had fiddled around with the concept of the submarine for hundreds of years. All kinds of prototypes have been built but they all hit the same stumbling block. How to devise an effective means of propulsion?