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101 Inventions That Changed the World in the Last 100 Years
something that looked like a helicopter, but it was just a drawing. After a long period of development, Igor Sikorsky made a series of successful flight tests on his VS-300 between 1939 and 1941. Albeit relatively
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100 Famous Inventors and Their Best Invention Ideas
was quite similar, but the cooling process used ammonia vaporization to reach -25°C temperature. 60. Igor Sikorsky In 1910, Sikorsky built a (somewhat) successful helicopter model propelled by a 15-horsepower