NASA is working with Lockheed Martin to develop an airplane that can fly faster than the speed of sound without making a sonic boom.
원문출처 : https://www.cnn.com/travel/article/nasa-x-plane-supersonic-passenger-airplane/index.html
원문출처 : https://www.cnn.com/travel/article/nasa-x-plane-supersonic-passenger-airplane/index.html