Last month, Lockheed Martin and NASA jointly revealed the X-59 experimental aircraft , which is expected to fly at 1.4 times the speed of sound (925mph) without generating an explosive sonic boom. The sleek jet is expected to play an instrumental role in bringing back supersonic commercial air travel. But what if I tell you that researchers are working on a submarine that could travel more than three times faster than the X-59 jet? Yes, you read that right, and it is possible to travel at those speeds underwater, at least theoretically. Back in 2016, a team of researchers at Penn State Applied Research Laboratory funded by the US Navy started the development work on a revolutionary submarine that can attain supersonic speeds. Obviously, the biggest problem for vessels reaching high speeds both on the surface of water or below it is the huge amount of drag created while moving through it. But there’s a simple solution to overcome drag underwater – a bubble. The researchers are wor...