Complex sentence: It is so powerful that, prior to the 1947, it was thought that aircraft engines would not be powerful enough to overcome the drag without breaking up in midflight, which led to the concept of a "sound barrier".
Split into simpler sentences: It is so pronounced that, prior to 1947, it was thought that aircraft engines would not be powerful enough to overcome the enhanced drag or that the aircraft would be at risk of breaking up in midflight. It led to the concept of a "sound barrier".