Engineers at Bell Aviation were uncertain that a winged aircraft could fly at supersonic speeds, but they knew a bullet could.  So they adopted the basic shape of a .50-caliber bullet for the fuselage of the X-1.  The simplicity of the aircraft's shape belied the sophistication that went into developing the airfoils and other systems.   The wings, however, were not complicated.  The Army stipulated that the wings of the X-1 be straight, despite the growing awareness of the value of sweeping them back.