The spindle is the perfect aerodynamic shape but, at speed below Mach 5, this type of body does not produce enough lift to keep on flying. Any attempt to add a wing collides with the problem known as area rule during supersonic flight that consists of a proportional increase of drag.
In 1942 the technical team of aerodynamics of the AVA (Aerodynamische Versuchs Anstalt) led by Dr. Ing. Alexander Lippisch, built a heart-shaped model of a delta wing, with a 60º swept, that proved to be an ideal supersonic body. Tests performed in the Göttingen wind tunnel showed that the body offered the minimum drag at over Mach 1, using less power that any of the other tested configurations. Known as Überschall Delta, this shape was unstable during flight, given the technology available at the time, and therefore it could not be used as a base to build a supersonic airplane.
Most of the research work done by Lippisch during the rest of the war had the objective to create a delta wing apt for stable and long range supersonic flight.