Abstract: In a method and an apparatus for automatically fabricating a physical prototype, an initial prototype is created, which need not satisfy the specified performance characteristics. An initial Jacobian matrix relates changes in the prototypes design variable physical features to changes in the prototype performance characteristics. The prototype is tested to determine the error between the specifications and the prototype performance characteristics. The initial Jacobian is applied to this error to generate a change order signal for the physical features. This change signal is input to a prototyping apparatus, preferably automatic and rapid, which physically changes the prototype. The prototype is again tested for satisfaction of the specifications. If necessary, the prototype is changed again and again.