The earliest example of equine footwear we have is made of animal hide and dates from about 600 B.C. This primitive hoof protector looks more like a horse bootie than what we think of today as a horseshoe. It was probably stuffed with dried grass or other available natural material and tied on with hide thongs.
The spiral model is a software development process combining elements of both design and prototyping-in-stages, in an effort to combine advantages of top-down and bottom-up concepts. The spiral model was defined by Barry Boehm in his article A Spiral Model of Software Development and Enhancement from 1985. This model was not the first model to discuss iterative development, but it was the first model to explain why the iteration matters.
The U.S. initiated ICBM research in 1946 with the RTV-A-2 Hiroc project. This was a three-stage effort with the ICBM development not starting until the third stage. However, funding was cut after only three partially successful launches in 1948 of the second stage design, used to test variations on the V-2 design.