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Simon, in advocating for a Science of Design, proposed a linear Rational Model of design as his science's central concept. Such a model occurs naturally to engineers. Indeed, it has been independently formally set forth several times: e.g., by Simon, by Paul and Beitz, and by Royce. Having a visual, geometric representation of a design process model is crucial, for designers are spatial thinkers. We most easily learn, think about, share, and talk in terms of a model with a clear geometric picture. But the linear, step-by-step Rational Model is misled in goal and approach. It does not accurately reflect what real designers do, nor what the best design thinkers identify as the essence of the design process. Science and design are fundamentally different activities. The goal of a Science of Design is also misleading. Its Rational Model leads to the too-early binding of requirements, leading in turn to bloated products and schedule/budget/performance disasters. The Rational Model has persisted in practice despite its inadequacies and plenty of cogent critiques. This is because builders and clients need contracts. Several alternative process models have been proposed. I find Boehm's Spiral Model the most promising. We also need to develop alternative contracting processes, perhaps adapting those from the building community.