The document discusses UX simulation as a design process for rapidly generating viable interaction models. It proposes that UX simulation uses expedient technologies to quickly build interactive models, focusing on viability over variety. This allows testing concepts earlier to identify issues. The process involves immersion, concept mapping, generative whiteboarding to select a viable first concept, then coding it to fidelity to reach a "critical mass" that enables further refinement. Examples of successfully applying UX simulation to printers, MP3 players, and phones are provided.