This important volume contains the 21 prize-winning papers presented at the Twentieth United States Army Science Conference under the sponsorship of the Assistant Secretary of the Army for Research, Development and Acquisition. The theme of the conference was “Science and Technology for Force XXI — the Force of the Twenty-First Century”. Original scientific and technical papers — written by U.S. Army civilian and military scientists and engineers — addressed the role of science and technology in providing a competitive edge for Force XXI. The papers in this book are in the following key technical areas: advanced materials and manufacturing including structures and energetics; microelectronics and photonics; sensors and information processing including communications; high-performance computing and simulation including modeling, displays, artificial intelligence, and virtual reality; advanced propulsion technologies including mobility and lethality; power generation, storage and conditioning including directed energy; biological, chemical and nuclear defense; life, medical and behavioral sciences including individual sustainability and soldier-system interface; environmental sciences and geosciences including atmospheric, space and environmental protection; engineering sciences including robotics, mechanics, fluid dynamics and survivability.