This document is intended to be a companion to previous books by the author: Partners in Freedom: Contributions of the Langley Research Center to U.S. Military Aircraft of the 1990's, and Concept to Reality: Contributions of the Langley Research Center to U.S. Civil Aircraft of the 1990's. Material included in the previous volumes provides informative and significant examples of the impact of applications of aeronautics research conducted by the NASA Langley Research Center on important U.S. civil and military aircraft of the 1990s. These contributions occurred because of the investment of the Nation in the innovation, expertise, and dedication of a staff of researchers and their unique facilities at Langley. Within that research environment, literally thousands of revolutionary concepts and advanced technologies for aeronautics have emerged, directed at challenges and barriers that impede the advancement of the state of the art in aircraft design and mission capabilities. Unfortunately, in the world of technology only a handful of advanced concepts are ever applied, due to a number of reasons. Factors that inhibit the application of advanced research technology are numerous and varied in nature, including cost, environmental impact, safety, complexity, reduced or inadequate funding and human resources, world events, perceived or actual risk, technical barriers, and others. The objective of this publication is to discuss the importance of innovation and the role of revolutionary advanced concepts within the aeronautics research community, and to provide information on typical advanced research projects conducted by Langley and its partners on topics that have not yet been applied by the military or civil aviation industry to production aircraft. Detailed information is first provided to describe each advanced concept, the projected benefits that could be provided if the technology is applied, and the challenges faced by the NASA research team to reduce the risk of application. Next, descriptions of specific research activities on the concepts identify the key projects, accomplishments, personnel, and facilities involved in the development of each concept. Finally, perspectives are provided on the current status of the subject concepts, including discussions of factors or future events that might intensify interest in their use for future applications. Many of the concepts described herein are subjects of ongoing NASA research thrusts, for which significant technical challenges are in the process of being addressed. Some of the research activities discussed were conducted and completed in past NASA projects; however, evolving requirements for military or civil aircraft systems demand a reexamination of the potential and current feasibility of the principles involved. This document is intended to serve several purposes. As a source of collated information on revolutionary concepts, it will serve as a key reference for readers wishing to grasp the underlying principles and challenges related to specific revolutionary concepts. Hopefully, such information will provide valuable background that can serve as starting knowledge bases for future research efforts and minimize the so-called "reinvention of the wheel" syndrome. The information identifies major obstacles to advanced aeronautics technology, thereby providing a sensitivity for multi-faceted research projects to ensure a higher likelihood of application. A definition of current barriers to application is extremely valuable for use in the future, when new breakthroughs in various technical disciplines may eliminate or minimize some of the critical barriers that have traditionally blocked the application of some of these specific revolutionary concepts. Finally, a review of the material will hopefully inspire the nontechnical (as well as technical) communities that aeronautics is not a "mature science" and that considerable opportunities exist to revolutionize the future.