Tim Lieuwen is a Professor of Aerospace Engineering at the Georgia Institute of Technology. He has authored a research-based book, Unsteady Combustor Physics. He has published over 50 refereed journal articles, over 100 conference publications, eight book chapters and two edited books. Lieuwen is an expert on combustion, including such issues as emissions, efficiency and alternative fuels, and has worked with General Electric, Siemens, Exxon Mobil and others. He works on clean combustion technologies and alternative fuels with the Department of Energy, NASA and the Department of Defense. He holds six patents. Dr Lieuwen is an associate editor of the Journal of Propulsion and Power, Combustion Science and Technology, and the Proceedings of the Combustion Institute. He is a member of the Editorial Review Board of the AIAA Publication Committee and a recipient of the AIAA Lawrence Sperry Award. Dr Lieuwen is on the Propellants and Combustion Technical Committee and the Air Breathing Propulsion Technical Committee of the AIAA and the Combustion and Fuels Committee of the ASME. Vigor Yang is the William R. T. Oakes Professor and Chair of the School of Aerospace Engineering at the Georgia Institute of Technology. He received his PhD from the California Institute of Technology. Prior to joining the faculty at the Georgia Institute of Technology, he was the John L. and Genevieve H. McCain Chair in Engineering at the Pennsylvania State University. His research interests include combustion instabilities in propulsion systems, chemically reacting flows in air-breathing and rocket engines, combustion of energetic materials, and high-pressure thermodynamics and transport. He has supervised more than 40 PhD and 15 MS theses. He is the author or co-author of more than 300 technical papers in the areas of propulsion and combustion, and has published 10 comprehensive volumes on rocket and air-breathing propulsion. He was the recipient of the Penn State Engineering Society Premier Research Award, and several publication and technical awards from AIAA, including the Air-Breathing Propulsion Award (2005), the Pendray Aerospace Literature Award (2008) and the Propellants and Combustion Award (2009). Dr Yang was the editor-in-chief of the AIAA Journal of Propulsion and Power (2001–9) and is the editor-in-chief of the JANNAF Journal of Propulsion and Energetics (2009–) and editor of the Cambridge Aerospace Series. He has served on the editorial advisory boards of Combustion and Flame, Progress in Energy and Combustion Science, Combustion, Explosion, and Shock Waves, Propellants, Explosives, and Pyrotechnics, The International Journal of Fluid Machinery and Systems, the Journal of Aeronautics, Astronautics, and Aviation, the Journal of the Chinese Institute of Engineers and Progress in Astronautics and Aeronautics. He has been a consultant to many US rocket and gas-turbine engine companies as well as government organizations. Dr Yang is a Fellow of the American Institute of Aeronautics and Astronautics (AIAA) and the American Society of Mechanical Engineers