Hindawi Publishing Corporation International Journal of Aerospace Engineering Volume 2012, Article ID 715706, 2 pages doi:10.1155/2012/715706 Editorial Chemical Rocket Propulsion David Greatrix, 1 Ivett Leyva, 2 Dario Pastrone, 3 Valsalayam Sanal Kumar, 4 and Michael Smart 5 1 Department of Aerospace Engineering, Ryerson University, Toronto, ON, Canada M5B 2K3 2 Aerophysics Branch, Air Force Research Laboratory, Edwards AFB, CA 93524, USA 3 Dipartimento di Ingegneria Meccanica e Aerospaziale, Politecnico di Torino, 10129 Torino, Italy 4 Department of Aeronautical Engineering, Kumaraguru College of Technology, Coimbatore, Tamil Nadu 641006, India 5 School of Mechanical and Mining Engineering, The University of Queensland, Brisbane, QLD 4072, Australia Correspondence should be addressed to David Greatrix, greatrix@ryerson.ca Received 31 October 2012; Accepted 31 October 2012 Copyright © 2012 David Greatrix et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. We are pleased to present to you this special issue on chemical rocket propulsion. It is hoped that experts and nonexperts alike will enjoy the discussion of a number of international research efforts that are taking place across the breadth of this diverse field, as conveyed by the authors of the papers appearing herein. The submitted papers certainly reveal the wide number of disciplines (chemistry, fluid dynamics, structures, etc.) that currently play important roles towards ultimately producing effective chemical rocket systems. Recently, an important milestone has been reached in the history of chemical rocket propulsion, with the retirement of the Space Shuttle. The end of one era brings the dawn of a new era in space transportation, with the anticipation that, with time, new and better flight vehicles will come on the scene and flourish in their respective applications. Almost surely, those new vehicles will still be propelled in large part by chemical rocket systems, systems that have been updated and improved over those of the previous generation through the efforts of today’s researchers and engineers. Liquid-propellant rocket engines continue as the preem- inent chemical rocket propulsion system, from millinewton spacecraft thrusters to meganewton first-stage engines for space launch vehicles. Although it is commonly perceived that liquid rocket engines are a mature technology, there are still many active research areas. For example, replacing highly toxic and expensive-to-handle propellants used in hypergolic systems with greener, less toxic propellants is a current challenge. As the thrust demands go up, achieving longer life for monopropellant systems especially remains an objective. For missions beyond Earth’s orbit, proven relight capability for upper stage engines, and long-term storage for cryogens, will become some of the engineering issues researchers will face. Liquid propulsion will remain a critical component in launch systems in the foreseeable future. In conjunction, the interest in making these systems more reliable, more durable, and less expensive to develop and acquire for a number of diverse flight mission applications will continue, and the engineering challenges associated with these objectives will have to be met. Solid-propellant rocket motors maintain their impor- tance in meeting the propulsion needs for a number of flight applications, big and small. While solid rockets have had, for a long time now, the reputation as being the cost-effective, ready-to-go option, research continues on improving all aspects of their performance, including their safety and friendliness to the surrounding environment. For example, ammonium dinitramide (ADN) appears to be making inroads as a potential greener replacement for ammonium perchlorate (AP) as an effective oxidizer for a number of solid propellants. There is some interest in going to higher chamber pressures to increase thrust-related performance; at higher pressures, one may encounter the need to more actively inhibit the appearance of combustion instability symptoms during a given motor’s operation. Manned suborbital flights powered by hybrid rocket engines have recently become reality, mainly due to reasons related to low cost and safety. Potential applications of hybrid rockets range from microgravity platforms to launchers and landing vehicles, but researchers must face some challenges, in part due to the peculiar combustion process of hybrid