The global increase in air travel will require commercial vehicles to be more efficient than ever before. Advanced engine hot section materials are a key technology required to keep fuel consumption and emission to a minimum in next-generation gas turbines. Ceramic matrix composites (CMCs) are the most promising material to revolutionize gas turbine hot section materials technology because of their excellent high‐temperature properties. Rapid surface recession due to volatilization by water vapor is the Achilles heel of CMCs. Environmental barrier coatings (EBCs) is an enabling technology for CMCs, since it protects CMCs from water vapor. The first CMC component entered into service in 2016 in a commercial engine, and more CMC components are scheduled to follow within the next few years. One of the most difficult challenges to CMC components is EBC durability, because failure of EBC leads to a rapid reduction in CMC component life. Key contributors to EBC failure include recession, oxidation, degradation by calcium‐aluminum‐magnesium silicates (CMAS) deposits, thermal and thermo‐mechanical strains, particle erosion, and foreign object damage (FOD). Novel EBC chemistries, creative EBC designs, and robust processes are required to meet EBC durability challenges. Engine-relevant testing, characterization, and lifing methods need to be developed to improve EBC reliability. The aim of this Special Issue is to present recent advances in EBC technology to address these issues. In particular, topics of interest include but are not limited to the following: • Novel EBC chemistries and designs; • Processing including plasma spray, suspension plasma spray, solution precursor plasma spray, slurry process, PS-PVD, EB-PVD, and CVD; • Testing, characterization, and modeling; • Lifing.

What has happened to George Adamski since he wrote the famous incidents in Flying Saucers Have Landed? Since the memorable November 20, 1952, when he first made personal contact with a man from another world? Since December 13, 1952 when he was able to make photographs within 100 feet of the same saucer that had brought his original visitor? Inside The Space Ships is Adamski’s own story of what has happened to him since then. It begins with his first meeting, a few months later, with a second man from another world—his first meeting with one who speaks to him. This second visitor brings him to a Venusian Scout (flying saucer) and this, in turn, brings him to a mother ship. Later lie is conveyed in both a Saturnian Scout and a Saturnian mother ship. Adamski tells us what transpires in these space craft and what the men and women from other worlds have told him. Adamski’s photographs of flying saucers, originally published in Flying Saucers Have Landed, have since become world-famous as other witnesses in other parts of the world have succeeded in taking photographs identical with his. Now, however, in Inside The Space Ships, Adamski gives us 16 photographs and illustrations, no longer of Scouts (flying saucers) mostly, but of the great space ships from which they are launched. The main group of these photographs was taken in April, 1955, and neither the photographs nor a description of them has ever been published before.

This is the first major publication on liquid-rocket combustion devices since 1960, and includes 20 chapters prepared by world-renowned experts. Each chapter focuses on a specific aspect of liquid-propellant combustion and thrust chamber dynamics, and is incorporated into the volume in a well-organized, cohesive manner. There are contributions from nine different countriesChina, France, Germany, Italy, Japan, the Netherlands, Russia, Sweden, and the United States.