As market competition for space access heats up, there is a renewed interest in air-breathing technology. At the same time, remarkable launch cost reductions in more conventional boosters are imminent due to the efforts of SpaceX and other firms.
It is beneficial to everyone to explore alternate technological paths, since no one can predict which paths will pan out and produce an economical and reliable vehicle. Most or all of the concepts currently under consideration use winged vehicles to avoid vertical takeoffs and to reduce the required engine size for takeoff. Work on more advanced concepts is also underway.
Currently, two countries, Japan and India, are in the planning stage while the British company Reaction Engines will soon begin a major test of critical engine components of its Skylon vehicle concept.
For more information see NSS Board Member John Strickland’s article in The Space Review: Current strategies towards air-breathing space launch vehicles.