In 1987, N Tanatsugu published "Analytical Study of Space Plane Powered by Air-Turbo Ramjet with Intake Air Cooler." part of Japan's ISAS (now JAXA) study into an Air-Turbo Ramjet (ATR, later ATREX after the addition of an expander cycle) intended to power the first stage of a TSTO spaceplane. ATREX was superseded by the Preecooled Turbojet (PCTJ) and Hypersonic Turbojet studies. A liquid nitrogen precooled hydrogen burning test engine was flown at Mach 2 at Taiki Aerospace Research Field in September 2010.