>flying or in development You've forgotten about ULA's Delta IV and Delta IV Heavy, NASA's SLS, and JAXA's H-IIA and H-IIB. Delta IV Heavy is currently the mo

>flying or in development You've forgotten about ULA's Delta IV and Delta IV Heavy, NASA's SLS, and JAXA's H-IIA and H-IIB. Delta IV Heavy is currently the most capable rocket in the world and uses liquid hydrogen throughout (no solid boosters).