Later, after the prototype for Venturestar, the X-33 was cancelled, the composite multilobe hydrogen tank technology was improved by Northrop Grumman and passed

Later, after the prototype for Venturestar, the X-33 was cancelled, the composite multilobe hydrogen tank technology was improved by Northrop Grumman and passed tests: https://news.northropgrumman.com/news/releases/northrop-grumman-nasa-complete-testing-of-prototype-composite-cryogenic-fuel-tank https://news.northropgrumman.com/news/releases/northrop-grum... Anyway, the architecture of Venturestar is in my opinion misguided since it's not optimized for cost. It would not have brought us cheap routine spacefligh even if it was technically possible. Hydrogen is very complicated for operations. The engine has a huge surface area and a lot of components. Single stage vehicles only exist on paper, and have abysmally low payload even on paper. None have flown to orbit, though there are some stages that have flown operationally that had theoretical single stage capability (but not with reusable hardware penalty). On the other hand, single stage simplifies operations tremendously. SpaceX has very good approach. Two stages with simple fuels, first stage doing propulsive landing to pad (ie not fished from the ocean, like they originally planned). The second stage is unsolved currently, but there are a lot of potential solutions to that.