re: et defends ET
My idea for an even larger booster has two advantages: 1) the dual ET's would be unmodified except for attach hardware and plumbing and 2) the bell of the upper stage engine could sit somwhat between the ET tops thus making for a shorter overall vehicle. A 150 ton lifter could be made with a 27' diameter payload fairing at under 312'. The upper stage would be a cut down ET using 2 center sections and using the Delta 4 LO2 tank mounted inside. Because the dual keel payload support structure is a simple frame, it could be assemble in sections.