CaLV to Get Bigger Fuel Tanks

Bigger Prop Tank Was Key To NASA’s RS-68 Decision, Aviation Now

“NASA opted for the Pratt & Whitney Rocketdyne RS-68 engine to power its next-generation moon rocket in part because the factory that built the Saturn V can still handle the 33-foot diameter tankage that went into it.”

NASA Alters Its Course To The Moon. Again. Is the Program Heading For Trouble?, Tom Jones, Popular Mechainics blog

“The downside of the RS-68 decision is that the Cargo Launch Vehicle’s core fuel tanks must grow from a planned width of 27.5 feet to 33 feet (as wide as the old Saturn V’s first stage). That’s because the RS-68, although more powerful than the SSME (650,000 lbs. of thrust vs. 420,000) is a heavier, less efficient engine, requiring more fuel to lift the same amount of payload to orbit. The larger stage diameter will prevent NASA from using its existing external tank production line at Michoud, LA for the new rocket; instead it will have to invest in new production tooling at the same site. Those “shuttle heritage” savings are dwindling fast.”

Engine may be moon-trip choice, Huntsville Times

“When the plan to return to the moon was announced, Cowing said, “people inside and outside of NASA thought that it would just take shuttle hardware and create the rockets needed to go to the International Space Station and on to the moon. “That doesn’t seem to be the case. We are seeing a slow drift away from shuttle-derived hardware, and now there’s probably going to be a mix of shuttle hardware and” expendable rockets, Cowing said.” … “To Cowing, NASA is “in reality just creating two brand-new rockets – one for crew and one for cargo. In the end, there will probably be little of today’s shuttle” used in the rockets.”