RE: Space Directive Un, Part Duex...no trois..no....
December 16, 2017 at 6:14 am
(This post was last modified: December 16, 2017 at 6:26 am by Anomalocaris.)
At the end of the Apollo program, the conventional wisdom was the shuttle was the wave of the future, conventional disposable rockets like the Saturn series were a dead end. Hence all the tooling for manufacturing the Saturn series rockets were sold for scrap as a way to keep budget pressure from causing the space agency to backslide from state of the art shuttle to the proven but believed to be obsolete Apollo infrastructure. Thus it was intentionally made impossible to restart production of any major components of the Saturn rockets without a huge investment to rebuild the industrial base.
However, by the year 2002, when the shuttle had two catastrophic fatal accidents under its belt and proved nowhere near as economical to operate as the old Saturn hardware, much less as spectacularly economical as in the claims made for the shuttle in the mid 1970s, interest fell back onto a new conventional heavy lift disposable rocket in the same class as the Saturn 5. When reviewing what was learned from the original Saturn 5 program and whether any design and material from Saturn 5 can be resurrected for use, the J-2 LOX Engined used in stage 2 and 3 of Saturn 5 was judged to have been a sufficiently good design even by early 2000s standards that it was determined production of the engine should be resumed for use in new NASA heavy lift rocket upperstage. However tooling for continued production had to be made from scratch, as original tooling were gone. So it was decided to take the opportunity to leverage 40 years of progress in manufacturing technology to build better tooling that could in turn make many of the engine’s components better and lighter. For example instead of laboriously brazing all the cooling channels to the rocket’s exhaust bell, cooling channels are now directly milled into the exhaust bell wall with CNC milling machine.
However, mission creep set in. Once it was determined New tooling could make some components better, it was decided to explore whether the design of the engine could be revised to take better advantage of the better components. Eventually the new version, J-2S, was so improved that it shared virtually nothing with the original j-2 engine from the Apollo era, from specification, to performance, to any shared components. It is now a whole new engine requiring a whole new production process.
However, by the year 2002, when the shuttle had two catastrophic fatal accidents under its belt and proved nowhere near as economical to operate as the old Saturn hardware, much less as spectacularly economical as in the claims made for the shuttle in the mid 1970s, interest fell back onto a new conventional heavy lift disposable rocket in the same class as the Saturn 5. When reviewing what was learned from the original Saturn 5 program and whether any design and material from Saturn 5 can be resurrected for use, the J-2 LOX Engined used in stage 2 and 3 of Saturn 5 was judged to have been a sufficiently good design even by early 2000s standards that it was determined production of the engine should be resumed for use in new NASA heavy lift rocket upperstage. However tooling for continued production had to be made from scratch, as original tooling were gone. So it was decided to take the opportunity to leverage 40 years of progress in manufacturing technology to build better tooling that could in turn make many of the engine’s components better and lighter. For example instead of laboriously brazing all the cooling channels to the rocket’s exhaust bell, cooling channels are now directly milled into the exhaust bell wall with CNC milling machine.
However, mission creep set in. Once it was determined New tooling could make some components better, it was decided to explore whether the design of the engine could be revised to take better advantage of the better components. Eventually the new version, J-2S, was so improved that it shared virtually nothing with the original j-2 engine from the Apollo era, from specification, to performance, to any shared components. It is now a whole new engine requiring a whole new production process.
