>>1670626>Mainly because they were too damn big and heavy to transport in one piece from Utah to Florida. Mainly because the ignition process, landing in water, and being towed back to shore cause issues.
>So are Falcon 9 boosters.Booster + upper stage vs. two SRBs + connectors to ET + ET + orbiter. Falcon 9 booster could and has been launched and recovered by itself.
>A simpler method of recoveryDoesn't scale, as seen by the ET not being recovered. No possibility of flyback.
>which permits more payload by avoiding the need to reserve propellant for landingFalcon 9 isn't primarily payload-limited. It's been cannibalizing Falcon Heavy launches because they've massively increased its capacity while preserving and enhancing its recovery abilities. It's economical even without launching max expendable payload (which it has the flexibility to do, if desired).
> it will be so reliable that it won't even need an abort system to safely be used as such.LES are only used in the first stages of launch, then get jettisoned. They're by no means a requirement for safe operation, nor do crewed vessels have anything during the majority of time they spend in orbit or returning. Incidentally, NASA approved and even complimented SpaceX's emergency/abort procedures for Lunar Starship.
>the same level of scrutiny It's not even about levels of scrutiny. The STS architecture is inherently trouble-prone and relatively fragile. It was also capped to 12 or so flights a year, well below an economical flight cadence.
>are exactly what drove STS to such outrageous costsSTS costs a lot because it's 1970s tech applied to an extremely large vessel which leapfrogged all possible incremental designs to fulfill a wide and conflicting set of mission roles. Note that SLS, which is expendable and which will use components modified for expendability, performance, and "affordability" manages to be even more expensive, even more production-limited, and have even lower launch cadences.
