>>11116936cont.
So yeah, the core stage of SLS is NOT a Shuttle ET, it's not even similar from a structural point of view, because it carries the RS-25 engines in a group of 4 at the base rather than a group of three on an orbiter bolted up on the side of the tank. The boosters are NOT the same, because adding a 5th segment increases overall internal pressure an thrust enough that the entire thing needs to be redesigned. Obviously there's an upper stage now, which is a modified Delta IV upper stage, and another one in development which can actually deliver a decent payload (the idea was that the core stage and boosters would be ready before they could develop the EUS from scratch, so they planned on using the Delta stage to make up the difference and avoid delays. Instead the core stage and boosters took so long that they could have had the EUS done by now had they focused on it, basically it's turned the idea into a useless waste of time).
The biggest problem with SLS is that it's trying to shoehorn very specialized technology from a shitty and super expensive launch vehicle into a new vehicle in order to save cost, and it's so mismanaged that they're actually inflating costs instead. Also, at the end of the day they're getting a pretty shit launch vehicle out of it anyway, using terribly inefficient boosters in a booster-sustainer design with an under-powered core stage and a feebly upper stage. A better design would have increased the number of boosters to three, the number of core engines to 6, and the feeble upper stage with a larger and more powerful one which would actually be useful for completing the final burn to orbit with heavy payloads. Increasing the core engines from 4 to 6 would make it less under-powered, and adding a third Booster would give it enough thrust to achieve a nice TWR and get out of the atmosphere on solid fuel alone, lighting the core stage engines in-flight before booster burnout.
