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Comment by _ph_ | Hacker News Reader

While the article was focused on the Raptor engine, it shows how great an engine the RS-25 of the space shuttle was. It was crazy expensive, but as the shuttle was reused, one could justify the cost. The sad thing is, this engine will be used in the SLS - with no reuse what so ever. If anything describes the insanity of the SLS system, then this. They are flying the most expensive rocket engine ever in fully disposable mode. Even worse. After ending the shuttle program, the engines were of course preserved, so at least the first SLS flights are going to waste the origininal shuttle engines.

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> It [RS-25] was crazy expensive, but as the shuttle was reused, one could justify the cost.

The engines had to be taken apart, thoughtfully checked because some of the blades in the pump may get fisures or get broken, replace the bad parts and then ensembled again. It was more like a refurbishment o rebuild, than a easy cleanup.

From https://en.wikipedia.org/wiki/Criticism_of_the_Space_Shuttle...

> increased ongoing maintenance costs related to keeping the reusable SSMEs in flying condition after each launch, costs which in total may have exceeded that of building disposable main engines for each launch.

In the report of Feynman about the Challenger disaster https://history.nasa.gov/rogersrep/v2appf.htm he is clearly not happy with the RS-25 and he think that they could cause a big failure in the future. [They didn't fail in the other missions, but it may be some luck.]

NASA just constantly boxes itself into corners like these, going with the “least worst” option.

Here’s an interesting article talking about how they came to the conclusion that the RS-25 was the only way to go;

https://www.nasaspaceflight.com/2016/01/nasa-defends-restart...

Does NASA have any choice? It seems like the political environment in which they operate makes it essentially impossible to pursue any kind of sane long-term strategy.

There is an absolutely solid book on the subject of how NASA comes to make decisions. The Space Shuttle Decision[1]. I say solid and not good because it's easily the most boring book I've read this year being composed entirely of bureaucracy.

1. https://history.nasa.gov/SP-4221/contents.htm

I've read that the RS-25 level of "reuse" was highly qualified, they required a significant rebuild between flights because they pushed the margins so hard. Wikipedia says "refurbished" https://en.wikipedia.org/wiki/Space_Shuttle_main_engine

But you're generally right about the insanity of the Senate Launch System.

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