In german (i am a native speaker) Raketenwissenschaft is the equivalent. It is used the same way "rocket science" is used in english.
For example it is used to say that something is / or is not a complex thing.
For example: "Webdesign ist keine Raketenwissenschaft."
Here are some more good examples:
http://www.linguee.de/deutsch-englisch/uebersetzung/keine+raketenwissenschaft.html
Some of them i have heard in real life in the same phrasing. I said similar things myself. I think the "rocket science" part of ksp can be translated very well into the german language.
