alt Hacker NewsA lot of amazing recommendations well worth the visit.
The one that's missing is my favorite one though: the sister museums in Sinsheim and Speyer: https://sinsheim.technik-museum.de/en/
They have both Concorde and Tu-144, the full interior of a 747 and a big space exhibit, including the Buran space orbiter. Last year they added a submarine to the collection, next to a massive amount of other exhibits.
I came here to say the same. The location is a bit hard to get to. But if you are in the area, also visit the town of Heidelberg, it is close by and worth the trip.
I went there as a child and loved it, in particular the UBoat you can enter. Next time I am going to Germany I plan to visit it again.