Add water on some planets and moons like Europa I know it's not in Simplerockets but for mods so you can land on the moon and brake through the ice covering the surface and launch a submarine into the ocean and explore it

I have a list of things that should be added: SRBs, more fuel tanks, more engines, solar panels have a use,batteries, launch escape system, biomes(sea, mountains, dessert etc), nuclear engines, fairings and finally astronauts and the ability to walk around and plant flags.

Edit : I have checked. It is already possible to do most things I have suggested.

I am not sure with seas (probably more work), but artifacts for sure.

An idea would be to design them as parts similar to the pod, with some specificities :
- They are persistent (similar to pods) -> already possible (make it pod type)
- They are hidden in the building menu (similar to pods) -> already possible (add "hidden="true"")
- They can not be controlled by the player -> already possible (don't name it pod-1)
- They can be fixed in place (planet surface), or float around (as any craft). -> already possible
- A value tells the range from which they can be detected (if we have have a sensor. More sensors, means better detection). No value means that the artifact can be detected from anywhere.
- Maybe a message could be given when docking to the artifact ?

The good point with that system :
- Technically, it probably is relatively little work (it is based on the parts system and persistent pods. Only the detection range is new). Of course, aside from the system, there is the content creation... ( a lot of work)
- Being based on parts, it is possible to add docking ports, fuel tanks,...
- Being based on parts, they are modable. New artifacts could be added by player in the universe.
- Being based on pods, they could be found in space and on planets.

It would add to the scenery to include a launch pad and/or launch tower rather than just having a rocket sitting on the ground.