Fuel idea for all forms of Propulsion.

Well the concept of hydrogen is a good level of balance in its current state but i believe it could be improved on for all other forms of propulsion as a form of stepping stones of progression.

For instance first you should start from rover tech these should be able to have three forms of fuel one being the current battery as in real life we do have electric cars but the second form of fuel would be combustion utilising petroleum that would need to be refined and third would be the final tier uranium.

Next would be aerospace tech that would need petroleum refined into jet fuel via other materials thus slightly more expensive then regular petroleum thus not making rovers obsolete as this would be a measure of cost vs convenience cheaper fuel means being stuck to the floor more expensive fuel means being able to take to the air and also being able to use uranium as a final tier of fuel.

Hydrogen is already in a good stage as of now for balance.

As for ion thrusters i would say gas should be the fuel for them to work being the ionisation process required to allow the thrusters to work this could be improved with different more advance forms of gas starting from oxygen to a new gas type to improve efficiency would also open opportunity to gas collection with the new weather system that when there is a storm the collector will get to work.

This in turn adds more functions to rovers also as they would be able to be on alien planets collecting this gas to then return back to base to be refined into substance that would work for the ion thrusters.

This also adds to future developments of the game expanding into a hole new branch of tech.