I think the simulation costs should be separated effectively in two pieces forgeting about the distance modifier in favor of a preset complexity parameter as it doesn't make sense that a simulation costs more just because it is harder to get there. The two charges should be: 1. Enviroment Modeling (once): You need to create a model of the enviroment to run a simulation, whichever the vessel is (fixed price depending on complexity). 2. Vessel Simulation (for each simulation): Depending on weight (or other criteria) the simulation has a base cost multiplied by complexity of the simulation. The cost of Enviroment Modeling should vary with complexity in mind: Orbit simulations can be modeled without ever been there from the begining of the game just based on the size and properties observed from Kerbin. Nevertheless, Jool should be more expensive to run a simulation than Eve or Duna and those more expensive than Dress or Moho because the moons add complexity (pretended of course) to the system. All these should be relatively cheap as you can calculate an entire tour with manouver nodes. Atmospheres on the other hand are very complex to model, so that, are very expensive and cannot be modeled without aquiring data, A.K.A. having been there. A good reason to send a probe ahead. I don't know how bodies without athmosphere are treated by the game, maybe the time warp limit can be used for those at a lower price than atmospheres. The atmospheric/surface model could be "purchased" from the upgrades menu (or similar) or charged on the first simulation. Simulation ending (or aditional charge message) upon entering athmosphere would be needed of course. Summary: 1. You can simulate KSC launches and orbits as it is now from the begining although orbit simulations should be cheaper than launch simulations. 2. You can simulate orbits arround other bodies after paying a small amount to first create the model. These should be relatively cheap. 3. To simulate an athmospheric flight or landing first you need to visit the body to aquire the data and pay a relatively big amount of cash for the model. These simulations are more expensive but not too much. I know it may sound complex but I think it ends being less complicated than what you said.