Watching "Mars" on National Geographics I try to calculate what the cost would be to bring anything usefull back to Earth. More specifically I wonder what fuel-payload ratio a rocket could have when lifting off from Mars. I want to use Tsiolkovsky's rocket equation Δv = ve ln(m0/mf) or Δv = Isp g0 ln(m0/mf) That contains g (9,8) and I thought I could replace it with g for Mars (3.7) but that gets me nowhere since that a lower g results in a lower Δ v, when it should not. The fule-payoad ratio of a Saturn V for high orbit is about 60:1 (m0/mf). Cost for one launch about 1 billion $. I want to calculate how many launches are needed to bring the parts and fuel to Mars needed to assemble and tank a rocket, that can lift some payload and landing vehicle from Mars and bring it back to Earth. For that I need a Tsiolkovsky equation with a differnt ”g”, so to say. Isp I assume to be the same for both Saturn V and return rocket. Any suggstions?