Could you give some advice on how to make an Hohlmann Transer? I had a look at the wiki (kerbal and the original one) for the last hour, but I still haven't figured out how to interpret the numbers. If I have understood the concept correctly I should apply thrust until I have reached a certain speed, then wait a certain amount of time and then apply thrust in the opposite direction until my speed is correct, in order to change the orbit (in this case from a lower one to a higher one). What I don't understand is which number in your program corresponds to what action. If I, for example, want to change from a 100km to a 120km orbit, what is it exactly I need to do?