Your opinion of mods is a little biased. They do have nothing to do with the proportion of the player's influence on the game or the required skills you need. Apart from MechJeb. But that's pretty much the only big mod you can consider a true autopilot. In fact, mods usually make the game more complex and therefore often even more difficult. But I guess if you're new to the game, it's probably best to stick to vanilla for the time you got used to the game. I did it the same way when I noobed through the Kerbol system. Okay, let's leave that aside. Interplanetary transfers! Your first destination should either be Duna or Eve. They're closest to Kerbin and their orbits have pretty much the same inclination, so they're the easiest planets to go to. First and most important, you have to know when to begin your transfer. The planets have to be aligned correctly. This is your time window and phase angle. For example, if you want to go to Duna, you should begin your transfer when Duna is 44.36° ahead of Kerbin (angle of Kerbin - Kerbol - Duna). Duna has to be ahead, because Duna's orbit is further away from Kerbol than Kerbin's. On the other side, going to Eve, which is closer to Kerbol, requires a transfer when Eve is -54.13° behind Kerbin. Of course, you can transfer at other times, too, but you need least deltaV when transfering at these times. How do you know this stuff? Well, you can trial and error, calculate it yourself or use websites such as the kspwiki or http://ksp.olex.biz/ or mods like protractor. Protractor only delivers numbers for you. Nothing more. Next thing is to know at which point to escape your orbit around Kerbin. This is the ejection angle. In case of transfering to Duna, the ejection angle is 150.91° (angle of Kerbin's prograde vector - Kerbin - ship). I really suggest to check http://ksp.olex.biz/ to see what I mean. Just mess around with maneuver nodes in the map window when the planets are aligned. Place a node, zoom out and look what happens when you go for the prograde. Try to create the closest interception possible. When you have one, perform your burn and adjust your interception on the way to your destination. The earlier you adjust your interception during your transfer, the less deltaV you'll need. But you can adjust it more precise when your closer. Use atomic engines because they're most efficient. When you're in the Sphere of Influence (SOI) of Duna or Eve, use their atmosphere to aerobreak and to create an orbit around the body. This means, you put your periapsis to an altitude where the atmosphere decelerates your ship just enough to close the orbit but not that much that it gets caught and crashes onto the planet. There is no exact number for that. It depends on your ship, the atmosphere and gravity, your speed and so on. I really recommend to hit F5 before doing that. Good Luck!
