I've been messing about with mechjeb lately, and I've found that I can get my (rather heavy) craft into a 150km orbit with a gravity turn starting at 40km and ending at 80. Those are just semi-random values I plugged in and have had some luck with. However, I have a feeling this is because I gave myself a massive safety margin with fuel, and it's likely not the most efficient method. I've been using a slightly modified DualEva craft that I found on the forum, I've added more fuel for all stages, and a few long burn SRBs (from the KW pack) to the first stage. Takeoff weight is 495t. I am assuming (coming from a background with very little in the way of physics or mathematics) that the optimal start/end height, as well as the shape of the turn, is dependent on a variety of factors (TWR, aerodynamics, acceleration, etc.) What formula/rule of thumb could I use to determine a more efficient gravity turn? If you need, I can try and provide you some more data about the craft in question, or I can try it on the unmodified DualEva craft, the .craft file for which is located on this forum (it also requires less addons, I believe). The entire reason I modified the craft in the first place is that I had insufficient fuel to execute a Trans-Munar Injection once I'd achieved my orbit, which led me to believe that my takeoff was inefficient. Here are a couple of preconceptions that I have, please correct me if I am wrong: -Higher TWR=greater acceleration. -Lower acceleration demands a more vertical flight path (higher start for gravity burn) to minimize the amount of time spent in atmosphere. -My current end-height for the gravity turn (80km) is not a terrible idea, as it is out of the atmosphere, and makes the trip to the apoapsis easier and drag-free. -A steeper angle of ascent is better than a shallow one, especially for heavier craft/lower TWR. -The highest TWR should be at launch, the further you are from the surface, the lower the effect of gravity/atmospheric resistance. Ideally, I'd like to have a good number to plug into the ascent autopilot, as well as a usable formula to apply to future craft. This is the most stable design that I use right now (most of my other designs utilize a lot of fairings, and the later stages within them tend to torque a bit, vastly reducing efficiency, but they look way too cool to not build.) My later designs will hopefully be more stable. Thanks in advance for your answers. I've found that this is one of the friendliest and most helpful game communities I've come across in many years.