Remember, if you want to insert into orbit with a set perigee, you need to have zero vertical velocity at that perigee if you want a circular orbit, you need to insert at zero vertical velocity and cut off your burn when perigee reaches apogee. Your goal is to get your stated apoapsis at about where you want your desired (parking/transfer/final, depending) orbital perigee to be. A deviation of ten to twenty degrees is not uncommon, and at the later stages of flight, won't affect the gravity losses all that much. Just pitch up to kill the negative vertical velocity. You can vary the "ending pitch" during flight to tune your actual insertion altitude, and don't be afraid to circularize after apogee. (Don't forget to turn off auto-stage so it cannot turn the engine on) Another way would be setting the engine toggle action group so you can disable the engines when you're coasting to AP. You'll turn it down later when you approach orbital insertion and you know what your final insertion altitude will be. starts around 1, ends at maybe 3 or 4), a turn shape of 45% and turn end of about least 150km will do just fine (your apogee will be rather higher).īecause of limited ignitions, you'll want to set the target altitude (in the main ascent panel) to much higher than you want, say 5000km. For your average two-stage rocket with a decent second-stage TWR (i.e. Next, you want to set your "turn end" altitude and your "turn shape" such that deviation from your velocity vector (the surface prograde indicator) is minimized. Set your "turn start" to Velocity: 100 m/s (or lower if your SLT is higher than 1.3 or so the higher your pad TWR, the lower speed you want to start your turn). Next, Click "Edit Ascent Path" from the Ascent Guidance window. A value of 3 to 5 should be fine, depending on how much control authority you have. It will keep your deviation from surface prograde to within that many degrees while in the thicker atmosphere. In the Ascent Guidance window, enable the "Limit AoA" control. This guide will teach you how to use MechJeb to fly a pitch program that works decently well for RSS. MechJeb can be used to fly an actual gravity turn: launch, pitch over to 85 degrees at 100m/s, and use MJ's attitude controls to stay fixed to Surface Prograde. Please first see the False KSP Lessons page regarding what Gravity Turns actually are.
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