![]() Firstly, you need to understand a little about how GTc works. Yes, there's one procedure I've implemented that helps considerably, which might be regarded as 'best practice'. Is there a best practice for adjusting SRB throttle in the VAB and letting GTc calculate new parameters when designing a mostly solid-fuelled rocket (think Vega-like) that only has a small liquid-fuelled upper stage for circularisation and manoeuvering? Try reducing the value on the sensitivity- the smaller that number, the lower the mod can take the throttle without just turning the engine off. If I'm aiming for 80km, it would be more efficient if it was more aggressive with the turn early instead of going high, right? But I guess that's going to make my speed even higher and less efficient. Do I just need to always launch a new craft 2 or 3 times all the way to "success", just revert to launch after that point and let it iterate closer to ideal? Or should I change something in the inputs to help it out? I think it's because of all the boosters it can't throttle down enough, but it also seems to keep the main engine throttle high for way too long (I get aerodynamic and heating effects pretty early, which I hear is not ideal). My ships routinely overshoot the desired AP. Sorry for what is probably another dumb question but I'm not finding it (partly because the name of this mod is very hard to search for, you just get people talking about gravity turns in general). (for example with an ISP of 345 and an initial TWR for 2 on the MUN simulation indicates 645 m/s to a 14km orbit, including circularization for a constant vertical velocity, vs 657 for best possible gravity turn) I've done some simulations in mathematica, (single stage) and get that a perfectly executed version of this (TTA fixed to 10s) slightly outperforms gravity turns for initial TWR of 1.5 to 3 on the Mun. It usually works on the first short and gets better DV to an actual gravity turn performed by GT. Once past the terrain, I set it back down to 20s or so. Then I just increase the time to AP setting enough to clear the terrain. The only way this fails is if there is higher terrain downrange. Prograde at this point is usually at most a degree or two above horizontal. Eventually this angle decreases to below prograde and the rocket follows prograde to orbit. This results in the craft pitching up and down (because of the PID controller I guess) around an ideal pitch angle of arccsc( Thrust/ (mass * (g - centrifugal force))) which decreases as horizontal velocity goes up and mass goes down. If it is over, GT follows prograde, if it is under, it pitches up to push the TTA up. I think GT keeps the vehicle at the starting pitch until prograde drifts down to that pitch.Then it looks to see if the time to Ap (TTA) is under or over the desired amount. ![]() ![]() When I execute this the rocket goes up, turns to the angle I indicate, vertical velocity stays at about 10m/s (a little more due to the time to turn), and starts to build up horizontal speed. For the starting angle, I use the maximum angle that keeps a vertical TWR of 1. In terms of GT settings, I set the starting velocity to 10m/s (or something small, but enough to give the vehicle time to get truly vertical) time to AP I set to 20s for both start and end. The idea is to use just enough vertical thrust to keep from crashing into the terrain. (Only recommended for vacuum launches, also I've been using 10x rescale and SMURFF so I have DV costs that are about sqrt(10) times larger, but I have much better mass fractions.) I've been using it to implement constant vertical velocity takeoffs. I just wanted to share some off-label use I've been getting out of GT. ![]()
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