![]() I did manage to work out the exhaust velocity of the stock engines. For now I use an online dV calculator to do that bit. Although I don\'t fully know how to integrate. I personally have recently been researching into the physics of the game. Superb video and tutorial! You would benefit the KSP community hugely by continuing with more tutorials. I could change any of the fixed values and observed that periapsis was highest for delta-V angles which brought the resultant elevation angle closest to zero. I calculated the resulting periapsis for a range of delta-V elevation angles. What I did was give myself a starting altitude, elevation angle, velocity, and a delta-V. This comes up a lot when entering Kerbin\'s SOI on the way back from the Mun. (And i could not find any version of this already worked out online).Įven a brute-force search over magnitude and angle (with a spreadsheet) would be quite impressive, but you\'d have to do it for each situation. OK I always seem to be the one to ask - how did you calculate that? I can see how to do so in principle - at a given position, a change in velocity vector delta-v will change the orbital energy and angular momentum, related to semi-major axis a and eccentricity e, and the periapsis is just a(1-e), but it seems like an involved calculation to find the direction (and magnitude) of the minimum delta-v required. You made me learn something.Ĭosine I think, unless someone needs to cosign your loan for the spacecraft An easier way to think about it is to change your vector until it it level with the horizon, and then add velocity prograde after that if needed. Looking more at the spreadsheet I had made, it seems that, for a given delta-V, the most effective direction to burn in to maximize periapsis is one that minimizes your velocity vector\'s elevation angle (the angle between it and the local horizon). ![]() Due to the cosign effect nature of this situation, my burn was very close to optimal. I did some calculations just before typing this reply, and it seems the most ideal angle to thrust at in the particular case of this video was around 73° above the local horizon. Can you explain a bit more about what you did to raise your periapsis at the end there? (What direction you want to burn and why?)Īt the time, I just knew that changing my velocity vector direction would be more effective than just burning prograde. If you do the algebra, you will find that the most fuel efficient vertical ascent is one in which drag equals weight. The Goddard Problem is finding the most fuel efficient way to vertically ascend through an atmosphere. There has to be somewhere between the two that fuel economy is maximized. You would also agree that not using enough power to leave the launchpad (because of gravity) is also very bad on your fuel economy. You would probably agree that going too fast chews up a lot of power, while having a very small marginal return of velocity gain. If you want to double your velocity, you need to quadruple your power (not including power to overcome gravity). The force do to air resistance is proportional to velocity to the second power. Air resistance is why there\'s an optimal thrust to weight ratio. If there is no air resistance, the obvious amount of thrust to use to maximize fuel economy is as much as possible. Could you explain why you reduced throttle at takeoff further? You said the Goddard Problem, but i\'m not sure how to apply it.
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