But the mass ratio is not a linear change. It also works on orbital periods too, but that's not important.Īnyway, how do we get all rockets to have exactly 0.31623 times less delta-v? The variables are the mass ratio (which is what KSP changes) and the exhaust velocity. This is fairly accurate, as 3200 m/s is a fairly standard launch into Kerbin orbit, and that corresponds to a real world delta-v of 10,000 m/s, which is about true of real rockets. It turns out that rockets need 0.31623 = 10^0.5 times less delta-v to get around the stock system as they do to get around the real solar system. (Technically it's closer to 0.09091 but let's not be too accurate, these are estimations after all) The rescale factor going from the Real Solar System to the Kerbol System is about 0.1. It turns out that the delta-v to pull off one manuever is multiplied by the square root of the rescale factor. Another equation, the Rescaled System equation, will help us. This equation, which many of you will have seen or even used before, is the embodiment of the rocket in equation form! And it can give us a hint as to how to scale rockets, we just need context for the Δv requirements. M0 = Initial mass, m1 = dry mass, Ve = Exhaust Velocity = 9.81 * Specific Impulse, Ln = Natural Log function, Δv = Delta V. But the specific impulse of the rocket engines themselves are more or less within reason for real world kerosene/liquid-oxygen or some hypergolic rocket engines (a reasonable fit for the density of KSP's fuels and engine throttleability, in fact.) This method isn't bad, but it's not physically correct either. This is accomplished by increasing the mass of engines, the dry mass of fuel tanks, and the mass of some structural and crew parts. So KSP has done two things to reduce the effectiveness of rockets and result in payload/fuel ratios that are much more reasonable (though still much better than real world mass ratios). This is all well and good if you're a space program on a budget, but it doesn't work so well if you're trying to make a video game with any kind of challenge. The mass ratio from payload to fuel would be huge. Real rockets, with realistic performance, would get insane performance in the stock system. KSP rockets are currently balanced against the 1/10th size solar system incorrectly.
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