Advanced Delta-V Guide

[EndIris]

Taking a brief break from KSP, figured I'd drop some knowledge here first. Discussion is welcome, I will gladly fix anything people can find that is off the mark.

These tables are to be used in combination with DeltaV maps to help you plan out your missions. The upper left table shows the DV to get from a moon of a planet to a target planet by dropping from the moon to its parent, and then ejecting with the help of the Oberth effect. For example, it would take a total of 270 DV to burn from low Minmus orbit into a low pass of Kerbin and another burn to an Eve flyby. Or, conversely, it would take 270 DV to come from Eve, decelerate at Kerbin periapsis, and circularize around Minmus.

The table below it shows the DV to get from a moon of a planet to a target planet without a burn to a low pass. For example, it would take 980 DV to eject directly from Vall to a Kerbin encounter. This one works in reverse as well, in that it would take 980 DV to insert at Vall coming from Kerbin. Below this chart there is a list of the cases in which it is beneficial to use the Oberth effect. 

The upper right table shows the altitude at which it takes the least DeltaV to eject from one planet to another, or one Jool moon to another. There is always a sweet spot between getting the benefits of the Oberth effect and the extra DeltaV it takes to climb out of a gravity well. From Kerbin, a 360km orbit takes the least DeltaV to eject to Jool, so that may be a good spot to assemble or refuel your ship. It will take more DV to get to 360km from a low orbit, though, so this altitude only minimizes the transfer DV. Like the other charts though, it works in reverse as well, so if you want to set up a comms satellite in a circular Eve orbit, the altitude at which the injection is the least is 30600km.

(For this chart, SOI means the optimal altitude is as high as possible inside the SOI, and 0 means the optimal altitude is as low as possible)

The Jool moon transfer table functions as a DeltaV map for the Jool system. For example, it would take 265 DV to eject from low Vall orbit to flyby Laythe. It also works in reverse, so a trip from low Vall orbit to low Laythe orbit and back without aerobraking would cost 265+600+600+265 DeltaV.  Below this chart, the sum of all the rows and columns for each body are listed. Bop would be the best place for a Jool refueling station because it takes the least total DeltaV to visit every other body one at a time.

Combining these charts can provide a lot of insight into your mission planning. Most people agree that the best place to refuel before an interplanetary mission is Minmus, and the charts agree with that. However, the optimal transfer altitude to Eve is very close to the orbit of the Mun. Refueling and transferring from the Mun is only 80 DV more, and it may pay for itself with easier timing and less inclination changes.

Another common misconception is that Pol is the best moon to refuel on in the Jool system. However, Bop requires much less DeltaV to transfer to and from the other moons in the system, and requires less DeltaV to go to and from Kerbin because of its higher orbital speed. Even Vall may be a better refueling stop than Pol; Laythe, Tylo, and Kerbin can all be more easily reached from Vall than from Pol's high and inclined orbit.

Additionally, many people use the Oberth effect of the parent planet when ejecting from a moon back to Kerbin. There is only one case in the game when it is obviously beneficial: when it is possible to exit Gilly at its apoapsis, swing all the way down to Eve, and eject to Kerbin. Oftentimes Gilly's orbit does not make this possible, but when it is, you can save over 100 DV. 

Disclaimers: most of the numbers were calculated, not taken from gameplay, and may not factor in SOI boundaries or other gameplay quirks. They do not factor in eccentricity or inclination, or the altitude of your starting or destination orbits. They are rounded for a reason. I took them from the sources below and edited a few places where there were obvious faults.

Sauce: 
https://forum.kerbalspaceprogram.com/index.php?/topic/116160-best-place-for-an-interplanetary-launch-facility/#comment-2070116
https://forum.kerbalspaceprogram.com/index.php?/topic/33699-efficient-hohmann-transfer-altitudes/

[James M]

Gonna have to try using this later  Thank you!