3.7x dV calculation

[NFunky]

bin-toys, I have what I think is a pretty simple maths question. I've mentioned before that I'm playing with Kerbol 3.7 and its really been making the game a lot of fun. The dockets and flight profiles are more realistic, so things like a two stage Mun lander actually make sense.

Anyway, I'm assbling a huge ship in LKO to bring your kerbals there, land at at least two seperate locations and return. My mother ship is designed so that I can just shuttle up more fuel tanks and plug them in for more dV for the tranfer burns, but I'm a bit stumped on the landers.

This

I just don't have any numbers to aim for. I've been going off of dV maps and guesstimating the multiplier based on stock Kerbin-to-orbit vs. 3.7x (about 3500 v 5500). Any suggestions on how to finding more accurate estimate would be great.

[Nich]

excel and do the math your self. There was a cheat sheet with every formula you need on the wiki but I cant find it now. All the parameters you need should be found in game but if the mod has not updated the info they can be derived pretty easily

[Streetwind]

A different method could be to send unmanned probes with plenty of fuel to every body in the system and scout out the numbers. Just learning how fast you're going in low orbit of your chosen target body is incredibly helpful, because then you can just add a rough 25% on top of that and call it your dV required for landing. Which is also equal to your dV for launching again. Works on every airless world. Worlds with atmosphere, you of course do a ballistic EDL that will require very little dV. But to launch again you need extra due to drag, so you might as well use the same estimate.

[NFunky]

My math skills are okay, but not great. What kind of formula and parameters would I use to calculate Duna-to-orbit dV? I assume I'll need planetary radius, gravitational acceleration, atmosphere height/pressure, etc. How should I put these together and crunch them?

Thanks.

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Ahh, that orbital speed plus 25% is a great rough guide. That should be a lot easier to calculate from planet radius and gravity alone. Good point on the atmospheric vs airless dV aswell. I'll make sure to bring lots of chutes.

BTW, exactly how much drag can I expect from Duna compared to Kerbun?

[cantab]

My understanding is that if the planetary radii are multiplied by x, the orbital radii also by x, and the surface gravity unchanged, then the delta-V requirements are multiplied by the square root of x.