Delta-V map

[Tommygun]

No, if you're transferring from Mün orbit to Kerbin orbit because you'll need every bit as much delta v to circularize around Kerbin as it cost you earlier to leave Kerbin orbit. You'll need less delta v only if you either aerobrake or go down like a missile without intent to orbit, you see, these values are for transferring from orbit of one body to orbit of another body.

OK, I didn't think about circulating and the faster returning speed, as I always just go straight back in on my return.

[SkyRender]

I'm glad people are still finding use for that dV map I made. I do need to update it a bit, of course, and should really provide some easier-to-understand instructions on how to use it too.

The biggest problem in providing a delta-V map is that space is more complicated than "drive to your destination". Your destination also has to be there when you are, and you have to be coming in from the right angle, and a dozen other little considerations factor in as well to just make the whole thing a mess. Trying to give only the most optimal values will lead to under-engineered ships for 99% of starting conditions, while only factoring in the worst-case scenario will lead to massively over-engineered ships that are far more delta-V endowed than necessary for the mission. My goal was to provide an average delta-V map, but even there I made a few mistakes (most notably for distant-planet intercepts; the values listed are closer to optimal than average). Once .20 comes out, I'll likely revise the values and issue a new version of the map.

[RoboRay]

Awesome. An updated version would be greatly appreciated.

Edited May 21, 2013 by RoboRay

[Wait- Was That Important?]

This chart is very, VERY wrong. It takes closer to 1000 dV from a Kerbin-like Kerbol orbit to get to Duna than 110.

If anyone wants an updated, more accurate version, it's here: http://i.imgur.com/dXT6r7s.png

Black is making a low orbit from sea level, Green is establishing an orbit around a body after making a transfer, Blue is an in-system transfer, Black is an interplanetary transfer.

[Francesco]

This chart is very, VERY wrong. It takes closer to 1000 dV from a Kerbin-like Kerbol orbit to get to Duna than 110.

it's not.

Skyrender's chart shows the delta-v value to reach Duna directly from LKO, not from "first escape Kerbin, then from a circular orbit around the Sun transfer to Duna" type of approach, which is what you are talking about: that way of interplanetary travelling is extremely inefficient.

[Specialist290]

EDIT: Whoops, nothing to see here.

[SkyRender]

That gives me an idea for the next version of the chart... Thanks for posting that, WWTI.

[GoDores]

One factor not mentioned is that generally you're moving a lot less mass on the return trip than you are moving outbound. This doesn't directly affect the dV requirements, which are independent of mass, but it makes a big difference in the fuel required to generate the needed dV, and fuel is generally a limiting factor.

For example, I recently ran a mission to Duna and Ike. I started from 300km LKO with two landers, two rover landing modules with two rovers each, and a probe module with five unmanned landing probes, all full of fuel, driven by my interplanetary transfer stage with the equivalent of four orange tanks and six LV-Ns.

Going from Kerbin orbit to Duna intercept burned over half the fuel in my transfer stage (2 orange tanks worth). But after operations in the Duna system, including dropping one rover and lander and a few landing probes on Duna, transferring to Ike and dropping the other lander, rover pair, and probes there, then picking up the Ike lander and going back to Duna to pick up its lander, I was left with just the two mostly empty manned landers and the transfer stage with less than 1/4 fuel left. That was plenty to return the stack to a 300km Kerbin orbit without aerobraking and still left me with 1/8 fuel in the transfer stage (which was left in orbit for refuel and reuse - I don't want to have to launch anything that massive again) and enough fuel to deorbit and land both of the crewed landers.

As I said, this doesn't have any impact on the dV requirements, but it makes a big impact on fuel planning. Just because you burn 3/4 of your fuel getting somewhere doesn't mean you don't have enough fuel to get home.

[CaptinKornflake]

Dude this is awesome

[jimbobslimbob]

Excellent stuff! Thank-you OP, I was looking for something like this

[Kerolyov]

Great chart, bit like an earlier poster I got caught out by circularization burn at Moho being way higher than the chart and ran out of fuel, luckily just a probe! Any tips on which planets can need extra delta V (like the Moho example) if you intercept slightly off ideal and how much extra delta V (compared to the charts) would you over-engineer by?

Edited September 6, 2013 by Kerolyov

[SkyRender]

Great chart, bit like an earlier poster I got caught out by circularization burn at Moho being way higher than the chart and ran out of fuel, luckily just a probe! Any tips on which planets can need extra delta V (like the Moho example) if you intercept slightly off ideal and how much extra delta V (compared to the charts) would you over-engineer by?

Any planet that has an inclination, you will need extra delta-V in large proportion to the change of angle of inclination you have to make to intercept. This can't realistically be accounted for because 1.) you can in fact intercept at the "wrong" angle as long as your orbits pass close enough, and 2.) the amount of extra fuel you have to burn to do so depends on how far out you are in your orbit when you make the correction burn for inclination (the slower you're going, the less expensive it is). I've actually done a single-pass Moho encounter before with no inclination adjustment, but I only pulled it off because the phase angles were literally perfect for it.

[tomf]

High eccentricity of your target (or departure) bodies orbit can have a similar effect. The body won't be where the chart expects or travelling at the expected speed. This tool http://alexmoon.github.io/ksp/ should give a much better estimate which takes eccentricity and inclination into account.

[SirJodelstein]

Uhhm are the interplanetary transfer estimates really taking inclination into account? I just started my first trip to Eve orbit, using 1040m/s dV prograde (950m/s escape +~100m/s to go down to Eves sun-orbital radius), but had to spend ~370m/s on the midpoint-burn to correct for the 2.1° inclination. This inclination-burn requirement was not on the map. Assuming this needs to be invested for a return trip as well, the Kerbals will have to wait for a rescue craft. Oh well, i guess thats a very Kerbal way to learn how to do interplanetary travels

or are the numbers for another transfer type? I think it is might be to correct for inclination during the ejection burn - does that use less dV total?

Edited June 12, 2013 by SirJodelstein

[tomf]

The alexmoon site has a few options, some which have a mid course inclination burn, some which do the inclination change during the initial burn.

[Wjolcz]

Could someone make a chart of Delta-Vs needed to reach low orbits of all the bodies?

[RoboRay]

Could someone make a chart of Delta-Vs needed to reach low orbits of all the bodies?

You mean like the one at the beginning of this thread? The numbers inside the circles representing the planets/moons are what you're asking for.

[Wjolcz]

I mean ascent Delta V. All I see there is Delta V needed for landing.

Edit: Oh wait... Nevermind. I am an idiot.

[Commander Zoom]

Don't fret too much, the labeling is (as others have noted) inconsistent or at least non-intuitive in some places.

[Joe Shmoe]

That looks similar to a delta-V chart from the KSP wiki

[Mefi282]

That helped me, thanks. Finally i know how many Delta V i need to have

[Atanar]

Still quite unrealistic. Why would anyone go to Jool low orbit if he want's to reach Pol?

[NovaSilisko]

Because it's much easier to present that way. There are a million different ways you can do things and the chart only covers one...

[SkyRender]

Because it's much easier to present that way. There are a million different ways you can do things and the chart only covers one...

Quite. That was my main problem in designing the delta-V map in the first place: the fact that there's so many possible ways to do things. In the end I decided that it was best to just list the approximate average delta-V. Of course I realize now that pretty much anything outside of the immediate Kerbin system can vary immensely depending on how out of phase you are when you launch and/or how much of an inclination adjustment you end up making, but that's hindsight for you.

[RoboRay]

Still quite unrealistic. Why would anyone go to Jool low orbit if he want's to reach Pol?

The chart shows 49 different planets/moons and parking/transfer orbits. You'd need 2400 more charts to show the ideal transfers for every possible origin/destination.

This chart is optimized for traffic departing or arriving at Kerbin, which covers the vast majority of all missions.

If you'd like to generate the rest, we would all appreciate it.