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metaphor

A more accurate delta-v map

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I noticed a few inaccuracies in other delta-v maps going around. They don't have the most efficient transfers. For example, you wouldn't go into a low orbit around Jool if your target is Pol. So I made this map. It's calculated using the Vis-viva equation and information from the Kerbal wiki. I based it on this design. The atmospheric take-off delta-v's were based on a few different trials I did.

How to use: start at Kerbin on the bottom, pick a planet/moon to go to, add up the delta-v's along the nodes to find the needed delta-v. This map assumes using the Oberth effect, so the delta-v's along the vertical starting from Kerbin are burned at Kerbin periapsis (except for Kerbol). The line on the left should burn towards Kerbin's retrograde and the line on the right should burn towards Kerbin's prograde. The delta-v's along the horizontal are burned at the other planet/moon's periapsis. The delta-v's along the vertical of another planet's moon are burned at that moon's periapsis.

Your delta-v may vary based on TWR, drag, using gravity assists, and the planet's position (its periapsis or apoapsis). Here is a slightly more detailed map showing the range of delta-v's based on periapsis/apoapsis values.

Any feedback is appreciated. Let me know if something is wrong with it, and feel free to make another graphic with this info if you can draw a better one.

Edit: "escape" means capture orbit if you're coming from Kerbin, and escape orbit if you're going the other way. It's the same parabolic orbit. For example, if you are in a Kerbin-Moho transfer orbit and you burn retrograde a little more than 2090 m/s at Moho periapsis, you will barely be captured by Moho. If you're in low Moho orbit and you burn prograde a little more than 320 m/s, you will barely escape Moho.

Also, ksp.olex.biz and alexmoon.github.io/ksp/ are really good websites for planning interplanetary transfers.

UUU8yCk.png

Here's the link if the image is too big for the screen.

edit: added orbit altitudes

As an example

example transfer

Let's say you're in a 70 km orbit around Kerbin. The purple orbit is keostationary orbit and the outer black orbit is the Mun's orbit. If you burn 680 m/s prograde at the blue dot, you will be on a keostationary transfer orbit, the green orbit. Then you can do one of two things. If you wait and burn 435 m/s prograde at the green dot, you will be in keostationary orbit. If you don't wait, and instead burn another 180 m/s at the blue dot, you will be on a Mun transfer orbit, the red orbit. Now if the Mun is there when you get to the red dot, you can burn 80 m/s retrograde at the Mun periapsis (~10 km) to get into a highly elliptical Mun orbit. If you burn another 230 m/s retrograde at the Mun periapsis, you will be in a low Mun orbit. From there it takes 580 m/s to land on the Mun. Then you can repeat the same steps backwards to get back to Kerbin (except now you can use aerobraking).

Edited by metaphor
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are these values for returning to Kerbin or leaving Kerbin?

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Wonderful thanks. I collect Delta V maps just to do and it have multiple reference sources lol. This makes #6.

Thanks again.

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Would you consider to post you collection here in the forum (maybe this thread) or in the Wiki to let others participate in your knowledge :)

are these values for returning to Kerbin or leaving Kerbin?

I think it's for both.

To get from Kerbin to Duna just follow the lines from Kerbin to Duna and sum all the numbers between the black dots. If you follow red arrows on your way, there's a possibility to save some delta-v due to aero-braking. I think from Duna to Kerbin it's the same amount of delta-v.

Edited by Crown
Added answer

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I would much appreciate a printer-friendly format of this!

EDIT: Particularly if you could get rid of the subpixel smoothing? Looks great on some LCDs, looks rather terrible elsewhere.

Edited by draeath

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are these values for returning to Kerbin or leaving Kerbin?

Both. It's reversible. Just follow the dots to the place you want and back. You can use aerobraking to save delta-v where the red arrows are (the aerobraking only works in one direction).

I would much appreciate a printer-friendly format of this!

I'm not sure what a printer-friendly format is. I made it in Paint.

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Would it bother you if I took your information and reflowed it into a different layout/format?

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Would it bother you if I took your information and reflowed it into a different layout/format?

Go ahead. I'm not very good with graphics. I mainly wanted the information since I didn't find it anywhere else and it took a few hours to calculate.

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Me either, but I've made process diagrams for work, and I could see this fitting that 'scheme' well enough. Think flowchart.

EDIT: here's what I use for that kind of thing, if you're curious!

Edited by draeath

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Both. It's reversible. Just follow the dots to the place you want and back. You can use aerobraking to save delta-v where the red arrows are (the aerobraking only works in one direction).
Ok, the red arrows just made it seem like it work best if it returning to Kerbin. Edited by AfailingHORSE

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I have one question about this chart:

I quite don't get it with the option for aero-breaking.

When doing a Duna-Kerbin transfer why do I have an option to aero-break for a Kerbin capture?

Example: when I want to go from a Kerbin capture to a low orbit I lower my periapsis into the Kerbin atmosphere (at this moment my parent body), fly several times through it to let the apoapsis drop and then I burn prograde at the apoapsis to rise my periapsis again to obtain a stable orbit.

During a Duna-Kerbin transfer the Sun aka Kerbol is my parent body (the one's of SOI I'm in). Doing a Duna-Kerbin transfer with aero-breaking with the same principle doesn't work, I think, because the Sun has no atmosphere tp aero-break in (or does it?).

Do I maybe interpret the chart wrong?

Printing the chart with the setting 'fine' did work from my view. The text is a quite tiny but I can read it.

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Ah, here's another tool folks can use if they would rather something a bit more... in-depth ;)

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I have one question about this chart:

I quite don't get it with the option for aero-breaking.

When doing a Duna-Kerbin transfer why do I have an option to aero-break for a Kerbin capture?

Example: when I want to go from a Kerbin capture to a low orbit I lower my periapsis into the Kerbin atmosphere (at this moment my parent body), fly several times through it to let the apoapsis drop and then I burn prograde at the apoapsis to rise my periapsis again to obtain a stable orbit.

During a Duna-Kerbin transfer the Sun aka Kerbol is my parent body (the one's of SOI I'm in). Doing a Duna-Kerbin transfer with aero-breaking with the same principle doesn't work, I think, because the Sun has no atmosphere tp aero-break in (or does it?).

Do I maybe interpret the chart wrong?

If you're in a Duna-Kerbin transfer orbit, your orbit intersects that of Kerbin. If your Kerbin periapsis is 70 km, then you will be going 3380 m/s at periapsis. If instead of a 70 km periapsis you use the atmosphere to bleed off 130 m/s, you will be going 3250 m/s and will be barely captured by Kerbin. If instead of 130 m/s you bleed off 130+20 m/s, you will be in an orbit with apoapsis at Minmus's distance. If instead you bleed off 130+20+70 m/s, you will be in an orbit with apoapsis at the Mun's distance, and so on.

So the aerobrakes on the transfers are from Kerbin's atmosphere when you're coming back to Kerbin. (The aerobrake arrows are one-way only.)

Edited by metaphor

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The Moho capture delta V requirement leaves me doubtful.

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[...]another tool[...]

Matlab and KSP. Thanks for this link.

If you're in a Duna-Kerbin transfer orbit, your orbit intersects that of Kerbin. If your Kerbin periapsis is 70 km[...]

Thanks. Now I get it. :)

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The Moho capture delta V requirement leaves me doubtful.

It's the average delta-v if you do a Kerbin-Moho transfer. It can be from 1490 to 2790 depending on where Moho is in its orbit. But since Moho is so close to the Sun, if you miss the phase angle and reach it at an angle you will need a significant amount more delta-v for capture.

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It takes less deltaV to land on and return from Gilly than it does to/from Mun. So get out there!

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You don't appear to have taken inclination and eccentricity into account?

http://alexmoon.github.io/ksp/ doesn't give moho captures for less than 3300 ish.

If you were going to an outer moon of Jool your very best plan is to aerobrake at Jool until you are just captured, then at your AP (at the edge of Jool's SOI raise you PE to the correct level and then lower your ap enough to get a capture.

The accuracy of the charts doesn't matter too much as there are always course corrections and imperfections so you are going to want to pack 10% extra fuel anyway.

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Another map to add to the references! Nice. What did you base the maximum plane change calculations on?

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You should add summary values under each planet/moon so that its obvious at first glance how much you will need for a full trip out - from Kerbin low orbit to the relative body - then all you need to do to work out a full return trip is double that figure and add the Kerbin escape value (4500).

The issue I have with this chart is I am not that interested in most of these numbers - all i want to know is how much fuel is required to get into Kerbin orbit, transfer to target, get into that orbit, and then land/take off at each planet/moon - the rest is pretty irrelevant for me.

Edited by nats

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You don't appear to have taken inclination and eccentricity into account?

http://alexmoon.github.io/ksp/ doesn't give moho captures for less than 3300 ish.

If you were going to an outer moon of Jool your very best plan is to aerobrake at Jool until you are just captured, then at your AP (at the edge of Jool's SOI raise you PE to the correct level and then lower your ap enough to get a capture.

The accuracy of the charts doesn't matter too much as there are always course corrections and imperfections so you are going to want to pack 10% extra fuel anyway.

I took inclination into account when calculating the maximum plane change maneuver. I made a different map considering the eccentricities by calculating the range of delta-v values possible when meeting at periapsis vs apoapsis. It's impossible to give a single number for all the combinations of inclination and eccentricity given by different transfer windows. I just put down the average transfer delta-v and then the maximum plane change assuming you're changing inclination somewhere along the transfer orbit. If you combine the transfer or capture burn with an inclination change you can get lower values.

That website gives a Moho insertion burn as low as 1800 m/s if you set earliest departure to day 200 or 300.

Your Jool outer moon capture trajectory is basically a bi-elliptic transfer. I'm not sure if it's less delta-v or not but I only considered Hohmann transfers.

Another map to add to the references! Nice. What did you base the maximum plane change calculations on?

Thanks. I assumed that the transfer burn is straight prograde, no normal component, and that you do the plane change somewhere along the transfer orbit. So the maximum plane change delta-v is v*sin(i), where v is the maximum speed you're going at any point in your orbit, and i is the inclination angle change. This is definitely not the most efficient way to change planes, since you can add a normal component to your transfer or capture burn and save a lot of delta-v that way. http://alexmoon.github.io/ksp/ has a complete transfer optimizer.

Edited by metaphor

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I managed to shoot from Laythe to Kerbin in 1750 m/s, from a highly inclined 60km orbit, then corrected at the cost of 200, but here the forecast is 2160, which is much more.

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The cheapest path to Kerbol is from Kerbol escape, not from low Kerbol orbit: it's a shave under 28 km/s.

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I managed to shoot from Laythe to Kerbin in 1750 m/s, from a highly inclined 60km orbit, then corrected at the cost of 200, but here the forecast is 2160, which is much more.

I'm assuming going to a low Jool periapsis before burning interplanetary. For Laythe and Tylo it might be better just to burn directly from their orbit. The delta-v numbers aren't the most efficient possible ones (you can get more efficient using gravity assists or burning directly interplanetary from moons etc.), the chart is just the delta-v for straight Hohmann transfers and burns at low periapses.

The cheapest path to Kerbol is from Kerbol escape, not from low Kerbol orbit: it's a shave under 28 km/s.

The number between low Kerbol orbit and Kerbol is what is required to land on Kerbol, not just to hit it. If you only want to hit or flyby a planet, you only need the delta-v up to the transfer orbit that goes to it.

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It`s good that the numbers are conservative. If I build a ship according to these numbers I would rather have the error of a little too much Dv than a little too little...

This looks a nice map. Very clear.

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