[Tutorial] Interactive Illustrated Interplanetary Guide and Calculator

[olex]

Now with actual data from KSP 0.17! Enjoy your interplanetary transfers!

Performing a transfer from an orbit of one body directly to an orbit of another one seems like serious business. A few guides published on the forums have a lot of maths and stuff, you may think this is too complicated to figure out.

Well, it is rocket science, but: it doesn't have to be complicated!

Based on the great Interplanetary how-to guide by Kosmo-not, and with invaluable help from maltesh with more maths, I have taken some time to build the Interactive Illustrated Interplanetary Guide and Calculator for KSP, available under:

http://ksp.olex.biz

Example calculation:

Edited October 12, 2012 by sal_vager

[Vanamonde]

I am continually astounded at the work people here will do for fun and to help other have fun.

[Kosmo-not]

This is going to help so many people. I think this thread should be stickied.

Great job, olex!

Edited August 18, 2012 by Kosmo-not

[Endeavour]

Great work! I agree this needs to be stickied. Very useful

[Ydoow]

Maybe I don't understand Planetary Phase angle,

But that picture looks like you're just measuring the angle between the Mun and Minmus. I thought you would just find the angle between your burn point and where the destination is projected to be.

And the second image isn't making things clear either...looks like you'd end up flying directly towards Kerbin, rather than Kerbin retrograde.

I dunno. I'm probably completely wrong in what I'm thinking it's trying to tell me, but that's my point.

I don't really understand what it's trying to tell me, and if I do, it's not making sense.

[olex]

The phase angle is nothing else but the angle between Mun and Minmus, for the example transfer between those two. It's equivalent to 180° minus what you described, the angle the destination planet/moon will cover during your transfer - to perform a transfer, you want to know when to start it, and the easiest way to figure that is to look for where the destination is, which is what the image is showing.

And the ejection angle is the angle at which you do your burn, given it relation to prograde/retrograde because those two are easiest to measure it against. It is not the angle the ship will fly through during the escape, that angle is exactly 90° smaller, so you will exit the origin's SoI parallel to its prograde or retrograde.

Probably the easiest way to see how these values work is to actually do a transfer using them. The Mun to Minmus transfer doesn't work 100% correctly due to complicated reasons, but Minmus to Mun works perfectly. Do that, and you will see how the escape and intercept trajectories form from these angles.

[2008dragon]

Wow very nice! I just made a spreadsheet to do this, but this calculator is wayyyy better and I'll probably use it instead

Edit: I tried downloading the bootstrap thing but I don't know how (it is probably too complex for me anyway but I wanted to mess around with it)

Do you have to pay for it or something? If I try to open it it will go into WinRar...

Edited August 19, 2012 by 2008dragon

[Ydoow]

The phase angle is nothing else but the angle between Mun and Minmus, for the example transfer between those two. It's equivalent to 180° minus what you described, the angle the destination planet/moon will cover during your transfer - to perform a transfer, you want to know when to start it, and the easiest way to figure that is to look for where the destination is, which is what the image is showing.

And the ejection angle is the angle at which you do your burn, given it relation to prograde/retrograde because those two are easiest to measure it against. It is not the angle the ship will fly through during the escape, that angle is exactly 90° smaller, so you will exit the origin's SoI parallel to its prograde or retrograde.

Probably the easiest way to see how these values work is to actually do a transfer using them. The Mun to Minmus transfer doesn't work 100% correctly due to complicated reasons, but Minmus to Mun works perfectly. Do that, and you will see how the escape and intercept trajectories form from these angles.

OH! Are you transferring from Minmus to the Mun?

I was under the impression we were launching from Kerbin!

Well...suddenly things make a bit more sense.

Was I just being stupid and didn't read, or should you write that somewhere?

The reason I assumed Kerbin was because the lines marking the angles centered down on Kerbin and because the game always starts on Kerbin.

[Oddbin]

The Kerbal community continually impresses. This is a fantastic piece of work. Good stuff.

[olex]

OH! Are you transferring from Minmus to the Mun?

I was under the impression we were launching from Kerbin!

Well...suddenly things make a bit more sense.

Was I just being stupid and didn't read, or should you write that somewhere?

The reason I assumed Kerbin was because the lines marking the angles centered down on Kerbin and because the game always starts on Kerbin.

Well, the screenshot has the calculator on the right with "Origin: Minmus" and "Destination: Mun" shown selected

It can be used to transfer from Kerbin to other planets, it's just there aren't any other planets to transfer to as of now. There's some guesstimated data for upcoming 0.17 planets in the calculator though, that one can play around with.

[deadshot462]

Awesome work. I was making some transfer calculations on Excel but this makes it a lot user-friendly lol. It'd be nice if there was a plugin that showed you the current phase angle between two bodies. and your current "ejection" angle ingame.

[Ydoow]

Well, the screenshot has the calculator on the right with "Origin: Minmus" and "Destination: Mun" shown selected

Well I guess I was just being stupid then lol

But yeah, trying to figure why we were measuring the angle between the Mun and Minmus, and then going retrograde to the Mun when we wanted Kerbin was very very confusing lol

[Ragewaar]

This is amazingly useful for someone like me, who is yet to reach the Mun! Really explains the principals well.

Will be trying again tonight with this tool

[olex]

Plugged the Eve data from this post by NovaSilisko, it's not complete though, and not guaranteed to be accurate either. The name Eve seems to be pretty confirmed by now, so it's in as well. Hard refresh the page (Ctrl-F5) if it isn't working for you to clear the old Javascript from cache.

[Enture]

I'm sitting at my desk, lost in awe and amazement at how a game can bring people to do real math and physics for the sake of just doing it. This piece of programming there, it's AWESOME! Congrats on you three, and thanks!

+1 for the sticky-proposal

[olex]

Updated the interface with the now apparently official names of 0.17 planets and moons, still no official orbital data on most of them though.

[togfox]

This is great and demonstrates how clever some forum members are.

It also highlights the need for us mere pilots to have tools available so we can measure phase and ejection angles.

[Shedao]

Wow

Big thanks for this great webapp (is that the right word?)! Looking forward to the 0.17 update.

[r_rolo1]

May I ask you why your calculator assumes that you are doing a clockwise orbit for a burn to get to the interior bodies, instead of the much more natural ( atleast from a Kerbin launch ) anti-clockwise one ? I assume that from a purely injection burn PoV it is more effective that way, but given the extra fuel costs to launch for a clockwise Kerbin orbit, choosing between a clockwise and a anti-clockwise starting orbit should probably be a option

[olex]

Good question. I guess because I assumed it for some reason during development and kept it that way I'll update the calculator with an option to choose parking orbit direction.

[antsp1]

Bravo! Thank you very much for this most excellent tool!

[togfox]

If im allowed to push the boundary just a touch, how hard is it to add a third body so we can time slingshots from one body to the next.

A trajectory from kerbin lko to mun to eve might be interesting.

[Kosmo-not]

If im allowed to push the boundary just a touch, how hard is it to add a third body so we can time slingshots from one body to the next.

A trajectory from kerbin lko to mun to eve might be interesting.

I can't recall Eve's orbital radius around Kerbol. Based on a calculation I did not too long ago on the best case scenario for a Mun slingshot (exit trajectory being perfectly prograde), a mun slingshot will beat an ejection from Kerbin up to a needed Kerbin SOI exit velocity of 1200 m/s. That corresponds to a target planet orbital radius of 24Gm or 8.3Gm. Since I don't think a slingshot like that is possible, those bounds would be tighter.

[zarniw00p]

That's a really nice piece of software.

But it seems that your calculator can't calculate direct transfer burns from one planets moon to another planet (e.g. Minmus -> Duna or Ike -> Kerbin). Are there any chances that this will be implemented in the future?

[olex]

That's a really nice piece of software.

But it seems that your calculator can't calculate direct transfer burns from one planets moon to another planet (e.g. Minmus -> Duna or Ike -> Kerbin). Are there any chances that this will be implemented in the future?

Currently, only transfers between bodies orbiting the same parent are possible to calculate. I will add parent-child transfers first (going from Jool orbit to one of the moons and other way around), and then possibly also indirect transfers like what you are talking about.