How to go anywhere else?

[Forty21112]

So, I'm having a blast landing and doing other stuff on the mun when I realized, 'There are other celestial bodies out there, and I do not know how to get there!'.

I can do a hohmann transfer, but I know that's not going to work. I don't have a single clue how and I think this might postpone my career save.

I'm sorry for the nooby question, considering I've been around lurking since 0.13.

Any help would be appreciated.

[TrooperCooper]

This: http://alexmoon.github.io/ksp/

and this: http://forum.kerbalspaceprogram.com/threads/47863-1-0-2-Precise-Node-1-1-3-Precisely-edit-your-maneuver-nodes

will get you going.

[AcidSludge]

It - basically - boils down to "moar boostaz".

But you can try something like this:

http://wiki.kerbalspaceprogram.com/wiki/Tutorial:How_to_get_to_Duna

[Tex_NL]

I know many people think MechJeb is cheating but that's completely beside the point. No one can deny the fact MechJeb is a greatl teaching tool.

If you too think it's cheating then simply don't use it in your career save. Instead play with it in a separate sandbox and learn how it plans interplanetary transfers.

[Geschosskopf]

So, I'm having a blast landing and doing other stuff on the mun when I realized, 'There are other celestial bodies out there, and I do not know how to get there!'.

I can do a hohmann transfer, but I know that's not going to work. I don't have a single clue how and I think this might postpone my career save.

I'm sorry for the nooby question, considering I've been around lurking since 0.13.

Any help would be appreciated.

Well, going to the other planets uses exactly the same principles as going to Mun or Minmus, it just needs more dV. To know how much, use one of the dV maps. Otherwise, interplanetary flight introduces only a couple of new wrinkles to the transfer burns.

The 1st of these is the transfer window (often mistakenly called "launch window"). This one really isn't "new" because if you've been going to Mun, you're already familiar with the idea of "burn prograde at Munrise" to intercept Mun. Same thing here, except because the other planet isn't orbiting Kerbin, you can't just go there any day you want. The transfer window is the point in time when Kerbin and the planet you're going to are aligned so that you need the least dV for the transfer burn. Technically, you can leave any time you want, but most of the time the dV cost is prohibitive so you want to leave on or about the date of the window. Besides, the dV maps assume you're leaving in the window. Being a few days off either way is no biggie, though, so don't sweat exactitude on this too much. There are all sorts of tutorials, websites, and mods out there to tell you when transfer windows to the various planets (and from there back to Kerbin) will come around.

The 2nd new concept is the ejection angle. This is the point on your parking orbit at Kerbin where you place the maneuver node for the transfer burn. Even when you place the node on the transfer window day and give it the right amount of dV, you won't hit the target unless you put the node in the right place, which is what actually aims you at the other planet. The same resources that tell you when transfer windows come around will also tell you the ejection angle

That's pretty much it in a nutshell. Give a look at the various resources other have mentioned and give it a go. It's not really any harder than going to Mun (and going to Duna requires barely any more dV than going to Minmus). Good luck.

[Forty21112]

@Tex: I've never thought about watching MJ do it before. Will do on a separate save. Thanks!

@Geschosskopf: So wait, I've looked thru the stuff, and it looks very complicated. I'm not a rocket scientist, so I need help.

Do you mind explaining some stuff? Maybe with a focus on getting there and staying there.

[ExaltedDuck]

Another helpful tool for learning is the maneuver nodes themselves. It cab easily overlooked just how much info they give you. To get a feel for how your position and timing affect your potential encounters, set up a node as a transfer to the altitude of mun or minmus then move the node and note how much the orbit changes and how the prograde/retrograde and radial/anti-radial inputs can change things both in terms of dv input and angles. It starts to make intuitive sense as to when and how to do most things. Then, plan transfers between mun and minmus. The same principles apply to interplanetary missions, just with Kerbol as the primary body instead of Kerbin.

Edited June 13, 2015 by ExaltedDuck

[Geschosskopf]

@Geschosskopf: So wait, I've looked thru the stuff, and it looks very complicated. I'm not a rocket scientist, so I need help.

Do you mind explaining some stuff? Maybe with a focus on getting there and staying there.

OK.... First off, if you're about doing this all manually, go to http://alexmoon.github.io/ksp/.

First off, up at the top, be sure to set it to whether you use 6-hr or 24-hr days. I use 24-hr because otherwise the numbers just get friggin' huge sometimes . Besides, my brain is wired for 24-hr days and 365-day years.

OK, then just fill in the boxes. For this example...

* 24-hr days (so we're speaking the same language)

* Origin: Kerbin (leave at default)

* Initial Orbit: 100 km (this is your parking orbit at Kerbin, where you wait for the window).

* Destination: Duna (leave at default)

* Final Orbit: 25km (This is the altitude of the Pe you want when you arrive. 25km is good for aerocapture, maybe... Anyway, this determines how close you come to Duna and will no doubt need to be tweaked a few times en route so don't worry about it too much).

* Check the "No insertion burn" box because you'll be aerocapturing. If you don't check this, the web page will also show you how much dV it will cost to circularize at the destination. Useful for airless places or if you don't want to risk aerocapture.

* Earliest Departure: Put in the current game date of your game (here, we'll use Year 1, Day 250 as an example). This tells the calcaltor where the planets currently are relative to each other.

* Transfer Type: Ballistic (default). This means you combine the inclination change with the main burn. If you do it right, this means you don't have to do a mid-course plane change, which saves a bit of fuel. However, this also complicates setting up the maneuver node manually (see below).

Now hit the PLOT IT! button. After a while, you'll see a graph with lots of colors on it. This is a "porkchop plot". The horizontal axis is gametime in the future marked in days from the earliest departure date you entered. The vertical axis is time of flight. The areas of colors represent relative amounts of dV required for the transfer burn, which shows the effects of not leaving during a window. Dark blue is the least dV, then on down the ROYGBIV spectrum so that red is the most dV. NOTE: You can click on any spot on the plot to use that point instead of what it picks for you.

You will see that thin black lines cross near the lower left of the plot in a dark blue area. That is the point of lowest dV coming up in the near future. The text to the right of the plot explains what all this means, as follows:

* Departure: Y1 D289 (don't sweat the time of day), so 39 days from today (which we're saying is day 250).

* Arrival: Y1 D354, when you get to Duna

* Time of Flight: 64 (24-hr) days. Useful if you need to pack life support.

* Phase Angle: This is a function of the departure date. It just says that on that date, the angle between a tangent to Kerbin's orbit and a line drawn from Kerbin to Dune will be 36.06^. This really isn't important to know as long as you have the departure date and the dV, but be sure to look at it in the map view when the departure date arrives so you know what it looks like. This will help you eyeball transfer windows in the future.

* Ejection Angle: VERY IMPORTANT. This is where you put your maneuver node for the transfer burn. It's measured from a tangent to Kerbin's orbit in the direction of its travel around the sun (aka Prograde) clockwise around the night side of Kerbin. In this case, it's 151^, You'll have to eyeball this if you don't have the Protractor or Precise Node mods or some such (MJ's Maneuver Node Editor). NOTE: Going to Duna, Dres, Jool, and Eeloo, this angle is clockwise around the night side of Kerbin. For trips to Eve and Moho, the angle is counterclockwise around the day side.

* Ejection dV: VERY IMPORTANT. This is the total dV for the transfer burn, 1064m/s in this case. But remember, we said we'd do this ballistic, so to set up the node, you have to break this down into prograde and vertical components. Fortunately, the web page does this for you if you hit the blue "i" button here, which shows 1058.7m/s prograde and 105.6m/s normal up. Now, when you create a node, it only shows the total amount of dV for all components so unless you have a mod like Precise Node that lets you enter in values for each component seperately, you'll have to do this in 2 steps. First pull the prograde handle until you have the 1058.7m/s showing, then carefully nudge the normal up until the total dV shows 1064. If you have placed the node at the correct ejection angle on the correct calendar day, then you should have the Duna encounter you want. But probably you won't quite have it, so you can slide the node a bit forwards and backwards on your orbit, and/or tweak the node handles until you get the encounter. Or you can just get close enough for government work and do a mid-course tweak later.

After that, you just do the burn. And if that's all the fuel you'll take, you'll stay there. If you're interested in coming back, you can repeat the process but start at Duna and head to Kerbin, set for a date after your arrival date. In this case, I'd leave Duna on Y2 D136 and arrive back at Kerbin Y2 D211, for a total time away of 287 (24-hr) days, which matters if you use life support.

Now, that's how to set up an interplanetary transfer node but there are a few difficulties with actually doing it, unless you use mods. The biggest issue is having to warp ahead and stop before passing the window. This is where Kerbal Alarm Clock is wonderful. So you put your ship in the 100km parking orbit, set an alarm for about 15 minutes before you want to leave, go into the tracking center, and warp full blast until the alarm stops the warp. Now your ship is about 3/4 of an orbit from when it will burn, which gives you plenty of time to create the node by hand.

So now you're at the right calendar day to do the burn, but you have to make the node, and the biggest problem there is eyeballing the ejection angle. Protractor will take the guesswork out of that, as will (IIRC) Precise Node, and certainly MJ's Maneuver Node Editor. Then add the dV to match what you got from the web page. Again, being able to enter exact numbers for each component via Precise Node or MJ is a big help compared to pulling and scrolling node handles.

The easiest way to set up the node, however, is to use MJ's "Advanced Transfer to Another Planet" function. The cool thing here is that it lets you create the node at exactly the right ejection angle months in advance of actually using it, so there's no last-minute pressure to get the node set up in the 15 minutes you have before your ship gets to it if you do it all manually as above. First, set your target planet, then open MJ's ATTAP function. It will display the same porkchop plot you see on the webpage. Zoom in and pick the darkest blue spot you can find, click there, and hit the "Create Node" button. Voila, you now have a node set for the correct date and time, at the correct ejection angle, and with the correct dV in both components. You can now create an alarm for this in Kerbal Alarm Clock (say 15 minutes prior to the burn) and warp there.

NOTE: In this case, you're just using MJ to create the node. You still have the option of doing the burn manually or letting MJ's autopilot do it.

Now, when you create the node so far in advance, it won't still be perfectly accurate come the actual departure day. So you can now use the 15 minutes you have to tweak the node's handles manually to get it back where you want it. And if you notice it says "Burn Time: N/A", you'll have to run the engines briefly so KSP can remember your TWR. If you need to do that, do it before tweaking the node because that will also screw it up slightly.

Anyway, that's about all there is to it. Have fun.

Edited June 13, 2015 by Geschosskopf

[LordCorwin]

Hello Forty21112, I had the same problem when I started moving other planets. The idea is: you can move to any planet whenever you want, but there are given moments when the ammount of fuel to spend is minimal and others when the ammount is HUGE. So you need tools to know when to start the maneuver.

TOOL 1: This is optional, but it simplifies your life. When doing planetary transfers, you need something that tells you exactly how much fuel you have in delta-v units. For that purpose you have for instance the Kerbal Engineering Mod. Once installed the mod, follow the instructions and you'll able to put the Science>Kerbal Engineering System in your rocket. It will give you lots of parameters such us your remaining delta-v

TOOL 2: This transfer calculator has been my friend for a very long time: ksp.olex.biz/ . Thanks Olex!!

* Your input data are: Origin planet (eg Kerbin), Target planet (eg Duna) and Current Orbit Height (Eg 90km). Better if it is circular.

* As a result, the calculator tells you what are the planet positions when you have to start the boost (Phase Angle), how much delta-v required (ejection burn delta-v), and in what moment of your orbit you must start (ejection angle).

So yes, if the planets must be in a certain position, may be you'll have to wait 250 days before starting the maneuver.

It is OK to be approximate but take the results seriously.

1) The ejection angle is VERY important. If the calculator says to you the Ejection angle is 162º, well, you can use 160º or 165º, but never more than that.

2) Also, if your burn takes 40seconds, it is OK (even better) to start 20 seconds before the Ejection angle point and finishing 20 seconds after the Ejection angle.

3) And finally, as everything is approximate, count that you'd need an extra 10% of delta-v, just in case.

Hope it helps.

Edited June 13, 2015 by LordCorwin

[FancyMouse]

think of doing a rendezvous to a space station on a different orbit within a period - that's pretty much the same thing for the matter of intercept.

[Sharpy]

Hello Forty21112, I had the same problem when I started moving other planets. The idea is: you can move to any planet whenever you want, but there are given moments when the ammount of fuel to spend is minimal and others when the ammount is HUGE. So you need tools to know when to start the maneuver.

Not quite; it may only convert to more travel time. You may need to do a few orbits for a better phase match, but in case of interplanetary transfers orbits are not under an hour, but of order of a year.

Still, my mission to Eve has the trajectory to capture by Eve all drafted, except it will happen in about 1,5 Kerbin years. The extra burn was really nothing much. Now if I wanted the same without waiting that long, the burn would be huge. (and in this case two things help: 1. Placing "dummy" (no speed change) maneuver nodes far ahead in your path to see where you will be in relation to the planet one orbit from now, and 2. getting

. (increase CONIC_PATCH_LIMIT in settings.cfg) which is especially important if you're using Oberth maneuvers to save up delta-V on your encounters. (performing your proper "escape burn" during a close Mun, Minmus or both fly-by.)

[mrklaw]

Everyone keeps saying how the ejection angle is the most important (phase less so because you're doing it by date if you use the online tools). But does stock KSP have any way to show you what angle you're setting a node at? Can you approximate by rotating the camera in map view so the orbit line is vertical and then eyeball it? Although if the angle really needs to be in single or even fractions of a degree that would be almost impossible.

[LordCorwin]

Everyone keeps saying how the ejection angle is the most important (phase less so because you're doing it by date if you use the online tools). But does stock KSP have any way to show you what angle you're setting a node at? Can you approximate by rotating the camera in map view so the orbit line is vertical and then eyeball it? Although if the angle really needs to be in single or even fractions of a degree that would be almost impossible.

Hehe, that's why I always have a 360º protactor with me

[GoSlash27]

Everyone keeps saying how the ejection angle is the most important (phase less so because you're doing it by date if you use the online tools). But does stock KSP have any way to show you what angle you're setting a node at? Can you approximate by rotating the camera in map view so the orbit line is vertical and then eyeball it? Although if the angle really needs to be in single or even fractions of a degree that would be almost impossible.

mrklaw,

Really it doesn't have to be that precise and it's not going to be. Your burn time isn't instantaneous, so your ejection angle isn't going to be exact.

The easy way to do it is to set a maneuver node approximately correctly and just slide it around until you get an intercept solution.

Once you've completed the ejection burn, you can fine-tune your prograde/ retrograde for a tighter solution. You can save the normal and radial burns for when you're halfway there (what we call the midcourse correction).

Personally, I think getting the phase angle right is far more important. I do that by keeping a small probe just outside Kerbin's SoI and using it's maneuver nodes to generate an intercept. The burn timer will show how long until the window opens up.

Best,

-Slashy