Jump to content

Plotting routes to the outer planets....


Recommended Posts

Hi,

I think I'm missing something here, I've been playing a while now, been to Mun, Minmus, Duna and Eve. However I'm sure I'm doing something wrong with plotting launch trajectories though.

I use olex's launch window calculator which is fine, however I then have to guess at my launch angles etc as KSP doesn't show them, so it's all done by eye. It can take ages to wait for the planet to come into alignment and if you overshoot you have to wait even longer even at full timewarp.

There has to be a quicker way? I toyed about with kerbal alarm clock but that didnt' seem to do what I wanted, no zoom to launch window feature.....

Please someone, fil me in, what do you do to make planetary launches viable? mods? tricks? I think I had a mod a while back that showed teh launch angles etc....engineer I think!? But it'd be extra nice if I could zoom automatically to that point.

Thanks, Kev

Link to comment
Share on other sites

I just launch the ship to LKO, then use a maneuver node.

KAC does have a transfer window calculator that you can use also.

Also, if you miss the transfer window, you can compensate by using more fuel.

Edited by Merinsan
Link to comment
Share on other sites

I haven't used it myself, but protractor might be just what you're looking for. It doesn't have any warp to capabilities (last I looked anyway) but shows angles between the planets in question, and when there's a good window, as well as the angle around Kerbin you should burn at.

I use Kerbal Alarm Clock coupled with precise node myself. Alarm clock actually does have a launch window feature (for when planets are aligned, not for anything like ejection angle), and precise node helps set up the maneuver since even 1 m/s can mean missing by tens of thousands of kilometers.

Link to comment
Share on other sites

I use a mod called PreciseNode that allows you to tweak with very fine detail the different velocity vectors of your maneuver nodes. It also shows the ejection angle of the planned maneuver. Works great with the data from Olex's launch window planner.

After executing the maneuver I tend to use Kerbal Alarm clock to set an alarm halfway to the destination for mid-course corrections. In the beta, and I have to assume in 1.0 as well, there were times I would do the burn and get the encounter, but for whatever reason by the time my ship made it out there, I didn't have an encounter anymore.

Link to comment
Share on other sites

One way, although not the most efficient, is to launch out of LKO into a solar orbit and then plot your course to whatever planet you desire. You can just set up the node then play with it until you get an intercept. Precisenode helps a lot.

Myself I use Mechjeb's pork chop plotter alongside kerbal alarm clock. Set up the node, set an alarm, wait until that time and then if I want set up a manual node or just let the autopilot do the burn. Often, if the node is a long time away, the node is not valid when it is time to burn so I need to set up another one anyway.

Link to comment
Share on other sites

Precise node looks like a very handy tool.

That's the issue I have, I forward time and might overshoot my window slightly, then I run out of fuel for the return trip.

Link to comment
Share on other sites

I use Mechjeb's porkchop plot. It is extremely handy - gives you timing, Delta-V etc. for all the possible trajectories over the next couple in-game years. :) Can also plot courses between moons in the same planetary SOI, say, the from the Mun to Minmus, or from Laythe to Vall. It's as automatic or manual as you want - you can use it to determine the ideal window time, then make the manouver node yourself or just let MJ warp to and perform the burn for you whilst you get coffee or make breakfast or something.

You still need to do your own mid-course corrections and plan for capture once you arrive, of course.

Link to comment
Share on other sites

What I'd suggest you do it is using Precise Node because it's simple better, and Protractor for the phase angle, the time you have to wait, and the time in your orbit you have to create your node.

So you wait for the angle watching Protactor, then 30 minutes before Protractor says you should leave (in Protractor, you click the angles to switch to time display), you create a node ahead when protractor says you should leave, say 20 minutes. Add the dV needed in Precise Node's prograde field, and you're pretty much set.

Ejection angle at this point is pretty much irrelevant.

Link to comment
Share on other sites

I use Alex Moon's Launch Window Planner in combination with a very stripped down version of PreciseNode that shows the ejection angle of the node underneath the node controls (in writing KSCSwitcher I learned how to do some things I didn't know how to do when I created PreciseNode, so now I have the mod I originally intended to write).

Link to comment
Share on other sites

You could always use Slashy's method for finding launch windows. Put a simple probe in solar orbit matching Kerbin's orbit, but just ahead of it. You can then use the probe to create maneuver nodes on the solar orbit which will allow you to see when a good transfer window is coming up.

Another alternative is to use Alexmoon's Launch Window Planner. That one gives a time rather than an angle between Kerbin and the target planet.

Near the time specified in the planner I create a maneuver node about where I think it should be on my orbit. I try to make sure I have a bit of time to fiddle with it before my ship gets close.

I give the maneuver node the amount of prograde that the transfer planner says.

I then zoom out a bit until I can see my new solar orbit line in dashed purple. I slide my maneuver node around on the orbit until the ejection trajectory is exactly parallel with my new orbit which is very important for efficiency. This simple method sets the ejection angle and determines the exact departure time.

At that point I zoom way out and hopefully see an encounter (if there's no significant plane change) or at least check to see that my orbit becomes close to tangential to my target orbit.

If no significant plane change is needed, I then fine tune the maneuver node while focusing the view on the target planet. This allows quite detailed control of your trajectory within the target's SOI.

If a significant plane change is needed, I wait until after the plane change burn is done and then place another maneuver node and fine tune the encounter.

Hope this helps.

Happy landings!

Link to comment
Share on other sites

  • 1 year later...

I personally first get into circular LKO and then go on KAC and set a timer for the next transfer, usually with a margin of just over half my orbital period. Then I go to the tracking station and set maximum time warp. KAC stops the time warp at the transfer time. Then I go on the interplanetary transfer calculator by Olex and find the "Ejection angle" and then I look to see if it's to prograde or retrograde. Now, I look at the "Orbit" tab of KER. If Olex's calculator said to prograde, I wait until "Angle to Prograde" = "Ejection Angle" and if it said to retrograde (I think you can infer this) I wait until "Angle to Retrograde" = "Ejection Angle" Then I just turn prograde and set the engines to max throttle and burn away, and, of course, shut off the engines when I get an encounter or the closest approach I can get. At the AN to the other planet, I set up a node to fine-tune my inclination. Then, just after that, I setup another node to get my encounter exactly as I want it, e.g. to get an aerobrake (I use Trajectories to help setting up aerobrakes), a gravity assist or just a really low periapsis to help me pull into an orbit with minimal Dv expendature.

Link to comment
Share on other sites

What I usually do is use MJs transfer window option and use it on a craft I already have up(typically a comm sat), set an alarm on KAC, and starting a week or so out I start messing with a node seeing what seems to be the best angle to transfer.  Then I'll launch the craft, if I haven't done so, make the transfer, and also do a mid course correction if needed.  

 

KER has options to calculate both the angle between your crafts angle compared to the planet/moon you're at, as well as the angle between where you're starting and your target.  You can also get the angles with some other mods, or even use a protracter on your screen plus math.  

There are also and mods sites you can use to determine the best angles to leave from.  

Link to comment
Share on other sites

Note that this question was posted two years ago-- the original posters have presumably long since figured out what they need to do.  :)

Locking thread to prevent further confusion.  If anyone has further questions or comments about how to plan interplanetary transfers, please feel free to spin up a new thread.

Link to comment
Share on other sites

Guest
This topic is now closed to further replies.
×
×
  • Create New...