Flight windows; how do you know when to launch?

[Captain Murphy]

I am certain this is a rather stupid question, but after an hour or so of searching for a definitive answer, I am still drawing blanks on this; how do you determine your flight window to another planet/moon? I was going off the quarter orbit idea for the Mun for Duna hoping it would work, but I ended up endlessly chasing it in its own orbit. If anyone has any insight or websites to send me off to, that would be awesome. I'm trying to keep mechjeb out of this as long as I can because it likes to set up nodes that are 99 days away, and I feel I am missing something here that I should learn for myself.
Thanks!

[koimeiji]

For the Mun? I just use maneuver nodes to see where the encounter is. For other planets? I use Kerbal Alarm Clock (A mod, helps you set alarms to warn you when you're reaching a certain point, like a maneuver or a planetary transfer window) There are also tools online that tell you when you should burn (http://ksp.olex.biz/).

[Captain Murphy]

I have no trouble getting to the Mun or Minmus. I was hoping to get to Duna, but haven't figured out how to sinc myself up with it. I was just hoping for a guide or some insight as to how to know when it's a good time to launch. I've seen people saying that they have such and such days left until their window opens, and I've wondered how they know that, and how I could find the information on launch windows. Hopefully not a mod, but if necessary I can pick one up.

[Fel]

Go to the official forum, and make a search (or google it), it will give you the angles you need.

But without mods, it will be judjing by eye (or your old geometry tools from school).

[Captain Murphy]

Was on forum and could only come up with angles from the sun. I'll check again to see if I missed missed anything pertinent. Otherwise I guess I can toss myself into solar orbit and navigate from there.

[koimeiji]

Again, please do refer to http://ksp.olex.biz/ as it calculates and shows you what angle Kerbin/Wherever you're launching from should be relative to your target. Not a mod, as I can see you don't want one.

[A Fat, Angry Serval]

If you have a large enough ship (for example, Macey Dean's Spirit of Kerbin), you could just perform a phased transfer from a solar orbit, similar to how MechJeb performs rendezvous maneuvers.

[[m00] insane_eon]

Protractor and spreadsheet! Woooooo! I'd use my sliderule too but I don't know where it is and there are no logarithms involved anyway. You could use the navball too but it's not got a very good resolution.

Multiply the transfer time by the angular velocity of the target to get an estimate of where it needs to be for a launch window.

[Captain Murphy]

Theshinesprites, That's actually what I have been using, but for some reason (most likely my absolute lack of math skills whatsoever) I am always stuck waiting 99 days for my nodes to come, and that's when I use mechjeb (don't really want to say what it is when I do it myself). I just want to know a rough area where the planets are that I should launch. For instance, the Mun should be just coming up over the horizon according to many people, even though it's easy enough to reach it by widening my orbit and keeping a bit faster an orbit than it.

And to insane_eon, you won't find someone as bad at math as I am here. I see the world in 1/16th's of an inch due to what I do, anything more than simple multiplication is something that I left behind in high school way too many years ago.

[Maverick]

Captain Murphy původně napsal:

...I am always stuck waiting 99 days for my nodes to come, and that's when I use mechjeb.....

And not using mechjeb will give you.........drum roll........ 99 days.

Tip: Mechjeb doesn't change the planet orbits. It just sets the node for best time to depart. As will the protractor, calculator, alarm clock or dead reckoning.

[Captain Murphy]

I didn't see any nodes telling me a good time to depart. I'll reset my launch and see if they show up, although I never noticed any nodes other than the three usual types. That best time to depart is what I'm looking for afterall. Pretty much was my only question here was how to tell from the spaceport how to know when is a good time to launch based on where my target is (again, mathematically challenged here).

[Captain Murphy]

And damn my grammar sucked there, but I hope you get what I mean.

[Raell]

What I do works pretty well and requires no fancy math. Start your mission when the planet you want to get to is farthest from you. This way when if you're going to an inner planet you retro burn and only need to cover a short distance to get an encounter. If you're going for a farther planet then you pro burn and only have to cover a short distance.

Waiting until planets are closer may seem like a shorter trip and with the right vehicle it could be but it's cheaper to just fiddle with the apoapsis when you're Far from it as close to the periapsis as you can be.

[Captain Murphy]

Thanks Cruentus. That's what I was looking for. I'll give your advice a shot. Seems easier than doing a ton of math that is far beyond me. Pretty much exactly what I was looking for. Not being a man of math, I am all about simple placement (where it needs to be when I launch) of planets in regards to me at the platform or in low Kerban orbit.

[Maverick]

Captain Murphy původně napsal:

I didn't see any nodes telling me a good time to depart. I'll reset my launch and see if they show up, although I never noticed any nodes other than the three usual types. That best time to depart is what I'm looking for afterall. Pretty much was my only question here was how to tell from the spaceport how to know when is a good time to launch based on where my target is (again, mathematically challenged here).

Curious why you need to do it from the spaceport? 99 days on the ground is exactly the same as 99 days in space :)

Set your orbit at 625km, select target and use your manouver node. Why 625? Because you can timewarp flatout and even a 128 day launch window only takes a couple of minutes.

If you're using MJ and you're mathmatically challenged, seems pointless doing it any other way.

[Captain Murphy]

I've been trying to do it as much as I can without mechjeb. I know I should, but I don't want to use it as a crutch. That being said, all I wanted to know was a general placement of my target planet before I went for it. I use the spaceport as a basis for that because it is a more constant starting point than, say in orbit, which can be anywhere from parking to out near the Mun, and even out to Minmus. I just see a lot of people on the KSP forums, rather than steam, talking about flight windows. I just want to know how they know that and a quickhand of how I can roughly guage that. I can use the mechjeb to do the work for me, but I'd much rather know how to do it manually as best I can without doing a lot of math. Maybe I'm asking too much, but it never hurts to ask the people who know their ♥♥♥♥ about this game better than I.