How large is a launch window?

[Koemf]

So the question is in the title: how large is a launch window? I'm planning to send fleets of ships at the same time to a planet, but I want to have some time in between so that I can maneouvre the first ship into orbit before the second one crashes or flies past the planet, so I want to know how much time I have to launch the ships from Kerbin.

(I can imagine that planets with larger gravity wells have bigger launch windows, is this true?)

Edited July 20, 2014 by Koemf

[sal_vager]

There's the moment where your craft can use the minimum amount of fuel to reach its destination, and every second before or after you'll need more fuel to reach the same point.

If you have the fuel, or delta V, to spare you can launch earlier or later, your "window" is only limited by the capabilities of your craft

[EdFred]

If you launch within a day or two either side of the perfect time you'll be fine. The variance in trying to get the dV burn "perfect" will have more effect than launching a day or two either side.

[Koemf]

Thx for you answers!

[SergeantBlueforce]

The period that the optimal 'window' remains open for is different from planet to planet.

I'd recommend the protractor mod. It shows the phase angle of a planet, time to the window, optimal Dv, and the position at which to begin the ejection burn.

[KerikBalm]

But in general - the less frequently a window comes, the "wider" that window is.

Moho windows come often, but they are "smaller" and the % extra dV you need for being a day late is more than the extra % dv you need for say... going to Jool

[Pecan]

Geschosskopf wrote an excellent tutorial on this: http://forum.kerbalspaceprogram.com/threads/70026-Flotillas-A-Primer-in-3-Chapters.

I read it just as I was at that stage of my adventures and it answered every question I had. Lol, although I didn't believe it at the time, it all turned out exactly as he said :-)

[kizentheslayer]

There's the moment where your craft can use the minimum amount of fuel to reach its destination, and every second before or after you'll need more fuel to reach the same point.

If you have the fuel, or delta V, to spare you can launch earlier or later, your "window" is only limited by the capabilities of your craft

So theoretically as long as i have enough fuel I should be able to launch whenever?

[helgeras]

Check out this launch window planner: http://alexmoon.github.io/ksp/

I think of the launch windows as the dark-blue areas of the plots it produces. Those are the opportunities for transferring with the least amount of delta-V.

Some times I go in light blue areas as well, it costs more delta-V, but that may be ok depending on my setup.

[Koemf]

The launch windown planner is really handy, but what is the difference between Ballistic, Mid-Course Plane Change and Optimal?

[ndiver]

I would be less restrictive concerning the length of a launch window, as i was wondering the same and had a look at it.

In my opinion, it depends of which margin do you accept / need.

If you look the launch window planner, you can see that around the optimal time, you often have a large period which cost you only 100m/s more than the optimal.

It allows you to send without stress vessels to a same destination.

As example, for Jool, with the settings Kerbin 100km - ballistic - Jool 400km, this +100m/s around the optimal ranges from Y2D226 to Y2D273 !

For Kerbin 100km - ballistic - Duna 100km, the +100m/s around the optimal ranges from Y1D205 to Y1D265.

You can send your vessels with a day between each of them and send 10 to 20 without stress.