Rendezvous Help

[spyker92]

I'm new to KSP, and I've recently put the first 2 parts of my first space station into orbit around Kerbin.

Despite a nasty off balance lift off, and hitting some debris on my way into orbit with the core module. (Absolutely terrible luck!) I was able to get it into a high circular orbit with help from mechjab planning the ideal route.

I followed up with putting my solar-power-section into orbit with a thankfully much less eventful launch and circularized it with the station core. Its now the same inclination and less then a kilometer lower in altitude of the station core.

But here's the problem, they're moving almost exactly the same speed with the solar array about a 100,000km "in front" of the core. And I have no idea how to get them next to one another for docking without utterly destroying one or the others orbit, which would force me to relaunch a new vehicle. I've looked at several tutorial videos and I've found very little insight on how to solve this problem. If anyone could give me some instruction, I would be most appreciative.

Thanks,

-Spyke

Related photo:

[Flixxbeatz]

100,000 kilometers? You mean meters.

Anyway, maneuver nodes are your friend. Use them wisely. The "Closest Approach" will be your guide.

[RoboRay]

It's not physically possible to rendezvous two craft in similar orbits without significantly altering one of their orbits. If you've got two people standing still on the opposite sides of a room and they want to shake hands, one of them has got to start walking.

Heck, even the little puffs of RCS you'll do during the docking will shift your Ap/Pe several kilometers. And it doesn't matter a bit. Matching velocities during the docking process automatically corrects those changes. That's what matching velocities is all about.

People that get hung up on trying to preserve "perfect" orbits during the rendezvous and docking phases are the ones that struggle the most and the longest to learn how to rendezvous and dock. Save yourself a lot of headaches and let that go. Ignore your orbital parameters while rendezvousing and docking, with the exception of making sure you don't actually drop into the atmosphere during the process.

Edited April 24, 2013 by RoboRay

[Noticeably FAT]

Lower the periapsis of the ship that needs to catch up. Yes, this will make your orbits not match. This is ok, they can't match if you need the ships to move relative to each other. When you do this, you should see some closest approach indicators on the map (1 if the orbits don't actually cross, 2 if they do). With each orbit you'll see the closest approach distance getting smaller (timewarp will help speed this process up). The lower the Pe, the more distance you'll shave off each time, but you run the risk of overshooting your target. Once your closest approach is at an acceptable distance, at the closest approach kill your relative velocity (click the velocity indicator on your navball until is displays Target, this is your current rV. Burn toward the retrograde indicator on the navball to reduce rV). Once it reads 0m/s, you'll find that you are back in a matching orbit.

[ThePsuedoMonkey]

Every maneuver changes your orbit, so don't worry about that (but don't change it so much that you can't fix it later). The idea is to change your orbit just enough to get close to the target on your next pass (the "closest approach" nodes that Captain mentioned). When you get to that pass, fix your orbit (don't be obsessive about it though) and make sure your velocity readout is relative to your target. Check the navball and use its readout to make a burn towards your target; do not face directly toward the target, rather on its opposite side as your prograde vector is currently pointing, as this will pull your prograde vector toward it without making you speed up too much. Keep that vector facing the target, but keep the speed in check. If you overshoot the target, then kill your relative velocity, take a breath, and make a tiny burn towards it again.

[Noticeably FAT]

People that get hung up on trying to preserve "perfect" orbits during the rendezvous and docking phases are the ones that struggle the most and the longest to learn how to rendezvous and dock. Let that go.

Agreed. You do want to pay a little bit of attention, if you manage to get your orbit dipping into the atmosphere you're probably going to have a bad day, and if you get your apoapsis out by the mun you're probably trying to make to large of corrections too fast, but other than that let the orbits be what they are and focus on the relative velocity.

[Greenlandys]

Exactly what other people have said, You need to change your ships orbit in order to catch your target. If you're behind the target, lower your periapsis by 10km or so, time warp, and watch as you magically start closing the gap between you and the target when your orbit do pass close again.

When you get close enough, then you just have to start using the target on the navball and retrograde / prograde points.

But yes, you have to just forget about having a perfect orbit while rendezvousing, Your orbit might go all over the place (If it says you're going to hit Kerbin, you've gone wrong somewhere) but when you get close enough, the orbits and speeds will be so similar that they'll have almost matched eachother.

[capi3101]

Perfectly matching orbits? Yeah...you're going to be waiting a while. Do what everybody else has said; get your periapsis lower and you can catch up. You might also need to adjust the angle of the orbit; you can do that by burning north or south at the ascending/descending nodes until the node says 0.0 degrees; that might not be an issue for you since it looks like you're using Mechjeb. Might want to check that all the same since you had issues during the ascent.

So you only have to lower the periapsis? That would've been nice to know a couple of days ago...