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crazyewok

Docking woes

Question

Im trying to figure out how to dock.

I have been useing the guides like here: http://forum.kerbalspaceprogram.com/threads/24670-Tutorial-Orbital-rendezvous-You-can-do-them!

But I I just cant get it, I can get within 0.2Km but i whiz past the station! If I try to reduce my speed I end up moveing 5Km in the wrong direction! What am I missing?

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There a lot of great tutorial videos out there, so check some of those out. Do you look at your relative velocity at your closest approach? It sounds like it's pretty high, but you want it to be as low as possible. It's somewhat counterintuitive, but you can't just thrust in the direction of your target. As you close in on your target, you want to do a series of small burns or RCS maneuvers to match your orbits and therefore lower your relative velocity. Ideally, your rVel should be almost nothing by the time you're 200m away.

Edited by brooklyn666

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Good thing you're getting that close to your station. Saves me a bunch of work.

When you get closer to your target, the velocity reading should automatically switch to "Target" mode. The prograde and retrograde markers will change spots, because they are now pointing to where you're moving relative to your target. So even if you appear to be moving in the retrograde direction of your orbit, you're still orbiting the same way but moving retrograde relative to the target (in this case your space station). So you need to slow your relative velocity (shown under "Target" in the velocity reading) so that you're not really moving away from the station. If you have a lower TWR, it might help to do your burn to reduce your relative speed to 0 earlier because when your rel. speed is at 0 you won't appear to be moving away or toward the station. Once you have your relative speed at around 0-3 m/s (try to get it as low as you can), point towards your station and either use RCS or little engine burns to inch towards the station. When you get there, try to keep your velocity under 2 m/s while you line yourself up for docking. At this point you should only use RCS. Slowly push in towards the port and the magnets should kick in and you're docked!

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Start slowing down before you're at your closest approach. If you're getting your relative velocity zeroed out at 5,000 m distance, that's really not that bad, especially for a beginner.

After your rel velocity is zeroed out, point towards your target, and burn until you're approaching at about 20-40 m/s, then slow down when you're close (<500 m). Then just RCS in.

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My method of contrary to every other user, so take this with a grain of salt.

I never had success with lateral docking movements once the craft was of any size. I do a process of jumping back and forth between crafts and making sure they are pointing in the right direction.

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Click on the Velocity indicator at the top middle of the guidance Gimbal. It will switch between Surface-relative velocity, Orbit-relative velocity and Target-relative velocity.

You should try not to be moving faster than 25m/s when closer than 1km to the target, and it is generally unwise to be moving faster than 5m/s when closer than 250 meters from the target. Attempting to docking two ports together at a speed higher than 2m/s may result in a collision.

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Yet another personal advice...

Practice makes perfect...

And you should choose a good practice ground...go to Minmus and do your docking practice there....

Reason... you will notice the 'important' point of how to rendezvous/dock....more easily there.

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I never really got to grips with any guides that suggested using the 'docking mode' provided ingame. It is however useful to know (and rarely spelled out anywhere) that you can reduce your closest approach to your target even as you slow the relative velocity, giving you a nice arcing brake line that looks super pro. While looking for your green pro/retro-grade markers to begin slowing to meet your target, also take a look at where the pink/purple target direction markers currently are. You really want these to line up. This is a docking approach (or collision course if you dont slow down). It may well shift a bit as you approach, but you can use the ijkl lateral RCS controls to keep the green (which will move) on the purple (which wont unless you use wasd) Once you get a bit more experience then you can make little radial burns to push the markers together whilst performing your brake. Its a wonderful fuzzy feeling when you can come to a stop under 500m.....just watch the jet wash, mainsails are NOT your friend (seriously, dont want crazy TWR for any of these stages really)

Edited by celem

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One thing that makes docking tons easier for me is to orient the docking port along the north/south axis if you're in an equatorial orbit. This keeps the port from rotating out of line as you orbit.

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Docking mode? Ha ha! I had forgotten about that and have been using my keyboard! But yeah, the easiest thing is to be sure you set target. If your navi is showing target velocity, that will be relative.

You do not want to directly burn towards or away from target since that will change your orbital altitudes and not actually bring yourself closer/further. The naviball when showing target will show your velocity towards and away from target. For beginners, it helps to use the maneuver nodes to plan yourself close to dock target. When at this close distance, use the target velocity to slow your relative then just slowly manually do a burn towards stop adjust until you get used to the mechanics.

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Still haveing trouble cracking this....... I get 0.1km 0.1KM! Yet I whizz by at 6ms and thats it.

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Still haveing trouble cracking this....... I get 0.1km 0.1KM! Yet I whizz by at 6ms and thats it.

1) Make sure that the other ship is designated as target (in map mode, click on it and select "set as target")

2) Your navball should automatically pop into target mode. If not, click on the indicator at the top that says "orbit" and click on it until it says "target"

3) The navball now shows speed relative to your target. Align with the retrograde indicator and burn (moderately) until your speed is close to (or preferably equal to) 0.

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If you whiz by at 6m/s, make sure your navball is set to "target", aim at the retrograde marker (which is now relative to the target) and burn until your relative speed is 0m/s. Now you're stopped next to the target.

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From what I've learned by watching mechjeb:

Once you get the encounter, brake relative to the target. Navball set to 'target' mode, and burn retrograde so you're approaching gently. Then tweak things so you're cruising in at a few m/s, before switching to RCS controls for final approach.

It's a LOT like planetary encounters, just with no SoI to get into.

If all else fails, you CAN just break down and install mechjeb like I did.

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Yes yes yes I have it in target mode and the correct target selected im not that useless.

I hace got to .3 Km and reduced the speed down to 2Kms but I cant get the speed lower and I cant get closer than .3Km unless I got at speed in which case I miss it.

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Hopefully you mean 2m/s otherwise you are coming in way too fast. Also, as you approach your target you are going to have to continually kill your relative velocity. If you are approaching at 2 m/s relative but your relative pro grade vector and your target pro grade vector are not aligned then you are going to miss. Both of these should be aligned until you are within about 180m, at which point you can set an individual docking port as your target and eyeball your way to it.

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I kill my velocity and then I lose my encounter! My closet encounter goes from 0.2 Km to 10+ KM!

This is starting to **** me off badly now.

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I kill my velocity and then I lose my encounter! My closet encounter goes from 0.2 Km to 10+ KM!

This is starting to **** me off badly now.

When are you killing your velocity?

First, get your encounter.

Second, fast forward until you get to your encounter.

Third, kill your velocity relative to your target.

I think you skipped step 2.

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First, get your encounter.

Done

Second, fast forward until you get to your encounter.

Done till im 1K away

Third, kill your velocity relative to your target.

Kill it and my ecounter goes from <0.5Km to 2Km + !

If I wait least I end up zooming past my eno****er and loseing the damed thing.

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My approach for newbies:

First, get your encounter

Second, put a maneuver to that encounter and fiddle with its controls until your target's and the maneuver final orbits match. That means they're more or less exactly the same line in space, from any angle.

Third, execute that maneuver (at appropriate time and place).

You'll end up close to your target (might be a bit further than your encounter was) and your velocities will be almost matching.

Anyway, it's normal that your distance with your target changes as you're killing your velocity. You travel some distance before you can stop a car, too. Usually the best approach is to kill your velocity gradually as you're approaching the target. For starters it's good to keep your relative velocity at about 1-2% of the distance and keep closing in, i.e. having the relative prograde marker over the target marker.

Edited by Kasuha

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Are you and your docking target traveling in the same direction? 2 km/s sounds like you're going retrograde.

Maybe post a picture of when you've killed the speed and the distance mysteriously increases.

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My approach for newbies

Thank you, but as the rest of the thread indicates, we've been over that. Whatever the OP's problem is, that is not it. He knows what to do, the problem is that he is not able to do it. Why, we're trying to figure out.

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Are you and your docking target traveling in the same direction? 2 km/s sounds like you're going retrograde.

Maybe post a picture of when you've killed the speed and the distance mysteriously increases.

Both me and the target are going along the same orbital direction.

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It sounds like you've nailed it, and just don't realize it!

If at any point you're under 5 km away, and you've zeroed relative velocity (or at least less than around 10 m/s), you're basically done using the map view; switch camera and move it to see both vessels at that point. Maybe you whizzed by a little and are farther than your closest predicted point, but now you are effectively close enough to ignore the orbits and move like you are in empty space.

At this point, you should Point toward target prograde and burn until you are approaching at some speed (20-40 m/s was a good estimate given earlier), then watch as you get closer. If you ever seem to be moving away instead of closer again, you can zero your velocity again (burn target retro until close to 0 m/s), then repeat pointing to target and burning. Once you're happy with how close you are (100 meters?), zero velocity again and enjoy floating next to your target.

You might be finding yourself heavy on the throttle and are overdoing your speed if you keep overshooting. Try burning only a little and time warping until you are closer rather than increasing your speed to close the distance faster. This way, it is easier to kill your velocity when you need to.

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