I Can't Dock, But I Know How

[A FAT KERBAL]

So I am building a Duna craft with a command pod, habitat module, and lander. My problem is I can't dock the things, I know how to dock but whenever I do it my relative velocity is always changing!

Do I need to be closer to stop this? 

Am I docking Wrong?

Help?

 

[HebaruSan]

It's hard to tell what you know or what problem you're having. Have you taken a look at any docking tutorials yet?

[A FAT KERBAL]

Yes, yes I  have docked many times before but now I just cant For Example I have two crafts on the same orbit but they are slowly moving away from each other.

I think the problem is that they might be too far away from each other. would that effect it?

[klgraham1013]

2 minutes ago, A FAT KERBAL said:

Yes, yes I  have docked many times before but now I just cant For Example I have two crafts on the same orbit but they are slowly moving away from each other.

I think the problem is that they might be too far away from each other. would that effect it?

In that case, your orbits are slightly different.  The orbit or your craft is slightly larger than the other craft.  Make your orbit smaller so you're moving faster than the other craft and try to find your closest approach. 

[RizzoTheRat]

How far apart?  I like to get within 5km or so by juggling nodes on the map screen before trying to dock on the craft view.

[Johnny Wishbone]

52 minutes ago, RizzoTheRat said:

How far apart?  I like to get within 5km or so by juggling nodes on the map screen before trying to dock on the craft view.

Sounds to me like the problem is less with docking and more with rendezvous. 5km separation is an eternity IMO. You should be able to get an intercept down to 500 METERS (not km) before trying to dock. 

 

[GoSlash27]

31 minutes ago, Johnny Wishbone said:

You should be able to get an intercept down to 500 METERS (not km) before trying to dock. 

My rendezvous ends at 20-30m before I begin the docking process. I definitely wouldn't attempt a docking from kilometers away.

Best,
-Slashy

[WolfCoAerospace]

7 minutes ago, GoSlash27 said:

My rendezvous ends at 20-30m before I begin the docking process. I definitely wouldn't attempt a docking from kilometers away.

As @GoSlash27 said, get closer to the ship that you would like to dock with. Don't be afraid to switch back and forth from both of your ships to ensure the docking ports being alligned.
Sincerely,
---Alex from WolfCo. Aerospace

[A FAT KERBAL]

seems that was my problem, I couldn't rendezvous correctly and to be honest the crafts were like 30-40 KILOMETERS apart XD I got them closer and now I got it

ty!

[Vanamonde]

This question about how to play the game has been moved to Gameplay Questions. 

[RizzoTheRat]

On ‎27‎/‎01‎/‎2018 at 11:18 PM, GoSlash27 said:

My rendezvous ends at 20-30m before I begin the docking process. I definitely wouldn't attempt a docking from kilometers away.

I don't try to get my rendezvous that close since I smashed 2 ships together after a burn 1/4 of the planet away   I usually aim for 100-500 meters, but IMO 5KM is about the maximum you can get away with. 

[Spricigo]

59 minutes ago, RizzoTheRat said:

I don't try to get my rendezvous that close since I smashed 2 ships together after a burn 1/4 of the planet away   I usually aim for 100-500 meters, but IMO 5KM is about the maximum you can get away with. 

My rule of thumbs is "stay 20s away from the target"

that means if I'm 5km away from the target i want to be approaching at close to but no more than 250m/s, 2km away  ~100m/s,...500m ~25m/s, 100m/s ~5m/s. That way I always have time to adjust before I crash. At same time I keep my velocity almost aligned to the target vector, so I end near but not exactly at the target position.

 

Mind you that is not an strict rule, so I end speeding a bit when I'm 'close to home'.

 

[GoSlash27]

What Spricigo said. My closure rate is a function of my distance to target.

Best,

-Slashy

[Guest]

On 27/01/2018 at 11:44 PM, Johnny Wishbone said:

You should be able to get an intercept down to 500 METERS (not km) before trying to dock. 

From where I'm at 20-30 km and 500 metres are both wrong. If you get the nodes to align within 5 km or so you can do the rest of the RV off the navball and not burn much (or any!) more fuel than if you had tweaked it to 0.5 km or less. For high-speed RV trying to get closer than that is a waste of time anyway; if you're burning down 500 m/s or more and aren't ridiculously overpowered your calculated RV point will shift by kilometers during your deceleration burn (if you're not MechJebbing it anyway). 

That said, I like to tweak my RV. I fiddle with the nodes to find the right spot, burn that down, and then fine-tune with RCS H and N (if available). I can get it down to 0.1 km if the planes are aligned that way and I want to... but honestly there's no point if there's any significant difference in orbital velocity at all. RV, switch to navball when closing in, push the retrograde marker, dock.

[Kryxal]

In any case, don't forget to allow time for the transition from main engines aligned target velocity-retrograde to RCS and aligned for docking, if you're not coming to a full stop.  A small craft might be able to just spin in 5 seconds, but something big without many reaction wheels might take a minute or more.  This is a bad thing if you're 30 meters out going 1 m/s, but not a problem at 120m, or 60m at .5 m/s.

[Wcmille]

On 1/27/2018 at 2:40 PM, A FAT KERBAL said:

Yes, yes I  have docked many times before but now I just cant For Example I have two crafts on the same orbit but they are slowly moving away from each other.

I think the problem is that they might be too far away from each other. would that effect it?

I have had three cases in the current build where the game flipped my thrust vector so that thrusting moved me away from my target. I fixed it by exiting the game and restarting.