Rondevousing'ness'ity

[Mahnarch]

I've only been playing since May and I still haven't been able to mate a station core and refueler.

I've been able to get the ships on the same angle and a 0.0km meet, at less than 20m/s but, they just fly by each other! The more I "adjust" the worse it gets.

Am I supposed to get the "encounter" circle thing (like with the Mun) when my ships will meet? I'm only getting the pink arrows as close as possible.

What about, if: I orbit 7 times to get closest encounter and then, on the 8th, it's too far?

I'm running out of hairs on my head, here.

OH! I can finally land on Mun within 10km of my desired location, consistantly, now! w00t!

Edited August 3, 2014 by Mahnarch
Engrish

[Master Tao]

Sounds like you have rendezvous mostly down – it's the actual docking that's still giving you trouble. It gives everyone trouble (During my first rendezvous, I EVA'd the 7 km gap).

There are very good docking tutorials in the Tutorial subforum, but there's also Scott Manley's excellent

.

My personal trick for docking is to place a maneuver node on the closest approach and then adjust it until the orbits match. That lets me set up most of my relative-velocity killing maneuver ahead of time. You know it's right when you get close approaches on the far side of the orbit.

[Wanderfound]

20m/s is an exceptionally high closing speed. That's okay when you're kilometres away, but by the time you get within a few hundred metres you want it down to the low single digits unless you've had a lot of practice at rendezvous.

Basic Rendezvous Tutorial

What to do when you get close:

Set the destination as a target and switch the navball to target mode. The yellow marker shows the direction that you're moving relative to the target (target prograde); the pink marker shows the direction that the target is actually in. Each of these markers also has an opposite mark showing the reverse direction.

If you burn directly towards the target prograde marker, you will increase your velocity relative to the target. If you burn directly towards the target retrograde marker, you will reduce your velocity relative to the target.

The simplest way to do it is to wait until just before your closest approach and burn directly at target retrograde (the one that looks like the normal yellow retrograde marker) until your relative velocity (shown at the top of the navball when in target mode) hits zero. Then point directly at the target (the pink marker) and gently burn towards him.

If you get the yellow marker on top of the pink one, that means that you're moving directly towards your target. To move the yellow markers, "push" retrograde and "pull" prograde. In other words, when you burn almost-but-not-quite prograde, the yellow prograde marker will move towards you. When you burn almost-but-not-quite retrograde, the retrograde marker will move away from you.

Once you get in close, keep your nose pointed at the target and use the RCS translation controls (JKLIHN) to fine tune your approach speed and direction.

PS: don't worry too much about your orbit during all of this. Once you end up next to your target with a zero relative velocity, you're going to automatically be in perfectly matched orbits.

How to get close:

First, get into orbit and match inclination, and set the station as a target. Don't worry about height yet.

Then, look at the target: is it in front of you or behind you? If it's in front, you need to lower your orbit to catch up (but not so low that you hit atmosphere). If it's behind, you need to raise your orbit to slow down. Don't bother about circularising, elliptical is fine.

Orbit until you get a close intercept (anything <10km will do), then circularise your orbit to match the target. You'll probably still be a touch off; add a small manoeuvre node (prograde if you're in front, retrograde if you're behind) that gets you a <1,000m intercept. Wait until just before closest approach, burn target retrograde to kill your relative velocity, then point at the target and gently approach. Watch the target/prograde indicators as you approach and burn or RCS to keep them aligned. Flip and kill velocity so that you come to a stop about 40m from the target and then dock.

[GoSlash27]

What wanderfound said.

I started out using the rule of 10 (10m/sec closing velocity for each km to target) and it's still a perfectly fine way of doing it if you're not in a hurry. Once you get comfortable with that, you can go faster.

My entire process:

Intercept

1) match target altitude and inclination

2a) if ahead of target, raise apoapsis. No need to go hog-wild here. if you're way out of phase, take a few extra orbits and save the fuel.

2b) if behind target, lower periapsis. Don't deorbit yourself!

3) on the orbit that will get you closest to the target, fine-tune your periapsis or apoapsis to set up an exact intercept at CPA

4) wait until you're 3/4 of the way around your intercept orbit, then commence rendezvous.

Rendezvous

1) use your heading indicator to "pull" your prograde marker onto the target's prograde marker, being careful not to exceed the 10x rule

2) flip retrograde and commence "pushing" your retrograde marker into alignment with the target's retrograde marker, being careful to keep your closure rate in accordance with the 10x rule.

3) at 30m to target, burn retrograde to make your closure rate zero.

Docking

1) pitch and yaw to match the target port's attitude.

2) engage RCS and fire as necessary to get your port behind the plane of the target port.

3) disengage RCS. adjust view and roll to align your view with your ship's motion. I pitch and yaw to verify that it will move as I expect.

4) turn on lights and engage RCS.

5) begin vertical and lateral translation as needed to line up directly behind the target port. check periodically to ensure clearance to target.

6) roll as necessary for payload alignment

7) translate forward at 0.2 m/sec until docked.

Best,

-Slashy

Edited August 3, 2014 by GoSlash27

[Pecan]

Rendezvous and docking are different skills that different people learn at different speeds. The only real advice is to be patient and keep practicing, you seem to have got all the basics done.

Practice with something small and easy (well, easier!) - Docking Drone, Chapter 5: http://forum.kerbalspaceprogram.com/threads/79658-Exploring-The-System-A-design-tutorial-campaign?p=1183116&viewfull=1#post1183116

[Mahnarch]

MasterTao; That's one of my hang ups. I adjust once I'm close but, everything I do make me move farther away!

I get the same thing when I EVA. I'm afraid to leave my ships in space because I end up adrift...

Wander: So the yellow DOES mean something?! I just ignored it, figuring it was height above Kerbin info.

I'mma have to look into that, again.

Slashy: I followed everything except "Docking #2"... What does "behind the plane of the target port" mean?"

In aviation, it means a point "beyond the lowest approach to minimum" in Instrument Conditions but, usually, a pilot in those conditions doesn't risk flying that far. I tried that once. My bladder got out of the airplane before I did!

Thanks, Pecan! I did try for smaller craft after (shh! "several") a few times trying to mate ginormous stations without even coming within 20kms. The smaller ones seem easier to move closer.

Edited August 3, 2014 by Mahnarch
Yarg!

[GoSlash27]

Mahnarch,

If you imagine a 2 dimensional plane parallel with the target docking port, I'm talking about getting on the proper side of it so's not to have a fender-bender in orbit. I always do that step first, before I begin translating to line up with it.

Best,

-Slashy

[Pecan]

Rest assured there's nothing wrong with finding these manoeuvres hard. Like a lot of things, once you get it you'll wonder why it took so long, but they ARE the hardest things in real-life as well as KSP. And we don't have a team of mathematicians and physicists with banks of computers planning every step for months before the mission is even approved.

There's also nothing wrong with letting MJ do it for you until you're ready for some more practice. Just promise yourself not to rely on it ^^.

[Tortoise]

20m/s is too fast.

For beginners, most people recommend being at less than 0.2m/s

And remember, your prograde follows you and your retrograde goes away from you.

And if you want to slow your velocity to 0, thrust in the opposite direction you're going. So when using RCS, aim at prograde and press N.

[Mahnarch]

Thanks for all the pro-tips.

I'm about to try again in a little while. Right now, I'm awaiting my window to go to Duna for the first time, ever!!

Knowing it's supposed to be hard to meet up does make it less stressful.