Rendezvous for dummies who inexplicably don't get it

[Sirrobert]

Well I've been playing with it' date=' and I'm starting to notice that trying to rendezvous in a 75km orbit around Kerbin isn't something for the faint of heart. So I moved my parking orbits up to 125km and I've had more luck.

But how would you set yourself up to catch up with your target when you manage to get your orbits matching? Been having issues with that.[/quote']

You'll never catch up with your taget if your orbit is matching but you aren't close.

You need to be on a different orbit (higher if you are ahead, lower if you are infront of the target), and than burn to make your apoaps/periaps touch the target orbit, and your craft is there at the same time as the target.

THAN you match velocitys/orbit. After you are already close

[Mr Shifty]

You'll never catch up with your taget if your orbit is matching but you aren't close.

You need to be on a different orbit (higher if you are ahead, lower if you are infront of the target), and than burn to make your apoaps/periaps touch the target orbit, and your craft is there at the same time as the target.

THAN you match velocitys/orbit. After you are already close

I tend to match orbits then increase (if behind the other ship) or decrease (if ahead) one side of it by 20km. For 100km initial orbit around Kerbin, a 20km difference between the orbital major axes will move you closer to the other ship by about 8 degrees per orbit, so it'll take a maximum of 24 orbits to catch up (if you start on the other side of Kerbin.) The advantage of the 20km difference is that, provided your inclination matches the other vessel's, you don't have to re-match orbits. Your closest approach to the other ship will be within 20 km, no matter what, and it's easy to do 'advanced' rendezvous from that distance.

[Oafman]

Or if all that is to compicated get mechjeb, set up rendezvous and watch what happens. After a couple of times watching mechjeb do its magic you will feel confident enough to try it out yourself. I learned that way and once you get the hang of it it's not that complicated.

I actually stopped using MJ autopilot for RVs. When I do an RV manually, I put myself in a slightly higher or lower orbit (maybe 5km or 10km difference) and then time warp until I'm close enough to move into the same orbit as my target and be very close to it.

But if I give this job to MJ, it always moves to a phasing orbit of 191km (i've been docking things at 82km) before plotting a Hohmann transfer to the target. This is obviously very inefficient, burning all that fuel to get up there and then back.

Is this just something it always does, or can i change the way it approaches an RV in the settings somewhere? I couldn't find anything.

[GoSlash27]

Intercept

Step 1: Get in the same orbit as your target.

Step 2: If the target is behind you...

2a: wait until you've just passed the CPA markers (red arrows)

2b: burn prograde until the 2 arrows are touching.

If the target is ahead of you...

2a: wait until you've just passed the CPA markers (red arrows)

2b: burn retrograde until the 2 arrows are touching *OR* until your periapsis is at minimum.

In either case, you don't have to complete the intercept in a single orbit if you're short on fuel or pushing minimums.

Note that when I say prograde and retrograde in this case, I'm referring to the direction of the orbit itself, and *not* the symbols on your nav ball.

I'll post the "rendezvous" part of it after work...

Edited June 16, 2014 by GoSlash27

[Pauly]

This is how I learned. Not the most fuel efficient way but man is it easy.

I still use this method when I am not worried about fuel and I want to rendezvous fast and easy.

[GoSlash27]

Rendezvous

about 3/4 of the way through your intercept orbit, you should see your green prograde marker get close to the target prograde (pink). At this point, you should...

1: burn to the opposite side of the pink prograde in order to "pull" the green prograde onto it.

2: Burn toward the target keeping the symbols overlapped until your closure rate is 10 times the range to target.

3: flip and begin burning retrograde, keeping your retrograde (green) on the target's pink retrograde, but this time by "pushing" it instead of pulling. You want to burn just enough to keep your closure rate 10 times the range to target.

4: At 30m range, you should reduce your closure rate to zero. You should now be in close formation with the target.

[Kryxal]

It's also worth being aware of where the target docking port is if you're using a "fixed" alignment or it's not something you can easily spin ... if the other ship has the port facing north life's easier if you can make that approach and be above it.

[Shiv]

Best method I've found thus far:

1) Launch

2) Circularize orbit ~40km below or above target orbit. (You want your eccentricity as close to 0 as you can get it, but it doesn't have to be exact) and get it in the same plane as the other orbit.

3) Make a maneuver node to intersect the target orbit.

4) Use maneuver node and PreciseNode to find where the target and myself will become closest. The good thing with PreciseNode is it can seemingly go into the 'future' where as the standard way of just running the maneuver node around the orbit seems to reset itself each time you make a complete circle.

5) Then simply burn to that position and dock. No need to circularize your new orbit as you'll dock long before it's an issue.

[Curiosity7907]

I like to divide RV(Rendezvous)  into 3 steps.

1.launch get into orbit  and do the first step of RV or hohmann transfer.

2.Matching velocities at the closest approach.

3.Docking.

I have done 1st and 3rd step but I can't do the 2nd step.

If I try to do the 2nd step I first fire pointing towards target then then I go towards target but I also start geting away from the target then I point towards prograde or retrograde and fire then I do come close sometimes but I get even more away Until I get way to far from my target.

That is why these days I use RV autopilot from mechjeb but problem with RV autopilot is it takes to much time manually I or anyone ellse can do it faster.

                                                                              That is why I think doing the 2nd step by using eva pack is much much better.

 

 

[cephalo]

Forgive me if this was already mentioned.

The very most important thing to know about rendezvous is this:

Maneuver nodes are draggable! You can drag the maneuver nodes along the orbital path!

If you don't know this, rendezvous are intolerable difficult.

[Plusck]

I'm actually

3 hours ago, Curiosity7907 said:

I like to divide RV(Rendezvous)  into 3 steps.

1.launch get into orbit  and do the first step of RV or hohmann transfer.

2.Matching velocities at the closest approach.

3.Docking.

I have done 1st and 3rd step but I can't do the 2nd step.

If I try to do the 2nd step I first fire pointing towards target then then I go towards target but I also start geting away from the target then I point towards prograde or retrograde and fire then I do come close sometimes but I get even more away Until I get way to far from my target.

That is why these days I use RV autopilot from mechjeb but problem with RV autopilot is it takes to much time manually I or anyone ellse can do it faster.

                                                                              That is why I think doing the 2nd step by using eva pack is much much better.

 

 

2nd step is actually the easiest because the NavBall gives you so much information. But you must NOT thrust towards the target - it's pointless.

Just make sure you are switched to target mode. Now, just like when landing or whatever, thrusting at a point near to the RETROGRADE marker will make it move AWAY from where you are pointing. Likewise, thrusting towards PROGRADE will move the marker TOWARDS where you point.

So to match velocities, first you bring your relative velocity to target down to a manageable level by thrusting retrograde (on target view). I like to get down to about 10m/s until I'm about 500m away, then down to 5m/s up to 150m then down to 0.1m/s while I set up docking.

Then you see where the retrograde marker is compared to the anti-target marker. You want to point to a spot that is as close as possible to 90° away from retrograde on the same side of the anti-target marker while still being able to see anti-target on the navball (so drawing a radial out from your pointer on the navball would go through retrograde, then the anti-target at the very edge of the navball).

Thrust away and watch retrograde get pushed over anti-target. Correct as necessary. Now you know you are heading directly towards your target at (hopefully) a slow speed. If you are already going very slow, or need to speed up, flip over and move the prograde over the target marker - this time you want to point on the other side of the target marker (so drawing a line across the navball would go through the prograde, then target, then your pointer). If you are going very very slowly, you don't even need to flip over and can use RCS and reverse thrust ("N") instead.

Finally, if you're any distance away then your slightly different orbits will make the target curve away from you. The prograde and retrograde will start moving away from target / anti-target over time, so you just need to keep on giving jabs to the sides to push prograde / retrograde around (or stay pointing towards the target and use RCS and the IJKL keys) so that they are always pointing to target / antitarget.

Edited December 8, 2015 by Plusck
correction

[Snark]

BTW, in case you guys haven't noticed, you're responding to a dead thread-- had no posts for a year and a half, until @Curiosity7907 necro'd it a few hours ago.

Forum etiquette generally suggests not reviving long-dead threads, unless there's some very good reason to do so.  It's usually unhelpful, and tends to generate confusion because the stuff you're responding to was written so long ago that there's a good chance it's completely irrelevant or nonsensical due to changes in the game since the original post.

[Plusck]

Ah well - didn't notice that. But I was answering Curiosity7907 anyway so I forgive myself

However, since it just so happened that I had to do a complicated rendezvous, I decided to document it to show how to do it efficiently. Using 1.0.5 and manoeuvre nodes, NOT burning needlessly (well, except for a mess I made at one point), and trying to be demonstrative.

So I went away and made this album:

KSP 1.0.5 orbital rendezvous

It's my first imgur album and I haven't sussed out the options for embedding properly and making it slideshow-ish. Hope it's useful