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LKO Catching up with the station


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I've setup a docking simulation to teach myself how to dock (and is my first time ever). But i can't seem to figure out a better way to rendezvous with the station. Must i stay on lower orbit to catch up with the station? Or is there a better way to achieve this faster and fuel efficient?

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Edited by TokiTech
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Staying as you are is fuel efficient.

If you want to get there sooner, you should raise your apogee to let the station catch YOU up. This can bring you into an intercept at the next descending node, therefore in under one orbit (probably between 30 mins and 2 hours) vs an unknown number of orbits at 20 - 25mins a go, to catch up as you are.

A good balance is to raise apogee above station orbit (and perigee TO station orbit), but aim for intercept on the 3rd orbit's descending node rather than the next pass. That way you know exactly how long it will take to phase and you'll only need about half as much delta-V to speed up and slow down again.

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When you're closing in on the target, it's important to match your velocity to the target (which I think is what you mean by 'having time to align with it'). The easy way to do that is make sure your speed display is set to Target (if it says Orbit or Surface, click on it till it changes to Target). Then find the retrograde marker on the navball and align to that. Wait until you're within a few hundred meters of your station, then thrust towards the retrograde marker until your speed gets to 0.0 m/s. At that point, you're travelling at the same speed and in the same direction as your target.

Then it's just a case of thrusting gently towards the target to close in for docking. If you're more than a few hundred meters away, you'll find your trajectory seems to drift off the target - this is because of differences in your orbit altitudes, so although you're travelling the same way at the same speed for a moment, gravity is affecting you differently. The closer together you are, the less this is an issue, so just keep correcting and soon you'll be right alongside.

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Thanks for tips guys, i'll let the station catch me up then. But i'm not sure if i can pull of the maneuver in time to align with it i'm too new with this! :blush:

Rendezvous and docking are two distinct skills and most people find one much easier to learn than the other. Like a lot of things it helps if you practice with small, easy to manoeuvre, ships first. Look in Chapter 4 of the tutorial in my signature for docking drones as an example (.PDF version and .craft file downloads in the OP).

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Changed my mind at the last moment, went on chasing the station lol. It seemed easier, around 4-5 circle orbits with some correction to get there. Made it with station 1.4km away. Also end up docking using only visual judgement. I tried to read the navball, control from docking port and set target port don't show anything meaningful to me.

Also had a freakout moment when i'm approaching too fast, i needed ESC to catch a breath, eventually i overshoot the station, turn around and stabilized the plane without drifting away... Rest of the story can be found there

http://forum.kerbalspaceprogram.com/threads/29533-What-did-you-do-in-KSP-today?p=1595667&viewfull=1#post1595667

no.. noo.. noooo! ESC NOPE'd!

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Rendezvous and docking are two distinct skills and most people find one much easier to learn than the other. Like a lot of things it helps if you practice with small, easy to manoeuvre, ships first. Look in Chapter 4 of the tutorial in my signature for docking drones as an example (.PDF version and .craft file downloads in the OP).

I see, even are different but both are essential for space travel in one skill package, a must learn. I'll check out your tutorials, thanks! :)

Edited by TokiTech
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You 'sort of need' both - rendezvous is precision transfer-orbit; you're aiming for a tiny object relatively close rather than a massive one far away. Docking isn't 'necessary' as such, but in-space refuelling does make things a lot easier than having to carry all the fuel you'll ever need right from the start.

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What I always found made it easier (personal preference) was to have my target docking port face directly south (down), and then the craft I'm controlling i will right click my docking port and select 'control from here' point it directly north (up) and then once i have selected the docking port as target on the other craft i have a visual representation on the navball when I'm close to get minor adjustments done. I'm able to dock, not an expert though so it may be making my life harder than I need to :)

Tweety

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A refinement to that ... don't think north and south (though in an equatorial orbit they are), think normal and anti-normal. They're basically the "fixed directions" in an orbit so you can align early on one and have an easy enough time matching it.

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I'm such a lazy docker. I used to do it "properly". Get close. Point one craft north, the other south. Use IJKLMN or whichever keys it is to translate and thrust.

Nw I get within 20m point the docking ports directly towards each other (this is a bit long winded as you need to set each one as the other's target and then point to target, switch ships, point to target, switch ships, point to target, etc. until they are close enough). Next I get within about 5m and repeat, then to touching distance and repeat and hope the magnets do their job.

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