Surface rendezvous

[LordCorwin]

Hello,

I've performed dozens of orbital rendezvous with no problem, but trying to land close to a target in surface... that's a different story.

Appart from selecting the target and matching the descending path close to the target visually, I'm not following any method, just try and error. Sometimes I get 20 meters away from the target, next time it's 5 km!.

So I'd like to know if there is a good procedure for surface rendezvous. I'm not asking for actual dock, but at least be always close to the target.

I've checked the Tutorial folder, but I haven't found anything.

Thanks in advance.

Lord

Edited June 10, 2015 by LordCorwin

[Brainlord Mesomorph]

Practice.

Sorry but that's the answer.

That and a lander that handles well (i.e. extra Delta V) so you can change you mind as you're coming down, (if the lander is a pig, its coming down were ever it wants)

[LordCorwin]

Practice.

Sorry but that's the answer.

Don't worry, it's what I thought :-)

[Feradose]

Not really. Notice that planets spin? That spin is your enemy, like every atmosphere when it comes to precise landing. Wings may help with the latter, but when there is no wings, all comes to observing. Where are you landing on? What is the altitude from sea level there? Im kidding. Try the trajectories mod and practice with it!

[smartie987]

You could install a mod that will calculate the drag that the ahtmosphere gives you and then overshoot just enough to pull the chutes at the right time. However I do think Brainlord Mesomorph is right.

[LordCorwin]

Not really. Notice that planets spin? That spin is your enemy, like every atmosphere when it comes to precise landing. Wings may help with the latter, but when there is no wings, all comes to observing. Where are you landing on? What is the altitude from sea level there? Im kidding. Try the trajectories mod and practice with it!

Haha, thanks, I'll try. I was also trying to stick to the Nav Ball, but I don't get it. I found it easy to use it in orbit, but not when apporaching to a target on surface.

No spin, no wings. Just a landing on the Mun.

[Feradose]

B-but planets and moons should be spinning! :shock:

[LordCorwin]

Yeah sorry, Mun was spinning, but not my probe :-)

[match]

Target your uhh target. Keep your retrograde indicator between the horizon and the target indicator. If retrograde indicator rises above your target, you will undershoot. If it stays below, you will overshoot. It is easier to correct an overshoot than an undershoot (for me, at least)

Practice practice practice!

[arise257]

On Mun, it's pretty straightforward -- no atmospheric resistance to compensate for and you can orbit at crazy-low altitudes. I used to use suicide drops to keep the approach lined-up and more predictable, but that comes at the expense of DV to land softly. Learning to transition from a suicide drop to a more gradual descent is when I got good at "sticking a landing" on-target. So yes, practice makes perfect -- but if you can spare the DV, a suicide drop might be your ticket.

- - - Updated - - -

I also forgot to mention that while it's no good for last minute adjustments (unless you're talking sub-5-ton crafts), using RCS to guide your descent is totally legit, especially if you're up high, but drifting off-course. Save your liquid fuel for slowing down and getting back off that rock.

[ajburges]

RCS is the only way to target landing zone in orbit. Less than .1 m/s high up can be a difference of hundreds of km.

If the body has no atmosphere, the trajectories mod can show you trajectory WRT surface in body fixed mode. Simply set a sub-orbital path that overshoots the target.

If the body has atmosphere, trajectories tries to simulate drag. (still issues with accuracy for stock) Overshoot the target and use aerodynamic surfaces to correct by breaking.

If it's Lathy or Kerbin, use a space plane with jets.

[tsotha]

You should really have a look at

video.

[LordCorwin]

Hello!

I will control de under-over-shoot stuff as indicated (navball, atmospheric drag, etc), and also I will check the video.

Thanks for all the replies, very much appreciated!

Lord

[SanderB]

I've done several surface rendezvous to within 1 inch (ie. docking one vessel on top of another) though this explanation is just about how to get within ~1km, with a target on a planet without an atmosphere that doesn't rotate too fast.

1) Get in a low circular orbit around the target planet, over the target as low as possible without intersecting with the surface.

2) Create an maneuver node over the target on the surface, and pull out the retrograde marker until all velocity is eliminated.

3) Set the target as the target from the map view.

4) Approach your maneuver node, face retrograde and set 100% throttle when the time to node is half that of the burn time. (If your surface TWR is <1.4, start your burn a little earlier.)

5) Destroy the node by clicking the red X to the right of the navball.

6) Keep burning retrograde, and gradually pitch up to keep your vertical velocity near 0m/s. The lower your TWR the more you have to pitch.

7) Push your retrograde marker onto the anti-target marker continually, and a little bit toward the horizon if you want to keep from crashing into the surface. The retrograde marker can be pushed with thrust on its far-side.

Use quicksave and load to practice. It takes some practice to perfect this. Use the Velocity^2/Acceleration*2 formula to determine if you need to decrease thrust, it isn't necessary to pause and use this formula to get nearby, but it is very helpful in order not to use too much fuel.

The video is a demonstration and a slightly less than perfect vertical surface docking.

Edited June 11, 2015 by SanderB

[cybersol]

The video is a demonstration and a slightly less than perfect vertical surface docking.

I'm getting this video is private?

EDIT: working now

Edited June 12, 2015 by cybersol

[SanderB]

, it should be visible. It shows up to me as public.

[LordCorwin]

Well, I think I've improved my skills now. See in the picture, I managed to recover a vessel & a Kerbal that were stranded on Mun's surface!

This involved to rendezvous close to the vessel on surface, save the Kerbal, turn upside down my ship while floating some meters above the vessel, use RCS with the navball to adjust the approximation to the vessel, and grapple it while floating half meter above it.

Many thanks to all of you, I couldn't do it without your help!!!.

Lord