Landing at specific points with a lander?

[Unholyundies]

Well as I am sure most have had this problem. That wonderful first landing on the mun and then realizing you have no fuel left. I would love to bring Jeb home and after countless missions always end up several hundred km away from Jebs lander. Anyone have any suggestions I have tried mech jeb and that didn't turn out so well. Any suggestions though are welcome.

[Duke23]

I'm not the best at this but I'm getting better. My advice is either do your deorbit burn relatively low or make sure you compensate for the rotation of the body (Mun shouldn't matter much). Line up your trajectory into the ground past your actual target because you'll burn some of that off as you burn retrograde for the landing. How much to aim past is hard to say, it'll be based on your speed, altitude, body rotation speed, and a little experience.

Another option is build a ship that can carry a small disposable rocket rover with a probe core. Then just land anywhere within about 30km and you're golden. Any rover really but a rocket rover with landing gear that can hop over craters is more forgiving imo and faster. Or bring enough fuel that you can land and then make short hops over to your target.

For me landing on target was worse than learning orbital rendezvous but a little patience and trying different things will go a long way.

Edited October 3, 2014 by Duke23

[SkyRex94]

Okay, as we're talking about the Mun we don't have to watch for the rotation as the mun is tidally locked.

So the EASIEST but most fuel consuming way of precise landing:

You obviously need an orbit going over your target as a starting position.

Now if you've a lander with a high TWR and a lot of spare fuel: simply burn retrograde directly over your target until your predicted path is a straight fall down on it. then you have to slow down your fall and smothely touch down.

The EFFICIENT way:

start the retrograde burn further away like a quarter or a third of an orbit if you have low TWR and/or less fuel. but watch where your predicted path hits the ground. This has to stay alway BEHIND your Target so it has to look like youre going to overshoot (several hundred km), since you'll lose more and more horizontal velocity during the braking. While you're doing your normal landing procedure the predicted path will move closer and closer to the target. And thats a matter of practise and experience, you should ideally be exactly onto your target when your predicted path is a straight down fall.

Use this and the rest is practise and soon you'll have more experience in doing it.

(Until you're trying it with an atmosphere, there you'll need even more practise and can't really counteract as soon as aerobraking begins. Unless you've a plane)

[Superfluous J]

It takes lots of practice to be sure, but the basic idea is:

1. Get your orbit so you're going over Jeb each time around.
   
2. Set up a maneuver node to crash land just past where Jeb is. Nailing just how far past is part of the "lots of practice" part.
   
3. Do that burn, then delete the node and set a new one up on the ground where your orbit crashes intersects it. Make that node stop you and note how much time it will take.
   
4. You'll come down and see Jeb's little icon on the surface. Set him as a target so you get a marker on your navball.
   
5. Do the burn for the maneuver node, but do it a little early so you stop right over Jeb. This is another "lots of practice" part
   
6. Now with any luck you're a few km above Jeb's head falling straight down. Land as normal. Don't sweat it if you're a few km away, the walk will do Jeb good. But as you keep practicing you'll eventually be able to land right next to him.
   

I frequently land on docking ports on my ground bases, so any level of accuracy is indeed possible.

[Duke23]

Yes tidal locking will make the rotation pretty much non existent, I didn't think of that. You definitely explained better than I did SkyRex. Terminology, how does it work.

[Vanamonde]

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

[Plusk]

This mod should help Trajectories. Helpfull little thing.

Edited May 23, 2021 by Snark
Link to defunct website removed by moderator

[Lhathron the Elf]

There is a fantastic mod called Trajectories (http://forum.kerbalspaceprogram.com/threads/93685-0-24-2-(Atmospheric)-Trajectories) which actually determines that for you. I've been using it for a while now and its absolutely FABULOUS! It compensates for the rotation of the planet as well as atmospheric effects. It also tells you what your planned flight path it as well as when you are in and out of the atmosphere in map view.

[tsotha]

Look at the third part Scott Manley's "Kerbal for beginners" series. He goes through exactly what you're trying to do.

[juanml82]

Plusk said:

This mod should help Trajectories. Helpfull little thing.

That or, alternatively, Mechjeb's landing guidance, which includes a landing predictor. If you manage to put your orbit at the right inclination so you're above your target, it's a matter of setting the navball to surface mode and burn retrograde to kill horizontal speed (do it with a node to calculate burn times - in orbit, surface/orbital modes will be the same) and then fall vertically near Jeb. I'll still advice to either bring a rover or make the rescue ship a rover, as it's likely you'll land a few kms away.

And, BTW, how do you match your inclination so your orbit goes above the target? You can set up a deorbiting maneuver combining a retrograde and normal/antinormal burn, but I feel the landing will be more precise if the inclination is right to begin with.

[Empiro]

One thing that has really let me be more precise is to remember to target the ship you want to land close to. You use the target and velocity retrograde markers you determine how your approach looks (I usually do my deorbit burn 1/3 of an orbit away from my target, and put myself a bit past my target). You'll want to keep the navball in surface mode, however.

The retrograde markers tell you very accurately where you burn to "push" the velocity retrograde so that you don't have any lateral deviation. Then, you keep the velocity retrograde marker slightly under the target retrograde marker (since as gravity pulls you down, your velocity retrograde will start pointing getting higher and higher toward the sky. Burn toward the sky to push the velocity marker down (basically killing your vertical velocity but not your horizontal), burn toward the horizon to kill your horizontal velocity. Burn somewhere in between to do one or the other while also slowing yourself down overall. With experience, you should be able to land within 1km of your target on the Mun.

[Unholyundies]

Thanks everybody for the suggestion I will give what I have not tried already a go and see where that gets me.

[Kerbart]

Here's how I do it (Mun specific but I don't see why the same approach wouldn't work on other bodies without an atmosphere):

• Set your target as "target" (just make sure your navbal is in orbit/surface mode or "going straight down" might not be as straight as you think)
  
• Get into low orbit (about 10km altitude)
  
• At a 90° angle in orbit adjust inclination. Adjusting incliniation at higher orbits is more efficient, but adds complexity, especially since it takes time to adjust your altitude and the planet/moon keeps rotating.
  
• Set up a navigation node to land on top of your target; go for a pretty deep descent
  
• Adjust navigation mode as you get close to adjust for rotation of the planet/moon
  
• While landing, aim to have the target marker between your velocity marker and the 90° inclination point. The longer you manage to do that the closer you'll land
  

When building a base I consider anything beyond 1km a "botched landing". I usually get within 500m with my best result sofar 140m.

[Plusk]

And, BTW, how do you match your inclination so your orbit goes above the target? You can set up a deorbiting maneuver combining a retrograde and normal/antinormal burn, but I feel the landing will be more precise if the inclination is right to begin with.

Target it, map mode will show you AN/DN nodes, burn acordingly, then descend. Or even easier, Kerbal Engineer tells you time to nodes.

[tsotha]

Bah. It's episode 9: