Landing close to a target on the Mun using the constant altitude landing method.

[al.wallace]

In one of my previous threads, the constant altitude landing method was mentioned (you can find more about it here : t.com/r/KerbalAcademy/comments/1wxt6v/how_is_it_best_to_land_on_planets_without/cf6cj20)

I have tried this method and it has worked, to some degree of sucess. I have managed to use it to land about 2000-4000KM from my target on the Muns surface (in stock KSP!). This is good for my landing missions that have a rover to carry kerbals across the surface, but not for missions where there is no rover but just the kerbals EVA suits.

So i'm asking for help in how to land closer to the target using this landing method, the distance should be a good munar hike away from the target, something like the distance the Apollo astronauts walked to and fro, but scaled down for Kerbals.

So any help?

Thanks in advance (:

AGM.WALLACE

[Ogre420]

You can use these mods...

Percise node....
http://forum.kerbalspaceprogram.com/threads/47863

Trajectories....
http://forum.kerbalspaceprogram.com/threads/104694-0-90-Trajectories-v1-1-0-%282014-12-24%29-atmospheric-predictions

Or mechjeb....
http://jenkins.mumech.com/job/MechJeb2/

[KasperVld]

My own method is to set the craft you want to land next to as a target, then set the navball to surface mode. The trick is then to keep the antitarget vector on the same degree as the retrograde vector, but closer to the horizon. For example, your target is perfectly east (90 degrees) to you which means the antitarget vector is at 270 degrees, so long as this situation persists you'll be getting closer to the target. To prevent falling short you need to keep the retrograde vector closer to the horizon than the antitarget vector.

You keep this balance until the antitarget vector is on the zenith of your navball, or 'pointing up'. That means you're right above the target and you can drop down. At this point your retrograde should be right on top of the antitarget.

I hope it's clear enough, and I think you'll need to try it two or three times before you get the hang of it, but it works so well you can find yourself accidentally landing on top of your target!

[al.wallace]

Originally posted by KasperVld:

My own method is to set the craft you want to land next to as a target, then set the navball to surface mode. The trick is then to keep the antitarget vector on the same degree as the retrograde vector, but closer to the horizon. For example, your target is perfectly east (90 degrees) to you which means the antitarget vector is at 270 degrees, so long as this situation persists you'll be getting closer to the target. To prevent falling short you need to keep the retrograde vector closer to the horizon than the antitarget vector.

You keep this balance until the antitarget vector is on the zenith of your navball, or 'pointing up'. That means you're right above the target and you can drop down. At this point your retrograde should be right on top of the antitarget.

I hope it's clear enough, and I think you'll need to try it two or three times before you get the hang of it, but it works so well you can find yourself accidentally landing on top of your target!

How would I get the retrogade vector to stay exactly on the anti target vector?

[Aethon]

Umm. Constant altitude landing method was much more useful when the other planets (only Mun and Minmus at the time- Can't remember which version) were very flat and had low mountains. Now there is just too much terrain for it to be a safe beginner method.

This is what I do.

Try to keep stuff around the equator. Start from a 15 km orbit, set the ship you want to land near as a target, and make a maneuver node half way around the planet from where you want to land. Pull out the retro vector to drop your periapse about km or 2 before you fly over the target as low as you feel comfortable. Depending upon where you must land, shoot for a periapse of around 5-6 km. If your ship is far away from the maneuver node, you'll need to slide this node forward in time along your orbit to keep your periapse slightly in front of the target

If you need to make an inclination change, do it 90 degrees away from the target. About 20 to 30 km out, burn retro so your impact point is 20 km or so beyond your target. Now quickly put a maneuver node on your trajectory, slide it forward in time to your impact point, and pull it retro until it flips around. This will tell you how long you have to burn to kill all your orbital velocity. Use this as a guide.

Start burning as your target comes into view and move your impact point closer and closer to the target using throttle control. I ususally try to overfly the target most of the way. I have a tendency to undershoot. As you fly over, burn hard to kill your orbital v and drop straight or nearly so, down on top of the target, thus avoiding the terrain.

TL/DR : Careful!

Hope this helps!

[Quivico]

Originally posted by agm.wallace:

Originally posted by KasperVld:

My own method is to set the craft you want to land next to as a target, then set the navball to surface mode. The trick is then to keep the antitarget vector on the same degree as the retrograde vector, but closer to the horizon. For example, your target is perfectly east (90 degrees) to you which means the antitarget vector is at 270 degrees, so long as this situation persists you'll be getting closer to the target. To prevent falling short you need to keep the retrograde vector closer to the horizon than the antitarget vector.

You keep this balance until the antitarget vector is on the zenith of your navball, or 'pointing up'. That means you're right above the target and you can drop down. At this point your retrograde should be right on top of the antitarget.

I hope it's clear enough, and I think you'll need to try it two or three times before you get the hang of it, but it works so well you can find yourself accidentally landing on top of your target!

How would I get the retrogade vector to stay exactly on the anti target vector?

Thrust in the opposite direction you want it to go.

Increase the distance from the vector to increase its change further.

[Syd Khaos]

CAL can be REALLY dangerous on Minmus...just FYI. You get down past a certain point and them mountains can sneak up on ya =P

But on the upside the green smears left by Kerbals kinda blend into terrain...

[Bubba Fett]

I assume you mean you're landing 2000 to 4000 meters from the target rather than km.
I do trips with the EVA pack longer than that all the time.

When I land I like a steeper trajectory. I usually start from about 30 km and make a maneuver node to drop me just past my target. By using a node from high altitude you can land at targets that are quite a ways off your orbital path.
Once I do my de-orbit burn I freefall most of the way and only start slowing in the last 2 to 3km.
I keep checking the map on the way down doing minor corrections to keep my impact spot just past the target. The reason is that when you decellerate you're also going to kill horizontal speed and drop straight down. You want to be over your target when that happens.
Then you just do your final decelerate and landing.

If you're not using mods and you're landing at an object on the surface, make sure your target is selected before you start your de-orbit burn. Not only is it handy to see on the nav ball, you'll also want the distance readout toggled with F4. In stock your altitude is to sea level not the terrain so this lets you tell aproximate radar altitude without going to the IVA view.

If you do use mods, MechJeb is highly recommended. The Translatron can control your throttle to hold you at a specific vertical speed. (or hover) The SmartASS surface panel has a button to keep your pitch and roll at 0 unless you override with the controls.
And you can easily make custom windows for every occasion. My landing window shows Radar Alt, Vertical speed, Horizontal speed, Time to Suicide burn, and Time to Impact.

An easy mode landing with MJ is: Burn your de-orbit node, On the way down set your translatron to -10m/s but don't activate it. Make sure to click outside it's window to return focus and control back to KSP. Use the SmartASS panel to point retrograde and be ready to switch to the Up button in the surface section. Once your time to suicude burn gets to about 5 seconds you click the Keep Vert button on the Translatron and Mechjeb will use full throttle to slow you to -10m/s and hold that rate. While you decend you should have time to change the rate to -1 or 0 and focus outside the window by activating the Up button in the surface section of the SmartASS. The execute button will activate the new rate when you're near the ground.

The Trajectories mod that Vaprak mentioned will help with precision landings where atmospheric drag is an issue but not on the Mun. Still it's a great mod and I use it to land near the KSC after missions all the time. Including precision areobraking after a Mun mission.

Precise Nodes also won't help with the landing, but will make it easier to get a good encounter.

Of course the number one tip for precison landings anywhere it to quicksave before you start just in case you mess it up really bad. :^)

edit: KasperVld's comment reminded me of one further tip. If your ship has RCS for docking with an orbiting lab you can use it to kill your last couple of m/s of horizontal speed. It's more precise than pitching or rolling the ship for low velocities.

[KasperVld]

Originally posted by agm.wallace:

How would I get the retrogade vector to stay exactly on the anti target vector?

If you're familiar with docking, it's actually very similar to that with the added challenge of gravity.