[Question] Instrument readings to align an orbit with a land target

[hypervelocity]

Hi guys!!! How is everyone doing? Hope everything's great!!!

I am writing with this doubt I have regarding landing manoeuvres.

I am sending several payloads to the Moon to start my Lunar refueling base and obviously I want to land them as close as I can to link them up and get it working.

My precise problem arises when I need to adjust my orbit's inclination to the land target -> is there any instrument readings I can use to perform this in an accurate fashion? I am using MechJeb but I don't get the relative inclination to target measure when selecting a land object as my target (almost surely because it woulnd't make sense as any orbit could fly over a given land point and have different lunar-relative inclinations). I have (unefficiently) worked around this by plotting fake lunar-impact manoeuvre nodes to find out how closely-aligned I am with my land target, but I wish I had an instrument that could show me my relative inclination to any given land target by a simple reading while in orbit.

Surely I am missing something in MechJeb or probably there's an easy way to calculate it given the orbital information MechJeb does provide.

Any help you guys could provide will be greatly appreciated!!!! Many thanks in advance!

Edited November 1, 2015 by pvnkb1tch

[sebi.zzr]

You can use "auto landing pilot",just click on your landed stuff,select "land at target" and MJ will do everything for you.Don't be surprised if it lands too close.

[maltesh]

If you've got a Kerbal on the ground, my recommendation is that you have that Kerbal plant a flag to use as your Mechjeb Landing Target.

If you don't, a pretty-accurate rule of thumb is that 1 second of arc latitude = (radius of body in km / 200 km) in meters.

As a result, on the Mun, for every second of arc north or south in the MJ Landing Autopilot UI, the intended landing point is pretty darn close to 1m north or south of the object you're planning to land near.

[hypervelocity]

You can use "auto landing pilot",just click on your landed stuff,select "land at target" and MJ will do everything for you.Don't be surprised if it lands too close.

thanks for the suggestion sebi!!! I have tried the auto landing pilot but it didn't work out (I am playing with the Real Solar System/Realism Overhaul mods) - it never gets it right. Also, I would like to learn how to do it manually without the auto pilot :D

[adge]

I do believe that Kerbal Engineer will provide a relative inclination read-out, even when targeting a ground-based target, when using the Rendezvous option.

[sebi.zzr]

thanks for the suggestion sebi!!! I have tried the auto landing pilot but it didn't work out (I am playing with the Real Solar System/Realism Overhaul mods) - it never gets it right. Also, I would like to learn how to do it manually without the auto pilot :D

Sorry,if i upset you,but even in RSS,MJ is quite accurate on non atmospheric bodies.Anyhow,even if it isn't,you can at least look at what autopilot is doing when plotting autoland and by that you can learn how to be more accurate.MJ is not just "auto for everything",it's also a great learning tool.

regards

[Acet]

I do manual landings all the time.

Rough guide:

- Select a landed ship, flag or kerbal as target.

- Quicksave!

- Reduce your PE and aim it to the West of where you want to land. The least steep you descent is, the further to the West you should aim. This is because the planet will rotate as you descend so you need to account for descent time and flatter descents take longer.

- Put a manouver node at the point where your descent will intercept the planet. Adjust it so that it reduces all speed to zero. This will tell you time and direction that you should fire your engines to stop.

- Fire at full power about 10% - 20% AFTER the point when the manoeuvre node tells you to start. If you do it right on the dot you will be too short.

At this point your aim is to have your horizontal speed down to zero at the point when the target retrograde markers is exactly centred in the blue side of navigation ball. When this happens it means you're right on top of your target and can simply drop down.

- As you're doing final approach (some kilometers from target) you will notice the target retrograde marker moving roughly towards the centre of the navbal. What you want is to make sure it goes to its centre. The way to do this to make small adjustments by firing your engine to make sure that in the navball you always have 3 indicators in a line: your ship's retrograde indicator -> your target's retrograde indicator -> the centre of the blue side of the navball. The closest the target's retrograde indicator gets to the centre of the navball the closest your own retrograde indicator should be of it, ending with all of them at that centre point.

You need to think of it as a game where your ship's retrograde indicator pushes the target's retrograde indicator away from it. The furthest your ship's indicator is from the centre the strongest it is pushing the other one way, and if it's at the centre then the push is zero. By firing your ships engines when it's pointing away from its own retrograde indicator you push that retrograde indicator away, with the aim being to keep that 3 indicator alignment i pointed up.

- When you're about 500 m away from target you eyeball it for final landing - this is the part where you mostly start ignoring the navbal since as you get very close to it the target's retrograde indicator will quickly drift away from centre. At this point I usually do small burns to send my ship towards the desired landing area and maintain a hoover as it slowly drifts sideways. Once you're on top of where you want to land, aim the ship to its own retrograde indicators and do a controlled burn following that indicator - by aiming at the retrograde indicator rather than straight down you will both kill horizontal and vertical speed.

If everything went well, thumbs up, otherwise it's time to load that quick save.

I strongly suggest you train in Minmus first, before try the Mun - Minmus has less gravity so everything happens slower and you're less likely to quickly gain tens of m/s of descending speed as result of a few seconds of distraction, which is what happens when doing it in the Mun.