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Planet Ascend/Descend Node


XLjedi
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When intercepting a target or another planet, there's a nice ascending/descending node with a dotted line that shows you the optimum spot to adjust the orbit inclination.  How would I get something like that to appear when I intercept Minmus and the orbit is a bit off?  I want to align the orbit to the equator before I send my lander down.

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The nodes of a planet or craft is where your orbital plane crosses theirs and actually doesn't match the planet's equator inherently.

Most planets in KSP have low orbital tilt, so the equator does match the orbital plane in many cases, but Minmus is not one of those cases.

To get a perfectly equatorial orbit in the stock game, I can only think of 3 ways:

  1. Cheat something into an equatorial orbit of Minmus.
  2. Accept a contract to put a satellite into an equatorial orbit of Minmus.
  3. Accept a contract to rescue someone or something from an equatorial orbit of Minmus.

Any of those will give you a reference orbit you can then match with your craft that you want to be equatorial.

There is another option: eyeball it and accept that if you can't tell the difference it doesn't matter :)

Edited by 5thHorseman
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Stock bottom left panel gives you info about your post-maneuver inclination. (I think so, I know it shows Pe/ap for sure) Drop the node wherever you think the equator is, and balance the maneuver until it says 0.0°

Edited by The Aziz
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Thanks for all the responses.  I do have KER installed so I had to try to rely on the orbit inclination value.  I must not have had it perfect, because I could not get it closer than 1°.  ...but that was close enough.  I was thinking there might be a way to get the equatorial line of a planet to display in stock, but I guess not.  Do any of the scanning tools do that maybe?  

Eventually, I would like to place a station in orbit with close to exact equatorial orbit for each planet/moon.

9 hours ago, 5thHorseman said:

The nodes of a planet or craft is where your orbital plane crosses theirs and actually doesn't match the planet's equator inherently.

You are correct, I guess I was thinking in terms of the equator as an orbit with zero altitude.  ...and is there any way to select the planet that you are orbiting as a target so it would display the ascend/descend node relative to the equator. 

I imagine something like this would also be helpful when trying to reposition from equator to polar orbit. 

Edited by XLjedi
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For this task, I use two tools:

  1. Kerbal Alarm Clock to place an alarm on either the AN or DN.  With no other target set, the default reference is the orbited bodyKAC then gives a count-down to the arrival.
  2. KER giving a heads-up display of lon/lat and also of inclination

The main thing to realize is that, as long as you are lat degrees North or South of the equator, you cannot make inclination any less than this amount.  You are therefore flying an asymptote toward the equator.  Close in on it fast, but then burn off as much of the lateral component you need in order to avoid overshoot.  Use a trickle as you get close to that equator to reduce the inclination to as close to zero as you like, spending as much time as you can bear for the accuracy desired.

Edited by Hotel26
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1 hour ago, XLjedi said:

Thanks for all the responses.  I do have KER installed so I had to try to rely on the orbit inclination value.  I must not have had it perfect, because I could not get it closer than 1°.  ...but that was close enough.  I was thinking there might be a way to get the equatorial line of a planet to display in stock, but I guess not.  Do any of the scanning tools do that maybe?

None of the scanning tools do it, but if your goal is to have an equatorial indicator that appears in flight view as well as map view, then I may have a solution for you.  Waypoint Manager allows you to place waypoint markers according to latitude and longitude, and you may set them at whatever altitude you like.  Since you know your longitude from Kerbal Engineer, it should be trivial to establish an equatorial waypoint marker at your orbital altitude and longitude.  You are still responsible for adjusting your orbital inclination to align with the waypoint marker, but you get the visual indicator that you want.  Furthermore, you can establish a series of four waypoints spaced at ninety degrees so as to check your inclination and alignment over the whole plane.

The point I am not certain about is whether the waypoints are hard-coded to disappear after you encounter them.  If so, then they provide a one-time check and provided that you can eliminate all of them, then you can know that your orbit is acceptably equatorial.  If not, then they provide a continuous check and you can eliminate them after you have established your station or what-have-you to whatever level of precision you prefer.

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I didn't realise KAC could do it as per Hotel26's post above.

The only other mod I know can do it is kOS, which allows you to programme your own stuff within the KSP environment.  I just started overhauling my inclination script the other night and now measure the angle between the North vector (which is a built in parameter for each planet) and the vector from the ship to the centre of the body.  This gives me the exact time of the next ascending or descending node.  Once I've worked out the maths for it this should allow me to time my burn so that I end up on the correct longitude of the ascending node as well as the right inclination.

Edited by RizzoTheRat
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16 hours ago, 5thHorseman said:

The nodes of a planet or craft is where your orbital plane crosses theirs and actually doesn't match the planet's equator inherently.

Most planets in KSP have low orbital tilt, so the equator does match the orbital plane in many cases, but Minmus is not one of those cases.

To get a perfectly equatorial orbit in the stock game, I can only think of 3 ways:

  1. Cheat something into an equatorial orbit of Minmus.
  2. Accept a contract to put a satellite into an equatorial orbit of Minmus.
  3. Accept a contract to rescue someone or something from an equatorial orbit of Minmus.

Any of those will give you a reference orbit you can then match with your craft that you want to be equatorial.

There is another option: eyeball it and accept that if you can't tell the difference it doesn't matter :)

@5thHorseman  Actually, the thought of just cheating something into orbit temporarily had never crossed my mind but does seem so obvious now. 

That may very well be my preferred approach.  Then once I have my station properly aligned, I can just wipe it.

Edited by XLjedi
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On 2/4/2020 at 8:23 PM, Hotel26 said:

For this task, I use two tools:

I just had to perform this very thing, using a craft with solely Wolfhound propulsion.  Using the technique I described, I was satisfied when I achieved 0.00074 inclination.  The limiting factor then was 1 click of throttle for as short one can for finer adjustments.  I didn't bother but for some kind of adjustments (particularly orbital period to sync with other satellites) where you'd kind of like millisecond accuracy (as fine as KER will show), I have further used the technique of limiting the thrust of an engine (even RCS/ion) to 0.5% to make those final adjustments.  So I think it's possible to do even better than the 0.00074 I just demonstrated.

I actually think this is less work (and more satisfying) than putting up a temporary reference marker via, ahem, nefarious means...  Whatever gets the job done satisfactorily, though...

Edited by Hotel26
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@Hotel26  Meh... I don't mind cheating a scaffold into orbit for a minute. 

In my mind that's no worse than using two mods as a "cheat".  If I made a mod that used an invisible part to do the same exact thing, in order to add certain "target orbits" to my guidance system, it would then not be a cheat?

This is something the spacecraft would just have in the guidance system and is more of a UI programming shortfall than anything.  I also have a docking alignment indicator mod that I don't consider a cheat.  ...anymore than I would consider Kerbal Alarm or the KER features a cheat.  These are all things a spacecraft would just have.

But, I do need to install Kerbal Alarm anyway... and I already have KER, so maybe I give it a try?

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