Contract Specifications specifically strange?

[Tiberius Kerman]

Okay, I have a contract to put a satellite in orbit around Kerbin with a specific Apoapse and Periapse, along with a 180 degree 'incline' (which I am interpreting as counter rotational equatorial orbit) and a 125 degree "Angle/Argument of Periapse".

Sounds like everything is there but with a reverse angle orbit, there is no ascending node so I have nothing to base the Angle/Argument of Periapse against.  I don't have a relative vector or anything off the equator to move the satellite against to set 125 degrees.  I've tried burning fuel and moved the craft 120" hoping to get lucky with a green check mark.  All other specifics have been met for the orbit to within 10 meters (figure that's precise enough).  Can't get my contract vendor to check me off on it.

Any ideas?  My forehead and the wall it routinely strikes are now making obscene comments to each other every time I walk by.  I find it mildly disturbing...

[Snark]

Moving to Gameplay Questions.

55 minutes ago, Tiberius Kerman said:

Okay, I have a contract to put a satellite in orbit around Kerbin with a specific Apoapse and Periapse, along with a 180 degree 'incline' (which I am interpreting as counter rotational equatorial orbit) and a 125 degree "Angle/Argument of Periapse".

Yes, that's correct, "180 degrees inclination" means a retrograde orbit.

55 minutes ago, Tiberius Kerman said:

Sounds like everything is there but with a reverse angle orbit, there is no ascending node so I have nothing to base the Angle/Argument of Periapse against.  I don't have a relative vector or anything off the equator to move the satellite against to set 125 degrees.  I've tried burning fuel and moved the craft 120" hoping to get lucky with a green check mark.  All other specifics have been met for the orbit to within 10 meters (figure that's precise enough).  Can't get my contract vendor to check me off on it.

If you go to the map view, your target orbit should be displayed as a glittering line in some distinctive color (different from the usual colors used for displaying vessel orbits).

If you eyeball it-- i.e. you look at your current orbit, and you look at the target orbit-- do they match up?  Have you laid your orbit right on top of the target one?

If you haven't... then do that.    If you have and it still hasn't checked off the contract, it's possible you could have hit a bug (one thing to try is to do a quicksave and then quickload, that sometimes un-wedges it).

Could you post a screenshot of your map view so we can see how your actual orbit looks, compared with the target one?

[OHara]

Tiberius, if visually matching orbits doesn't work, there is a bug that matches your problem almost exactly (#13508 ).  

The last time it came up on the forum is here: (link)

Edited December 5, 2018 by OHara

[Tiberius Kerman]

15 hours ago, Snark said:

Moving to Gameplay Questions.

Yes, that's correct, "180 degrees inclination" means a retrograde orbit.

If you go to the map view, your target orbit should be displayed as a glittering line in some distinctive color (different from the usual colors used for displaying vessel orbits).

If you eyeball it-- i.e. you look at your current orbit, and you look at the target orbit-- do they match up?  Have you laid your orbit right on top of the target one?

If you haven't... then do that.    If you have and it still hasn't checked off the contract, it's possible you could have hit a bug (one thing to try is to do a quicksave and then quickload, that sometimes un-wedges it).

Could you post a screenshot of your map view so we can see how your actual orbit looks, compared with the target one?

Hmmm... yes, this is the case and I thought I was using the little greenish yellow dotted line correctly.  My Periapse and Apoapse seem to be perfectly on target...

Where my issue comes in, at least according to the cat with the crazy hair that hangs out at the dumpster with me, is that this 'Angle or Argument' of Periapse seems to be related to the orientation of the elliptical nature of the orbit in relation to the body it orbits... Kerbin in this case.  The cat is absolutely certain that if I aim the rocket at or away from Kerbin, it rotates the ellipse in relation to the body I'm orbiting.

I tested that feline theory with those dotted lines and sure enough it seems to work perfectly.  I've decided to name the cat Newton, because he weighs a ton when he jumps on me trying to steal the food I've found in the dumpster from me, and our relationship is relatively new.  But I don't know what I'm supposed to be 125 degrees in relation to... the Sun-Kerbin Orbital line, radial line?

I'm hoping to solve this angle thingy so that maybe the other Engineers might let me move my box into the VAB.  The spaceproof paint I've put on the box is, sadly, not rain proof and I have to keep repairing the box.

13 hours ago, OHara said:

Tiberius, if visually matching orbits doesn't work, there is a bug that matches your problem almost exactly (#13508 ).  

The last time it came up on the forum is here: (link)

Thank you for the help.  I have matched the geometry exactly but the angle-argument of it is what I can't verify.  I need some kind of reference line to set that.  It would be the ascending node if the orbit wasn't to be 180 degrees, but at 180, now what do I do?  Newton, the crazy cat that is now mocking my typing skills, says if I ask louder I might get more help.  I don't think that works as my volume is set as loud as I can make it but the text doesn't seem any louder... one issue at a time I suppose.

Edited December 5, 2018 by Tiberius Kerman
grammar, Newton mocking it

[OHara]

19 hours ago, Tiberius Kerman said:

180 degree inclination [...] and 125 degree Argument of Periapsis.

 

2 hours ago, Tiberius Kerman said:

  But I don't know what I'm supposed to be 125 degrees in relation to...

The 125° argument of periapsis is the angle between periapsis adn the ascending node.  With a 180° reverse equatorial orbit, though, the location of the ascending node is undefined.  That is exactly the problem with KSP reported in bug 13508:
Equatorial satellite launches do not specify a longitude of ascending node, but the contract still checks this when evaluating the orbit. 

The KSP programmers seem to intend for us  to visually align orbits, but the code that checks completion of the contract tests the angles.  If the contract text states the longitude of the ascending node that it expect, and if you enjoy celestial navigation, you can give the orbit a 179° inclination at the right point relative to the fixed stars, and complete the contract, just for the satisfaction of beating the bug:

 

[bewing]

33 minutes ago, OHara said:

Equatorial satellite launches do not specify a longitude of ascending node, but the contract still checks this when evaluating the orbit.

Except that it doesn't.

The requested orbits are just defined as ellipses in space. They are only reported to you using Keplerian orbital coefficients on the contracts because that's the most standardized format. Yes, you are supposed to match the visual orbit.

If you really want to play games with LAN then you can have your inclination up to 2.9 degrees off, and the contract will still complete. But since the inclination is then non-zero, those Keplerian values will still be defined.

Additionally, the Argument of Periapsis has nothing to do with specifying the orbit. That number is about specifying time and location. If you are already in an orbit, sometimes you want to know exactly what point in that orbit your craft occupies. That's what the Argument of Periapsis tells you. You feed in an exact time, and you get out the exact position of your craft on the ellipse. Or vice versa, of course. But that value is not tested at all for contracts.

More to the point, those Keplerian values are completely unnecessary. They are shown on the contract for your amusement only. The only values you really need are the relative An and Dn on the requested orbit, and maybe the Pe/Ap. Depending on the number of stars on the contract, you may need to get everything matching to a high degree of accuracy. But "10 meters" is way closer than you need. 10 kilometers is about the closest you ever have to get.

Note that most of the time when people have the same problem that you are having, it means they are orbiting in the wrong direction. Even the ones that swear they have their ship in a retrograde orbit suddenly discover that retrograde is not the direction they thought it was.

So really, snark had it right. If you are in control of the proper craft, and all the checkmarks on the contract are green, and your orbit is right on top of the requested orbit, and the An and Dn values on the requested orbit say ZERO, then the contract should complete. If it doesn't, then that's a bug -- but we've seen it happen. There are a few things you can do to force the contract to complete. Sometimes a tiny burn will do it. Sometimes switching focus to another craft and then back again will do it. Sometimes you have to use the Debug menu. But really, it's best to take a screenshot with as much info showing as possible and then post it here.

[Snark]

1 hour ago, bewing said:

Additionally, the Argument of Periapsis has nothing to do with specifying the orbit. That number is about specifying time and location. If you are already in an orbit, sometimes you want to know exactly what point in that orbit your craft occupies. That's what the Argument of Periapsis tells you. You feed in an exact time, and you get out the exact position of your craft on the ellipse.

Just a nit (and not especially relevant to the question here)-- I don't think that's what "argument of periapsis" is.  What you just described is the anomaly.

The argument of periapsis is, in fact, about specifying the orbit-- it defines the orientation of the major axis of the ellipse.  It's undefined for perfectly circular orbits.  Imagine that you have an elliptical orbit in the X-Y plane.  Picture a line that goes from the central body out to the apoapsis.  The argument of periapsis will indicate what direction (in the X-Y pane) that it points-- e.g. in the +X direction, or -X, or +Y, or -Y, or some angle in between.  "What o'clock is the apoapsis at", basically.

References:

• https://en.wikipedia.org/wiki/Argument_of_periapsis
• https://en.wikipedia.org/wiki/True_anomaly

 

[bewing]

Ah, you're right. I was just going by memory. It still doesn't matter though.