Positive Vs. Negative Phase Angle - Basic Physics Questions

[Sovnheim]

Dear All,

Ever since I've been playing KSP, I've become a huge fan of orbital physics and how to apply them in KSP.

I must say I'm a complete beginner in the field of orbital physics, and I'm having trouble grasping the concept of phase angles. In my understanding, the phase angle is the angle made by two objects orbiting a third object. But quite often, the phase angle is negative, and that's the part I don't understand.

If the second satellite in orbit is behind the first one's orbit, the phase angle should be between 180° and 360°. However, KER's measurements sometimes indicate negative angles, like -310°, which confuses me.

I have looked around on the Internet without much succes, hence my question here. Can someone help me understand the principle ?

Thank you very much !

[Carsogen]

Hi there Sovnheim, I believe it's just which direction KER 'looks' to calculate it. For example, 3 o'clock is 1/4 of the way around the clock, or -3/4 around the clock. It just depends which way around the clock you go.

So -310 degrees is the same as +50 degrees.

Hope this helped!

Cas.

EDIT: Realized I had misinterpreted the question and fixed my answer

Edited October 9, 2014 by Carsogen

[FTWG4M3RS]

-310 is actually 70 not 50

[diomedea]

-310 is actually 70 not 50

Sure, if there were 380° (not 360) in a full circle.

[Carsogen]

-310 is actually 70 not 50

Don't know where you get that one from

310 + 70 = 380

Although knowing KSP there could be 380 degrees in one revolution

Cas.

EDIT: Ninja-fied

[Sovnheim]

-310 is actually 70 not 50

OK, NOW I'm confused

I'd agree with you Carsogen, but why would KER have to "look" in a specific direction in the first place ? Why would it randomly give me a positive or negative number since both are the same thing ?

Also, this doesn't seem neither scientific nor necessary. Having negative numbers just screws my Excel files over.

[Superfluous J]

I remember some discussion on the KER thread somewhere, that he just uses the numbers KSP gives him. If KSP says it's -310 degrees who is he to argue?

But really there is no significance to it. Somewhere a programmer just did a bunch of calculations and didn't bother to make sure he resultant number fell within the -180 to +180 range. There is literally no more to it than that.

[Sovnheim]

That's really weird.

If you say so, it doesn't matter then - I'll just tweak my Excel files to make sure that it takes into account negative values.

Thanks a lot !

[Vanamonde]

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

[Carsogen]

why would KER have to "look" in a specific direction in the first place ? Why would it randomly give me a positive or negative number since both are the same thing?

Also, this doesn't seem neither scientific nor necessary.

Sorry I guess I didn't explain it very well the reason that it's like this is probably just because that's how it was coded originally and now everything runs off it. They could have made it any version of how it is (eg from -180 to 180, or the other direction be positive).

I hope I haven't just made it more confusing for you

Cas.

[James_Eh]

I have to reinstall MJ to check, I had a hissy fit a couple of versions ago and dropped it, but I don't recall that it ever gave a negative angle. Just anything from 0 (direct equatorial perfect "oh-look-at-me" orbit) to 90 (polar N-S) to 180 (perfect retrograde) to 270 (polar S-N) and back to zero.

But now that I read what I wrote, it seems to me that I should have been able to make it toggle back and forth between 359 and 0 by wobbling around the equator, and I don't recall ever seeing that. I pretty much guarantee I would have with my umptyteen spaceplane disasters over time...

<edit> Move along, move along... "Phase angles", right. Duh.

Edited October 10, 2014 by James_Eh
I'm dumb