A question about orbits.

[Megadeath]

This is really a language question. In reading this forum I've often seen eastern, or clockwise orbits referred to as prograde. Is this really correct usage? It's just been bugging me that real rocket scientists could have a situation where the instructions to burn prograde could be interpreted with diametrically opposed meanings.

[Crzyrndm]

It's prograde because it's following the surface velocity imparted by the planets rotation (ie. burning towards the orbital velocity vector which is the definition of prograde direction). It's only east because that's the direction Kerbin rotates

Edited June 27, 2015 by Crzyrndm

[Tex_NL]

... eastern, or clockwise orbits referred to as prograde. ...

Don't you mean COUNTER clockwise?

A clockwise orbit would mean you turn west during your gravity turn resulting in an orbit opposite to

[Evanitis]

A question I could easily google for, but I rather let you demonstrate your immense knowledge. Are there planetary bodies in the stock Kerbol system where the prograde orbit is clockwise? And in our solar system?

[Awaras]

A question I could easily google for, but I rather let you demonstrate your immense knowledge. Are there planetary bodies in the stock Kerbol system where the prograde orbit is clockwise? And in our solar system?

In KSP, no. In the Solar system:

[Juicy]

"Clockwise" is a tricky one to decide. First, you have to decide which side of the planet is up. But, to make that decision, you'll have to figure out what side of the star it's orbitting is up as well, even just for reference.

Be thankful KSP doesn't feature multiple star systems (yet!), since then we'd also have to figure out the top side of the galaxy. Just for reference, ofcourse. And that would get even worse if we expand to universe levels, with multiple galaxies floating around.

There is no up in space! Ergo, there is no left or right in space, so there is no clockwise or counter clockwise either. It's all relative, depending on your position and viewing angle. Prograde and retrograde become much simpler concepts then, it's either forward or backwards, with other directions being derivates of those.

[Evanitis]

Whoa... That picture makes me kinda' glad that it's standardized in KSP. It would be maddening to manually land on a body with some of those inclinations... Though it could be a fun challenge too.

[Mesons]

Don't you mean COUNTER clockwise?

A clockwise orbit would mean you turn west during your gravity turn resulting in an orbit opposite to

This is why angular velocity and angular momentum are represented by cross-products, perpendicular to the orbital velocity. CW/CCW depend on where you view the system from, but if you consistently apply a right-handed convention, the direction is unambiguous.

[mikegarrison]

Once upon a time there was a big cloud of dust and supernova debris that had a net rotation. As these bits of space junk ran into each other, they gathered into a sun and some planets. When they did this, everything ended up mostly spinning in the same axis as the original rotation of the cloud.

[KerikBalm]

"Clockwise" is a tricky one to decide. First, you have to decide which side of the planet is up. But, to make that decision, you'll have to figure out what side of the star it's orbitting is up as well, even just for reference.

Indeed, counterclockwise/ clockwise, east/west... those are arbitrary definitions... prograde is always prograde.

https://en.wikipedia.org/wiki/Axial_tilt#Two_standards

Note that there are two standard methods of specifying tilt. The International Astronomical Union (IAU) defines the north pole as that which lies on the north side of the invariable plane of the Solar System;[5] under this system Venus' tilt is 3°, it rotates retrograde, and the right hand rule does not apply. NASA defines the north pole with the right hand rule, as above;[4] under this system, Venus is tilted 177° ("upside down") and rotates direct. The results are equivalent and neither system is more correct.

If I tell you to burn East at venus... you'll have to ask if I'm using the NASA system, or the IAU system.

If I tell you to burn prograde, you burn prograde, easy.

Luckily in KSP, there is no confusion, because all objects have zero axial tilt and no retrograde rotation.

[Arkalius]

Prograde, in almost any context, means the direction of your relative velocity around the central body of your orbit.

When used to describe an orbit itself, it means an orbit of less than 90 degrees equatorial inclination.

The context is almost always enough to understand what is meant when the term is used.

[Awaras]

Whoa... That picture makes me kinda' glad that it's standardized in KSP. It would be maddening to manually land on a body with some of those inclinations...

Nah, all it would take would be some fine-tuning of your approach vector some time before entering the target planet's SOI...

Realistic planet orbit inclinations would be a much bigger headache.

Edited June 27, 2015 by Awaras

[wossname]

Aliens may prefer to build clocks where that hands go the other way to human-made clocks. It's best to call ahead and confirm before you begin your journey.

[lajoswinkler]

Different rotations would be a great addition. It's not a big deal. As Awaras said, it just takes fine tuning upon approach (or during the first burn).

[wossname]

Different rotations would be a great addition. It's not a big deal. As Awaras said, it just takes fine tuning upon approach (or during the first burn).

It could even be setup in the difficulty menu either as an "on/off" or perhaps as a graduated slider for increasing the inclination and axial tilt for each planet/moon.

[lajoswinkler]

I wouldn't go that far. Those are special properties of each body. One doesn't have to be able to reach every corner of the system as soon as they start playing, and some places should put a player through hell to reach them.

[Evanitis]

Different rotations would be a great addition.

Or even a mod.. I was somehow convinced it's something that was made long ago - to my surprize I found nothing like that. Well RSS has axial tilts, but I don't think I can play that on my potatoe.

I wonder if that's just a variable I can easily find if I read around were to look...

[Starhawk]

I seem to recall someone saying that axial tilt would be problematic to implement with the current Unity engine.

Haven't heard anything about whether the new engine will change that.

Happy landings!

- - - Updated - - -

Realistic planet orbit inclinations would be a much bigger headache.

http://image.slidesharecdn.com/ch15-thesolarsystem-140806091208-phpapp02/95/ch15-the-solar-system-51-638.jpg

I must disagree.

Moho has an inclination of 7 degrees, while Eeloo's is 6.15.

And, of course, Pluto isn't a planet at all.

Happy landings!

[moogoob]

A planet with a Triton-style retrograde moon would be a pretty cool addition to KSP. And I had no idea Venus' day was retrograde. I wonder what caused it to slow down?

[Miro Beero]

In KSP, no. In the Solar system:

http://www.redshift-live.com/binaries/asset/image/17231/image/The_axes_of_rotation_of_the_eight_planets.jpg

You missed Pluto:

http://www.cbc.ca/news/technology/pluto-ceres-and-an-exciting-summer-for-space-exploration-bob-mcdonald-1.3129249

[Awaras]

You missed Pluto:

http://www.cbc.ca/news/technology/pluto-ceres-and-an-exciting-summer-for-space-exploration-bob-mcdonald-1.3129249

Pluto is not a planet. (the inclination picture I posted before is OLD).

If I'm going to include it, I'd also have to include ceres and a bunch of other objects.

Edited June 27, 2015 by Awaras

[Miro Beero]

Pluto is not a planet. (the inclination picture I posted before is OLD).

If I'm going to include it, I'd also have to include ceres and a bunch of other objects.

I grew up with Pluto being a planet. Its day will come again!

I will wait till July 14, 2015 when "New Horizons" probe will fly by Pluto (the planet) :-)

[LABHOUSE]

It is a planet, as are all other dwarf planets.

[Vaporo]

I seem to remember KittopiaTech being able to reverse the rotation of planets. If I remember right, it was a single checkbox called something like "rotation reversal on/off." Presumably, it is a variable present somewhere in the planet generation code that KittopiaTech just accesses. I also think it worked if you just entered a negative number into the rotation period field.

Edited June 28, 2015 by Vaporo