How will the nav ball work with axial tilt?

[t_v]

Going off of the assumption that there is some sort of indicator for up/down/north/south/east/west like the nav ball in ksp1, how will it function when transitioning between spheres of influence? In KSP 1, “east” was always the same direction because all bodies had no axial tilt relative to each other. Will the indicators suddenly switch when you enter the SOI of a planet that is spinning upside down?

[Superfluous J]

I can only assume so, otherwise it wouldn't make sense.

If North on the navball is not matched with North in your current sphere of influence, it may as well not show it.

[pandaman]

As I understand it, East is the 'spinward' direction so, if you face that way, North will be to your Left, irrespective of the axial tilt and orbital inclination relative to the 'Sun'.

I would expect the Navball will adjust to show the infomation relative to the SOI  you are currently in, as it does already, it just isn't obvious because it doesn't change it's tilt because it doesn't need to.

[jastrone]

they could make it like real life and make it slowly point the right direction depending on how close you are

[SciMan]

I doubt it will "slowly point the right direction depending on how close you are" because that would make it absolutely useless far away from the planet, and you need it to be accurate everywhere, not just "close to the planet". What would happen to one of those low-thrust high mass spacecraft that has to "spiral" its way out of a planets gravity well, if the navball wasn't always perfectly accurate? You'd never be able to plot an accurate interplanetary course, or accurately adjust said course, that's what would happen. Nobody wants "artificial difficulty" in the game, and that's exactly what this sounds like.

It's certainly not like real life. IRL, your instruments are based on something called an Inertial Navigation System, and while yes older ones were based on actual gyroscopes and therefore could drift over time, craft that used them would be able to calibrate the INS in-flight by using instruments to sight several stars and knowing the time of day to a high degree of accuracy, and doing a lot of complicated math.
Modern INS are based on Ring Laser Gyroscopes, which are so good that you might as well say they don't drift at all, and you can almost instantly get a position fix by using the GPS receiver that you almost certainly have onboard for other purposes (as a matter of fact, these days INS is usually a back-up to GPS, only used when you can't get a good GPS signal). And yes, GPS can be used in space, the equations change and you have to account for the doppler shift of the radio signals due to the high speed that orbital flight entails, but it's perfectly doable and in fact I think SpaceX's Starlink satellites actually use GPS to coordinate their locations in their satellite constellation (I could be wrong, but why not use what's already there?). With over 300 satellites launched to date, it's the simplest way to avoid satellite collisions in that constellation.

EDIT: As to how the nav-ball itself will work with axial tilt, I think you will be able to have it switch between several modes (both automatically and at-will, similar to how the KSP 1 altimeter works, but with some automation).
Modes I just thought up include:

• Aligned with local equator
• Aligned with the ecliptic plane of bodies orbiting a planet (useful for transferring between a planet and it's moons)
• Aligned with stellar ecliptic plane (useful for interplanetary travel)
• Aligned with galactic ecliptic plane (useful for interstellar travel)
• Perhaps "aligned to custom beacons" as well, that way it would allow you to set up your own local coordinate system for something like setting up a colony.

That last one is iffy, and I'm not even sure how it would work that makes it different from one of the other modes in a meaningful way unless you're somewhere like near the poles of a planet or moon.

Edited October 22, 2021 by SciMan

[K^2]

I would prefer each SoI to have its own coordinate system and the attitude indicator to just change with SoI change just like the altitude indicator does now.

[OHara]

KSP1's navball changes quite dramatically upon a SOI change.

New players occasionally get confused, but seem to figure it out quickly.

Principia allows different planets to have rotation axes in different directions, and allows different navball frames of reference, but one does not force the other.  You can always choose to use the navball aligned to the body in whose SOI you currently are, as in stock KSP.

[SciMan]

Yeah nothing I said prevents you from setting the navball to "stay aligned with the SOI of the planet you're in". As a matter of fact, that would probably be the default.

However, you'd have additional modes to work with, for doing things like planning out an interplanetary trajectory easier. Something like being in Kerbin orbit but having the navball aligned to the Kerbol's SOI. In this mode, you'd get navball markers for prograde, retrograde, etc. that consider both your path around Kerbin AND what effect that has on your path around the sun, and the velocity indicator would indicate your velocity in Kerbol orbit (taking into account the influence of your velocity around Kerbin).

Same idea applies on the Mun or Minmus for instance, you'd be able to set the navball to indicate what your orbit around whichever of those moons you're orbiting means for your orbit around Kerbin, and additionally you'd be able to even set your navball to indicate your trajectory around the sun (while orbiting the Mun or Minmus).

This is done to make it easier to do interplanetary trajectories from ANY body to ANY body in the entire game, including directly from a moon of a planet in one solar system to a moon of a planet in another solar system (tho to be fair unless we can get these interstellar ships to burn at like 5g then the burns for that would likely continue across a few SOI borders, so that might complicate things on the "thrust while on rails" side of things, but that's not for this topic).

Essentially, it makes it so you can tell the game to do the math to figure out your true solar orbit velocity vector no matter where you are, which is critically important for calculating interplanetary trajectories. This would make it so you could actually use a calculator (or other more advanced tools) to figure out a maneuver node, instead of having to "fiddle with it" to get what you want.
Granted, that's not for everyone, and KSP encourages "fiddling with things" in general, but the advantage is that it would make it much easier to calculate out trajectories that use gravity assists to get where you want to go.