Multiple engine orientations - does navball/maneuvre node vectors update?

[CorBlimey]

Does the thrust vector and, more importantly, the ship's orientation to prograde and other vectors (for maneuvre nodes and manual burns) adjust to take into account the currently powered up engines?

I am currently building a space station with either a nuclear engine or, to start with hopefully, just a Poodle engine as its primary thruster but it would be nice if I could fit this or a interplanetary ion engine module on later connected to a docking port.

The engine modules would probably be either docked at the 'front' of the main station module or docked to a perpendicular bay and so would not be in the 'default' location of thrusting straight 'up' the stack.

I can tell that thrust obviously is accounted for (e.g. when shutting down jets engines) correctly but does the orientation to prograde etc vectors take it in to account?

Apologies for the drawing - perhaps it explains my question

Edited January 2, 2015 by CorBlimey

[Jason Patterson]

The prograde/retrograde vectors are based on the vessel's velocity, not on the thrust of its engines. As the engines apply thrust and change the velocity, the markers will move accordingly, but they will not (and should not) solely because an engine is pushing the vessel "sideways" instead of "forward." Addtionally, maneuver nodes indicate the direction of a required velocity change; they do not reference the direction of the engines' thrust at all.

However, if you want to have the entire navball reorient, that is possible as well. Suppose in your drawing that you wanted to launch with the box you've marked Toys pointed forward on the ship, but at a later point, you want the crew module to be the front (as far as the navball is concerned, that is.) If you put a controllable part at each of those positions (a command module or probe core - a docking port might work here as well, I can't recall) then you can right click on the part whose orientation you want the navball to reference and choose "Control From Here." The navball will reorient so that the object you chose is in control. You can change back at any time with a right click. You would launch with the Toys in control, and when you wanted to switch engines, switch control to the Crew module, rotate the vessel, and make your burn.

[cantab]

As stated, the heading on the navball is the heading of the controlling part. That can be a manned or unmanned command module, a docking port, or a claw. (An occupied external seat works, not sure about an unoccupied one). You can right-click any of these parts and choose "control from here". The engines are irrelevant.

Stability Assist and the other SAS options also take the heading of the controlling part. If you're controlling from a part on the extremities of your ship it may move around as the ship flexes and SAS will respond to that, which can cause instability. Controlling from a part firmly connected to the main engines and/or fuel tanks can give more stable behaviour.

In your example the front docking port of the interplanetary engine module or the probe core you have on it would probably be a good part to control from.

[CorBlimey]

The prograde/retrograde vectors are based on the vessel's velocity, not on the thrust of its engines. As the engines apply thrust and change the velocity, the markers will move accordingly, but they will not (and should not) solely because an engine is pushing the vessel "sideways" instead of "forward." Addtionally, maneuver nodes indicate the direction of a required velocity change; they do not reference the direction of the engines' thrust at all.

However, if you want to have the entire navball reorient, that is possible as well. Suppose in your drawing that you wanted to launch with the box you've marked Toys pointed forward on the ship, but at a later point, you want the crew module to be the front (as far as the navball is concerned, that is.) If you put a controllable part at each of those positions (a command module or probe core - a docking port might work here as well, I can't recall) then you can right click on the part whose orientation you want the navball to reference and choose "Control From Here." The navball will reorient so that the object you chose is in control. You can change back at any time with a right click. You would launch with the Toys in control, and when you wanted to switch engines, switch control to the Crew module, rotate the vessel, and make your burn.

Ok thanks - I understand about the vectors being based on velocity (which I would point out is a speed and an angle to something, angle being the important part).

They are displayed on the navball relative to an orientation and are interpreted by reference to x,y and z planes relative to something. You say that that something can be changed to the docking port so that is the solution as long as my additional module engine thrust vector is straight through the docking port (which I will make sure it is by sticking to a stack).

So, I think I understand what you are saying. I can simply switch control to the docking port of the additional engine module to make my burns in the right direction.

Now I can merrily proceed with building the core of the station whilst I wait to unlock the tech for the additional modules.

Thanks!

p.s. thanks cantab for explaining about SAS and flex

Edited January 2, 2015 by CorBlimey

[Jason Patterson]

To be clear, the direction of the navball markings and the velocity marks on it are based on the reference frame for your SOI (or Target/Surface, if you have those selected), not the parts - not in any way at all. If you are flying due east with 0° inclination, then you switch the control to a new object, the navball will turn and reorient to that part, but every one of the orbital vector marks will be in the exact same place that they were previously. It's just as if you've spun the ship around to face in a new direction.

It can be annoying to fly if it is significantly off, but a velocity vector that is parallel to your control orientation works just as well, though it tends to induce rotation. Sometimes you are stuck with a less than perfect option though.

Edited January 2, 2015 by Jason Patterson