Possible Missing Coriolis Term in vessel.orbital_reference_frame
afnanwioe456 opened this issue ยท 1 comments
What happened?
I've noticed that when transforming velocity vectors from ECI to vessel.orbital_reference_frame, the calculation appears to include only the rotation and relative velocity terms. Since orbital_reference_frame always aligns its y-axis with the velocity direction of the vessel, it should inherently have an angular velocity relative to ECI. A Coriolis term may be missing in the transformation. Could you confirm if this behavior is intended, or if this is indeed an oversight?
How can someone else reproduce it?
import krpc
import numpy as np
conn = krpc.connect()
sc = conn.space_center
v = sc.active_vessel
vt = v.velocity(v.orbit.body.non_rotating_reference_frame)
velocity = np.array(vt)
pt = v.position(v.orbit.body.non_rotating_reference_frame)
position = np.array(pt)
T = velocity / np.linalg.norm(velocity)
h = np.cross(position, velocity)
N = h / np.linalg.norm(h)
W = np.cross(N, T)
orientation = np.vstack((T, W, N)).T
angular_velocity = h / np.linalg.norm(position) ** 2
t = conn.space_center.target_vessel
tv_orf = np.array(t.velocity(v.orbital_reference_frame))
tp_orf = np.array(t.position(v.orbital_reference_frame))
tv_eci = np.array(t.velocity(v.orbit.body.non_rotating_reference_frame))
tp_eci = np.array(t.position(v.orbit.body.non_rotating_reference_frame))
rotation = orientation.T
coriolis_effect = np.cross(angular_velocity, tp_orf)
print(f'Should be: {rotation @ (tv_eci - velocity - coriolis_effect)}')
print(f'Got (left-handed): {tv_orf}')
print(f'Without coriolis term: {rotation @ (tv_eci - velocity)}')
What is your environment?
Python 3.10
krpc 0.5.2
ksp 1.12.3
Anything else we need to know?
No response
Another more straightforward way to reproduce the issue is to place two satellites on the same circular orbit but with different phases. Calling vessel_1.velocity(vessel_2.orbital_reference_frame) returns a non-zero value. However, based on the definition of the reference frame, the transformed velocity should be zero.