Lucy
655f1c9af6
- orbital_elements.py: elliptical + hyperbolic orbit support - orbit_drawer.py: orbit point generation with SOI truncation - soi_calculator.py: SOI crossing time calculator - frame_transition.py: reference frame switching - test_orbital.py: 147 assertions, all passing - visual_test.py: pygame flyby visualization
91 lines
2.3 KiB
Python
91 lines
2.3 KiB
Python
"""
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Reference-frame transitions for patched-conics SOI handling.
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When a body enters a planet's sphere of influence its orbital
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elements must be re-expressed relative to the planet. On exit
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the reverse transition occurs.
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"""
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from typing import Tuple
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from orbital_elements import OrbitalElements, orbital_elements_from_cartesian
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def sun_state_to_planet_orbit(
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body_x: float,
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body_y: float,
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body_vx: float,
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body_vy: float,
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planet_x: float,
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planet_y: float,
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planet_vx: float,
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planet_vy: float,
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mu_planet: float,
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epoch: float,
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) -> OrbitalElements:
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"""
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Convert a body's sun-frame state to a planet-relative orbit.
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Parameters
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----------
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body_* — body position & velocity in sun frame
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planet_* — planet position & velocity in sun frame
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mu_planet — planet's gravitational parameter
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epoch — time of transition
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Returns
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-------
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OrbitalElements describing the body's trajectory around the planet.
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"""
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x_rel = body_x - planet_x
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y_rel = body_y - planet_y
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vx_rel = body_vx - planet_vx
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vy_rel = body_vy - planet_vy
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return orbital_elements_from_cartesian(
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x_rel, y_rel, vx_rel, vy_rel, mu_planet, epoch,
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)
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def planet_orbit_to_sun_state(
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orbit_planet: OrbitalElements,
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planet_x: float,
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planet_y: float,
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planet_vx: float,
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planet_vy: float,
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t: float,
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) -> Tuple[float, float, float, float]:
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"""
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Convert a planet-relative orbit back to sun-frame state at time t.
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Returns (x, y, vx, vy) in sun frame.
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"""
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x_rel, y_rel, vx_rel, vy_rel = orbit_planet.compute_state_at(t)
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return (
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x_rel + planet_x,
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y_rel + planet_y,
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vx_rel + planet_vx,
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vy_rel + planet_vy,
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)
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def planet_orbit_to_sun_orbit(
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orbit_planet: OrbitalElements,
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planet_x: float,
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planet_y: float,
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planet_vx: float,
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planet_vy: float,
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mu_sun: float,
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t: float,
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) -> OrbitalElements:
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"""
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Full round-trip: planet-relative orbit → sun-frame orbital elements.
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Used after SOI exit to put the body back into a heliocentric orbit.
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"""
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x_sun, y_sun, vx_sun, vy_sun = planet_orbit_to_sun_state(
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orbit_planet, planet_x, planet_y, planet_vx, planet_vy, t,
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)
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return orbital_elements_from_cartesian(
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x_sun, y_sun, vx_sun, vy_sun, mu_sun, t,
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)
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