claudes_game/scripts/precalc_extreme_timescales.py

#!/usr/bin/env python3
"""
Precalculate expected values for test_extreme_timescales.
All values in SI units (meters, m/s, seconds).
Output local-frame values relative to parent body.
"""
import math

G = 6.67430e-11

def orbital_period(a, parent_mass):
    """T = 2*pi*sqrt(a^3/mu)"""
    mu = G * parent_mass
    return 2.0 * math.pi * math.sqrt(a**3 / mu)

def orbital_energy(r, v, craft_mass, parent_mass):
    """E = 0.5*m*v^2 - G*m1*m2/r"""
    mu = G * parent_mass
    ke = 0.5 * craft_mass * v**2
    pe = -mu * craft_mass / r
    return ke + pe

def circular_velocity(a, parent_mass):
    """v = sqrt(mu/a) for circular orbit"""
    mu = G * parent_mass
    return math.sqrt(mu / a)

# Body definitions (from TOML)
earth_mass = 5.972e24
earth_radius = 6.371e6
sun_mass = 1.989e30

# Spacecraft definitions and calculations
spacecraft = [
    {
        "name": "Fast_Orbit_LEO",
        "mass": 1000.0,
        "parent_index": 0,  # Earth
        "parent_mass": earth_mass,
        "a": 6.771e6,
        "e": 0.0,
        "nu": 0.0,
    },
    {
        "name": "Mercury_Like_Orbit",
        "mass": 1000.0,
        "parent_index": 1,  # Sun
        "parent_mass": sun_mass,
        "a": 5.79e10,
        "e": 0.2056,
        "nu": 0.0,
    },
    {
        "name": "Long_Period_Orbit",
        "mass": 1000.0,
        "parent_index": 1,  # Sun
        "parent_mass": sun_mass,
        "a": 5.2e11,
        "e": 0.0489,
        "nu": 0.0,
    },
    {
        "name": "Low_Altitude_Orbit",
        "mass": 1000.0,
        "parent_index": 0,  # Earth
        "parent_mass": earth_mass,
        "a": 6.471e6,
        "e": 0.0,
        "nu": 0.0,
    },
    {
        "name": "Super_Synchronous_Orbit",
        "mass": 1000.0,
        "parent_index": 0,  # Earth
        "parent_mass": earth_mass,
        "a": 4.5e7,
        "e": 0.0,
        "nu": 0.0,
    },
    {
        "name": "Geosynchronous_Orbit",
        "mass": 1000.0,
        "parent_index": 0,  # Earth
        "parent_mass": earth_mass,
        "a": 4.2164e7,
        "e": 0.0,
        "nu": 0.0,
    },
]

print("# ===========================================================================")
print("# Precalculated values for test_extreme_timescales")
print("# ===========================================================================")
print()

for sc in spacecraft:
    name = sc["name"]
    parent_mass = sc["parent_mass"]
    a = sc["a"]
    e = sc["e"]
    mu = G * parent_mass

    period = orbital_period(a, parent_mass)
    v_circ = circular_velocity(a, parent_mass)

    print(f"# --- {name} ---")
    print(f"# semi_major_axis = {a:.10e} m")
    print(f"# eccentricity = {e}")
    print(f"# parent_mass = {parent_mass:.10e} kg")
    print(f"# orbital_period = {period:.6f} s")
    print(f"# orbital_period = {period / 60.0:.4f} minutes")
    print(f"# orbital_period = {period / 86400.0:.4f} days")
    print(f"# circular_velocity = {v_circ:.6f} m/s")

    if e == 0.0:
        r = a
        v = v_circ
        energy = orbital_energy(r, v, sc["mass"], parent_mass)
        print(f"# circular orbit: r = {r:.10e} m, v = {v:.6f} m/s")
        print(f"# total_energy = {energy:.6f} J")
    else:
        # For eccentric orbits, at nu=0 (periapsis):
        r_peri = a * (1 - e)
        v_peri = math.sqrt(mu * (2/r_peri - 1/a))
        energy_peri = orbital_energy(r_peri, v_peri, sc["mass"], parent_mass)
        print(f"# eccentric orbit (nu=0=periapsis):")
        print(f"#   r_peri = {r_peri:.10e} m")
        print(f"#   v_peri = {v_peri:.6f} m/s")
        print(f"#   total_energy = {energy_peri:.6f} J")

    print()

# Geosynchronous period check
geo_a = 4.2164e7
geo_period = orbital_period(geo_a, earth_mass)
sidereal_day_hours = 23.93447
sidereal_day_seconds = sidereal_day_hours * 3600.0
geo_period_hours = geo_period / 3600.0
print("# --- Geosynchronous period check ---")
print(f"# Geosynchronous period: {geo_period_hours:.6f} hours")
print(f"# Sidereal day: {sidereal_day_hours} hours")
print(f"# Period error: {abs(geo_period_hours - sidereal_day_hours):.6f} hours")
print(f"# Period error: {abs(geo_period - sidereal_day_seconds):.6f} seconds")
print()

# Jupiter-like 10-year propagation
jupiter_sc = spacecraft[2]
jupiter_a = jupiter_sc["a"]
jupiter_mu = G * jupiter_sc["parent_mass"]
jupiter_n = math.sqrt(jupiter_mu / jupiter_a**3)  # mean motion
prop_time_10yr = 10.0 * 365.0 * 86400.0
expected_mean_anomaly = jupiter_n * prop_time_10yr
expected_orbits = expected_mean_anomaly / (2.0 * math.pi)
print("# --- Jupiter-like 10-year mean anomaly ---")
print(f"# Mean motion n = {jupiter_n:.15e} rad/s")
print(f"# Propagation time = {prop_time_10yr:.1f} s ({prop_time_10yr / (365.0*86400.0):.1f} years)")
print(f"# Expected mean anomaly = {expected_mean_anomaly:.6f} rad")
print(f"# Expected orbits = {expected_orbits:.6f}")
print(f"# Expected true anomaly change = {expected_mean_anomaly % (2*math.pi):.10f} rad")
print()

# Period consistency test: Mercury-like from different starting true anomalies
mercury_sc = spacecraft[1]
mercury_a = mercury_sc["a"]
mercury_e = mercury_sc["e"]
mercury_period = orbital_period(mercury_a, jupiter_sc["parent_mass"])
# Wait, Mercury's parent is Sun, not Jupiter
mercury_parent = sun_mass
mercury_period = orbital_period(mercury_a, mercury_parent)
print("# --- Period consistency (Mercury-like from different true anomalies) ---")
print(f"# Mercury-like period: {mercury_period:.6f} s")
for nu0_deg in [0, 90, 180, 270]:
    nu0 = math.radians(nu0_deg)
    print(f"# Starting nu = {nu0_deg} deg ({nu0:.10f} rad)")
    # After one full period, true anomaly should return to same value
    # (modulo 2*pi)
    print(f"# After 1 period: true anomaly should return to {nu0_deg} deg")
print()

# Low altitude orbit: check altitude above surface
low_sc = spacecraft[3]
low_a = low_sc["a"]
low_altitude = low_a - earth_radius
print("# --- Low altitude orbit ---")
print(f"# Semi-major axis: {low_a:.10e} m")
print(f"# Earth radius: {earth_radius:.10e} m")
print(f"# Altitude above surface: {low_altitude:.10e} m ({low_altitude/1000.0:.1f} km)")
print()