diff --git a/scripts/compute_rendezvous_params.py b/scripts/compute_rendezvous_params.py new file mode 100644 index 0000000..72f3c55 --- /dev/null +++ b/scripts/compute_rendezvous_params.py @@ -0,0 +1,204 @@ +#!/usr/bin/env python3 +""" +Pre-compute Hohmann transfer rendezvous parameters for test validation. +Replicates the exact rendezvous module phasing logic from src/rendezvous.cpp. +Hardcoded from tests/test_rendezvous.toml — no TOML parser needed. + +Usage: python3 tests/compute_rendezvous_params.py +""" + +import math +import sys + +G = 6.67430e-11 + +# Central body +EARTH_MASS = 5.972e24 + +# Spacecraft orbits (from test_rendezvous.toml) +TARGET_R = 6.771e6 # 400 km altitude +TARGET_NU = 0.0 + +CHASER_R = 6.671e6 # 300 km altitude +CHASER_NU = 4.71238898038469 # 270 degrees + +MU = G * EARTH_MASS + + +def calc_mean_motion(radius, mass): + """n = sqrt(mu / a^3)""" + return math.sqrt(MU / (radius ** 3)) + + +def hohmann_transfer_time(r1, r2, mass): + """Half orbit of transfer ellipse.""" + a_transfer = (r1 + r2) / 2.0 + T_transfer = 2.0 * math.pi * math.sqrt(a_transfer ** 3 / MU) + return T_transfer / 2.0 + + +def required_separation(r1, r2, mass): + """ + Required angular separation at first burn. + chaser_pos - target_pos = target_angle - pi + """ + transfer_time = hohmann_transfer_time(r1, r2, mass) + n2 = calc_mean_motion(r2, mass) + target_angle = n2 * transfer_time + return target_angle - math.pi + + +def normalize_angle_2pi(angle): + """Normalize to [0, 2*pi).""" + while angle < 0.0: + angle += 2.0 * math.pi + while angle >= 2.0 * math.pi: + angle -= 2.0 * math.pi + return angle + + +def normalize_angle_pi(angle): + """Normalize to [-pi, pi].""" + angle = normalize_angle_2pi(angle) + while angle > math.pi: + angle -= 2.0 * math.pi + while angle < -math.pi: + angle += 2.0 * math.pi + return angle + + +def calculate_wait_time_for_hohmann(r1, r2, angular_separation, mass): + """ + Wait time before Hohmann transfer. + Positive = wait, negative = transfer already late. + """ + required_sep = required_separation(r1, r2, mass) + n1 = calc_mean_motion(r1, mass) + n2 = calc_mean_motion(r2, mass) + rel_angular_vel = n1 - n2 + + current_sep = normalize_angle_pi(angular_separation) + required_sep = normalize_angle_pi(required_sep) + + angle_to_close = required_sep - current_sep + + return angle_to_close / rel_angular_vel + + +def calculate_relative_orbit_period(r1, r2, mass): + """Time between consecutive phasing opportunities.""" + n1 = calc_mean_motion(r1, mass) + n2 = calc_mean_motion(r2, mass) + rel_angular_vel = abs(n1 - n2) + return 2.0 * math.pi / rel_angular_vel + + +def calculate_next_hohmann_wait_time(r1, r2, angular_separation, mass, min_wait_time): + """ + Like calculate_wait_time_for_hohmann, but advances to next phasing + opportunity if wait_time < min_wait_time. Always returns non-negative. + """ + wait_time = calculate_wait_time_for_hohmann(r1, r2, angular_separation, mass) + rel_period = calculate_relative_orbit_period(r1, r2, mass) + + while wait_time < min_wait_time: + wait_time += rel_period + + return wait_time + + +def main(): + print(f"Central body: Earth, mass = {EARTH_MASS:.6e} kg") + print(f"mu = {MU:.6e} m^3/s^2") + + print(f"\n=== INITIAL ORBITAL ELEMENTS ===") + print(f"Chaser_Lower: r = {CHASER_R:.6e} m, nu = {CHASER_NU:.6f} rad ({math.degrees(CHASER_NU):.2f} deg)") + print(f"Target: r = {TARGET_R:.6e} m, nu = {TARGET_NU:.6f} rad ({math.degrees(TARGET_NU):.2f} deg)") + + # Angular separation: chaser - target + angular_sep = CHASER_NU - TARGET_NU + angular_sep = normalize_angle_pi(angular_sep) + print(f"\nAngular separation (chaser - target): {angular_sep:.6f} rad ({math.degrees(angular_sep):.2f} deg)") + + # Mean motions + n1 = calc_mean_motion(CHASER_R, EARTH_MASS) + n2 = calc_mean_motion(TARGET_R, EARTH_MASS) + print(f"\nMean motions:") + print(f" n1 (chaser): {n1:.10f} rad/s") + print(f" n2 (target): {n2:.10f} rad/s") + print(f" n1 - n2: {n1 - n2:.10f} rad/s") + + # Orbital periods + p_chaser = 2.0 * math.pi / n1 + p_target = 2.0 * math.pi / n2 + print(f"\nOrbital periods:") + print(f" Chaser: {p_chaser:.2f} s ({p_chaser/3600:.2f} h)") + print(f" Target: {p_target:.2f} s ({p_target/3600:.2f} h)") + + # Hohmann transfer + tt = hohmann_transfer_time(CHASER_R, TARGET_R, EARTH_MASS) + a_t = (CHASER_R + TARGET_R) / 2.0 + print(f"\n=== HOHMANN TRANSFER ===") + print(f" Transfer semi-major axis: {a_t:.6e} m") + print(f" Transfer time: {tt:.6f} s ({tt/60:.2f} min)") + + # Required separation + req_sep = required_separation(CHASER_R, TARGET_R, EARTH_MASS) + req_sep_norm = normalize_angle_pi(req_sep) + print(f"\n=== REQUIRED SEPARATION ===") + print(f" Raw: {req_sep:.6f} rad ({math.degrees(req_sep):.2f} deg)") + print(f" Norm: {req_sep_norm:.6f} rad ({math.degrees(req_sep_norm):.2f} deg)") + + # Relative orbit period + rel_period = calculate_relative_orbit_period(CHASER_R, TARGET_R, EARTH_MASS) + print(f"\nRelative orbit period: {rel_period:.6f} s ({rel_period/3600:.2f} h)") + + # Detailed phasing calculation + print(f"\n=== PHASING CALCULATION ===") + current_sep = normalize_angle_pi(angular_sep) + print(f" Current separation (normalized): {current_sep:.6f} rad ({math.degrees(current_sep):.2f} deg)") + print(f" Required separation (normalized): {req_sep_norm:.6f} rad ({math.degrees(req_sep_norm):.2f} deg)") + + angle_to_close = req_sep_norm - current_sep + print(f" Angle to close: {angle_to_close:.6f} rad ({math.degrees(angle_to_close):.2f} deg)") + + wait_time = calculate_wait_time_for_hohmann(CHASER_R, TARGET_R, angular_sep, EARTH_MASS) + print(f" Raw wait_time: {wait_time:.6f} s ({wait_time/3600:.2f} h)") + + # Wait times for various DT values + dt_values = [0.1, 0.5, 1.0, 2.0, 5.0, 10.0] + print(f"\n=== WAIT TIME vs DT (via calculate_next_hohmann_wait_time) ===") + for dt in dt_values: + wt = calculate_next_hohmann_wait_time(CHASER_R, TARGET_R, angular_sep, EARTH_MASS, dt) + arrival = wt + tt + steps = int(arrival / dt) + 1 + print(f" DT={dt:6.1f} s: wait={wt:12.2f} s arrival={arrival:12.2f} s steps~{steps}") + + # Recommended values for TIME_STEP = 0.1 + dt = 0.1 + wt = calculate_next_hohmann_wait_time(CHASER_R, TARGET_R, angular_sep, EARTH_MASS, dt) + arrival = wt + tt + max_steps = int(arrival / dt) + 1000 + + print(f"\n=== RECOMMENDED FOR TEST (DT=0.1) ===") + print(f" wait_time: {wt:.2f} s") + print(f" arrival_time: {arrival:.2f} s") + print(f" expected_steps: {int(arrival / dt)}") + print(f" max_steps (with margin): {max_steps}") + print(f" safety_limit (1 yr): {3600.0 * 24.0 * 365.0:.2f} s") + print(f"\n Milestone step indices:") + print(f" just_before_departure: {int(wt / dt)}") + print(f" after_departure: {int(wt / dt) + 1}") + print(f" just_before_arrival: {int(arrival / dt)}") + + # Verify against C++ test output + print(f"\n=== COMPARISON WITH C++ TEST OUTPUT ===") + print(f" Python wait_time: {wt:.2f} s") + print(f" C++ test wait_time: 60062.7 s") + print(f" Python arrival: {arrival:.2f} s") + print(f" C++ test arrival: 62804.5 s") + print(f" Match: {abs(wt - 60062.7) < 0.1 and abs(arrival - 62804.5) < 0.1}") + + +if __name__ == '__main__': + main() diff --git a/scripts/simulate_rendezvous.py b/scripts/simulate_rendezvous.py new file mode 100644 index 0000000..7c29783 --- /dev/null +++ b/scripts/simulate_rendezvous.py @@ -0,0 +1,431 @@ +#!/usr/bin/env python3 +""" +Full analytical propagation simulation of the Hohmann rendezvous scenario. +Replicates the exact physics from src/orbital_mechanics.cpp and src/maneuver.cpp. + +Step-by-step trace to find where the 11,578 km separation comes from. + +Usage: python3 tests/simulate_rendezvous.py +""" + +import math +import sys + +G = 6.67430e-11 +MU = G * 5.972e24 # Earth + +# ---- Vector operations ---- +def vadd(a, b): return (a[0]+b[0], a[1]+b[1], a[2]+b[2]) +def vsub(a, b): return (a[0]-b[0], a[1]-b[1], a[2]-b[2]) +def vscale(v, s): return (v[0]*s, v[1]*s, v[2]*s) +def vmag(v): return math.sqrt(v[0]**2 + v[1]**2 + v[2]**2) +def vdot(a, b): return a[0]*b[0] + a[1]*b[1] + a[2]*b[2] +def vcross(a, b): return ( + a[1]*b[2] - a[2]*b[1], + a[2]*b[0] - a[0]*b[2], + a[0]*b[1] - a[1]*b[0] +) +def vnorm(v): + m = vmag(v) + if m < 1e-15: return (0, 0, 0) + return (v[0]/m, v[1]/m, v[2]/m) + +def normalize_angle(angle): + while angle < 0.0: angle += 2*math.pi + while angle >= 2*math.pi: angle -= 2*math.pi + return angle + +def normalize_angle_2pi(angle): + while angle < 0.0: angle += 2*math.pi + while angle >= 2*math.pi: angle -= 2*math.pi + return angle + +def normalize_angle_pi(angle): + angle = normalize_angle_2pi(angle) + while angle > math.pi: angle -= 2*math.pi + while angle < -math.pi: angle += 2*math.pi + return angle + +# ---- Kepler equation solvers (exact C++ logic) ---- +def get_initial_trial_value(mean_anomaly, eccentricity): + return (mean_anomaly + eccentricity * math.sin(mean_anomaly) + + ((eccentricity**2 / 2.0) * math.sin(2.0 * mean_anomaly))) + +def solve_kepler_elliptical(mean_anomaly, eccentricity): + E = get_initial_trial_value(mean_anomaly, eccentricity) + E_prev = E + 2.0e-10 + for _ in range(50): + if abs(E - E_prev) < 1e-10: + break + E_prev = E + sin_E = math.sin(E) + E = E - (E - eccentricity * sin_E - mean_anomaly) / (1.0 - eccentricity * math.cos(E)) + return E + +def eccentric_to_true_anomaly(eccentric_anomaly, eccentricity): + if abs(1.0 - eccentricity) < 0.01: + E = eccentric_anomaly + e = eccentricity + cos_E = math.cos(E) + sin_E = math.sin(E) + denom = 1.0 - e * cos_E + cos_nu = max(-1.0, min(1.0, (cos_E - e) / denom)) + sin_nu = max(-1.0, min(1.0, sin_E * math.sqrt(1.0 - e*e) / denom)) + return math.atan2(sin_nu, cos_nu) + tan_half_E = math.tan(eccentric_anomaly / 2.0) + tan_half_nu = math.sqrt((1.0 + eccentricity) / (1.0 - eccentricity)) * tan_half_E + return 2.0 * math.atan(tan_half_nu) + +# ---- Propagation (exact C++ propagate_orbital_elements) ---- +def propagate(elements, dt, parent_mass): + a = elements['a'] + e = elements['e'] + nu = elements['nu'] + mu = MU # fixed for this sim + + if e < 1.0: + n = math.sqrt(mu / a**3) + E = 2.0 * math.atan(math.sqrt((1.0 - e) / (1.0 + e)) * math.tan(nu / 2.0)) + M = E - e * math.sin(E) + M = M + n * dt + E_new = get_initial_trial_value(M, e) + E_prev = E_new + 2.0e-10 + for _ in range(50): + if abs(E_new - E_prev) < 1e-10: + break + E_prev = E_new + sin_E = math.sin(E_new) + E_new = E_new - (E_new - e * sin_E - M) / (1.0 - e * math.cos(E_new)) + nu_new = 2.0 * math.atan(math.sqrt((1.0 + e) / (1.0 - e)) * math.tan(E_new / 2.0)) + result = dict(elements) + result['nu'] = nu_new + return result + else: + # Hyperbolic (not needed for this test) + raise NotImplementedError("hyperbolic propagation not needed") + +# ---- Cartesian from orbital elements ---- +def orbital_to_cartesian(elements, parent_mass): + a = elements['a'] + e = elements['e'] + nu = elements['nu'] + inc = elements['inc'] + Omega = elements['Omega'] + omega = elements['omega'] + mu = MU + + p = a * (1.0 - e*e) + r = p / (1.0 + e * math.cos(nu)) + + # Orbital plane position/velocity + x_orb = r * math.cos(nu) + y_orb = r * math.sin(nu) + + vx_orb = -math.sqrt(mu / p) * math.sin(nu) + vy_orb = math.sqrt(mu / p) * (e + math.cos(nu)) + + # z-x-z rotation: Rz(Omega) * Rx(inc) * Rz(omega) + # Apply Rz(omega) first + cos_w = math.cos(omega) + sin_w = math.sin(omega) + x1 = x_orb * cos_w - y_orb * sin_w + y1 = x_orb * sin_w + y_orb * cos_w + + # Then Rx(inc) + cos_i = math.cos(inc) + sin_i = math.sin(inc) + x2 = x1 + y2 = y1 * cos_i + z2 = y1 * sin_i + + # Then Rz(Omega) + cos_O = math.cos(Omega) + sin_O = math.sin(Omega) + pos = (x2 * cos_O - y2 * sin_O, + x2 * sin_O + y2 * cos_O, + z2) + + # Same rotation for velocity + vx1 = vx_orb * cos_w - vy_orb * sin_w + vy1 = vx_orb * sin_w + vy_orb * cos_w + vx2 = vx1 + vy2 = vy1 * cos_i + vz2 = vy1 * sin_i + vel = (vx2 * cos_O - vy2 * sin_O, + vx2 * sin_O + vy2 * cos_O, + vz2) + + return pos, vel + +# ---- Cartesian to orbital elements ---- +def cartesian_to_elements(pos, vel, parent_mass): + mu = MU + r = vmag(pos) + v = vmag(vel) + + # Specific orbital energy + specific_energy = -mu / r + v**2 / 2.0 + + # Semi-major axis + if abs(specific_energy) < 1e-10: + a = 1e10 + else: + a = -mu / (2.0 * specific_energy) + + # Angular momentum + h_vec = vcross(pos, vel) + h = vmag(h_vec) + + # Eccentricity vector + r_dot_v = vdot(pos, vel) + e_vec = ((v**2 - mu/r) * pos[0] - r_dot_v * vel[0]) / mu, \ + ((v**2 - mu/r) * pos[1] - r_dot_v * vel[1]) / mu, \ + ((v**2 - mu/r) * pos[2] - r_dot_v * vel[2]) / mu + e = vmag(e_vec) + + # True anomaly + if e < 1e-10: + nu = 0.0 + else: + cos_nu = vdot(pos, e_vec) / (r * e) + cos_nu = max(-1.0, min(1.0, cos_nu)) + if abs(cos_nu) > 1.0 - 1e-10: + h_cross_e = vcross(h_vec, e_vec) + denom = r * e * h + sin_nu = vdot(pos, h_cross_e) / denom if denom > 1e-10 else 0.0 + else: + r_cross_h = vcross(pos, h_vec) + denom = r * e * h + sin_nu = vdot(r_cross_h, e_vec) / denom if denom > 1e-10 else 0.0 + nu = math.atan2(sin_nu, cos_nu) + if nu == -math.pi: + nu = math.pi + nu = normalize_angle(nu) + + # Inclination + if h > 1e-10: + i = math.acos(h_vec[2] / h) + else: + i = 0.0 + + # RAAN + n_vec = (0, 0, 1) + n = vcross(n_vec, h_vec) + n_mag = vmag(n) + if n_mag > 1e-10: + Omega = math.acos(n[0] / n_mag) + if n[1] < 0.0: + Omega = 2*math.pi - Omega + else: + Omega = 0.0 + + # Argument of periapsis + if e > 1e-10 and n_mag > 1e-10 and i > 0.01: + cos_omega = vdot(e_vec, n) / (e * n_mag) + n_cross_e = vcross(n, e_vec) + sin_omega = vdot(n_cross_e, h_vec) / (e * n_mag * h) + omega = math.atan2(sin_omega, cos_omega) + if omega < 0: omega += 2*math.pi + elif e > 1e-10: + omega = math.atan2(e_vec[1], e_vec[0]) + if omega < 0: omega += 2*math.pi + else: + omega = 0.0 + + return {'a': a, 'e': e, 'nu': nu, 'inc': i, 'Omega': Omega, 'omega': omega} + +# ---- Hohmann transfer calculations ---- +def hohmann_transfer_time(r1, r2): + a_t = (r1 + r2) / 2.0 + T = 2*math.pi * math.sqrt(a_t**3 / MU) + return T / 2.0 + +def required_separation(r1, r2): + tt = hohmann_transfer_time(r1, r2) + n2 = math.sqrt(MU / r2**3) + target_angle = n2 * tt + return target_angle - math.pi + +def calc_mean_motion(radius): + return math.sqrt(MU / radius**3) + +def calculate_wait_time_for_hohmann(r1, r2, angular_separation): + required_sep = required_separation(r1, r2) + n1 = calc_mean_motion(r1) + n2 = calc_mean_motion(r2) + rel_angular_vel = n1 - n2 + + current_sep = normalize_angle_pi(angular_separation) + required_sep = normalize_angle_pi(required_sep) + + angle_to_close = required_sep - current_sep + return angle_to_close / rel_angular_vel + +def relative_orbit_period(r1, r2): + n1 = calc_mean_motion(r1) + n2 = calc_mean_motion(r2) + return 2*math.pi / abs(n1 - n2) + +def calculate_next_hohmann_wait_time(r1, r2, angular_sep, dt): + wait_time = calculate_wait_time_for_hohmann(r1, r2, angular_sep) + rel_period = relative_orbit_period(r1, r2) + while wait_time < dt: + wait_time += rel_period + return wait_time + +# ---- Burn application ---- +def apply_burn(pos, vel, direction, delta_v, parent_mass): + """Apply impulsive burn in local orbital frame.""" + # direction: 'prograde', 'retrograde', 'normal' + if direction == 'prograde': + d = vnorm(vel) + elif direction == 'retrograde': + d = vscale(vnorm(vel), -1) + elif direction == 'normal': + h = vcross(pos, vel) + d = vnorm(h) + else: + raise ValueError(f"Unknown direction: {direction}") + + new_vel = vadd(vel, vscale(d, delta_v)) + return pos, new_vel + +# ---- Dump state helper ---- +def dump_state(label, chaser, target, chaser_pos, chaser_vel, target_pos, target_vel, sim_time): + """Print state at key simulation milestones, matching test_rendezvous.cpp dump_state.""" + c_r = vmag(chaser_pos) + t_r = vmag(target_pos) + c_sep = vmag(vsub(chaser_pos, target_pos)) + print(f"\n*** {label} (t={sim_time:.1f}s) ***") + print(f" Chaser: r={c_r:.0f} m, nu={chaser['nu']:.6f} rad ({math.degrees(chaser['nu']):.1f}°) " + f"a={chaser['a']:.0f} e={chaser['e']:.6f}") + print(f" pos={chaser_pos}, vel={chaser_vel}") + print(f" Target: r={t_r:.0f} m, nu={target['nu']:.6f} rad ({math.degrees(target['nu']):.1f}°) " + f"a={target['a']:.0f} e={target['e']:.6f}") + print(f" pos={target_pos}, vel={target_vel}") + print(f" Separation: {c_sep:.0f} m") + + +# ---- Full rendezvous scenario ---- +def main(): + # Initial conditions from test_rendezvous.toml + TARGET_R = 6.771e6 + TARGET_NU = 0.0 + CHASER_R = 6.671e6 + CHASER_NU = 4.71238898038469 # 270 degrees + + print("=== INITIAL STATE ===") + print(f"Chaser: r={CHASER_R:.1f} m, nu={math.degrees(CHASER_NU):.1f} deg") + print(f"Target: r={TARGET_R:.1f} m, nu={math.degrees(TARGET_NU):.1f} deg") + + # Create orbital elements (coplanar, circular) + chaser = {'a': CHASER_R, 'e': 0.0, 'nu': CHASER_NU, + 'inc': 0.0, 'Omega': 0.0, 'omega': 0.0} + target = {'a': TARGET_R, 'e': 0.0, 'nu': TARGET_NU, + 'inc': 0.0, 'Omega': 0.0, 'omega': 0.0} + + chaser_pos, chaser_vel = orbital_to_cartesian(chaser, 5.972e24) + target_pos, target_vel = orbital_to_cartesian(target, 5.972e24) + + print(f"Chaser pos: {chaser_pos}, vel: {vmag(chaser_vel):.1f} m/s") + print(f"Target pos: {target_pos}, vel: {vmag(target_vel):.1f} m/s") + + # Angular separation + angular_sep = chaser['nu'] - target['nu'] + angular_sep = normalize_angle_pi(angular_sep) + print(f"\nAngular separation (chaser - target): {math.degrees(angular_sep):.1f} deg") + + # Hohmann parameters + hohmann_tt = hohmann_transfer_time(CHASER_R, TARGET_R) + dv1 = math.sqrt(MU * (2/CHASER_R - 2/(CHASER_R + TARGET_R))) - math.sqrt(MU/CHASER_R) + dv2 = math.sqrt(MU/TARGET_R) - math.sqrt(MU * (2/TARGET_R - 2/(CHASER_R + TARGET_R))) + print(f"\nHohmann transfer: tt={hohmann_tt:.1f} s, dv1={dv1:.2f} m/s, dv2={dv2:.2f} m/s") + + # Phasing + dt = 0.1 + wait_time = calculate_next_hohmann_wait_time(CHASER_R, TARGET_R, angular_sep, dt) + arrival_time = wait_time + hohmann_tt + print(f"Wait time: {wait_time:.2f} s") + print(f"Arrival time: {arrival_time:.2f} s") + print(f"Steps: {int(arrival_time/dt)}") + + # ---- Run simulation ---- + print(f"\n=== SIMULATION (dt={dt}) ===") + sim_time = 0.0 + steps = 0 + chaser_executed = False + arrival_executed = False + + while steps < int(arrival_time / dt) + 1000: + chaser, target, chaser_pos, chaser_vel, target_pos, target_vel = \ + update_simulation(chaser, target, sim_time, dt, dv1, dv2, wait_time, arrival_time, + chaser_pos, chaser_vel, target_pos, target_vel, + chaser_executed, arrival_executed) + sim_time += dt + steps += 1 + + if steps == 1: + dump_state("T=0 (initial)", chaser, target, chaser_pos, chaser_vel, target_pos, target_vel, sim_time) + if steps == int(wait_time / dt): + dump_state("JUST BEFORE DEPARTURE", chaser, target, chaser_pos, chaser_vel, target_pos, target_vel, sim_time) + if steps == int(wait_time / dt) + 1: + dump_state("AFTER DEPARTURE BURN", chaser, target, chaser_pos, chaser_vel, target_pos, target_vel, sim_time) + if steps == int(arrival_time / dt) - 1: + dump_state("JUST BEFORE ARRIVAL BURN", chaser, target, chaser_pos, chaser_vel, target_pos, target_vel, sim_time) + + if not chaser_executed and sim_time >= wait_time: + # Execute departure burn + print(f"\n *** DEPARTURE BURN at t={sim_time:.1f}s ***") + print(f" Before: pos={chaser_pos}, vel={chaser_vel}") + chaser_pos, chaser_vel = apply_burn(chaser_pos, chaser_vel, 'prograde', dv1, 5.972e24) + print(f" After: pos={chaser_pos}, vel={chaser_vel}") + chaser = cartesian_to_elements(chaser_pos, chaser_vel, 5.972e24) + chaser_executed = True + print(f" Chaser: r={vmag(chaser_pos):.0f} nu={math.degrees(chaser['nu']):.1f}° " + f"a={chaser['a']:.0f} e={chaser['e']:.6f}") + + if not arrival_executed and sim_time >= arrival_time: + # Execute arrival burn + chaser_pos, chaser_vel = apply_burn(chaser_pos, chaser_vel, 'prograde', dv2, 5.972e24) + chaser = cartesian_to_elements(chaser_pos, chaser_vel, 5.972e24) + arrival_executed = True + print(f"\n *** ARRIVAL BURN at t={sim_time:.1f}s ***") + print(f" Chaser: r={vmag(chaser_pos):.0f} nu={math.degrees(chaser['nu']):.1f}° " + f"a={chaser['a']:.0f} e={chaser['e']:.6f}") + + dump_state("AFTER ARRIVAL BURN", chaser, target, chaser_pos, chaser_vel, target_pos, target_vel, sim_time) + + # Final comparison + c_sep = vmag(vsub(chaser_pos, target_pos)) + c_r = vmag(chaser_pos) + t_r = vmag(target_pos) + c_vel = vmag(chaser_vel) + t_vel = vmag(target_vel) + print(f"\n=== FINAL STATE ===") + print(f"Chaser: r={c_r:.0f} m, nu={chaser['nu']:.6f} rad ({math.degrees(chaser['nu']):.1f}°)") + print(f" pos={chaser_pos}, vel={chaser_vel}") + print(f"Target: r={t_r:.0f} m, nu={target['nu']:.6f} rad ({math.degrees(target['nu']):.1f}°)") + print(f" pos={target_pos}, vel={target_vel}") + print(f"Separation: {c_sep:.0f} m") + print(f"Speed: chaser={c_vel:.2f} target={t_vel:.2f} m/s") + print(f"Radius error: {abs(c_r - t_r):.6f} m") + print(f"Chaser eccentricity: {chaser['e']:.15f}") + print(f"Target eccentricity: {target['e']:.15f}") + break + + +def update_simulation(chaser, target, sim_time, dt, dv1, dv2, wait_time, arrival_time, + chaser_pos, chaser_vel, target_pos, target_vel, + chaser_executed, arrival_executed): + """Propagate one timestep for both spacecraft.""" + chaser = propagate(chaser, dt, 5.972e24) + target = propagate(target, dt, 5.972e24) + + chaser_pos, chaser_vel = orbital_to_cartesian(chaser, 5.972e24) + target_pos, target_vel = orbital_to_cartesian(target, 5.972e24) + + return chaser, target, chaser_pos, chaser_vel, target_pos, target_vel + + +if __name__ == '__main__': + main()