Refactor: Integrate spacecraft into SimulationState

Merge spacecraft management into simulation module:
- Move Spacecraft struct from maneuver.h to spacecraft.h
- Add spacecraft array to SimulationState (spacecraft, craft_count, max_craft)
- Remove separate SpacecraftState struct and related functions
- Update create_simulation() to require max_craft parameter
- Move spacecraft update logic into update_simulation()
- Make load_spacecraft_config() internal helper, called by load_system_config()
- Update all test files to use new API with 3-parameter create_simulation()
- Handle max_craft=0 case gracefully (no spacecraft allocation)

Test results: 26/27 passing (1 pre-existing SOI test unrelated to changes)

src/config_loader.cpp

@@ -3,7 +3,9 @@
 #include <cmath>
 #include <cstring>
 #include "simulation.h"
-#include "spacecraft.h"
+
+static bool parse_toml_spacecraft(toml_datum_t craft_table, Spacecraft* craft);
+static bool load_spacecraft_from_toml(SimulationState* sim, toml_result_t result);
 
 static bool extract_vec3_from_table(toml_datum_t table, Vec3* pos) {
     toml_datum_t x = toml_get(table, "x");
@@ -157,80 +159,40 @@ bool load_system_config(SimulationState* sim, const char* filepath) {
     }
 
     sim->body_count = body_count;
-    toml_free(result);
-
-    initialize_bodies(sim);
 
     strncpy(sim->config_name, filepath, sizeof(sim->config_name) - 1);
     sim->config_name[sizeof(sim->config_name) - 1] = '\0';
 
-    printf("Loaded %d bodies from %s\n", body_count, filepath);
+    // Load spacecraft from the same config file (before freeing TOML data)
-    return true;
+    if (!load_spacecraft_from_toml(sim, result)) {
-}
+        toml_free(result);
-
-static bool parse_toml_spacecraft(toml_datum_t craft_table, Spacecraft* craft) {
-    toml_datum_t name = toml_get(craft_table, "name");
-    if (name.type != TOML_STRING) {
-        return false;
-    }
-    strncpy(craft->name, name.u.s, 63);
-    craft->name[63] = '\0';
-
-    toml_datum_t mass = toml_get(craft_table, "mass");
-    toml_datum_t parent_idx = toml_get(craft_table, "parent_index");
-
-    if (mass.type != TOML_FP64 || parent_idx.type != TOML_INT64) {
         return false;
     }
 
-    craft->mass = mass.u.fp64;
+    toml_free(result);
-    craft->parent_index = (int)(parent_idx.type == TOML_INT64 ? parent_idx.u.int64 : (int)parent_idx.u.fp64);
-
-    toml_datum_t position = toml_get(craft_table, "position");
-    if (position.type != TOML_TABLE || !extract_vec3_from_table(position, &craft->local_position)) {
-        return false;
-    }
-    craft->position = craft->local_position;
 
-    toml_datum_t velocity = toml_get(craft_table, "velocity");
+    initialize_bodies(sim);
-    if (velocity.type == TOML_TABLE) {
-        if (!extract_vec3_from_table(velocity, &craft->local_velocity)) {
-            return false;
-        }
-    } else {
-        craft->local_velocity = {0.0, 0.0, 0.0};
-    }
-    craft->velocity = craft->local_velocity;
 
+    printf("Loaded %d bodies from %s\n", body_count, filepath);
     return true;
 }
 
-bool load_spacecraft_config(SpacecraftState* craft_state, SimulationState* sim, const char* filepath) {
+static bool load_spacecraft_from_toml(SimulationState* sim, toml_result_t result) {
-    toml_result_t result = toml_parse_file_ex(filepath);
-    if (!result.ok) {
-        printf("Error: Could not parse TOML config file: %s\n", filepath);
-        printf("TOML Error: %s\n", result.errmsg);
-        return false;
-    }
-
     toml_datum_t spacecraft = toml_get(result.toptab, "spacecraft");
     if (spacecraft.type != TOML_ARRAY) {
-        printf("No spacecraft array found in config file: %s (optional)\n", filepath);
+        printf("No spacecraft array found in config file: %s (optional)\n", sim->config_name);
-        toml_free(result);
         return true;
     }
 
     int craft_count = spacecraft.u.arr.size;
     if (craft_count == 0) {
-        printf("No spacecraft found in config file: %s\n", filepath);
+        printf("No spacecraft found in config file: %s\n", sim->config_name);
-        toml_free(result);
         return true;
     }
 
-    if (craft_count > craft_state->max_craft) {
+    if (craft_count > sim->max_craft) {
-        printf("Error: Too many spacecraft (%d) for state (max: %d)\n",
+        printf("Error: Too many spacecraft (%d) for simulation (max: %d)\n",
-               craft_count, craft_state->max_craft);
+               craft_count, sim->max_craft);
-        toml_free(result);
         return false;
     }
 
@@ -239,14 +201,12 @@ bool load_spacecraft_config(SpacecraftState* craft_state, SimulationState* sim,
         toml_datum_t craft_table = spacecraft.u.arr.elem[i];
         if (!parse_toml_spacecraft(craft_table, &craft)) {
             printf("Error: Failed to parse spacecraft at index %d\n", i);
-            toml_free(result);
             return false;
         }
 
         if (craft.parent_index < 0 || craft.parent_index >= sim->body_count) {
             printf("Error: Spacecraft '%s' has invalid parent_index %d (valid: 0-%d)\n",
                    craft.name, craft.parent_index, sim->body_count - 1);
-            toml_free(result);
             return false;
         }
 
@@ -254,15 +214,50 @@ bool load_spacecraft_config(SpacecraftState* craft_state, SimulationState* sim,
         craft.position = vec3_add(parent->position, craft.local_position);
         craft.velocity = vec3_add(parent->velocity, craft.local_velocity);
 
-        int idx = add_spacecraft(craft_state, &craft);
+        int idx = add_spacecraft(sim, &craft);
         if (idx < 0) {
-            printf("Error: Failed to add spacecraft to state\n");
+            printf("Error: Failed to add spacecraft to simulation\n");
-            toml_free(result);
             return false;
         }
     }
 
-    printf("Loaded %d spacecraft from %s\n", craft_count, filepath);
+    printf("Loaded %d spacecraft from %s\n", craft_count, sim->config_name);
-    toml_free(result);
     return true;
 }
+
+static bool parse_toml_spacecraft(toml_datum_t craft_table, Spacecraft* craft) {
+    toml_datum_t name = toml_get(craft_table, "name");
+    if (name.type != TOML_STRING) {
+        return false;
+    }
+    strncpy(craft->name, name.u.s, 63);
+    craft->name[63] = '\0';
+
+    toml_datum_t mass = toml_get(craft_table, "mass");
+    toml_datum_t parent_idx = toml_get(craft_table, "parent_index");
+
+    if (mass.type != TOML_FP64 || parent_idx.type != TOML_INT64) {
+        return false;
+    }
+
+    craft->mass = mass.u.fp64;
+    craft->parent_index = (int)(parent_idx.type == TOML_INT64 ? parent_idx.u.int64 : (int)parent_idx.u.fp64);
+
+    toml_datum_t position = toml_get(craft_table, "position");
+    if (position.type != TOML_TABLE || !extract_vec3_from_table(position, &craft->local_position)) {
+        return false;
+    }
+    craft->position = craft->local_position;
+
+    toml_datum_t velocity = toml_get(craft_table, "velocity");
+    if (velocity.type == TOML_TABLE) {
+        if (!extract_vec3_from_table(velocity, &craft->local_velocity)) {
+            return false;
+        }
+    } else {
+        craft->local_velocity = {0.0, 0.0, 0.0};
+    }
+    craft->velocity = craft->local_velocity;
+
+    return true;
+}

src/config_loader.h

@@ -6,6 +6,5 @@
 #include "../ext/tomlc17/src/tomlc17.h"
 
 bool load_system_config(SimulationState* sim, const char* filepath);
-bool load_spacecraft_config(SpacecraftState* craft_state, SimulationState* sim, const char* filepath);
 
 #endif

src/main.cpp

@@ -106,8 +106,9 @@ int main(int argc, char** argv) {
 
     // Create simulation with time step of 60 seconds
     const int MAX_BODIES = 100;
+    const int MAX_SPACECRAFT = 50;
     const double TIME_STEP = 60.0;  // 60 seconds per step
-    SimulationState* sim = create_simulation(MAX_BODIES, TIME_STEP);
+    SimulationState* sim = create_simulation(MAX_BODIES, MAX_SPACECRAFT, TIME_STEP);
 
     // Load system configuration
     if (!load_system_config(sim, args.config_file)) {

src/maneuver.cpp

@@ -1,5 +1,6 @@
 #include "maneuver.h"
 #include "physics.h"
+#include "spacecraft.h"
 #include <cmath>
 
 Vec3 calculate_prograde_dir(Vec3 local_velocity) {

src/maneuver.h

@@ -2,6 +2,7 @@
 #define MANEUVER_H
 
 #include "physics.h"
+#include "spacecraft.h"
 
 enum BurnDirection {
     BURN_PROGRADE,
@@ -13,16 +14,6 @@ enum BurnDirection {
     BURN_CUSTOM
 };
 
-struct Spacecraft {
-    char name[64];
-    double mass;
-    Vec3 local_position;
-    Vec3 local_velocity;
-    Vec3 position;
-    Vec3 velocity;
-    int parent_index;
-};
-
 // Direction calculation functions (local frame)
 Vec3 calculate_prograde_dir(Vec3 local_velocity);
 Vec3 calculate_retrograde_dir(Vec3 local_velocity);

src/simulation.cpp

@@ -1,4 +1,5 @@
 #include "simulation.h"
+#include "spacecraft.h"
 #include <cassert>
 #include <cstdlib>
 #include <cstring>
@@ -6,11 +7,20 @@
 #include <cmath>
 
 // Create a new simulation
-SimulationState* create_simulation(int max_bodies, double time_step) {
+SimulationState* create_simulation(int max_bodies, int max_craft, double time_step) {
     SimulationState* sim = (SimulationState*)malloc(sizeof(SimulationState));
     sim->bodies = (CelestialBody*)malloc(sizeof(CelestialBody) * max_bodies);
+    
+    if (max_craft > 0) {
+        sim->spacecraft = (Spacecraft*)malloc(sizeof(Spacecraft) * max_craft);
+    } else {
+        sim->spacecraft = NULL;
+    }
+    
     sim->body_count = 0;
     sim->max_bodies = max_bodies;
+    sim->craft_count = 0;
+    sim->max_craft = max_craft;
     sim->time = 0.0;
     sim->dt = time_step;
     sim->config_name[0] = '\0';
@@ -23,10 +33,28 @@ void destroy_simulation(SimulationState* sim) {
         if (sim->bodies) {
             free(sim->bodies);
         }
+        if (sim->max_craft > 0 && sim->spacecraft) {
+            free(sim->spacecraft);
+        }
         free(sim);
     }
 }
 
+// Add a spacecraft to the simulation
+int add_spacecraft(SimulationState* sim, Spacecraft* craft) {
+    if (sim->craft_count >= sim->max_craft) {
+        printf("Error: Cannot add spacecraft - simulation full (%d/%d)\n",
+               sim->craft_count, sim->max_craft);
+        return -1;
+    }
+
+    int new_idx = sim->craft_count;
+    sim->spacecraft[new_idx] = *craft;
+    sim->craft_count++;
+
+    return new_idx;
+}
+
 // Add a body to the simulation at runtime
 int add_body_to_simulation(SimulationState* sim, CelestialBody* body) {
     if (sim->body_count >= sim->max_bodies) {
@@ -163,6 +191,35 @@ void update_simulation(SimulationState* sim) {
     }
 
     compute_global_coordinates(sim);
+    
+    // Update spacecraft
+    for (int i = 0; i < sim->craft_count; i++) {
+        Spacecraft* craft = &sim->spacecraft[i];
+
+        if (craft->parent_index < 0 || craft->parent_index >= sim->body_count) {
+            continue;
+        }
+
+        CelestialBody* parent = &sim->bodies[craft->parent_index];
+
+        rk4_step(&craft->local_position, &craft->local_velocity,
+                 sim->dt, craft->mass, parent->mass);
+    }
+    
+    // Compute spacecraft global coordinates
+    for (int i = 0; i < sim->craft_count; i++) {
+        Spacecraft* craft = &sim->spacecraft[i];
+
+        if (craft->parent_index >= 0 && craft->parent_index < sim->body_count) {
+            CelestialBody* parent = &sim->bodies[craft->parent_index];
+            craft->position = vec3_add(parent->position, craft->local_position);
+            craft->velocity = vec3_add(parent->velocity, craft->local_velocity);
+        } else {
+            craft->position = craft->local_position;
+            craft->velocity = craft->local_velocity;
+        }
+    }
+    
     sim->time += sim->dt;
 }
 

src/simulation.h

@@ -3,6 +3,8 @@
 
 #include "physics.h"
 
+struct Spacecraft;
+
 // Celestial body structure
 struct CelestialBody {
     char name[64];
@@ -24,17 +26,23 @@ struct SimulationState {
     CelestialBody* bodies;
     int body_count;
     int max_bodies;
-    double time;              // simulation time (seconds)
+    
-    double dt;                // time step (seconds)
+    Spacecraft* spacecraft;
-    char config_name[256];    // name of the config file loaded
+    int craft_count;
+    int max_craft;
+    
+    double time;
+    double dt;
+    char config_name[256];
 };
 
 // Simulation management functions
-SimulationState* create_simulation(int max_bodies, double time_step);
+SimulationState* create_simulation(int max_bodies, int max_craft, double time_step);
 void destroy_simulation(SimulationState* sim);
 
 // Dynamic body management
 int add_body_to_simulation(SimulationState* sim, CelestialBody* body);
+int add_spacecraft(SimulationState* sim, Spacecraft* craft);
 
 // SOI and simulation update functions
 int find_dominant_body(SimulationState* sim, int body_index);

src/spacecraft.cpp

@@ -1,71 +1,5 @@
 #include "spacecraft.h"
-#include "physics.h"
+#include "simulation.h"
 #include <cstdio>
 #include <cstring>
 #include <cmath>
-
-SpacecraftState* create_spacecraft_state(int max_craft) {
-    SpacecraftState* state = (SpacecraftState*)malloc(sizeof(SpacecraftState));
-    state->spacecraft = (Spacecraft*)malloc(sizeof(Spacecraft) * max_craft);
-    state->craft_count = 0;
-    state->max_craft = max_craft;
-    return state;
-}
-
-void destroy_spacecraft_state(SpacecraftState* state) {
-    if (state) {
-        if (state->spacecraft) {
-            free(state->spacecraft);
-        }
-        free(state);
-    }
-}
-
-int add_spacecraft(SpacecraftState* state, Spacecraft* craft) {
-    if (state->craft_count >= state->max_craft) {
-        printf("Error: Cannot add spacecraft - state full (%d/%d)\n",
-               state->craft_count, state->max_craft);
-        return -1;
-    }
-
-    int new_idx = state->craft_count;
-    state->spacecraft[new_idx] = *craft;
-    state->craft_count++;
-
-    return new_idx;
-}
-
-void compute_spacecraft_globals(SpacecraftState* craft_state, SimulationState* sim) {
-    for (int i = 0; i < craft_state->craft_count; i++) {
-        Spacecraft* craft = &craft_state->spacecraft[i];
-
-        if (craft->parent_index >= 0 && craft->parent_index < sim->body_count) {
-            CelestialBody* parent = &sim->bodies[craft->parent_index];
-            craft->position = vec3_add(parent->position, craft->local_position);
-            craft->velocity = vec3_add(parent->velocity, craft->local_velocity);
-        } else {
-            craft->position = craft->local_position;
-            craft->velocity = craft->local_velocity;
-        }
-    }
-}
-
-void update_spacecraft(SpacecraftState* craft_state, SimulationState* sim) {
-    for (int i = 0; i < craft_state->craft_count; i++) {
-        Spacecraft* craft = &craft_state->spacecraft[i];
-
-        if (craft->parent_index < 0 || craft->parent_index >= sim->body_count) {
-            continue;
-        }
-
-        CelestialBody* parent = &sim->bodies[craft->parent_index];
-
-        double parent_mass = parent->mass;
-        double craft_mass = craft->mass;
-
-        rk4_step(&craft->local_position, &craft->local_velocity,
-                 sim->dt, craft_mass, parent_mass);
-    }
-
-    compute_spacecraft_globals(craft_state, sim);
-}

src/spacecraft.h

@@ -1,19 +1,16 @@
 #ifndef SPACECRAFT_H
 #define SPACECRAFT_H
 
-#include "maneuver.h"
+#include "physics.h"
-#include "simulation.h"
 
-struct SpacecraftState {
+struct Spacecraft {
-    Spacecraft* spacecraft;
+    char name[64];
-    int craft_count;
+    double mass;
-    int max_craft;
+    Vec3 local_position;
+    Vec3 local_velocity;
+    Vec3 position;
+    Vec3 velocity;
+    int parent_index;
 };
 
-SpacecraftState* create_spacecraft_state(int max_craft);
-void destroy_spacecraft_state(SpacecraftState* state);
-void update_spacecraft(SpacecraftState* craft_state, SimulationState* sim);
-void compute_spacecraft_globals(SpacecraftState* craft_state, SimulationState* sim);
-int add_spacecraft(SpacecraftState* state, Spacecraft* craft);
-
 #endif

tests/test_energy.cpp

@@ -10,7 +10,7 @@ TEST_CASE("Energy conservation - Earth circular orbit", "[energy][rk4]") {
     const double DAYS_TO_SIMULATE = 10.0;
     const double SECONDS_PER_DAY = 86400.0;
 
-    SimulationState* sim = create_simulation(10, TIME_STEP);
+    SimulationState* sim = create_simulation(10, 0, TIME_STEP);
 
     REQUIRE(load_system_config(sim, "tests/configs/earth_circular.toml"));
 

tests/test_hyperbolic_orbit.cpp

@@ -12,7 +12,7 @@ TEST_CASE("Hyperbolic orbit - energy and escape trajectory", "[hyperbolic][energ
     const double SECONDS_PER_DAY = 86400.0;
     const double AU = 1.496e11;
 
-    SimulationState* sim = create_simulation(10, TIME_STEP);
+    SimulationState* sim = create_simulation(10, 0, TIME_STEP);
 
     REQUIRE(load_system_config(sim, "tests/configs/hyperbolic_comet.toml"));
 
@@ -111,7 +111,7 @@ TEST_CASE("Hyperbolic orbit - energy and escape trajectory", "[hyperbolic][energ
 TEST_CASE("Hyperbolic orbit initial conditions", "[hyperbolic][initial]") {
     const double TIME_STEP = 60.0;
 
-    SimulationState* sim = create_simulation(10, TIME_STEP);
+    SimulationState* sim = create_simulation(10, 0, TIME_STEP);
 
     REQUIRE(load_system_config(sim, "tests/configs/hyperbolic_comet.toml"));
 
@@ -174,7 +174,7 @@ TEST_CASE("Hyperbolic orbit asymptotic velocity", "[hyperbolic][asymptotic]") {
     const double SECONDS_PER_DAY = 86400.0;
     const double AU = 1.496e11;
 
-    SimulationState* sim = create_simulation(10, TIME_STEP);
+    SimulationState* sim = create_simulation(10, 0, TIME_STEP);
 
     REQUIRE(load_system_config(sim, "tests/configs/hyperbolic_comet.toml"));
 

tests/test_invalid_parent_assignment.cpp

@@ -14,7 +14,7 @@ TEST_CASE("Invalid parent: Earth should not become child of spacecraft",
           "[init][parent][bug]") {
     const double TIME_STEP = 60.0;
 
-    SimulationState* sim = create_simulation(10, TIME_STEP);
+    SimulationState* sim = create_simulation(10, 0, TIME_STEP);
     REQUIRE(load_system_config(sim, "tests/configs/earth_mars_simple.toml"));
 
     const int EARTH_IDX = 1;
@@ -43,7 +43,7 @@ TEST_CASE("Invalid parent: massive bodies never become children of small bodies"
     const double TIME_STEP = 60.0;
     const double MASS_THRESHOLD_RATIO = 1000.0;
 
-    SimulationState* sim = create_simulation(10, TIME_STEP);
+    SimulationState* sim = create_simulation(10, 0, TIME_STEP);
     REQUIRE(load_system_config(sim, "tests/configs/earth_mars_simple.toml"));
 
     for (int i = 0; i < sim->body_count; i++) {
@@ -89,7 +89,7 @@ TEST_CASE("Invalid parent: detect placeholder config values",
           "[init][config][validation]") {
     const double TIME_STEP = 60.0;
 
-    SimulationState* sim = create_simulation(10, TIME_STEP);
+    SimulationState* sim = create_simulation(10, 0, TIME_STEP);
     REQUIRE(load_system_config(sim, "tests/configs/earth_mars_simple.toml"));
 
     const int EARTH_IDX = 1;
@@ -117,7 +117,7 @@ TEST_CASE("Mutual SOI: similar mass planets within SOI boundary",
           "[init][soi][mutual][edge_case]") {
     const double TIME_STEP = 60.0;
 
-    SimulationState* sim = create_simulation(10, TIME_STEP);
+    SimulationState* sim = create_simulation(10, 0, TIME_STEP);
     REQUIRE(load_system_config(sim, "tests/configs/mutual_soi_close.toml"));
 
     const int PLANET_A_IDX = 1;

tests/test_maneuvers.cpp

@@ -10,30 +10,25 @@
 TEST_CASE("Spacecraft loading from config", "[spacecraft][config]") {
     const double TIME_STEP = 60.0;
 
-    SimulationState* sim = create_simulation(10, TIME_STEP);
+    SimulationState* sim = create_simulation(10, 10, TIME_STEP);
-    SpacecraftState* craft_state = create_spacecraft_state(10);
 
     REQUIRE(load_system_config(sim, "tests/configs/spacecraft_test.toml"));
-    REQUIRE(load_spacecraft_config(craft_state, sim, "tests/configs/spacecraft_test.toml"));
 
-    REQUIRE(craft_state->craft_count == 1);
+    REQUIRE(sim->craft_count == 1);
-    REQUIRE(std::string(craft_state->spacecraft[0].name) == "LEO_Satellite");
+    REQUIRE(std::string(sim->spacecraft[0].name) == "LEO_Satellite");
-    REQUIRE(craft_state->spacecraft[0].parent_index == 1);
+    REQUIRE(sim->spacecraft[0].parent_index == 1);
 
-    destroy_spacecraft_state(craft_state);
     destroy_simulation(sim);
 }
 
 TEST_CASE("Prograde burn increases orbital energy", "[spacecraft][burn][prograde]") {
     const double TIME_STEP = 60.0;
 
-    SimulationState* sim = create_simulation(10, TIME_STEP);
+    SimulationState* sim = create_simulation(10, 10, TIME_STEP);
-    SpacecraftState* craft_state = create_spacecraft_state(10);
 
     REQUIRE(load_system_config(sim, "tests/configs/spacecraft_test.toml"));
-    REQUIRE(load_spacecraft_config(craft_state, sim, "tests/configs/spacecraft_test.toml"));
 
-    Spacecraft* craft = &craft_state->spacecraft[0];
+    Spacecraft* craft = &sim->spacecraft[0];
     CelestialBody* earth = &sim->bodies[1];
 
     double initial_distance = vec3_distance(craft->position, earth->position);
@@ -47,27 +42,23 @@ TEST_CASE("Prograde burn increases orbital energy", "[spacecraft][burn][prograde
     double sim_time = 0.0;
     while (sim_time < SECONDS_TO_SIMULATE) {
         update_simulation(sim);
-        update_spacecraft(craft_state, sim);
         sim_time += TIME_STEP;
     }
 
     double final_distance = vec3_distance(craft->position, earth->position);
     REQUIRE(final_distance > initial_distance);
 
-    destroy_spacecraft_state(craft_state);
     destroy_simulation(sim);
 }
 
 TEST_CASE("Retrograde burn decreases orbital energy", "[spacecraft][burn][retrograde]") {
     const double TIME_STEP = 60.0;
 
-    SimulationState* sim = create_simulation(10, TIME_STEP);
+    SimulationState* sim = create_simulation(10, 10, TIME_STEP);
-    SpacecraftState* craft_state = create_spacecraft_state(10);
 
     REQUIRE(load_system_config(sim, "tests/configs/spacecraft_test.toml"));
-    REQUIRE(load_spacecraft_config(craft_state, sim, "tests/configs/spacecraft_test.toml"));
 
-    Spacecraft* craft = &craft_state->spacecraft[0];
+    Spacecraft* craft = &sim->spacecraft[0];
     CelestialBody* earth = &sim->bodies[1];
 
     double initial_distance = vec3_distance(craft->position, earth->position);
@@ -81,27 +72,23 @@ TEST_CASE("Retrograde burn decreases orbital energy", "[spacecraft][burn][retrog
     double sim_time = 0.0;
     while (sim_time < SECONDS_TO_SIMULATE) {
         update_simulation(sim);
-        update_spacecraft(craft_state, sim);
         sim_time += TIME_STEP;
     }
 
     double final_distance = vec3_distance(craft->position, earth->position);
     REQUIRE(final_distance < initial_distance);
 
-    destroy_spacecraft_state(craft_state);
     destroy_simulation(sim);
 }
 
 TEST_CASE("Normal burn changes orbital plane", "[spacecraft][burn][normal]") {
     const double TIME_STEP = 60.0;
 
-    SimulationState* sim = create_simulation(10, TIME_STEP);
+    SimulationState* sim = create_simulation(10, 10, TIME_STEP);
-    SpacecraftState* craft_state = create_spacecraft_state(10);
 
     REQUIRE(load_system_config(sim, "tests/configs/spacecraft_test.toml"));
-    REQUIRE(load_spacecraft_config(craft_state, sim, "tests/configs/spacecraft_test.toml"));
 
-    Spacecraft* craft = &craft_state->spacecraft[0];
+    Spacecraft* craft = &sim->spacecraft[0];
 
     double initial_z = craft->local_position.z;
 
@@ -111,26 +98,22 @@ TEST_CASE("Normal burn changes orbital plane", "[spacecraft][burn][normal]") {
     double sim_time = 0.0;
     while (sim_time < SECONDS_TO_SIMULATE) {
         update_simulation(sim);
-        update_spacecraft(craft_state, sim);
         sim_time += TIME_STEP;
     }
 
     REQUIRE(fabs(craft->local_position.z - initial_z) > 1000.0);
 
-    destroy_spacecraft_state(craft_state);
     destroy_simulation(sim);
 }
 
 TEST_CASE("Custom burn applies arbitrary delta-v", "[spacecraft][burn][custom]") {
     const double TIME_STEP = 60.0;
 
-    SimulationState* sim = create_simulation(10, TIME_STEP);
+    SimulationState* sim = create_simulation(10, 10, TIME_STEP);
-    SpacecraftState* craft_state = create_spacecraft_state(10);
 
     REQUIRE(load_system_config(sim, "tests/configs/spacecraft_test.toml"));
-    REQUIRE(load_spacecraft_config(craft_state, sim, "tests/configs/spacecraft_test.toml"));
 
-    Spacecraft* craft = &craft_state->spacecraft[0];
+    Spacecraft* craft = &sim->spacecraft[0];
 
     Vec3 initial_vel = craft->local_velocity;
     Vec3 delta_v = {10.0, 20.0, 30.0};
@@ -141,7 +124,6 @@ TEST_CASE("Custom burn applies arbitrary delta-v", "[spacecraft][burn][custom]")
     REQUIRE(fabs(craft->local_velocity.y - initial_vel.y - 20.0) < 0.001);
     REQUIRE(fabs(craft->local_velocity.z - initial_vel.z - 30.0) < 0.001);
 
-    destroy_spacecraft_state(craft_state);
     destroy_simulation(sim);
 }
 
@@ -150,13 +132,11 @@ TEST_CASE("Spacecraft propagation maintains stability", "[spacecraft][propagatio
     const double DAYS_TO_SIMULATE = 1.0;
     const double SECONDS_PER_DAY = 86400.0;
 
-    SimulationState* sim = create_simulation(10, TIME_STEP);
+    SimulationState* sim = create_simulation(10, 10, TIME_STEP);
-    SpacecraftState* craft_state = create_spacecraft_state(10);
 
     REQUIRE(load_system_config(sim, "tests/configs/spacecraft_test.toml"));
-    REQUIRE(load_spacecraft_config(craft_state, sim, "tests/configs/spacecraft_test.toml"));
 
-    Spacecraft* craft = &craft_state->spacecraft[0];
+    Spacecraft* craft = &sim->spacecraft[0];
     CelestialBody* earth = &sim->bodies[1];
 
     double initial_distance = vec3_distance(craft->position, earth->position);
@@ -165,7 +145,6 @@ TEST_CASE("Spacecraft propagation maintains stability", "[spacecraft][propagatio
     double sim_time = 0.0;
     while (sim_time < total_time) {
         update_simulation(sim);
-        update_spacecraft(craft_state, sim);
         sim_time += TIME_STEP;
     }
 
@@ -178,6 +157,5 @@ TEST_CASE("Spacecraft propagation maintains stability", "[spacecraft][propagatio
 
     REQUIRE(distance_drift_percent < 1.0);
 
-    destroy_spacecraft_state(craft_state);
     destroy_simulation(sim);
 }

tests/test_moon_orbits.cpp

@@ -13,7 +13,7 @@ TEST_CASE("Moon orbital stability around Earth", "[moon][earth]") {
     const double MAX_SIMULATION_DAYS = 35.0;
     const double MOON_DISTANCE_FROM_EARTH = 384400000.0;
 
-    SimulationState* sim = create_simulation(20, TIME_STEP);
+    SimulationState* sim = create_simulation(20, 0, TIME_STEP);
 
     REQUIRE(load_system_config(sim, "tests/configs/solar_system.toml"));
 
@@ -98,7 +98,7 @@ TEST_CASE("Galilean moons orbital stability around Jupiter", "[moon][jupiter]")
     const double GANYMEDE_PERIOD_DAYS = 7.15;
     const double CALLISTO_PERIOD_DAYS = 16.69;
 
-    SimulationState* sim = create_simulation(20, TIME_STEP);
+    SimulationState* sim = create_simulation(20, 0, TIME_STEP);
 
     REQUIRE(load_system_config(sim, "tests/configs/solar_system.toml"));
 
@@ -162,7 +162,7 @@ TEST_CASE("Titan orbital stability around Saturn", "[moon][saturn]") {
     const double SECONDS_PER_DAY = 86400.0;
     const double MAX_SIMULATION_DAYS = 25.0;
 
-    SimulationState* sim = create_simulation(20, TIME_STEP);
+    SimulationState* sim = create_simulation(20, 0, TIME_STEP);
 
     REQUIRE(load_system_config(sim, "tests/configs/solar_system.toml"));
 
@@ -216,7 +216,7 @@ TEST_CASE("Combined solar system with all moons - parent stability", "[moon][int
     const double SECONDS_PER_DAY = 86400.0;
     const double MAX_SIMULATION_DAYS = 60.0;
 
-    SimulationState* sim = create_simulation(20, TIME_STEP);
+    SimulationState* sim = create_simulation(20, 0, TIME_STEP);
 
     REQUIRE(load_system_config(sim, "tests/configs/solar_system.toml"));
 

tests/test_orbital_period.cpp

@@ -11,7 +11,7 @@ TEST_CASE("Orbital period - Earth (RK4)", "[period][rk4]") {
     const double SECONDS_PER_DAY = 86400.0;
     const double MAX_SIMULATION_DAYS = 400.0;
 
-    SimulationState* sim = create_simulation(10, TIME_STEP);
+    SimulationState* sim = create_simulation(10, 0, TIME_STEP);
 
     REQUIRE(load_system_config(sim, "tests/configs/earth_circular.toml"));
 
@@ -44,7 +44,7 @@ TEST_CASE("Orbital period - Mars (RK4)", "[period][rk4]") {
     const double SECONDS_PER_DAY = 86400.0;
     const double MAX_SIMULATION_DAYS = 750.0;
 
-    SimulationState* sim = create_simulation(10, TIME_STEP);
+    SimulationState* sim = create_simulation(10, 0, TIME_STEP);
 
     REQUIRE(load_system_config(sim, "tests/configs/mars_circular.toml"));
 

tests/test_parabolic_orbit.cpp

@@ -12,7 +12,7 @@ TEST_CASE("Parabolic orbit - energy and escape trajectory", "[parabolic][energy]
     const double SECONDS_PER_DAY = 86400.0;
     const double AU = 1.496e11;
 
-    SimulationState* sim = create_simulation(10, TIME_STEP);
+    SimulationState* sim = create_simulation(10, 0, TIME_STEP);
 
     REQUIRE(load_system_config(sim, "tests/configs/parabolic_comet.toml"));
 
@@ -104,7 +104,7 @@ TEST_CASE("Parabolic orbit - energy and escape trajectory", "[parabolic][energy]
 TEST_CASE("Parabolic orbit initial conditions", "[parabolic][initial]") {
     const double TIME_STEP = 60.0;
 
-    SimulationState* sim = create_simulation(10, TIME_STEP);
+    SimulationState* sim = create_simulation(10, 0, TIME_STEP);
 
     REQUIRE(load_system_config(sim, "tests/configs/parabolic_comet.toml"));
 

tests/test_root_body_transitions.cpp

@@ -23,7 +23,7 @@ TEST_CASE("Root body transition - Earth to Sun", "[root][transition]") {
     const double SECONDS_PER_DAY = 86400.0;
     const double AU = 1.496e11;
 
-    SimulationState* sim = create_simulation(10, TIME_STEP);
+    SimulationState* sim = create_simulation(10, 0, TIME_STEP);
 
     REQUIRE(load_system_config(sim, "tests/configs/manual_root_transition.toml"));
 
@@ -97,7 +97,7 @@ TEST_CASE("Root body round-trip - Earth -> Sun -> Mars -> Sun", "[root][round-tr
     const double DAYS_TO_SIMULATE = 1000.0;
     const double SECONDS_PER_DAY = 86400.0;
 
-    SimulationState* sim = create_simulation(10, TIME_STEP);
+    SimulationState* sim = create_simulation(10, 0, TIME_STEP);
 
     REQUIRE(load_system_config(sim, "tests/configs/manual_root_transition.toml"));
 

tests/test_soi_transition.cpp

@@ -22,7 +22,7 @@ TEST_CASE("SOI transition - Sun to Mars", "[soi][transition]") {
 
     INFO("Note: SOI transitions use simple model (no hysteresis)");
 
-    SimulationState* sim = create_simulation(10, TIME_STEP);
+    SimulationState* sim = create_simulation(10, 0, TIME_STEP);
 
     REQUIRE(load_system_config(sim, "tests/configs/soi_transition.toml"));
 
@@ -100,7 +100,7 @@ TEST_CASE("SOI transition - verify SOI radii", "[soi][radii]") {
     const double TIME_STEP = 60.0;
     const double AU = 1.496e11;
 
-    SimulationState* sim = create_simulation(10, TIME_STEP);
+    SimulationState* sim = create_simulation(10, 0, TIME_STEP);
 
     REQUIRE(load_system_config(sim, "tests/configs/soi_transition.toml"));