diff --git a/docs/technical_reference.md b/docs/technical_reference.md
index 51dc1d2..ec32da4 100644
--- a/docs/technical_reference.md
+++ b/docs/technical_reference.md
@@ -58,15 +58,21 @@ struct CelestialBody {
     char name[64];
     double mass;              // kg
     double radius;            // meters
-    Vec3 local_position;      // position relative to parent (meters)
-    Vec3 local_velocity;      // velocity relative to parent (m/s)
-    Vec3 position;            // global position (meters from origin)
-    Vec3 velocity;            // global velocity (m/s)
+    int parent_index;         // index of gravitational parent (-1 for root body like Sun)
+    float color[3];           // RGB color for rendering
+
+    // Orbital elements from config (Keplerian elements)
+    OrbitalElements orbit;
+
+    // Global frame (from origin)
+    Vec3 global_position;    // meters from origin
+    Vec3 global_velocity;    // m/s
+
+    // Local frame (relative to parent)
+    Vec3 local_position;      // meters from parent
+    Vec3 local_velocity;      // m/s relative to parent
+
     double soi_radius;        // sphere of influence radius (meters)
-    int parent_index;         // index of gravitational parent (-1 for root)
-    float color[3];           // RGB for rendering
-    double eccentricity;      // orbital eccentricity (0 = circular)
-    double semi_major_axis;   // meters
 };
 ```
 
@@ -91,16 +97,18 @@ struct SimulationState {
 };
 ```
 
-### OrbitalElements (simulation.h)
+### OrbitalElements (orbital_mechanics.h)
 ```cpp
 struct OrbitalElements {
-    double time_days;
-    double semi_major_axis_au;
+    union {
+        double semi_major_axis;       // for elliptical (e<1) and hyperbolic (e>1)
+        double semi_latus_rectum;     // for parabolic (e≈1)
+    };
     double eccentricity;
-    double specific_energy;
-    double distance_to_sun_au;
-    double distance_to_ref_body_au;
-    double velocity_magnitude;
+    double true_anomaly;
+    double inclination;
+    double longitude_of_ascending_node;
+    double argument_of_periapsis;
 };
 ```
 
@@ -109,11 +117,18 @@ struct OrbitalElements {
 struct Spacecraft {
     char name[64];
     double mass;
+    int parent_index;
+
+    // Orbital elements from config
+    OrbitalElements orbit;
+
+    // Global frame (from origin)
+    Vec3 global_position;
+    Vec3 global_velocity;
+
+    // Local frame (relative to parent)
     Vec3 local_position;
     Vec3 local_velocity;
-    Vec3 position;
-    Vec3 velocity;
-    int parent_index;
 };
 ```
 
@@ -225,7 +240,7 @@ Burn execution system for spacecraft orbital maneuvers. Supports multiple burn d
 - Maneuvers track execution state and timestamp
 
 ### Config Loader (config_loader.cpp/h)
-TOML-based config parser using tomlc17 library. Auto-calculates circular orbit velocities and SOI radii.
+TOML-based config parser using tomlc17 library. Auto-calculates circular orbit velocities from orbital elements and SOI radii.
 
 **Key functions:**
 - `load_system_config()` - main entry point, loads bodies/spacecraft/maneuvers from config file
@@ -234,7 +249,6 @@ TOML-based config parser using tomlc17 library. Auto-calculates circular orbit v
 - `parse_toml_maneuver()` - parses maneuver entries
 - `load_spacecraft_from_toml()` - loads spacecraft array from config
 - `load_maneuvers_from_toml()` - loads maneuvers array from config
-- `initialize_bodies()` - combined initialization: velocities, SOI radii, and local coordinates
 
 **Config format details:**
 - TOML arrays: `[[bodies]]`, `[[spacecraft]]`, `[[maneuvers]]`
@@ -242,6 +256,7 @@ TOML-based config parser using tomlc17 library. Auto-calculates circular orbit v
 - `parent_index = -1` indicates root body (star)
 - Supports nested orbits (planets with moons)
 - All numeric values accept integers or floats
+- Uses orbital elements table (Keplerian elements) instead of state vectors
 
 **Config format (TOML) - Bodies:**
 ```toml
@@ -249,21 +264,25 @@ TOML-based config parser using tomlc17 library. Auto-calculates circular orbit v
 name = "Sun"
 mass = 1.989e30
 radius = 6.96e8
-position = { x = 0.0, y = 0.0, z = 0.0 }
 parent_index = -1
 color = { r = 1.0, g = 1.0, b = 0.0 }
-eccentricity = 0.0
-semi_major_axis = 0.0
+orbit = {
+    semi_major_axis = 0.0,
+    eccentricity = 0.0,
+    true_anomaly = 0.0
+}
 
 [[bodies]]
 name = "Earth"
 mass = 5.972e24
 radius = 6.371e6
-position = { x = 1.496e11, y = 0.0, z = 0.0 }
 parent_index = 0
 color = { r = 0.0, g = 0.5, b = 1.0 }
-eccentricity = 0.0
-semi_major_axis = 1.496e11
+orbit = {
+    semi_major_axis = 1.496e11,
+    eccentricity = 0.0,
+    true_anomaly = 0.0
+}
 ```
 
 **Config format (TOML) - Spacecraft:**
@@ -271,12 +290,15 @@ semi_major_axis = 1.496e11
 [[spacecraft]]
 name = "LEO_Satellite"
 mass = 1000.0
-position = { x = 0.0, y = 6.771e6, z = 0.0 }
-velocity = { x = 7660.0, y = 0.0, z = 0.0 }
 parent_index = 1
+orbit = {
+    semi_major_axis = 6.571e6,
+    eccentricity = 0.0,
+    true_anomaly = 0.0
+}
 ```
-- `position` and `velocity` are in local frame relative to parent
-- `velocity` is optional (defaults to zero if omitted)
+- Uses `orbit` table for orbital elements (same as bodies)
+- Altitude can be used instead of `semi_major_axis` (convenience feature, added to parent radius)
 
 **Config format (TOML) - Maneuvers:**
 ```toml
@@ -292,15 +314,36 @@ delta_v = 500.0
 - `direction`: "prograde", "retrograde", "normal", "antinormal", "radial_in", "radial_out"
 - `delta_v`: velocity change magnitude in m/s
 
+### Config Validator (config_validator.cpp/h)
+Validation module that ensures config files define physically realistic systems. Called automatically after loading config and initializing orbital objects.
+
+**Key functions:**
+- `run_all_config_validations()` - master validation function that calls all validators
+- `validate_parent_index_ordering()` - ensures parent indices are properly ordered
+- `validate_orbital_elements()` - checks orbital elements for valid values
+- `validate_initial_positions()` - ensures bodies aren't inside their parent
+- `validate_mass_ratios()` - checks parent-child mass ratios for hierarchical consistency
+- `validate_soi_overlap()` - detects bodies with overlapping spheres of influence
+- `validate_nested_orbits()` - ensures moons orbit within stable boundaries
+
 **Validation rules:**
 - Body count must not exceed `max_bodies`
 - Spacecraft count must not exceed `max_craft`
 - Maneuver count must not exceed `max_maneuvers`
 - Body `parent_index` must be < body index or -1 (root)
-- Parent-child distance must exceed combined radii
 - Spacecraft `parent_index` must reference valid body
 - Maneuver `spacecraft_name` must reference existing spacecraft
 - Maneuver names must be unique within config
+- Eccentricity must be >= 0
+- Parabolic orbits (e≈1) require `semi_latus_rectum` (not `semi_major_axis`)
+- Elliptical/hyperbolic orbits require `semi_major_axis` (not `semi_latus_rectum`)
+- Elliptical orbits (e<1) require positive `semi_major_axis`
+- Bodies with `eccentricity < 1` and `semi_major_axis <= 0` are rejected
+- Parent-child distance must exceed combined radii
+- Spacecraft must be at least parent's radius away
+- **Mass ratio validation**: For root children with radius > 50% of parent, mass ratio >= 1000
+- **SOI overlap validation**: Bodies sharing same parent must not have overlapping SOIs
+- **Nested orbit validation**: Moons (small radius, circular orbits) must orbit within 5x parent SOI
 
 ### Renderer (renderer.cpp/h)
 Raylib 3D visualization system. See **[docs/rendering.md](rendering.md)** for complete documentation including:
@@ -418,11 +461,19 @@ GUI-only application with interactive 3D visualization.
    - Loads bodies array from `[[bodies]]`
    - Loads spacecraft array from `[[spacecraft]]`
    - Loads maneuvers array from `[[maneuvers]]`
-2. `initialize_bodies()` → combined initialization:
+2. `initialize_orbital_objects()` → combined initialization:
+   - Converts orbital elements to local position/velocity for all bodies
    - Calculates circular orbit velocities for all bodies (using vis-viva equation)
    - Computes sphere of influence radius for each body (Hill sphere)
-   - Sets local coordinates (position/velocity) for all bodies
+   - Sets local coordinates (position/velocity) for all bodies and spacecraft
    - Initializes spacecraft global coordinates
+3. `run_all_config_validations()` → validates loaded configuration:
+   - Checks parent_index ordering
+   - Validates orbital elements
+   - Checks mass ratios between parent and child bodies
+   - Detects overlapping SOIs between bodies sharing same parent
+   - Validates nested orbit boundaries (moons within parent's SOI)
+   - Ensures initial positions don't collide with parent body
 
 ### Main Simulation Loop
 1. `update_simulation()` → for each body: