I don't remember what I did but it was probably important

Assets/Scripts/RCSController.cs

@@ -2,15 +2,92 @@ using UnityEngine;
 
 public class RCSController : MonoBehaviour
 {
-    // Start is called once before the first execution of Update after the MonoBehaviour is created
-    void Start()
+    [Header("References")]
+    public Rigidbody rb;
+    public FuelTank fuelTank;
+
+    [Header("RCS Settings")]
+    public bool rcsEnabled = true;
+    public bool consumeFuel = true;
+    public float maxTorque = 2000f; // N*m
+    public float torqueResponseRate = 6000f; // N*m per second
+    public float leverArm = 2f; // meters
+    public float Isp = 250f; // seconds
+    public float inputDeadzone = 0.05f;
+
+    [Header("Input")]
+    public Vector3 controlInput; // x = yaw, y = pitch, z = roll (-1 to 1)
+
+    [Header("Output")]
+    public Vector3 appliedTorque = Vector3.zero; // world space
+    public float fuelFlowRate = 0f; // kg/s
+
+    private const float g0 = 9.80665f;
+    private Vector3 currentLocalTorque = Vector3.zero;
+
+    void FixedUpdate()
     {
-        
+        if (!rcsEnabled || rb == null)
+        {
+            appliedTorque = Vector3.zero;
+            currentLocalTorque = Vector3.zero;
+            fuelFlowRate = 0f;
+            return;
+        }
+
+        Vector3 clampedInput = new Vector3(
+            Mathf.Abs(controlInput.x) < inputDeadzone ? 0f : Mathf.Clamp(controlInput.x, -1f, 1f),
+            Mathf.Abs(controlInput.y) < inputDeadzone ? 0f : Mathf.Clamp(controlInput.y, -1f, 1f),
+            Mathf.Abs(controlInput.z) < inputDeadzone ? 0f : Mathf.Clamp(controlInput.z, -1f, 1f)
+        );
+
+        float pitchInput = clampedInput.y;
+        float yawInput = clampedInput.x;
+        float rollInput = clampedInput.z;
+
+        Vector3 targetLocalTorque = new Vector3(pitchInput, yawInput, rollInput) * maxTorque;
+        float maxDelta = torqueResponseRate * Time.fixedDeltaTime;
+        currentLocalTorque = Vector3.MoveTowards(currentLocalTorque, targetLocalTorque, maxDelta);
+
+        Vector3 fueledLocalTorque = ApplyFuelLimit(currentLocalTorque);
+        appliedTorque = rb.rotation * fueledLocalTorque;
     }
 
-    // Update is called once per frame
-    void Update()
+    private Vector3 ApplyFuelLimit(Vector3 desiredLocalTorque)
     {
-        
+        fuelFlowRate = 0f;
+        if (!consumeFuel || fuelTank == null)
+        {
+            return desiredLocalTorque;
+        }
+
+        if (leverArm <= 0f || Isp <= 0f)
+        {
+            return desiredLocalTorque;
+        }
+
+        float torqueMagnitude = desiredLocalTorque.magnitude;
+        if (torqueMagnitude <= 0f)
+        {
+            return Vector3.zero;
+        }
+
+        float requiredForce = torqueMagnitude / leverArm;
+        fuelFlowRate = requiredForce / (Isp * g0);
+        float fuelRequested = fuelFlowRate * Time.fixedDeltaTime;
+        float fuelProvided = fuelTank.RequestRcsFuel(fuelRequested);
+
+        if (fuelProvided < fuelRequested && fuelRequested > 0f)
+        {
+            float scale = Mathf.Clamp01(fuelProvided / fuelRequested);
+            return desiredLocalTorque * scale;
+        }
+
+        return desiredLocalTorque;
+    }
+
+    public void SetControlInput(Vector3 input)
+    {
+        controlInput = input;
     }
 }