diff --git a/balloon_learning_environment/env/balloon/acs.py b/balloon_learning_environment/env/balloon/acs.py
index ff9f513..7a672c4 100644
--- a/balloon_learning_environment/env/balloon/acs.py
+++ b/balloon_learning_environment/env/balloon/acs.py
@@ -27,17 +27,17 @@
         np.array([100.0, 100.0, 300.0, 400.0, 400.0]),  # power
         fill_value='extrapolate'))
 
-
+    
 _PRESSURE_RATIO_POWER_TO_EFFICIENCY: interpolate.interp2d = (
-    interpolate.interp2d(
-        np.linspace(1.05, 1.35, 13),  # pressure_ratio
-        np.linspace(100.0, 400.0, 4),  # power
+    interpolate.RegularGridInterpolator(
+        (np.linspace(1.05, 1.35, 13),  # pressure_ratio
+        np.linspace(100.0, 400.0, 4)),  # power
         np.array([0.4, 0.4, 0.3, 0.2, 0.2, 0.00000, 0.00000, 0.00000, 0.00000,
-                  0.00000, 0.00000, 0.00000, 0.00000, 0.4, 0.3, 0.3, 0.30, 0.25,
-                  0.23, 0.20, 0.15, 0.12, 0.10, 0.00000, 0.00000, 0.00000,
-                  0.00000, 0.3, 0.25, 0.25, 0.25, 0.20, 0.20, 0.20, 0.2, 0.15,
-                  0.13, 0.12, 0.11, 0.00000, 0.23, 0.23, 0.23, 0.23, 0.23, 0.20,
-                  0.20, 0.20, 0.18, 0.16, 0.15, 0.13]),  # efficiency
+                 0.00000, 0.00000, 0.00000, 0.00000, 0.4, 0.3, 0.3, 0.30, 0.25,
+                 0.23, 0.20, 0.15, 0.12, 0.10, 0.00000, 0.00000, 0.00000,
+                 0.00000, 0.3, 0.25, 0.25, 0.25, 0.20, 0.20, 0.20, 0.2, 0.15,
+                 0.13, 0.12, 0.11, 0.00000, 0.23, 0.23, 0.23, 0.23, 0.23, 0.20,
+                 0.20, 0.20, 0.18, 0.16, 0.15, 0.13]).reshape(13, 4),  # efficiency
         fill_value=None))