diff --git a/src/pg_rad/configs/__init__.py b/src/pg_rad/configs/__init__.py
new file mode 100644
index 0000000..a9a2c5b
--- /dev/null
+++ b/src/pg_rad/configs/__init__.py
@@ -0,0 +1 @@
+__all__ = []
diff --git a/src/pg_rad/configs/defaults.py b/src/pg_rad/configs/defaults.py
new file mode 100644
index 0000000..9523c84
--- /dev/null
+++ b/src/pg_rad/configs/defaults.py
@@ -0,0 +1,10 @@
+# --- Physics defaults ---
+DEFAULT_AIR_DENSITY = 1.243  # kg/m^3, Skåne
+
+# --- Simulation defaults ---
+DEFAULT_SEED = None
+DEFAULT_ACQUISITION_TIME = 1.0
+
+# --- Source defaults ---
+DEFAULT_PATH_HEIGHT = 0.0
+DEFAULT_SOURCE_HEIGHT = 0.0