diff --git a/orbitx/PhysicEntity.py b/orbitx/PhysicEntity.py
index a7d7fc7..66f8357 100644
--- a/orbitx/PhysicEntity.py
+++ b/orbitx/PhysicEntity.py
@@ -4,6 +4,9 @@
 
 
 class PhysicsEntity(object):
+    habitat_hull_strength=50
+    spacestation_hull_strength=100
+    cannot_land=0 #reserved for small astroid, to be changed
     def __init__(self, entity):
         assert isinstance(entity, protos.Entity)
         self.name = entity.name
@@ -15,9 +18,16 @@ def __init__(self, entity):
         self.heading = entity.heading
         self.fuel = entity.fuel
         self.throttle = entity.throttle
-        self.attached_to = entity.attached_to
-        self.broken = entity.broken
-        self.artificial = entity.artificial
+        self.attached_to =""
+        if hasattr(entity,"attached_to"):
+            self.attached_to = entity.attached_to
+        self.broken=False
+        if hasattr(entity,"broken"):
+            self.broken = entity.broken
+        self.artificial=False
+        if hasattr(entity,"artificial"):
+            self.artificial = entity.artificial
+
 
     def as_proto(self):
         return protos.Entity(