The calculated distance (air line) between Ascheberg and Castrop-Rauxel is approximately 20 miles respectively 33 kilometers.
By car or train, the actual journey to Castrop-Rauxel is certainly longer, as only the direct route (as the crow flies) between Ascheberg and Castrop-Rauxel has been calculated here.
Air line (approximately)
33 kilometers
18 nautical miles