The calculated distance (air line) between Haltern am See and Bochum-Hordel is approximately 17 miles respectively 27 kilometers.
By car or train, the actual journey to Bochum-Hordel is certainly longer, as only the direct route (as the crow flies) between Haltern am See and Bochum-Hordel has been calculated here.
Air line (approximately)
27 kilometers
14 nautical miles