The calculated distance (air line) between Mevasseret Tsiyyon and Ashkelon is approximately 35 miles respectively 57 kilometers.
By car or train, the actual journey to Ashkelon is certainly longer, as only the direct route (as the crow flies) between Mevasseret Tsiyyon and Ashkelon has been calculated here.
Air line (approximately)
57 kilometers
31 nautical miles