text:  This is The Conversation on Hawaii Public Radio. I'm Catherine Cruz. Spare parts aren't always easy to come by, whether you're in the middle of the ocean or on a battlefield. Today we look at technology that is being tested out during the military's RIMPAC exercises. It's in use in the battle in Ukraine, and as we speak, a Navy ship of Oahu is testing out a 3D printer on board. It's working on a replacement part to fix its faulty water system.