It has dawned on me that any ship named Valiant is bound to die somehow. The SS Valiant was destroyed by the esper insanity of the Galactic Barrier. The USS Valiant was killed by first contact with the people of Eminiar VII in 2217. The production list of Constitution class ships on TOS included a USS Valiant on the final list of 14 ships, which seems to indicate that ship was lost prior to 2267. The Defiant class USS Valiant was destroyed by the Jem'Hadar in the 24th century, while under the command of dumb space cadets. And last we left off in Star Trek: Nemesis, there was a new USS Valiant which assuredly would have gone kaboom if given enough time.