The SS Valiant was an Earth starship that was in service in the mid-21st century. In 2065, the Valiant embarked on a mission of deep space exploration. (ENT: "In a Mirror, Darkly, Part II", display graphic)
During the expedition, the Valiant encountered a magnetic space storm that overwhelmed her impulse engines and swept the vessel into the energy barrier at the edge of the galaxy. The galactic barrier caused severe damage to the Valiant, and the death of six crewmen. One of the crewmen affected by the barrier began to develop extremely powerful psychokinetic abilities, posing a threat to the ship. In an effort to stop this individual, who was growing more dangerous, the captain of the Valiant gave the order to destroy his own ship. Just prior to its destruction, the Valiant ejected its own disaster recorder.
By 2265, the Valiant had been missing for two hundred years. The Valiant's disaster recorder was recovered by the starship USS Enterprise, as the Enterprise was preparing to probe outside the galaxy. Reviewing the data recovered from the memory banks of the recorder, the crew of the Enterprise discovered the final fate of the Valiant. (TOS: "Where No Man Has Gone Before")
|Starships named Valiant|
|SS Valiant • USS Valiant • USS Valiant (NCC-74210) • USS Valiant (NCC-75418)|
Background information Edit
The year of launch and the type of mission for SS Valiant were stated on a computer screen graphic in ENT: "In a Mirror, Darkly, Part II". The episode VOY: "Friendship One" suggests, however, that the launch might have actually occurred a few years later. In the episode, the Friendship 1 probe, launched in 2067, was said to have paved the way for all the manned missions sent out to contact other species.
Although the Valiant's call letters aren't established in "Where No Man Has Gone Before", they were said to be VAL 115 in the episode's script. The script also referred to the ship, interchangeably, as both the USS Valiant and the SS Valiant, but most commonly with the former of those prefixes. It was additionally described in the script as a galactic survey cruiser. 
The Valiant was again referred to as a galactic survey cruiser in Star Trek Maps (1980), which also gives the vessel the registry NCC-S1104. According to the same source, the ship exited the galaxy at a vertical upward angle slightly towards the galactic center and encountered the galactic barrier approximately 780 light years away from Earth. The same account of an upward trajectory was repeated in Star Trek Star Charts (2002; p. 10). However, the point at which the ship encountered the barrier was depicted to be approximately two thousand light years away from Earth.
A reference model of the Valiant was built by Greg Jein and photographed by author Mike Okuda for representation in both editions of his Star Trek Chronology (1993 and 1996) as well as in all editions of his Star Trek Encyclopedia, becoming one of the very few conjectural designs ported over into that otherwise strictly canon work.  On its hull, the ship was named Valiant, with no USS or SS. The model was also marked with the registry number ADC-11031 and the number 02 on the bridge module. Of Jein's design, an appreciative Okuda has stated, "I'm not sure, but I think it may be Greg's homage to "Dark Star," whose registry also had an ADC prefix. Greg built the Dark Star ship model, and he knows I'm a big fan of that film." Jein delivered his model to Okuda without warp nacelles, but it was decided to add these after all, reusing nacelles from the Bonaventure model Jein had also constructed for Okuda's Chronology project. (X) According to Doug Drexler, this model influenced the design of the SS Conestoga, a ship also launched in the 2060s, created for the Star Trek: Enterprise episode "Terra Nova". (X)
The model had been one of four Jein had constructed for Okuda out of his own volution, and free of charge. In return, both Okuda and Drexler had tried hard during their tenure on the Star Trek franchise to get Jein's designs elevated into canon, and while they succeeded for the the Daedalus-class, and Bonaventure models, the Valiant was not one of them (the other one having been a pre-Original Series-era Romulan warbird).