Challenger Class Heavy Transport Tug
Namesake Hull Registry: NCC-3985
The Tri-Warp configuration allows Challenger Class HTTs to serve as the Command Hull for Tripod and Quadpod Astrotrains, the largest deployment of Excelsior-superclass Container starcraft, producing a sufficient warp bubble to contain a maximum of sixteen standardized Starfleet Quartermaster Command, Warp-assisting Container units per Command Hull.
Astrotrain linkage allows for multiple "One-Four" linkups, producing full-length Challenger Class Astrotrains on the order of "Four-Sixty-Fours" to "Five-Eighties".
Impulse decks on Challenger Class hulls are expanded to accommodate the heavy-duty ASR Series V "Selipnir" impulse engines. Under full load, Challenger Class HTTs can achieve a Delta-V of 60KPS (60,000 kilometers per second) in fifty seconds.*
Three LN-88 Mod 5 Linear Warp Engines, deployed in a "roll-bar" configuration, allow Challenger Class HTTs to sustain cruising speeds of Warp Factor 7 under a full load of sixteen Containers. Acceleration speeds are noticeably slower, as the extended warp-bubble takes additional seconds to be fully emitted by the warp engines and sustained by the Warp Sustainer Units on each Container. Acceleration time from OCM (Onset of Critical Momentum) to Warp 7 averages around twenty-five seconds.*
*Above performance figures are constant regardless of number of "Command Links" in an extended Astrotrain, as the multiple Command Hulls apply equal force-to-scale; all drive systems linked by FTL, subspace command signalry.
Categorized as Heavy Free-Configurable Support Vessels, Challenger HTTs are deployed under the auspices of Starfleet Quartermaster Command.
The civilian counterparts to Challengers are referred to as Superchief Warbonnets. The only system difference is a deemphasized tactical profile.
Challenger Class HTT registry numbers run from NCC-3900 to NCC-3999.
The hull registry of class-leader Starship Challenger (TTH-3985) is the series number of the final surviving example of that class of ancient Terran compound steam locomotives for which the Challenger Heavy Transport Tug is named.

*breaks out of character*
Many thanks to Our Host, MarcusStarkiller, for this charming and flattering gift.