Doppler Class 

The Doppler class transport was the first efficient high-tonnage transport using dilithium moderated warp drive in service in the Federation. Its predecessors, on which it was primarily based, included the Ptolemy and Keppler class transports. However, these transports suffered from lack of power when fully loaded. Possessing a larger engineering section which could support a more powerful impulse engine, the Doppler quickly filled a much needed role in Starfleet logistics.

With Cargo Pod