In starship classification, a heavy cruiser is a large multi-purpose starship. They are designed to perform and excel at a wide range of missions and tasks. The Heavy Cruiser has long been the primary ship of the Starfleet. They offer the best multi-mission platform and vessels of this type are the mainstay of their respective eras. They are similar to Explorers, with two exceptions:
1 - Heavy Cruisers are intended for shorter duration missions than Explorers, usually 5 years or less.
2 - Heavy Cruisers are built in greater numbers than Explorers.
The Constitution class, Excelsior class, Ambassador class, and Sovereign class were all designated as heavy cruisers.