For those interested here is a quick comparison of the cargo hauling capabilities of the TMP Enterprise (Constitution), Reliant, Excelsior and Constellation classes.

The TMP Enterprise we know the most about. Her secondary hull has 8,707m3 for cargo and 12,740m3 for the shuttlebay. The combined volume for both cargo and shuttlebay is 21,447m3.

Because we don't know as much about the other classes as to how and where different sections are partitioned off, the comparison will subtract the Enterprise engineering volume of 32,220m3 from the other ship's secondary hull to get an estimate of how much combined cargo and shuttlebay volume they have.

Reliant's combined cargo+shuttlebay volume is 52,601m3 or 2.5x Constitution's.

Excelsior's combined cargo+shuttlebay volume is 157,738m3 or 7.4x Constitution's.

Constellation's combined cargo+shuttlebay volume is 341,789m3 or 15.9x Constitution's. However the primary hull is part of the body so if we subtract out the same amount of primary hull volume the Constitution has then the combined cargo+shuttlebay volume is 310,356m3 or 14.4x Constitution's.

Real world-wise there were various factors that resulted in the Constitution's permanent retirement such as the model was difficult to film, handle and maintain compared to the other models.

In-universe, we can note that the other classes can haul quite a bit more cargo making them far more useful than the Constitutions during a time of expansion and peace post-TUC. The cigar shaped secondary hull on the Constitutions is the limiting factor, IMHO.

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