To correct DonKarnage, the Asia Class carries both Photons and Missiles and 8 fighters (F4??) , due to the technology of the time.
It seems to be the thing with Star Trek props model makers to just rehash an existing ship model and this goes back to seeing the SS Botany Bay used as an unmannde interplanetary ore carrier in the TOS Episode "The Ultimate Computer".
I think with ENT it was a case of, "We'll just rehash the Akira model and use that to save a few bob.... the viewers won't notice a thing!!"
If you consider that pre-warp Earth space flight, which would have been interplanetary using Chemical Thristers, Particle Thrusters, Ion, Fission (DY-100), Fusion, Sub Atomic Impulse Power (to give it the full name), etc.
These sub-light ships and craft would be balistically shaped with aromured noses or shields to cope with dust and meteorite hits due to the semi and near relaivistic speeds that they attain.
The early starships, such as the "SS Bonaventure" and "SS Valiant", would have had shipwrights drawing on sublight ship knowledge and building skills to design warp powered starships.
It isn't too far to imagine that a logical experimental Warp Drive development step would have been to strap Warp Drive onto a DY-100 for longer duration test flights. The "Pheonix" was obviously even less suited to duration space travel of more than a few hours, due to the obvious lack of toilet facilities and other amenities.
The Warp Core was probally Anti-Matter spiked Fusion powered, so of limited range.
In TAS the "SS Boneventure" is supposed to be the first Warp Drive star ship, which some idiots think means the original Warp Drive ship, which is a wrong assumption.
The "Pheonix" is a "Craft", not a ship. There is a big difference between a ship and a craft in nautical terms.
The thing is I would expect commercial space ship builders to initially convert some of the existing sublight and maybe Fusion powered interplanetary ships and craft to Warp Drive, mainly to tap the new matket of inter-stellar commerce.
This means that there was obviously a logical progression of commercial starships before the "J-Class" appeared in the beginning of the 2100's, starting with the "A-Class" obviously of course. Now there's something to speculate, develop and model.
The "Edison Class" shown by Data in the TNG Episode "Mariposa" (the ship in the story line) is a typical example of an early DY-100 derived commercial starship line as it retains all the features of earlier DY type ships.
Anyone else spot that it was the "Edison Class" star survey ship from "The Space Flight Chronology" book??