The sheer size of the USS Kelvin and her 800-strong crew creates a number of problems. She apparently exists in both the Prime Universe (PU) and Abramsverse (Ab), her destruction having been accepted as the source of the juncture between the two timelines, yet she’s much larger than any ship Starfleet apparently possessed until well into the 24th-century. It’s possible that the Kelvin was in fact designed to be an experimental long-range expeditionary vessel. In the Ab, the Enterprise is the first vessel to undertake a five-year mission, but it’s possible that in both the PU and Ab the Kelvin was the first to carry out, perhaps, a four-year mission, explaining the presence of families on-board, just like the Enterprise-D. Her success in the PU not only demonstrated to Starfleet that it was possible to streamline such missions with much smaller ships and crews for the sake of efficiency, but was also so successful that Starfleet honoured her by bestowing her arrowhead insignia on the entire fleet, as it appears in Star Trek Discovery, though this was eventually (and for a somewhat brief period) limited to the flagship in favour of unique mission patches once again. In the Ab, the adoption of the same symbol fleet-wide would simply be indicative of how profoundly her fate had effected the morale of the Federation and its turn towards being a more militant and assertive power. This could be backed up by the presence of a model of the Kelvin alongside other noteworthy ships in both the final episode of the PU but non-canon Star Trek Continues and in Marcus’s office in Into Darkness.
In the Ab, however, the destruction of such a large and heavily armed starship, perhaps even Starfleet’s most powerful, at the hands of a mysterious vessel several times larger than herself, shocked the Federation to such an extent that starship design was completely rethought. As the World Wars proved, there’s nothing like war or the threat of conflict to bring about revolutionary technologies (such as jets, rockets and nuclear arms). A major clue to support this theory is the PU model of the USS Biddeford NCC 0718 in Admiral Alexander Marcus’s office. It’s possible that even in the PU, the Constitution Class was in late stages of planning even as the Kelvin was in service in 2233, the year she was destroyed in the Ab. As his involvement in the design and construction of the USS Vengeance shows, Marcus was heavily involved in the development of advanced starship design.
The model of the Biddeford suggests that the Constitution Class had already been designed, but the shocking loss of the Kelvin provoked Marcus and his department to go back to the drawing board and redesign it several times larger and more powerful. Following the attack, the name and registry was reassigned to a Newton Class while the Constitution Class was entirely redesigned. Judging by the Vengeance, Marcus had clearly come to the conclusion that this approach was best. This would explain the change from the PU Enterprise’s construction at the San Francisco Shipyards to the Ab Riverside Shipyard- the dramatic change in the construction specifications necessitating a much larger area, such as can be found in rural Iowa. Without the destruction of the Kelvin in the PU, this approach was never even considered, leading to a much smaller Constitution Class. It also explains why the Klingon Empire retreated from conflict with the Federation in the Ab, finding its overpowered fleet too difficult to contend with. It may also explain the confusing registry of the Constellation NCC 1017. The Biddeford and Constellation may have both been planned as test-ships before the Constitution was finally commissioned and named as the first true member of her class, explaining the early registry numbers.
To hypothesise, the destruction of an entire fleet composed of these massive ships at Vulcan at the hands of Nero and the subsequent destruction of the Narada brought about largely by a small boarding party convinced Starfleet that it was taking a poor approach, compounded further by the revelation that the aggressor had in fact originated not just from the distant future but from a parallel universe. This would explain why a model of the Vengeance can be found in Marcus’s office despite the project supposedly being top-secret: even before the destruction of Vulcan, Starfleet was planning to construct the Dreadnought Class but scrapped it, only to have the vessel built in secret by Marcus anyway, likely with the complicity of others in the Federation Council and Admiralty who were likewise unconvinced that the solution didn’t lie with immense vessels.
This change in policy came about too late to disrupt other gargantuan and fundamentally flawed construction projects, such as the Starbase Yorktown, the near destruction of which at the hands of one former MACO demonstrating further the inadequacies of this approach. Needless to say, with engineering expertise and crew training now having become accustomed to ships on this scale, a return to more modest sizes was only slowly untaken. The Ab Enterprise-A, though of a new class to her predecessor, remained on the same massive scale.
The logic of both the PU and Ab Starfleets is based on proportionality. The PU Starfleet was, until its encounter with Borg, exposed to rival powers that remained on roughly the same technological level as itself, maintaining militaries of similar proportions and capacities in more-or-less even playing ground, despite its multipolarity. Even encounters with advanced species such as the First Federation were judged benign enough as to not necessitate any real overhaul of the fleet. The Ab Starfleet, however, was threatened relatively early on by a relentlessly hostile foreign power about which it knew nothing. For all it knew, the Narada could have been only the vanguard of a much larger force, necessitating a radical militarisation program. The PU Starfleet’s encounter with the Borg likewise necessitated a massive build-up of forces, including the return to service of antique vessels such as the Miranda Class, and a shake-up in starship design, bringing about classes of tougher ships oriented more towards warfare than to peaceful exploration such as the Defiant, Akira and Sovereign Classes, an approach that saw it claim victory in the Dominion War. In other words, encounters with advanced hostile species in both the PU and Ab saw rapid developments in ship design, though in very different ways.
In the Ab, however, the destruction of such a large and heavily armed starship, perhaps even Starfleet’s most powerful, at the hands of a mysterious vessel several times larger than herself, shocked the Federation to such an extent that starship design was completely rethought. As the World Wars proved, there’s nothing like war or the threat of conflict to bring about revolutionary technologies (such as jets, rockets and nuclear arms). A major clue to support this theory is the PU model of the USS Biddeford NCC 0718 in Admiral Alexander Marcus’s office. It’s possible that even in the PU, the Constitution Class was in late stages of planning even as the Kelvin was in service in 2233, the year she was destroyed in the Ab. As his involvement in the design and construction of the USS Vengeance shows, Marcus was heavily involved in the development of advanced starship design.

The model of the Biddeford suggests that the Constitution Class had already been designed, but the shocking loss of the Kelvin provoked Marcus and his department to go back to the drawing board and redesign it several times larger and more powerful. Following the attack, the name and registry was reassigned to a Newton Class while the Constitution Class was entirely redesigned. Judging by the Vengeance, Marcus had clearly come to the conclusion that this approach was best. This would explain the change from the PU Enterprise’s construction at the San Francisco Shipyards to the Ab Riverside Shipyard- the dramatic change in the construction specifications necessitating a much larger area, such as can be found in rural Iowa. Without the destruction of the Kelvin in the PU, this approach was never even considered, leading to a much smaller Constitution Class. It also explains why the Klingon Empire retreated from conflict with the Federation in the Ab, finding its overpowered fleet too difficult to contend with. It may also explain the confusing registry of the Constellation NCC 1017. The Biddeford and Constellation may have both been planned as test-ships before the Constitution was finally commissioned and named as the first true member of her class, explaining the early registry numbers.
To hypothesise, the destruction of an entire fleet composed of these massive ships at Vulcan at the hands of Nero and the subsequent destruction of the Narada brought about largely by a small boarding party convinced Starfleet that it was taking a poor approach, compounded further by the revelation that the aggressor had in fact originated not just from the distant future but from a parallel universe. This would explain why a model of the Vengeance can be found in Marcus’s office despite the project supposedly being top-secret: even before the destruction of Vulcan, Starfleet was planning to construct the Dreadnought Class but scrapped it, only to have the vessel built in secret by Marcus anyway, likely with the complicity of others in the Federation Council and Admiralty who were likewise unconvinced that the solution didn’t lie with immense vessels.

This change in policy came about too late to disrupt other gargantuan and fundamentally flawed construction projects, such as the Starbase Yorktown, the near destruction of which at the hands of one former MACO demonstrating further the inadequacies of this approach. Needless to say, with engineering expertise and crew training now having become accustomed to ships on this scale, a return to more modest sizes was only slowly untaken. The Ab Enterprise-A, though of a new class to her predecessor, remained on the same massive scale.
The logic of both the PU and Ab Starfleets is based on proportionality. The PU Starfleet was, until its encounter with Borg, exposed to rival powers that remained on roughly the same technological level as itself, maintaining militaries of similar proportions and capacities in more-or-less even playing ground, despite its multipolarity. Even encounters with advanced species such as the First Federation were judged benign enough as to not necessitate any real overhaul of the fleet. The Ab Starfleet, however, was threatened relatively early on by a relentlessly hostile foreign power about which it knew nothing. For all it knew, the Narada could have been only the vanguard of a much larger force, necessitating a radical militarisation program. The PU Starfleet’s encounter with the Borg likewise necessitated a massive build-up of forces, including the return to service of antique vessels such as the Miranda Class, and a shake-up in starship design, bringing about classes of tougher ships oriented more towards warfare than to peaceful exploration such as the Defiant, Akira and Sovereign Classes, an approach that saw it claim victory in the Dominion War. In other words, encounters with advanced hostile species in both the PU and Ab saw rapid developments in ship design, though in very different ways.