For the first sixty years of the Federation's existence, all of Starfleet's logistical needs were handled by the cargo services of the member worlds. As trade and commerce was usually more important to these worlds than warfare or even exploration, their cargo fleets were the largest the worlds possessed. These ships were contracted by the Federation to carry whatever was needed to wherever it was needed.
These ships, however, were unarmed and mostly much slower, less technologically sophisticated, and certainly less protected, than their Starfleet counterparts. With their low warp speeds the journey between destinations was very much still a long-term affair and as such the majority of these vessels were family-run.
Even with the advancing of technology through the late 22nd Century and into the 23rd, Federation expansion and growth was still slow. With no appreciable threat beyond opportunistic pirates there was no need for faster transports. While it was still dangerous for their crews, even mounting as much weaponry on these old freighters as their engines could power up was not enough to dissuade a raider, and Starfleet patrols were usually enough to deter or rescue them if they got into trouble.
This attitude changed in 2218 with the escalation in hostilities with the Klingons. While obviously encountered nearer their space, the Klingons had previously dismissed the Earthers as beneath their notice and their Federation as a purely political construct with no depth or real ties of alliance between their member worlds. As such, any "Earther" vessel encountered was treated as the Klingons treated any other minor world: with high-handed arrogance and un-moderated disdain and belligerence.
With the turn of Earth's 23rd Century T.C.E. and in light of the Federation's steady expansion, the Klingons reassessed this still-toddling political alliance and rated it slightly higher: that of a potential enemy. As such, the Klingons began to actively harass Federation colonies and shipping and confront Starfleet vessels.
With Federation shipping being raided and sometimes blatantly captured, Starfleet was forced into a defensive stance providing escort ships for civilian vessels in ever-more dangerous space. This took them from their primary missions of exploration and planetary defence.
With incidents escalating in frequency and danger over the years, it became clear that there were no-go zones for un-escorted transport vessels. Shipping was diverted away from these areas into Starfleet-patrolled space-lanes where possible, but the colony worlds and outposts within these zones still needed passenger services, supplies, and trade.
By the late 2220s Starfleet had taken to appropriating standard cargo ships and freighters out of the star yards and completing them with Starfleet-level shielding, navigational systems, and warp engines. Limited defensive weaponry was also fitted, to a level consistent with the ship's warp reactor rating. As these uprated vessels were also now crewed by Starfleet personnel, they were the start of Starfleet's own logistical fleet. Indeed, Starfleet Transport Command was officially incorporated in 2230 to administer this new fleet division.
While these measures were effective in reducing the risk that civilian cargo crews were exposed to, re-appropriating civilian cargo ship hulls off the slipways for ad-hoc, hodge-podge uprating was very definitely a temporary, stop-gap measure. By the late 2230s the Klingons were still not letting up and it was clear that Starfleet would benefit from a dedicated class of logistical transport vessel.
A quick and simple solution was designed, in the shape of the Sherman and Independence classes of light tansports. These small ships were dedicated to bulk and general purpose cargo respectively. Simple, standardised construction to almost commercial standards, coupled with uncomplicated flight control systems and extremely limited tactical systems ensured their rapid construction, and their numbers grew quickly over a small span of years. Shermans were used all over the Federation to transport fuels, liquids, grains, and other like commodities whereas the Independences were loaded up with small products carried in the standard cargo crates of the last hundred years.
These ships, mounting Starfleet propulsion technology from the start, instantly doubled the current top speed and shielding level of civilian freighters. Housing small crews solely to operate the ship, they carried no auxiliary craft and had no dedicated logistical staff, merely seconded starship-qualified crew from "Starfleet proper". All logistical work was done at their destinations by the staff there.
However, these ships were small, both in crew, size, and cargo capacity. Often, to transport sufficient amounts of their cargo, several ships had to be used and travelled in convoy to their destination. In these instances they were invariably escorted by a much larger vessel than their value warranted, in case a smaller vessel could not safely protect and shepherd all of them to their destination. A popular tactic of the more bold raiders was to knock off one transport and make no attempt at the others, offering the escort a dilemma: stay with the greater number, or rescue the straggler?
Over the next decade of their operation it was clear once agan that a larger, faster transport was needed. The next problem was: what should it be designed to carry?
With the introduction of the entire planned run of one hundred and forty (140) vessels from 2250 to 2264, concurrent with cargo pods being built in their hundreds, the Ptolemy class was well received in service. Their crews praised them for their reliability, durability, rugged toughness, and their creature comforts. The Federation Merchant Marine ship masters and their private sector compatriots gave thanks for their introduction as it pulled them off the most dangerous runs and risky duties. In this manner they served ably and with distinction – in logistics circles, anyway – for twenty years from their introduction. Losses were low and productivity was very high.
With the last of their number being introduced a short span of years before the first practical installation of New Technology aboard starships, it was clear after that point that the pace of technology was leaving them behind; ships just five years old were beginning to become outdated. Not obsolete, merely "old-style". While the front-line ships of the Star Fleet underwent massive refits to all systems internal and external, brought about by the development and introduction of the linear warp drive, the ships of the Ptolemy class - much like the ships of the Achernar sub-class of the classic Constitution heavy cruiser were considered conversely too new to bring them back in for uprating. Furthermore, in the case of the Ptolemy class, it was determined that the logistical ships had no need of such massive upgrades.
Indeed, so heavily used and relied upon were the Ptolemy class that pulling one off active duty for what was projected at an eight-to-ten-month uprating was to create a major disruption in Fleet logistics. To do this for even half the class of 140 ships was not realistic. It was further determined that while uprating an existing tug would take a year less than constructing a new one to modern specifications, the benefit returned from saving that time and those resources was not with the investment nor the disruption in service this would cause with civilians contracted to do the least dangerous work and the tug fleet itself re-deployed to cover the gaps for the length of time foreseen.
In fact, contrary to the argument for new cruisers vs. uprated old cruisers, it was actually more sensible and resource-savvy to build new ships to the latest specifications than to take an existing ship off of active duty for a year of uprating.
Further, there was another, more down-to-earth reason for not uprating the transport/tug fleet: it simply wasn't necessary. Much like Terra's Lockheed C-130 Hercules transport aircraft of that planet's 20th and 21st Century, he Ptolemy class was perfectly suited to its role. Again, much like the C-130, the only reasonable improvements that could be made were more modern flight control and operations systems, and more powerful engines.
Looking at the Ptolemy class with the same eye, it was successfully argued in 2270 that warp six or eight were still sufficient for her cargo delivery schedules, so introducing engines capable of warp ten or twelve (Original Cochrane Units) was simply not needed. Especially in the light that all current and projected linear nacelle production capacity being needed for the front-line starship uprating. Without that need for speed, there was also no need of the massive hull reconfiguration that the cruisers and escorts were currently undergoing to accommodate the intermix shaft arrangement necessary for the linear warp nacelles.
This argument successfully made, the Ptolemy class ships retained their original, "Classic" look and a new class of transport/tug was indeed designed and introduced. Based on the middle ground of the New Technology advances, and in fact almost completely duplicating the Ptolemy's eminently suited layout, the new Ragnok class began entering service in 2273 for a projected run of a further one hundred (100) units.
During the late-2270s however, with the LN-64-powered Enterprise attaining warp twelve and the LN-60-powered Constitution and Ragnok reaching warp eleven, it was decided that a minor updating of the Ptolemys was a desirable outcome.
Already proceeding was a similar minor uprating of members of the Achernar sub-class to the new Endeavour sub-class specifications. This involved a new bridge module, main sensor & deflector dish, and the new specially-designed "Fleetwing" LN-52 Self-Contained, Non-Networked linear warp nacelles. These new engines duplicated the circumferential warp nacelles' built-in power-generation capabilities thereby negating the need for the placing of intermix shafts throughout the ship, and thus a rebuild. With additional bracing and reinforcement at key hull joins and stress locations, these nacelles allowed the ships to reach speeds up to the structural limits of their earlier hull construction.
With this development, and with sufficient numbers of the new Ragnok class able to take up any slack from Ptolemys going out of service, their uprating was now possible and the venerable workhorses of the Starfleet could be afforded some rest and recuperation.
Starting in mid-2278, uprating was scheduled for Ptolemys coming off their latest transport runs. Taking approximately three-to-five weeks, it would include:
With over 130 members of the class still in service, and the new Ragnok class still itself in production, it was probable (and indeed came to pass) that not all vessels of the class would receive this uprating. Those that did received increased service longevity and the ability to cruise at warp eight like their brand new Ragnok-class cousins, though their absolute maximum velocity was limited to warp ten, on pain of imminent structural failure for breaching it.
So while the successor Ragnok class is now at the forefront of Starfleet's logistical efforts, the Doppler sub-class is still never far behind them, and scores of "Classic" Ptolemys can still be found plying their trade along the Federation's space lanes.
In this manner, all three generations of this classic design continue to serve the logistical needs of an ever-growing United Federation of Planets and its Star Fleet.
2218
Klingons reassess the steadily expanding Federation and see it as a potential threat. Active harassment of Starfleet and Federation border colonies begins in earnest.
2225
The need for Starfleet-crewed transports in the danger zones becomes apparent. Starfleet begins appropriating commercial freighter hulls from the yards and completes them outfitted with Starfleet-level technology in shielding and engines.
2230
The threat level has only increased. Starfleet designs and introduces the Sherman and Independence classes of protected transports. These small, medium-speed general cargo ships are successful in taking civilian ships off the most dangerous runs, but still require dedicated escorts.
Starfleet Transport Command – later known as LogFleet – is incorporated to administer this new division's responsibilities.
2241
The Klingon attack on the Archanis IV colony starts the Four Years War with the Empire.
2245
The end of the Four Years War with the Battle of Axanar ending in a massive defeat for the Empire.
2246
The ease with which the Klingons disrupted Federation commerce and trade during the war brought home how vulnerable such links were. Added to the inflexibility of the current Starfleet protected transports, the need for a fast, armed, multi-purpose transport was revealed. Requirements gathering and preliminary design work began.
2247
Based on these requirements, famed designer Franz Joseph invents the cargo pod system of modular external cargo holds.
Design work begins on a tug unit to tow these pods.
2248
Design work is finalised on the tug unit. Due to the simplicity of its design and its use of tried and trusted components, approval for a class is given. Construction contracts are given to fifteen (15) shipyards around the Federation for a class run of an unprecedented one hundred and forty (140) units.
Similarly, the five (5) initial cargo pod designs are put into production.
2250
The Ptolemy-class (TT 3801) Transport/Tug enters service.
2264
The last Ptolemy-class (TT 3940) Transport/Tug U.S.S. Von Maanen enters service.
2267
The Organian Peace Treaty between the Federation and Empire is signed and enforced.
2268
Phase II technology begins to be installed in new-build vessels.
2270
Linear Warp technology begins to be installed in new-build vessels.
New Technology uprating is deemed unnecessary for the Ptolemy class; it is simpler to build a new class to the latest specs. With the demand for these ships high, and with the peace with the Klingons, appropriations are given for a modern class of transport/tug.
2271
The new class of transport/tug, named "Ragnok" – after a Tellarite engineer who was famed for getting projects completed efficiently and on time – has been designed and construction begun, for an expected run of one hundred (100) units. Using exactly the same layout as the Ptolemy class merely in Phase II/New Technology components, the ships are quickly and easily constructed.
2273
The Ragnok-class (TT 4000) Transport/Tug enters service.
2277
With sufficient numbers of Ragnok-class ships in service, the Ptolemy class is given the go-ahead to undergo partial uprating to boost their speed and upgrade their flight control systems. Tugs completing their current missions will be brought in for a three-week uprating. The uprating will mirror that of the Endeavour sub-class of heavy cruisers, including the installation of Tikopai-style bridge modules, Achernar-style increased deflector grid coverage for the primary hull, "Fleetwing" LN-52 Self-Contained Non-Networked (SCNN) linear warp nacelles and their new pylon configuration, and specifically-targeted hull reinforcement to handle the higher warp-speed stresses.
2278
The first ships of the hybridised "Phase II Uprated" Ptolemy sub-class enters service.
2282
The last Ragnok-class (TT 4099) Transport/Tug U.S.S. Flying Scotsman enters service.