The Prometheus-class freighters were designed during the period of stable galactic trade before the great expansion. They were used extensively throughout Alliance areas as a reliable and safe method of cargo delivery.

The most famous of the Prometheus-class was the Pegasus, which was used by a group of explorers to visit uncharted regions beyond the rim in the first 10-year mission that kicked off the great expansion. The Pegasus was a third-generation Promethus-class freighter with minor improvements but the same basic structure.

Because the Prometheus-class was developed during a period of great stability, it had limited weaponry, but could survive aggression through a unique built-in ten-fold redundancy that allowed the ship to break into up to 10 pieces. This would make it hard for a single aggressor to target the ship, and even if one or two of the pieces were destroyed, the majority of the ship could survive to reunite and continue the voyage.

It was this feature that prompted the explorers to choose the Pegasus for their exploratory mission.

Very few Prometheus-class vessels still survive. The Prometheus itself has eight of its ten units preserved in the Space Freighter Museum on Terra, though most engine parts and much of the guidance systems were scavenged for other ships before the museum took possession.

The Pegasus is the only completely intact freighter of its kind, still technically in service at the Ionian shipyards, but in essence, not more than a tourist destination. Its engines power up but it is no longer considered safe to fly.

Beyond these two vessels, five of the units of the Proteus, the first official first-generation ship (Prometheus considered a prototype) exist at the Centauri Station History Museum. Three units of the Palau (a third-generation ship) are preserved at the Smithsonian on Terra. An estimated 17 single units of various freighters still exist in smaller museums, or in some cases as operating local shuttles.

Prometheus-class architecture
The freighter strung together 10 separable units in series. From outside, the ship appeared as a long 10-segment single ship. A central unit (exact position depended on the generation and could be customised) served as the main bridge and command center. Two more units, usually at either side, served as barracks. The remaining units were devoted to cargo space, though the unused space in the Bridge and Habitation Units could also carry cargo.

Each non-bridge unit had a small command center with space for Navigation, Ops, Engineering, and Tactics. These would be used to fly the units when separated from the bridge unit. Each non-habitation unit had a compressed habitation area that could unfold to a larger habitation area. Each unit also had its own engine, life support, fluids, etc. The entire freighter was equipped with light weaponry, which could be customised to be distributed equally among the units, or concentrated in the bridge unit.

The engine crystals ran in series throughout the ship. Every unit could house both a central drive crystal and a smaller supplemental crystal. They all worked in series to relay propulsion through the ship until they vented out the aft unit. A freighter’s chief engineers could choose to put central drives in each unit, but few could afford the expense. More commonly, a central drive would be placed in a cargo unit dubbed the Engine unit. The other units would carry supplemental crystals. A unit with a supplemental crystal could fly for 4 months before needing replenishment. A central crystal could carry a single unit almost indefinitely.

Along with propulsion, fluids, other fuels, exhausts, and life support ran in a series of closeable piping throughout the ship. At the junctions between the units, all pipes could be matched to the next unit or redirected back through an auxiliary system within the unit. Each unit also had emergency stores, hydroponics capability and other essential life support.

Separation protocols
To be viable as a defense mechanism, separation had to be fast and flexible. On the mechanical side, a sheet-wall system could close off propulsion and fluids and redirect them within the units contained systems in less than 10 seconds. Electromagnets forced mechanical couplings aside in under 10 seconds. Generally given the command to separate, the units could disengage from one another and fly significant distances apart in under 30 seconds.

The more difficult part of separation was the personnel aspect. All units were connected by a five-lane conveyor. The lanes closest to the deck moved slowly but each lane closer to the hull moved twice as fast as the one before it. The fifth lane moved at a breakneck speed to provide fast transport. Protocol called for all units to have personnel trained in piloting and engineering stationed within them at all times. In addition, tactical and ops officers were to be no more than two units away from assigned units. They had less than 20 seconds after an alarm to whip down the conveyor to their unit before separation.

Captains of Prometheus-class freighters could choose to separate into all 10 units or smaller amounts of multiple units, known as segments. The most common use of this function was not in defense, but for delivery efficiency. When entering a system, the captain might order the freighter broken into three segments, with each segment delivering goods to a different destination. The segments would then return to an agreed on port to reunite after all deliveries were made.

Defensive moves
The most successful use of the Prometheus-class separation feature as a defense mechanism was by the Pegasus. Even before their famous ten-year mission, the Pegasus crew was well-known as the best-trained in separation protocol. They took pride in a 15-second separation time, even for crew. This high level was necessary because of the more dangerous deliveries the Pegasus took. During its ten-year mission, the Pegasus developed this protocol to an astounding efficiency. Between crew training and engineering improvements, the Pegasus achieved 10-second separation on a few occasions.

Most Prometheus-class freighters were not this well trained and separation was usually achieved in the 40-second range. This accounted for the high level of unit loss when freighters were attacked. While this may seem disappointing, before the Prometheus-class, freighters had a 10% survival rate after pirate attack. With the Prometheus-class freighter, you could sacrifice units and still deliver the majority of the cargo, which was a vast improvement over total loss of a ship. Survival rate of pirate attack improved to 70% overall and 90% among Prometheus-class vessels.

The decline of Prometheus-class
After the great expansion, freighter companies began to favor heavily armed, faster single freighters over the Prometheus-class. The separable unit feature still survives in some freighters ability to separate into three or four pieces on short notice, but the engine and armament requirements prevent modern freighters from having the flexibility and speed of separation the Prometheus-class had.

The last Prometheus-class vessel to engage in an actual cargo run is thought to be the Pegasus delivering medical supplies to Orgon VI.