Two proposed ugrades merely replace the core with the 5E3 and 5E6 versions. The 5E3 version, with the same upgrades to keep the current top speeds will free up 1 SU, while the 5E6 version will free up 5 SU. Although the improvements are minor, the ability to carry more cargo for the same amount of fuel is an important consideration.
A third proposed upgrade is to replace the existing Navigational Deflector with two to three Auxiliary Deflectors, for a total of 3-4 Auxiliary Deflectors. Using some of the saved space for additional power systems, the design can save 2 to 13 SU. Two Auxiliary Deflectors would be kept on at all times to prevent a stray electron from turning the ship inside out.
Cargo format:
Cargo handling is done by activating Auxiliary Power, transporting the selected SSC to the cargo Transporter pad, then performing whatever work is required. Hazardous/non-transportable cargo is kept at the rear of the cargo bay, right next to the massive door, for easy jettisoning in case of any problems.
The Main Cargo Bay is sixty million cubic meters, with one meter of space on the back, each side, and two meters along the top for inspection and maintenance. On the fron there is six meters of clearance to allow for sections of the cargo to be moved out to allow for physical examination of a specific container.
Cargo loading operations are performed by placing laser pointers and rangefinders along the front of the cargo block, pointing forward, to the sides, top, and bottom. By measuring the ranges, and seeing how far from the walls of the cargo hold, the ship can know to a fraction of a degree how accurate the block is to alignment inside, along with the distance to the nearest millimeter how far along the cargo block has moved and needs to be moved.
An additional 20,000 cubic meters is used, 10,000 per side, to allow for additional access to the main cargo region, and to provide Engineering space in case the tractor beams or power feeds have technical issues. Cargo cranes, grav sleds, portable tractor projectors, and other protable cargo manipulation equipment is stored in here, to make the crew's life easier. Not easy, just easier.
The remaining 1.446 million cubic meters is divided up into a large storage bay along the dorsal area of the main hull, plus a series of internal bays that run along behind the shuttle bays. The main storage bay is 833,000 cubic meters; 175 meters long, 140 meters wide, and 34 meters tall, large enough to fit a Defiant Heavy Escort inside with an average of two meters of space all atound the vessel, allowing for a shirt-sleeve environment when performing maintenance or repairs. A cargo hold taking up 33,000 cubic meters is attached at the rear of the Defiant hold, and is normally used to keep repair equipment, spare parts, and weaponry when a Defiant is being given a lift. This smaller bay is 7.6 meters long, 135 meters wide, and 32 meters tall. The sides of the bay open over the main hull's cargo bay, allwoing for easy access to transfer an SSC of spare parts to the Defiant hold, and removing an empty. This access is via a sealing door, and is normally closed. The top of the door has pressure sensors that physically prevent the door from opening if anything with a pressure of over 4 millibars, or about half the average pressure made by a human foot. It will also not open (again physical and electronic safeties) if the Defiant bay is a vacuum.
The remaining 580,000 cubic meters are divided into a pair of 280,000 cubic meter holds, stretching along the sides of the ship from the rear of each side of the wrap-around shuttle bay to nearly the nacelle pylons in the rear. The final 20,000 cubic meters is a central cargo bay that runs underneath the main hull of the ship, and above the main cargo section. Cargo is moved from the side cargo bays in the SSC it was stored in, and is unpacked here. When an SSC is emptied, the empty is put back in the side cargo bay, and another is brought on board to replace it. The doors to the side cargo bays are normally kept closed, to prevent any potential depressurization. Airlocks are provided every fifty meters to move an SSC to the interior of the ship for utilization.
Shuttlebays:
Two sets of seven bays, each holding a Size 1 shuttlepod for emergency evacuation only. They are located every 110 meters along both sides of the cargo section, and have sufficient room inside to squeeze four humanoids each. Each pod also has a display showing all hmanoids within sventy-five meters (horizontally) of the bay to ensure nobody gets left behind. As the cargo bay is only supposed to be visited by ship's crew, not any passengers, there is less need to worry about someone wandering around in there.
If an emergency happens, anyone in the cargo bay is supposed to head to the nearet shuttlebay, and get inside the shuttlepod. Once everyone within seventy-five meters is inside the shuttle, the door automatically closes (there is a manual override to do it faster), and the shuttlepod launches. From there, the tractor beams on the main hull will pick up the pod and guide it into an empty slot. If there are too many pods to pick up, empty onesa re jettisoned or moved to the cargo bay to make room.
The entrances to the shuttlebays are painted with a variety of symbols and glowpaint so in the case of total loss of power and lighting people will know which way to go. The midpoint betwen each shuttle is also painted with the same materials, just different colors and symbols so people know which way not to go. The catwalks around the cargo bay have slides that can be triggered in case of emergency, and are powered by pressurized air, so even without power they still work.
The forward shuttle bay is wrapped around the front of the main hull of the freighter, and has the capacity for 11 Size of shuttles. There is a walkway below the brridge so anyone moving along that walkway can look over the shuttle bay to see the current status.
Standard cargo shuttles are the type 10, modified so they only carry the bare minimum of materials, and as much cargo capacity as possible. This allows two SSC to fit inside, and by installing tractor beams ventrally (and the associated Auxiliary reactors), more SSC can be carried underneath.
The cargo transporter is never used to transport cargo up for the block, as even moving one SSC every 5 seconds, it would take about three and a half months. If extra cargo transporters are available that can handle 8 ton loads this will reduce the time.