Ferries are the standard workhorses between the different space installations of the Tau Ceti / Valhalla system. Their drive module contains usually two robust small nuclear reactors ( Actually RTGs, which are very primitive but also very reliable ) as power generators.
The extensible spine of a ferry carries an amount of solid fuel rods which are fed from an automated system to the central drive nozzles reaction chamber. In front of the drive compartment rings of ice gets stacked before a travel, providing water ( for electrolysis - provdes O² for the solid fuel to burn as well as H² to be used in the CO² scrubbers and as fuel for the maneuver thrusters ) as radiation shielding between crew, freight and the reactors.
The Head contains the sensors as well as the navigation equipment, and can , whilst the rest of the ferry rotates to provide artifical gravity to docked habitat modules and the crew compartment, be rotated counterwise to ease navigation by providing a stable point of view. The dockable containers along the spine can be either habitable modules ( capacity of 4 to 8 persons ), shuttles or freight containers.
Legend: Orange: Communication, Control and Command Red: Rotation couplers and airlocks Yellow: Reactors, Engines, Drive Fuels Light Gray: Thrusters and main Heatsinks Green: Habitation module, hydroponics. Blue: Water tanks and radiation shielding Dark Gray: Spine and antenna booms Violets: Attached containers, 80m overall length ( 4x standard containers )
The launch rail that catapults a ferry from a space station or a habitat is a single rail that connects to anchors connected to the spine between the lower two container racks. To connect to the rail, the forward communication antennas get rotated out of the way by 90°.
Launch rails for crewed flights are usually between 15 and 60km long and provide between half and all of the needed acceleration for the main travel. Fuel ( both the rods for the main thruster as well as electrolysed Hydrogen and Oxygen for the four secondary thrusters ) is usually only expended for decelleration. For this, a Ferry locks down and rotates its thruster array to point toward its destination, and then slows down as is needed.
More detailed:
Ferries Long spindle with front cockpit, then a ring with small sleeping quarters and lounges at about 25% gravity through rotation during long-haul flight. Ring: 20m diameter and about 5m long, behind the cockpit, room for the 3 - 5 people crew.
Then spindle (Spine): Depending on the load lengthened or shortened, a pipe about 4m in diameter with a bulkhead every 10m against pressure loss. Three space containers are docked at an angle of 120 ° to the spindle. The first three containers are usually supplies, bio / hydroponic plant and additional living space for long-haul flights of more than one month. Thereafter, when assembled in the launch port, extensions of the spindle are mounted which receive additional containers. These can be further living containers for travelers, more supplies, training rooms, greenhouses, and finally the freight containers. Each container is usually 20 x 8 x 8 m, and can be accessed via a small lock on the spindle. Larger containers are 40 x 8 x 8 m and connect to two docking rings on the spindle, when they are designed to be accessible from the spine.
At the end of the spindle sits the engine capsule. There are, depending on the mission profile, one to four small RTG reactors for 2 to 40 years of mission time. Radiation is blocked by annular tanks between the reactors and the cargo. Maneuver fuel is water, which serves as a shield and is divided by the reactors by electrolysis into hydrogen and oxygen. Central, for the braking phase, is the main engine, which uses rubber as solid fuel and nitrous oxide as the oxidizer. The N²O for the main engine is stored in a ring of boulder shaped tanks stacked between the rearmost annular water tanks - the radiation shield and emergency drive fuel - and the auxiliary annular water tank, that is used for the consumables and athmosphere controls. The entire tank element is wrapped with a finned radiator ring which takes care of part of the excess heat from the reactors.
"I load with a dildo pure" (Put the dildo up my bum) is one of bitches jokingly used phrase that means the loading of a new rod rubber in the main engine. The main engine is primarily used to decelerate from cruising speed, and sometimes, if the starting port does not have sufficient accelerator catapult (smaller asteroid stations) also to increase the cruising speed.
After reaching cruising speed, the main engines are stopped and the ferry is set in slow rotation to generate artificial gravity inside. Usually only about 25 to 33% of the earth's gravity. Long-range missions often receive sheet metal cladding over the supply and residential containers for added protection against radiation and micrometeorites. The remaining open spaces are filled with Pykrete, a mixture of water ice and wood pulp. The wood pulp is often genauso valuable - from the point of view of habitats - as the ferry itself, as biomass has a higher commercial value than metals.
Alternatively, for travels into higher risk areas, a meshwire framework is pulled over the entire ships length, leaving only the three large heatsink-fins on the engine module and half of the finned ring around the rear tanks and the cockpit free. There is left enough space between the meshwire frame and the habitation module that it can remain rotating. Then there is crushed ice mixed with wood pulp filled into the mesh frame and finally water sprayed over the entire mesh to fill in the cracks and freeze the mesh frame into one solid ice shell. Before the thus equipped ferry is loaded onto the launch catapult, it receives an armor plate onto the forward opening of its ice jacket, which gets connected to the ships rigid parts, linking the shields cameras and radars to the ferries systems. In case of damage to the shields systems, the ferry can raise its own systems, melting them through the surrounding ice jacket.
