Spacefaring in Hollen's Prize
The beginning of the First Human Diaspora saw colony ships the size of cities, either sleeper or generation ships, hurtling into the depths of space on one-way voyages, taking years upon years to reach their intended targets. The colonists were forced to survive on their own, without aid from Earth.
Only decades after their arrival, signals streaked towards Sol, telling of success or failure.
The Warszawska-Thuringer drive saw a revolution in space flight, finally allowing vessels to travel faster than light without exceeding its speed.
How is that possible?
The Warszawska drive erects sizeable gravitic sails - a space-time distortion - in front and behind the ship, fanning out for kilometers. These sails allow the ship to capture gravity waves, and ascend into hyperspace, which has the handy attribute that a mile there equals many in the real world.
The higher the level of hyperspace, the closer everything is together; the upper levels have two disadvantages - they require wider and more efficient sails to reach, and they are more turbulent by far.
So far, ships are able to ascend up to epsilon layer - but scientists are sure there are layers beyond.
Alpha coils are required to travel hyperspace. They are huge, and impose a hard limit on the minimum size of a starfaring vessel.
In system, the Thuringer drive utilizes the smaller Beta coils to wrap the ship into a sheath of gravity, letting it to slide down a gravity well forever.
They allow the ship to reach several hundred g in acceleration - which of course is lethal to humans. This necessitated the development of inertia compensators, which provide artificial gravity, and negate the impact of acceleration on the ship's contents.
Both compensator and drive impose a limit on the ship's maximum acceleration; of those two, the compensator is most limiting. You can push your luck and step on the gas more, but the moment the compensator fails, it fails hard - exposing the crew to several hundred g of force, and turning them into a thin film of goo.
Heavy freighters can pull around 100g of acceleration; commercial ships usually make 250g, but can be much faster. Practicality imposes a limit of about 400g on the acceleration of dreadnoughts, but frigates peak at 900g.
The gravitic sheath has also massively influenced military doctrine, as it erects a gravitic anomaly above and below the ship.
*This anomaly is fairly conspicuous, thus active ships are far easier to detect than those moving by their inertia alone.
*The sheath field is practically impenetrable. Thus, ships are vulnerable from the front, the sides and especially the rear, where the sheath is wide open. But every vessel with an active gravitic drive is shielded from top and bottom. This is useful against direct-fire weapons, but missiles can navigate around the sheath halves.
Preparation for a hyperspace jump requires the ship to disengage its sheath and reconfigure the gravity field into the sail conformation.
The quality of the ship's crew, alpha coils and computer determines how long this takes.
Each star has a hyperspace limit in its gravity well, where ships can't travel to hyperspace. The heavier the star, the wider the limit.
Hyperspace is treacherous, with gravity currents, waves and storms akin to Earth's sea. Commercial shipping relies on charted safe routes, but even those do have an occasional nasty surprise.
Adventurous vessels, and most in the Fringe, rely on skilled astronavs to analyze the hyperspace ad hoc, and to guide the ship along safely. Well-crewed ships making long trips usually have a few astronavs onboard, so they can work in shifts - hyperspace piloting is a task AIs are notoriously bad at.
Ships travel at different speeds along the layers of hyperspace. Speeds are given for ships of 400g acceleration.
*Alpha layer: a light year takes a month.
*Beta layer: a light year takes ten days.
*Gamma layer: a light year takes three days.
*Delta layer: a light year takes a day.
*Epsilon layer: a light year takes 8 hours.
Not every route can be equally safely traversed at the same speed. Few ships can ever go to epsilon layer; most civilian traffic stays at gamma and below.