Slipspace

Slipspace, formally known as Slipstream space or Shaw-Fujikawa space, is a paradimensional realm consisting of 11 hyperspatial dimensions adjoining our "normal" spacetime of 3+1 dimensions. These extra dimensions allow a slipspace-capable spacecraft to travel in "directions" that do not exist in normal space, considerably shortening travel times. Thus, while it is sometimes colloquially referred to as such, slipspace is not in itself an "alternate dimension", but instead a bundle of them. While slipspace and its associated phenomena can be modeled and predicted with some degree of accuracy, there are always vagaries and anomalies that defy the standard models and continue to befuddle even smart AIs; it has additionally been postulated that humans (or any sapients with a comparable cognitive capacity) will never be able to fully comprehend slipspace.

Slipspace routes
A slipspace route, or sliplane, is a path through the interstices of slipstream space that connects two definite points in normal space. There may be an infinite number of potential sliplanes between two points in space, but only some of these can be feasibly accessed. The number of potential jump paths depends on the level of technology available, from the capacity of the drive to the computing power of the navigation interface. Notably, the shortest distance in realspace terms is not always the fastest one, owing to the non-Euclidean geometry of slipspace. Particularly efficient lanes are colloquially referred to as "eddies" or "currents". Like currents, many slipspace lanes are also more effective in one direction than the other: there may be multiple days' variance in travel speeds depending on which way a sliplane is being traversed.

Well-trodden slipspace lanes are (literally) a two-way street. On one hand, using established, well-optimized routes reduces the strain and power consumption of a drive, and in ideal conditions results in a speedy, comfortable journey. However, with the volumes of traffic experienced even by the Covenant in their key sliplanes, slipspace congestion due to the buildup of reconciliation debt already starts to become an issue; due to this, seasoned spacers often seek out less-known "shortcuts" outside the beaten path. Within the Covenant, the calculations for some regional routes were closely-guarded secrets hoarded by merchant guilds, families, or martial orders, and there are secret routes known only to pirates and rogues as well. Such routes may sometimes also present elements of risk unacceptable to the general population, but usually also carry hefty rewards in terms of speed and power expenditure.

Trailblazing -- traveling to uncharted space without established routes -- is no easy task, and always requires a proper navigator or navigation computer. Even then travel is slower and less predictable than along set routes, with a higher risk of running into anomalies. Having an experienced navigator can make any journey considerably faster as well as more reliable, though trips along well-established lanes tend to be fairly constant in speeds as the optimum calculations have been discovered and refined already.

Jump points and transit nodes
A transit points or interstellar jump point (IJP) is a formally identified volume of space, typically within a star system, that provides an established entry point for one or more charted sliplanes. It should be noted that slipspace can be accessed outside such definite points, but such "blind" jumps are subject to the limitations and challenges experienced when traveling outside pre-defined routes.

Since gravity's effects on the curvature of slipspace are both dramatic and unpredictable, optimal transit points are found some distance away from local gravity wells where the effects of astronomical bodies on the curvature of space-time are reduced. The typical transit points are located in major Lagrangian points or as far as the outskirts of a star system to minimize the gravitational interference of the local star. While superior drive systems such as those of the Covenant or Forerunners can compensate for these effects somewhat, enabling them to jump relatively close to planetary bodies (under the right conditions, even in atmosphere), human ships have historically been far more sensitive. Early on, this meant that a considerable portion of an interstellar journey might be spent at sublight velocities, traveling to the local transit point. Using a smart AI to perform the jump calculations can compensate for some of the gravitational effects, enabling ships to jump further away from optimum transit points.

A single system might include multiple transit points, which do not always link to the same destinations. As they are largely determined by gravitational interactions, transit points also change over time, and can even become unavailable when the local planets change alignments. Historically, this has meant that some systems have been effectively inaccessible for certain times of a year, as travel to those systems became considerably more taxing outside a relatively narrow time window. This also happens on larger scales along the millennia: as the stars themselves move, along with other interstellar objects such as molecular clouds, slipspace routes eventually diminish and die out, while new pathways are opened elsewhere.

Transit nodes are particularly advantageous IJPs that exist in intersections of efficient slipspace lanes, providing natural ingress and egress points for slipspace jumps. Sol, for example, is not a particularly efficient system for transiting to the greater human sphere, but provides a decent jump point to Epsilon Eridani, which, in turn, is a transit node system with efficient sliplanes opening up to nearly ten systems.

IJPs and transit nodes are most commonly limited to a specific volume either within or without a system; nodes deep in interstellar space can pose some logistical challenges especially when large amounts of traffic are concerned. Such nodes usually require one extra jump into the nearest viable system for a refueling and service port.

Navigating Slipspace
Slipspace navigation is a very peculiar science, one heavily reliant on almost impossibly complex higher-dimensional calculations. However, successfully plotting a jump is not simply about raw number-crunching but benefits from some level of intuition and creativity. Charting out slipspace routes and finding advantageous currents, IJPs or transit nodes is far from an easy task; one of the many counterintuitive aspects of slipspace travel is that the the geometry therein does not strictly correspond to realspace. Proximity or distance altogether have only partial relevance to the length of a journey, though some correlation between realspace and slipspace is apparent on the level of orders of magnitude. A seasoned navigator will be able to recognize patterns and trends in the features of slipspace that would go unnoticed by a novice or even a navigation computer, and it is this reliance on pattern recognition that keeps organic navigators relevant.

The gravity of masses in realspace and the resulting curvature of space-time is one of the most obvious points of intersection between normal space and slipspace, and the primary means by which the geometry of slipspace can be observed and mapped. While objects' gravity wells create distortions within the skein of the slipstream's higher-dimensional spacetime, those objects themselves are not tangible to ships traveling in slipspace; thus, a ship may pass "through" a planet while in slipspace as it is only present as a gravitational "shadow". However, particularly strong distortions, such as those created by massive stars, pulsars or black holes can create inescapable "pits" within the fabric of slipspace that unwary ships can be drawn into, while not affecting the object itself in realspace.

The interaction between gravity and the topology of slipspace also occurs on very subtle levels. For example, variances in the density of the interstellar medium affect the smoothness and even length of a slipspace passage, and early Shaw-Fujikawa drives in particular would often experience various accidents as the navigators failed to calibrate them to changes in local ISM density. This was one of the earliest hurdles with slipspace travel, as experimental ships would be abruptly jolted out of slip as they encountered the ripple caused by the Heliopause at the edge of the Sol system. Modern drives are largely able to perform such calibrations automatically, but strong changes in density such as molecular clouds can still require manual calibrations. Consequently, most slipspace routes are planned in such a way that they pass through as few ISM variances as possible, and dense molecular clouds and nebulae are marked as potential navigation hazards.

Because gravity wells cast "shadows" in slipspace that interact with one another and draw those locations "closer", large regions of starless space are both slower to cross and more challenging to navigate than those where stars and other major gravitational bodies are found in abundance. This is what makes the gulfs between galactic spiral arms and particularly the extragalactic void difficult to traverse.

Because of their limited use of AI and automation, the Covenant's use of slipspace is not as efficient as it could potentially be with the hardware available to them. Their drives are mechanically capable of longer jumps, but their reliance solely on biological navigators and stripped-down navigation computers imposes a considerable disadvantage. This is most clearly demonstrated by instances where the Covenant have been able to use Forerunner navigation devices, which have enabled jumps tens of times longer and faster than usually possible. Some biological beings, namely select breeds of Lekgolo computer-forms, are capable of offsetting this effect somewhat, and it is such computer-forms that are the most valued navigators within the Covenant.

These peculiarities also shaped the way the Covenant expanded. Humanity's interstellar expansion occurred almost system-by-system, with routes painstakingly calculated to optimum efficiency by AIs (often entire super-AI networks), which resulted in a densely inhabited core sphere. Meanwhile, the Covenant were considerably more at the mercy of the vagaries of slipspace and thus primarily relied on slipspace pathways most accessible to their drive technology, leading to their colonies being scattered in clusters across massive swathes of space.

Navigation beacons
Artificial beacons can also be used to ease point-to-point slipspace navigation. The Covenant used such beacons to facilitate traffic throughout their Arterial Network as well as Human-Covenant War-era invasion corridors. The Covenant's beacons also have have a stabilizing effect on local slipspace, achieved through the use of mediating crystal lattices similar to their Borer drives. During the Covenant War, the UNSC managed to reverse-engineer a rudimentary version of the technology from Covenant sources. These nav beacons were initially used to coordinate the operations of Naval battlegroups, though in the Phoenix Initiative era, they have found use in marking routes between colonies.

Kelguids
The kelguid is a Covenant navigation device reverse-engineered from a Forerunner equivalent. It abstracts the hyperspacial topology of slipspace into an easily understandable and navigable holographic format, mapping out gravity wells' "shadows" in slipspace, which a navigator can then interpret -- in conjunction with other nav data -- to plot journeys; a kelguid without a skilled reader is not much help. Humans also have corresponding charting devices, but their range, resolution or ability to parse complex hyperspacial phenomena into a readable form are nowhere near that of Covenant kelguids.

During the Human-Covenant War, the Covenant's high-resolution kelguids and powerful drives actually made it more difficult for them to find human worlds. This was due to the sheer number of jump trajectories available to them, coupled with them being functionally locked to higher "layers" of slipspace than their human counterparts. Where human navigation devices would show only a handful of optimum pathways to and from a given system, which largely defined the commercial slipspace corridors in human space, a Covenant kelguid might chart out dozens of potential slipspace pathways. This meant that Covenant navigators had many more sliplanes to choose from, and without the ability to dial down the devices' resolution, all they really could do is check every potential system along the available jump paths. However, this abundance of options was also a definite strategic boon to the Covenant. Using higher slipspace lanes, Covenant fleets would frequently bypass multiple systems of UNSC defenses and might suddenly emerge dozens of light-years inward from where they were last encountered. This inherent unpredictability effectively forced the UNSC to rethink their defensive strategy, as fixed fortresses along the sliplanes known to humanity were no longer useful.

Wayfinders
Forerunner Wayfinders are essentially the precursors to the kelguid, and function similarly, though their operational range as well as resolution are much higher, too high for human or even Covenant systems to take full advantage of as their drives are not capable of navigating slipspace with such precision. Wayfinders are peculiar in that they tend to be locked into highly specific destinations; whether this is by design or simply due to the younger civilizations' inability to fully utilize them is unclear. Wayfindes are still highly sought-after, as they usually point to reliquaries or at the very least worlds with some Forerunner presence in the past. Indeed, most key reliquaries found by the Covenant were not discovered by sweeping space system by system, but through the navigation data found in intact Wayfinders. Sometimes relics were found to be too far to reach, or the nav data was corrupted or unable to be interpreted by Covenant systems. However, there have been several times when a distant reliquary has been made accessible through a hyper-efficient sliplane programmed into a Wayfinder. An example of this is the  ' s (and later High Charity's) over 20,000-LY journey to Installation 05 and back, which would otherwise have taken months and multiple separate jumps.

Shaw-Fujikawa Translight Engine
Though they come in various configurations, all human drives are fundamentally based on the same technology originally developed by T. Shaw and W. Fujikawa. Wallace Fujikawa named the exotic physics package of the first slipspace drive "CODEN", which has since come to refer to the core functional components of the drive. By 2554, there have been six major generational shifts in the SFTE, each denoted by a CODEN series number. These generations represent major advances in the precision and velocity with which the drives are able to traverse slipstream space, as well as their overall reliability and efficiency. While crude, the SFTE architecture is still quite versatile in contrast to Covenant drives.

Covenant drive types
The Covenant uses three main kinds of slipspace drive. The first design is commonly known as the Blinker, used on most Covenant ships for the first two millennia of the Covenant's existence and up until this day. Their design lineage can be traced directly to those developed natively by the Sangheili and they saw little improvement since the Writ of Union. Due to their possession of the Forerunner Dreadnought, the Reformist San'Shyuum never experienced a pressure to develop slipspace drives of their own, and thus gave their blessings to the Sangheili's native drives to be used by the Covenant at large with only minor changes being made to their design over time. The blinkers are relatively similar in operation to humanity's Shaw-Fujikawa translight engines, and only marginally more efficient.

Blinkers exist in numerous configurations and subtypes, but the two most common kinds during the last ages have been the stardrive and the jumpdrive. The former is designed for interstellar travel, while jumpdrives are smaller and used for short in-system hops. Few civilian vessels are equipped with jumpdrives due to their expense and limitations imposed on their use in many trafficked systems, and they are mostly used on warcraft. Beyond these major types, there are numerous variations by different manufacturers and traditions with their own quirks and specifications.

The second major type is the Borer; essentially a bastardized version of a Forerunner drive. Although some early ages of the Covenant's High Antiquity had seen the development of a handful of ships with vaguely Borer-like drives, it was not until the careful study of Zhoist's Ten Cities of Edification that the Covenant managed to engineer an industrially-reproducible version of the technology. This breakthrough also had major ramifications on Covenant expansion, exploration, and the re-centralization of political power, coinciding with the Second Illumination. While nowhere near the speed or efficiency of an actual Forerunner slipspace drive, the Borers are still approximately ten times as powerful as traditional blinker drives. Like Forerunner drives, Borers use quantum-engineered crystal cores (coupled with esoteric field shaping techniques) to mediate slipspace, but like the drives themselves, they are merely a pale imitation of their Forerunner progenitors. These synthetic crystalline lattices, known as "Modulation matrices", are only created on High Charity; with the holy city's fall, the secret to their manufacture is assumed to be lost. Borers are also very sensitive devices, and require deft fine-tuning to function at their peak efficiency. It is also evident that Borers' limitations are partly due to their relatively poor optimization, owing largely to the Covenant's lack of AI navigators and various imperfections in the navigation interface, most of which could likely be fixed with relative ease by a smart AI.

By the latest ages of the Covenant, virtually all Ministerial warships and other key vessels were equipped with borers, and it was this innovation that ended the Long Discord, a prolonged era of splintering and strife across the Covenant Empire. However, blinkers remain in widespread use throughout the Holy Ecumene on most civilian vessels and in some local patrol fleets. As the use of Borers was so heavily tied with political power, and because of their holy origins, they are firmly in the realm of entrusted technology. However, in recent centuries, certain patterns of Borers have also began to circulate among the more wealthy citizens of the Covenant. As of the 9th Age of Reclamation, it can be estimated that less than 30% of all ships within the Covenant meta-civilization are equipped with borers, with the rest utilizing blinker drives.

The final type are actual Forerunner drives, pilfered from various artifact sites over the ages. Prior to the advent of the Borer drive, Forerunner drives provided the Covenant's only means of "fast" slipspace travel. They remain exceedingly rare, with their numbers estimated to be in the low hundreds, and mounted only on the most valuable of Covenant ships; the Hierarchs' personal vessels, Ministry courier ships, specifically blessed explorer craft, and the flagships of major armadas. Key flagships with Forerunner engines are known as ploughships, and can drag entire fleets in their wake across hundreds of light-years. As a drawback, such holy drives can be capricious and are susceptible to interference by intact Forerunner systems. As well, although an order of magnitude more powerful than the standard borer, it is estimated that even the Covenant cannot use these drives to their full potential.

Slipspace velocities
The first point about understanding velocities in slipspace is that the concepts of velocity or acceleration do not exist in slipspace, not as such. A large part of what is understood as slipspace velocity — the realspace time elapsed during a point-to-point journey — is dependent on the mechanical capabilities of the slipspace drive and navigation system (as well as the interface between the two), the computing power available, the skill of the navigator, and the topology of slipspace along that journey. While less intuitive to a layperson, it is thus more accurate to speak of slipspace "efficiencies" than velocities.

The capabilities and limitations of a slipspace-capable vessel are largely dependent on the "resolution" with which the drive and its navigation system are able to parse the fractal dimensions of slipspace; much like a high-resolution photograph allows one to zoom in without as much loss of detail. Another common analogy is visualizing slipspace as an infinite Russian Matryoshka doll, with each smaller figure representing a more efficient, higher "layer" of slipspace. The more advanced the drive, the "deeper" a ship is able to go. If a ship attempts to plot a course deeper than its safe operational ceiling, it risks becoming trapped within the hyper-dimensional event horizon, until the amount of energy and computing power required to escape become infinite. There are also "chasms" within certain regions of slipspace that can lead to the same outcome and are regarded as navigation hazards.

Slipspace efficiencies are sometimes colloquially measured in light-years per day, but any such measurement is bound to be inaccurate or at least vague for the aforementioned reasons. That said, some averages can be drawn from jumps along well-established routes using standard navigation systems and drive interfaces. The following lists average slipspace velocities per different drive types.

The year ranges have overlaps as they represent the periods each system remained in mainline use:
 * Shaw-Fujikawa drives
 * CODEN I (2291-2360): 0.7-5 LY/year
 * CODEN II (2356-2420): 1-4 LY/month (this breakthrough helped usher in the Domus Diaspora, as interstellar travel became considerably faster and more reliable.)
 * CODEN III (2379-2500): 1-3 LY/week (developed in response to the pressure of the Inner Colony Wars)
 * CODEN IV (2487-2550): 0.5-2 LY/day
 * CODEN V (2536-): 1-3 LY/day (mainline human speed for much of the second half of the Human-Covenant War and the early years of the post-war era)
 * CODEN VI (2554-): 5-10 LY/day (Loosely based on Covenant Blinkers acquired from Kig-Yar traders in the later years of the war, though still built within the Shaw-Fujikawa drive architecture. Not only are sixth-generation drives faster, they are also much more precise than prior UNSC drives. Coupled with modern navigation systems, this enables effective in-system "microjumps" for the first time, though nowhere near the precision enabled by Borer technology. Coden-VI drive numbers were initially limited even within the UNSC; the tech gradually percolates across the UNSC, then the civilian market, across the next two decades)
 * CODEN VII (2570s): 40-50 LY/day (The Coden-VII generation was a major overhaul of S-F systems based on Covenant Borer drive architecture, and kicked off more serious human expansion beyond the Local Bubble. Coden-VIIs are technologically inferior to pure Borers as the UNSC is as of yet incapable of perfectly synthesizing their crystalline modulation lattices, but they compensate for this with superior processing power and AI-assisted nav-computing)

In addition, by the early years of the post-war era, the UNSC managed to incorporate a small number of scavenged Covenant Borers on a handful of "keystone" vessels (following over a decade of intensive research). These were mostly deployed as battle group flagships and support vessels and used to drag their attendant task forces in the core ship's wake. These Borer-equipped vessels would serve as the fastest human starships until the advent of the Coden-VII generation.

Some of these improvements have as much to do with improvements in navigation techniques and higher-dimensional sensor capabilities as they do with the drives themselves. By the early CODEN generations, humanity had little idea of slipspace eddies or optimal transit points, let alone how to utilize them to their full effect; the notion of "rational jumps", which enable ships to "ride" slipspace currents to reach their destinations faster, only came about over a century later. Even now, the limited resolution of navigation interfaces means that fully optimized journeys remain out of reach. The holy grail of human slipspace travel, known as the Optimum Journey, is one which would utilize the best possible slipspace trajectory for a perfectly reliable transition; but only the Forerunners are suspected to have been capable of such precision.


 * Covenant drive types
 * Blinkers: 5-15 LY/day (Blinker speeds and capabilities can vary enormously between drive models, ranging from homegrown Kig-Yar drives to high-end ones manufactured by wealthy Sangheili clans.)
 * Borers: 40-60 LY/day
 * Forerunner drives: 500+ LY/day

Because of the inherent variance involved in slipspace travel, it is usually more informative to describe velocities through the time taken to traverse a specific point-to-point journey. To humanity at large, such example jumps are often that from Sol to Epsilon Eridani (4-7 days), or from one end of human-controlled space to the other along major routes (10-12 months).

What additionally affects longer interstellar journeys is the number of jumps as well as stops required for replenishing supplies, e.g. reactor coolant and consumables. The longer the jump, the more strain it tends to put on a drive, which is why slipspace routes are typically established around a chain of jumps with robust ports and supply facilities in each junction. As well, drives require constant adjustment and optimization, which can make a major difference in both safety and travel times. Moving large fleets and armadas around also takes considerably more time than single ships, as they require their own supply trains; this effect becomes even more pronounced when traveling outside pre-established routes and supply infrastructure, such as the gulf between the human and Covenant spheres; after first charting their invasion channels, the Covenant had to devote extensive amounts of resources to establishing supply operations and bases along these routes, and then to protecting these bases from counterattacks. Such considerations also define the maximum effective range of slipspace-capable craft.

Hazards
As any self-respecting higher-dimensional physicist would be quick to point out, slipspace is nothing like an ocean. However, this fact has not stopped countless generations of starfarers from cultures with a history of seagoing from comparing it to one. Like the sea, slipspace is ultimately unknowable and capricious, but can still be navigated with enough skill and experience. And like the ocean, it comes with its dangers.

Slipspace hazards come in various types and many different degrees of severity, from mere nuisances such as "slow zones" that increase travel times or strain drives considerably faster than usual, to regions of space where entire ships simply disappear. These hazards can either be natural or artificial in origin, though this distinction can be difficult to discern in the absence of conspicuous technology causing the disturbance. It has even been hypothesized that some of them may have been created by beings beyond what we understand as technology, or as aftereffects of esoteric weaponry deployed in the ancient past.

Some of the more notorious hazards are Forerunner Line installations and other slipspace interdictor systems. Even when not operating at their full power, these machines can close off tens of light-years of space from slipspace travel. These zones are not always static: an entire inhabited star cluster within the Covenant was once closed off for centuries by a partially active Forerunner slipspace jamming barge hurtling through it at relativistic speeds, only to be reopened as the craft continued along its path. Other examples of Forerunner technology may merely hinder slipspace travel or wreck havoc on sensors and drive interfaces; Covenant kelguids in particular are known to be sensitive to interference, which limits their usage in certain regions.

Slipspace anomalies can also have other treacherous effects. The temporal variance in travel times may be multiplied, with a ship arriving years, decades or even centuries after (or, in rare cases, before) it left, while its occupants experienced only the passage of a regular jump. Some slipspace routes can open up to entire labyrinths of dangerous higher-dimensional angles, trapping ships in unrecoverable fractal vortices.