Slipspace

The Fleet of Retribution exiting slipspace above Installation 00. The clean and controlled appearance of the slipspace egress ruptures is a distinctive hallmark of borer-type drives, owing to their surgical precision. Prior to the newer generations, the ruptures of Shaw-Fujikawa drives were much more chaotic in both operation and outward manifestation, appearing more like holes torn into space-time than surgically clean cuts.

Slipspace, formally known as Slipstream space or Shaw-Fujikawa space, is a paradimensional realm best known for enabling faster-than-light travel and thereby much of interstellar civilization.

Overview

Slipspace is a paradimensional subdomain adjoining our physical universe or so-called "realspace" or "normal space". It consists 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 also contains the dimensional set known colloquially as wavespace, currently the only known means of faster-than-light interstellar information transmission.

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. Even if technically possible, jumping within or near the gravity wells of stars or planets presents various risks. Even if a navigator were able to make successful jump calculations and the drive were capable of handling the jump, simply escaping a gravity well in slipspace can take far longer than it would in normal space, resulting in a much longer jump duration. At worst, jumping within a gravity well may lead to the ship never escaping that well, or anomalous time-dilation effects in which the ship experiences only subjective hours or days of jump time while years or more elapse in the outside universe.

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 drift 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 have partial relevance to the length of a journey, but other factors such as slipspace currents or the proximity of large masses also factor in. The gravity wells of stars and planets cast "shadows" within slipspace that interact with one another and draw those astronomical bodies "closer" to one another, creating interconnections we know as slipspace routes. 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". This also means that slipspace-capable craft cannot be weaponized as such. 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.

Without the proximity of gravitational mass shadows, slipspace navigation systems could not function as they would be unable to get a fix on their destinations. This also makes large starless voids difficult or impossible to navigate, hindering direct travel between the galactic spiral arms and especially extragalactic space, which is virtually impossible to plot a course into due to the lack of stars and extremely low density of gas and dust. This is not merely an issue with nav systems, as the presence of matter — however diffuse — creates "traction" within the fabric of the slipstream that the slipspace drive is able to "drag" a ship along. Because of this, most slipspace travel within the galaxy happens lengthwise along the spiral arms. Consequently, galactic civilizations only expand outward in patterns approximating a symmetrical sphere until they encounter the edges of their home spiral arm, at which point they typically begin to build up along the spiral arm in an elongated pattern. Only the Forerunners were capable of navigating the extragalactic void, and even by their standards, the portals to the Ark represented an impressive technological feat.

On the other hand, unusually dense concentrations of matter, such as some dense nebulae and dust clouds also pose issues for navigation, an extreme example being the five-kiloparsec ring around the galactic core, which cannot be reliably navigated by any of the known modern civilizations.

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 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 technology

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 and outposts in the new expansion regions such as the Cygnus Verge.

Kelguids

The kelguid is a Covenant navigation device reverse-engineered from a Forerunner equivalent. It abstracts the hyperspacial topology of slipspace into a navigable holographic format, mapping out gravity wells' "shadows" in slipspace, which a biological 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. Depending on the pattern, the maximum effective range of kelguids is typically around 50-200 light years depending on the properties of the local interstellar medium and gravitational interference. Navigator skill can compensate for this, but not indefinitely, and in unknown space navigators typically prefer to perform many shorter jumps to complete a journey than risk a longer and more efficient but unreliable jump.

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

Wayfinder is the Covenant name for a Forerunner navigation computer. While the Covenant have only managed to utilize some of the functions of these devices, they are exceedingly powerful and, being holy technology, one of the few exceptions to the Covenant's statutes against advanced computation. The core use of Wayfinders is to plot more efficient slipspace pathways, particularly to faraway destinations. Most native Covenant navigation systems have a range to how far they can safely plot jumps, with the reliable range capping at 50-200 light-years. Even if the Covenant have acquired coordinates to a destination thousands or tens of thousands of light-years away, they must either navigate to that destination in a series of shorter trailblazing jumps, or feed the coordinates to a Forerunner Wayfinder, which then produces a precise jump solution - an Optimum Journey. Since such navigation solutions tap into deeper layers of slipspace with less energy expenditure, they also result in far faster jumps than those plotted with Covenant kelguids.

A good example of this is the journey to Delta Halo: by inputting the coordinate data recovered from Alpha Halo's debris field into High Charity's Wayfinder, the Covenant were able to chart a range of jump solutions from the Local Bubble to Installation 05, located around 20,000 light-years spinward where the Orion Spur branches off from the Sagittarius Arm. Many other Forerunner reliquaries were discovered by the Covenant in the past in a similar fashion: the Covenant would recover Forerunner navigation data, either directly or indirectly (e.g. by deriving coordinates from wavespace beacons), and run the data through a Wayfinder to plot an Optimum Jump. Most of the Arterial Network is also charted this way, by either High Charity or the Wayfinders on a handful of lesser worldships and ministerial vessels. Once an Arterial trunk route was established to a system, it would quickly become a hub of growth in its region of space. Only a handful of Wayfinders exist in the entire Covenant, with the most renowned ones being located on the holy city, High Charity.

Slipspace drives

Shaw-Fujikawa Translight Engines

Though they come in various configurations, all human drives are fundamentally based on the same technology originally developed by Tobias Shaw and Wallace Fujikawa. 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 2590, there had been seven 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 and retains a considerable amount of room for improvement. Attesting to this fact is the continued relevance of the core design conceived by Shaw and Fujikawa while incorporating increasingly advanced systems from non-native drives into the drive architecture in the post-war era.

Notably, each CODEN generation also encompasses various subclasses created by different manufacturers and often for different purposes. For example, the drives installed on civilian intersystem transports are far inferior in capability to those aboard warships, which are larger, more sophisticated, and benefit from a superior power generation capability. The more advanced the tech becomes, the more pronounced this intra-generational variety.

Some of these advances have as much to do with improvements in navigation techniques and higher-dimensional sensor capabilities as they do with the drives themselves. By the first and second 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.

All CODEN generations have remained in service for some time even with the development of a newer generation, with older models gradually being shifted to auxiliary and civilian roles. The final endpoint of older drives at any given time is usually on automated logistics and cargo craft for which speed is not the foremost concern. Similar to other technologies, many Outer Colony societies have continued to use drive types phased out decades earlier as they retained spare parts and/or expertise to repair them while lacking the ability to purchase top-of-the-line drives.

Prior to the fifth CODEN generation, human ships were incapable of in-system jumps and usually had to move to the system outskirts before jumping due to the warping effect the local star's and planets' gravitational pull exerts on slipspace. Additionally, precision was an issue, as the jump's exit point could only be calculated on the level of distance from the major gravitational bodies and only partially controlled; as such, ships would often emerge many AUs from the planned destination. Navigation beacons could partly control this, though this was not often feasible; another issue was that during the Human-Covenant War, beacons on major colonies had to be deactivated so as to not lead the Covenant to human worlds. Fifth-generation drives could jump into slipspace from most Lagrangian points between a star and a major planet, albeit not planets too close to the star; so often the L3, L4 and L5 Lagrange points of outlying gas giants would be favored as prime jump points. Under AI nav control, fifth-gen drives could also perform short "hops" of a few AUs, though precision remained an issue and so most captains opted for sublight in-system travel, especially with the introduction of more efficient fusion drives in the late 2540s. Introduced in the post-war era, sixth-generation Shaw-Fujikawa drives allow in-system jumps with considerably improved precision, though they too must largely utilize a system's Lagrange points to avoid gravitational interference.

One notable issue with Shaw-Fujikawa drives during the Human-Covenant War was that they reacted with radioactive materials to create large bursts of Čerenkov radiation upon entry into realspace. This made slipspace-capable nuclear missiles impractical as a concept, as the Covenant was able to easily detect their arrival and destroy them. Any prowler that also wanted to operate under complete stealth conditions needed to offload their nuclear arsenal prior to leaving slipspace. It was not until the decades that followed the conflict that specialized slipspace drives with dampening fields were introduced to counter this.

Micro slipspace drives

In the 26th century, Shaw-Fujikawa drives had finally matured to the point where the UNSC was able to miniaturize the technology for cutters, subprowlers, and later space fighters. These micro slipspace drives are substantially smaller and more compact, and are particularly adept at navigating gravity fields and currents that are too dangerous for much larger vessels to traverse, although they still require a minimum distance from an astronomical body before they can be activated and cannot be used in atmosphere. As most vehicles they are mounted on lack the reactor output to keep them powered during use, many are built to use pre-charged batteries and capacitors that gives them a limited usage time. Generally, they are used more for tactical in-system maneuvers than travel, either to allow a ship to escape their pursuers or to strike at multiple targets separated by large distances.

Although more compact than regular Shaw-Fujikawa drives, micro-engines of this type come with a list of deficiencies that prevent them from being adopted en masse by the UNSC, not just their extraordinarily high cost. Micro-engines are far slower than true slipspace drives, and their limited travel time meant that they were only viable for jumping around a star system. While miniaturized drives tend to be more tolerant of gravity wells, they are routinely exposed to greater stress, and must be tuned or completely rebuilt after each mission. The last major issue is that micro slipspace drives often require external components or modifications to guarantee safety. Early models were so complex that they were reliant on an AI for consistent operation, and even after the launch of the CODEN-V and CODEN-VI, fighters still had to be designed to withstand the gravitational forces involved with transitioning between realspace and slipspace.

Covenant drive types

The Covenant use three main types of slipspace drive.

Blinkers

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 such as some models of gunboat and space fighter. Beyond these major types, there are numerous variations by different manufacturers and traditions with their own quirks and specifications. Compared to human drives, blinker types represent an eclectic gamut from Coden-III to VI in terms of speed, range and precision.

Borers

The second major type of Covenant drive is the Borer, essentially a bastardized version of a Forerunner drive. Like Forerunner drives, Borers use quantum-engineered crystal cores coupled with esoteric field shaping techniques to mediate slipspace around them, 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. Borers are remarkably precise, capable of pinpoint in-system jumps and even slipspace transitions to and from a planet's atmosphere, though this requires the use of special navigation devices.

Although the core design of the Borer dates back to the Covenant's High Antiquity, Borers were not easily reproducible for over a millennium due to the difficulty of sourcing the material for their modulation matrices. These essentially had to be scavenged from Forerunner relics, where they served various purposes. The crystals' quality was also variable; by Forerunner standards, many of the crystals found by the Covenant may have been regarded as defective or perhaps discarded after being spent over continued use. As a result, Borers remained rare until the careful study of Zhoist's Ten Cities of Edification. By reverse-engineering Forerunner machinery found on Zhoist, the Covenant managed to create an industrially-reproducible version of the modulation crystals - decidedly inferior to the Forerunners' slipspace crystals, but mass-producible. This breakthrough had major ramifications on Covenant expansion, exploration, and the re-centralization of political power, and has been cited as one of the factors that made the Second Illumination possible. 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.

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.

Forerunner drives

The Covenant also have access to a handful of true Forerunner drives, pilfered from various artifact sites over the ages. Sometimes called Prime Borers or Holy Engines, they remain exceedingly rare, numbering in handful of dozens at most. Consequently they are only mounted on the most valuable of Covenant ships; the Hierarchs' personal vessels, Ministry courier ships, specifically blessed explorer craft such as those dispatched to circumnavigate the galaxy, and the flagships of major armadas. Key flagships with Forerunner engines are known as ploughships, and can drag entire fleets in their wake across thousands of light-years.

Even as ships equipped with Forerunner drives were decommissioned, the drive was usually recycled on another ship. However, the mediating crystal flakes Forerunner drives rely on to function will wear out over time. While this typically happens over tens of thousands of jumps, most of the drives the Covenant acquired were already quite some time into their service life and so their core crystals were partly spent. Some had had their flakes entirely spent or removed, namely those found in ancient ship graveyards or refit ports. While the Covenant would later learn how to manufacture their own mediating lattices for use in their borers, native Forerunner systems would reject these, effectively rendering a drive with a spent slipspace crystal useless.

In addition, since the Covenant frequently used Forerunner drives for long, fast jumps which other ships may be incapable of, this also wore them down faster. One related issue was the fact that Forerunner drives were built to be used with very specific AI-assisted nav computer interfaces. Since the Covenant lack these, apart from the few Wayfinders, the Forerunner drives they use are both less efficient and spend their slipspace flakes faster than they would in their native Forerunner systems.

High Charity was equipped by the largest Forerunner drive discovered by the Covenant, which they called the Sefom Invictus. Though its core flake had begun to show signs of dimming in the Covenant's later ages, the drive still had perhaps over a thousand years of service life remaining.

Drive efficiency and transit times

The normal rules of space travel do not apply in slipspace, as the concepts of velocity or acceleration do not exist there, not as such. A large part of what is understood as slipspace "speed" — 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" or "transit times" than velocities. This also makes it complicated to conclusively define a ship's slipspace speed, as this is dependent on a myriad factors which are not always consistent.

While in slipspace, a ship effectively covers physical distance at different rates depending on the phase of the jump; these phases are commonly known as the ingress, coasting and egress stages. How much time is spent in each phase depends on both the drive type and the skill of the navigator. The more powerful the drive, the more pronounced this variance becomes; for example, war-era human transit times are still fairly consistent when compared against Covenant Borers, with which travel times can vary by an order of magnitude depending on secondary factors. As a general rule, jumping to or from gravity wells makes the ingress and egress phases much longer in duration.

Another obvious factor that affects transit times is what is colloquially known as "slipspace weather", or the presence or direction of slipspace "eddies". Jumps performed along an eddie tend to be smooth and up to 25% faster than average, whereas when jumping against an eddie, the effect is reversed to the ship's disadvantage. Since eddies and currents shift over time, this effect can have significant effects on the long-term commerce of slipspace-using civilizations.

Slipspace layers

On a fundamental level, capabilities and limitations of a slipspace-capable vessel are 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 a Russian Matryoshka doll, with each smaller figure representing a more efficient, higher "layer" of slipspace. These layers are not synonymous with slipspace dimensions; the eleven dimensions pervade all of slipspace, but the layers serve as a simplified way to explain the higher-dimensional "depth" aspect of slipspace which has no concrete equivalent in our physical universe. In theory, the number of layers is infinite, though only the "closest" ten can be reliably accessed by most civilizations.

As a general rule, the more advanced the drive, the "deeper" into slipspace a ship is able to go. In some cases advanced navigation solutions or an abundance of available power can compensate for the drive's innate limitations, but those limitations are still fairly established. If a ship attempts to plot a course deeper than its safe operational ceiling, or the navigator is careless, 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.

The more effective jump time (EJT) a ship spends in a deeper layer, the more distance it is able to cover with that jump; in many cases, especially with pre-war human drives, more effective jump time may be spent burrowing in and out of slipspace than in the coasting phase. The contrast between conventional Shaw-Fujikawa drive architecture and Borer-type drives is sometimes likened to that between a sledgehammer and a scalpel: a traditional S-F drive violently tears a hole into slipspace and then gradually passes into the first, second, and/or third layers in what could be described as an oblique angle. This not only requires considerable energy expenditure but it also constitutes much of the effective jump time. In comparison, Covenant and Forerunner Borer-type drives make an "incision" into the fabric of space-time, concentrating an enormous amount of pulsed power into a single point into which the ship slips, then immediately burrows through several layers directly (hence the name "Borer") and enters the "coasting" phase in which most of the effective jump time is spent. The egress is likewise rapid and precise.

Up until the sixth generation, human Shaw-Fujikawa drives utilized the first, second, and third layers of slipspace, with later models having access to higher layers. Covenant Blinkers use 1-4 depending on the pattern, while Borers routinely use 4-5; with Forerunner-sourced jump solutions, they can reach all the way up to the seventh layer. The operational ceiling of Forerunner drives is unknown, though it has been hypothesized to be as high as ten or twelve.

Jump range

As a general rule, covering long distances over one long single jump or "leap" is more energy-efficient and faster than a series of shorter jumps. However, various technical considerations place limitations on a drive's maximum jump range. For war-era UNSC vessels, a "long" jump might be over 30 light-years, with the peak length being around 70 to 100 light-years. For Borer-equipped Covenant ships, long jumps are typically ones exceeding ~200 light-years and peaking at around 20,000 light-years.

While it may be faster and more efficient, a long jump is not always the preferred option. Since most navigation systems are less reliable over long distances, the risk of encountering anomalies and hazards along the way grows far greater. When not accounted for by the navigation solution, even small gravitational disturbances caused by changes in the interstellar medium density or the proximity of astronomical bodies to the jump path can send a ship veering off course or worse. To avoid such dangers, it is common even for the Covenant to cover long distances in a series of shorter jumps, as they can be plotted more reliably than long single jumps. Only the data from Forerunner Wayfinders is trusted for jump solutions covering thousands of light-years. Covenant commercial and military supply routes typically cover distances of around 50-150 light-years in a rapid succession of individual jumps.

Maximum jump length is also dependent on how long a slipspace drive is safely capable of maintaining its slipspace field or "envelope" before having to be recalibrated or cooled down. Other factors affecting the length of interstellar journeys are 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.

Translight time dilation

Jump times are divided between the effective translight time (ETT), which translates to the length of the jump from the perspective of outside observers, and subjective translight time (STT), which indicates the length of a jump as perceived by the occupants of a ship traversing slipspace. While the two generally correspond to one another very closely, especially with traditional human drives, minute anomalies are always present, and ship crews always check and recalibrate their chronometers upon arrival at the target system. More variance between the two, or time dilation, emerges with deeper slipspace layers such as those used by the Forerunners or Wayfinder-plotted navigation solutions, and to some extent even the Covenant's borer drives. Namely, the longer a ship spends in a deeper layer of slipspace, the less subjective translight time its occupants experience compared to the effective jump time. For example, for a Forerunner ship jumping 20,000 light-years in five days, less than half that time might elapse for the occupants on board.

Travel speeds

Slipspace transit times are often colloquially measured in light-years per day, which represents the average transit time. However, any such measurement is bound to be inaccurate or at least vague for the aforementioned reasons. 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, war-era), or from one end of human-controlled space to the other along major routes (10-12 months, war-era).

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 range listed is the maximum safe range for a single jump when paired with contemporary navigation systems.

Shaw-Fujikawa drives

• CODEN I: 0.7 — 5 LY/year. Range ~15 LY. In service 2291 — c. 2370s

• CODEN II: 1 — 4 LY/month. Range ~20 LY. In service 2356 — c. 2420s
  • The first commercialized slipspace drives. This breakthrough helped usher in the Domus Diaspora, as interstellar travel became considerably faster and more reliable. During this time period, slipspace pathways were beginning to be properly understood and utilized for the first time.

• CODEN III: 1 — 3 LY/week. Range ~30 LY. In service 2379 — c. 2500s
  • Developed in response to the pressure of the Inner Colony Wars.

• CODEN IV: 0.5 — 2 LY/day. Range ~50 LY. In service 2487 — c. 2540s
  • Still common on civilian vessels such as freighters well into the Human-Covenant War.
  • The CODEN IV generation saw the introduction of the first micro slipspace drives, though these would only be perfected over the succeeding two generations.

• CODEN V: 1 — 3 LY/day. Range ~70 LY. In service 2536 — c. 2560s
  • Fifth-generation Shaw-Fujikawa drives were in mainstream service for much of the second half of the Human-Covenant War and the early years of the post-war era.

• CODEN VI: 5 — 15 LY/day. Range ~100 LY. In service 2555 — c. 2600s
  • Loosely based on Covenant Blinkers acquired from Kig-Yar traders in the later years of the war along with data gathered from salvaged Borer-type drives, 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 percolated across the UNSC, the Phoenix Initiative then the civilian market, across the next three decades.

• CODEN VII: 40 — 60 LY/day. Range ~600 LY. In service c. 2575 —
  • The seventh 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. Capable of precise microjumps as well as improved operability within gravity wells; atmospheric jumps still risky and not recommended.

• Non-native drives
  • In addition to human drives, the UNSC managed to incorporate a handful of scavenged Covenant Borers on several "keystone" vessels throughout the mid-to-late 2550s. This was largely thanks to the efforts of Project SPHINX and over a decade of intensive research, coupled with the capture of Huragok from the Ascendant Justice. 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.

Covenant drive types

• Blinkers: 5 — 15 LY/day. Range ~0.5 — ~100 LY (varies by model and nav solution)
  • 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 — 70 LY/day (Covenant nav systems) / 100 — 300 LY/day ("Smart" AI navigators) / 500 — 2000 LY/day (Forerunner nav systems). Range ~40 — 25,000 LY (varies by model and nav solution)
  • Based directly on Forerunner technology, Borers are technologically capable of achieving far greater effective velocities, but only when paired with specific Forerunner navigation interfaces such as Wayfinders, or nav solutions plotted by such devices; under ideal conditions, velocities of up to 2000 LY/day are achievable by most Borer-equipped ships in service with the ministries. "Smart" AIs are also capable of utilizing Borers more efficiently than most native Covenant navigation systems by plotting more complex jump trajectories via sheer number-crunching, though nowhere near as effectively as Forerunner-sourced nav systems.

• Forerunner drives / Prime Borers: 500 — 4000 LY/day. Range ~5,000 — ~50,000 LY? (varies by model and nav solution)
  • Forerunner drives are fast, but they are functionally instant only on local galactic distances. There appears to have been some difference in grades between different types of drive and/or ship, the keyship Anodyne Spirit traversed a distance of approximately 20,000 LY in just five days, thus covering about 4000 LY per day. This makes it by far the fastest ship in the modern era of the galaxy; Covenant ships with scavenged Forerunner drives tend to be considerably slower due to both power generation limitations and inefficiencies resulting from generally inferior Covenant nav systems and only semi-compatible interface-drive coupling.

Causal reconciliation

Causal reconciliation or particle reconciliation is a phenomenon in which space-time seemingly self-corrects after slipspace transitions, mending any paradoxes faster-than-light travel might otherwise be bound to cause. Large volumes of slipspace traffic accrue a "reconciliation debt", which in turn slows down slipspace travel locally or even on a larger scale depending on the length of the jumps and the amount of mass being moved. In extreme cases, an excess of traffic along a slipspace lane or region of space can even cause a permanent slipspace anomaly or "slow zone" to emerge. Though its exact nature or origin remains unknown, causal reconciliation appears to be a natural property of space-time.

For humanity, reconciliation remains a largely trivial concern for the most part as interstellar traffic remains relatively light and uses only the shallower layers. However, both minute variances in travel times as well as occasional anomalies and discrepancies have led to the phenomenon being discovered and documented by human science. The largest known anomaly by far occurred in September-October 2552, when Dr. Catherine Halsey and the Spartan-IIs recovered a Forerunner slipspace crystal on Reach, resulting in a seeming temporal paradox that would promptly self-correct itself to follow a chronologically linear chain of cause-and-effect, yet many overt discrepancies remained in the testimonies of the individuals involved.

With some of the more trafficked regions of the Covenant's Arterial Network, the effects of causal reconciliation are already noticeable. However, it was best documented by the Forerunners, whose enormous volumes of traffic across the galaxy made causal reconciliation a major concern. The Forerunners' quantum-engineered slipspace drive core crystals were able to offset the debt buildup somewhat, though due to the vastness of their Ecumene, it remained a persistent issue.

Slipspace portals

Slipspace portals or simply portals are a form of fixed or semi-fixed, artificially maintained slipspace channel between two specified points in space, often star systems. Portal transit is, as a general rule, faster and more reliable than drive-based jumps due to their stable nature. While Forerunner slipspace drives were powerful, their mass usage throughout the Forerunner Ecumene also accrued considerable space-time reconciliation debt with high-volume mass transit on a continual basis. Slipspace portals were thus established along the most trafficked routes as a more sustainable and efficient option. Since portals still spend reconciliation budget while active, they were only used when the traffic moving through would be more costly without a portal. Unlike localized translocation fields, slipspace portals require a vessel of some sort to move through, as transit is only instant over very short distances and may require the use of an onboard drive to mediate. To allow passage, portals typically require access codes transmitted by a ship or even a special type of vessel, known as a keyship, to unlock.

Portal networks existed between major Forerunner systems, acting as the Ecumene's interstellar superhighways. Some populated systems might have internal networks of portals for smoother transit between worlds separated by multiple AUs. The Forerunners destroyed most of these civilian portal networks during the Diluvial War to hinder the Flood's advance and prevent it from reaching Forerunner systems. Temporary portals might also be established during large-scale mining operations, for moving large military fleets across galactic distances, and finally for transporting species to the Ark and back into the galaxy in the Conservation Measure. The last known portal of this network is the Kenyan Excession located on Earth, though others may still exist across the galaxy, hidden and dormant.

Slipspace translocation

Slipspace translocation, colloquially known as teleportation, is the technology of moving individuals or objects through slipspace without a slipspace drive, effectively an application of slipspace portal technology on a smaller and more specific scale. Translocation requires sophisticated technology, with the most impressive examples thereof being of Forerunner origin. The Covenant also managed to reverse-engineer some basic translocation technology, though these were mostly found in fringe uses and only enabled successful transit over dozens or hundreds of meters. Meanwhile, Forerunner translocation grids often encompassed entire installations such as the Halos or shield worlds, enabling near-instant transit to most locations on or near those facilities. However, even Forerunner translocation is limited by the inherent properties of slipspace; since prolonged exposure to slipspace is dangerous, unshielded individuals can only be transported over very short distances, rarely exceeding 10,000 kilometers.

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.

One of the more common hazards is when a damaged or improperly-mounted slipspace drive substantially damages the fabric of slipspace itself. Normally, the rifts caused by Shaw-Fujikawa translight engines are very quickly repaired, as part of the deacceleration process also involves carefully knitting together the hole they cut. An improperly-maintained drive fails to close up this up correctly, and upon entering realspace, the ship's engine is destroyed and spits out megawatts of hard radiation. This leaves a 'scar' that spaghettifies and spit outs any ship into realspace that passes through its vaguely-defined boundaries. In general, these anomalies last between a few days to weeks before they dissipate, although there are known examples in the Human Sphere that have existed for years and years.

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.

Perception

Slipspace also has other anomalous effects that are less directly harmful. The very appearance of slipspace is unnatural and unsettling; an absolute nothingness deeper than vacuum itself that creates a bizarre "blind spot" effect of sorts in which trying to look into raw slipspace causes one's gaze to "slide off" of it. This is known to have profound psychological effects on some individuals, and as a result ships often close external viewports or cameras during jumps. "Slipspace madness" is also a phenomenon documented in some cultures, though it is rare. Humans documented such occurrences especially in their earliest explorations, and though slipspace travel has become considerably more mundane, some individuals still react to jumps stronger than others. Usually, such reactions remain on the level of vertigo and nausea. Some people have irrational fear of slipspace, either due to past experiences or fringe cultural or religious reasons. Some conspiracy theories claim that ships that jump into slipspace are actually torn apart atom by atom and then reconstituted in the destination, and though this is wildly inaccurate, such theories remain, particularly on Earth and SolCore. Some religious sects also shun the use of slipspace, believing it to be unnatural and possibly demonic by nature. The Xar-Shaa are exceptional with their species-wide refusal to use slipspace at all, with members of the species seemingly being driven to irrational dread and madness by simply being present during a jump.