Slipstream space

Slipstream Space (Slipspace for short), otherwise known as Shaw-Fujikawa Space by the United Nations Space Command, is a collective term for the seven non-visible infinitesimal quantum dimensions used for faster-than-light travel. Making a transition from place to place via slipspace is known as a "slip", or a "jump".

Background
Slipspace travel has been the UNSC's main way of traveling from planet to planet, and star-system to star-system since its discovery in 2291. Before this technology was discovered by Tobias Shaw and Wallace Fujikawa, mankind was never able to leave their home star system of Sol due to the constraints of relativistic theory, preventing faster-than-light travel. Now the UNSC traverses the galaxy in spacecraft to whole new worlds.

Mechanics
Slipspace is a tangle of intertwined dimensions (estimated to be nine), which lie underneath the three conventional spatial dimensions of the universe.

This new engine allowed ships to tunnel into "the Slipstream", technically called "Shaw-Fujikawa Space", after the scientists who proved its existence. Slipspace is a domain with alternate physical laws, allowing faster-than-light travel without relativistic side-effects (much like hyperspace from the popular Star Wars movies, though ships travel the Shaw/Fujikawa space much slower than hyperspace, as a ship in hyperspace could cross in minutes a distance that would take a ship in Shaw/Fujikawa space months. ). Faster-than-light travel is not instantaneous; "short" jumps routinely take up to two months, and "long" jumps can last six months or more, which is why most UNSC ships have cryo chambers. Slipspace can be thought of as our detectable universe (which, technically, it is) but with a greater number of dimensions. Our plane of existence is thought to have four dimensions (up-down, front-back, side-to-side, and time), but Cortana states in Halo: First Strike that Slipspace is an eleven-dimensional spacetime. Slipspace is currently theorized (in 2552) as a "tangle" of our plane's dimensions, rather like taking the classic "flat sheet" used to represent gravity and crumpling it up into a ball, thereby creating extra dimensions and shorter spaces between points.

The SFTE (Shaw-Fujikawa Translight Engine) generates a resonance field, which when coupled with the unusual physics of the Slipstream, allows for dramatically shorter transit times between stars; however, scientists note an odd "flexibility" to temporal flow while inside the Slipstream. Though no human scientist is sure why travel time between stars is not constant, many theorize that there are "eddies" or "currents" within the Slipstream—there is generally a five to ten percent variance in travel times between stars. This temporal inconsistency has given military tacticians and strategists fits, hampering an uncounted number of coordinated attacks. Shaw-Fujikawa engines allow ships to leave normal space and plow through Slipspace. Slipspace drives use particle accelerators to rip apart normal space-time by generating micro black holes. These holes are evaporated via Hawking radiation in a nanosecond. The real quantum mechanical "magic" of the drive lies in how it manipulates these holes in space-time, squeezing vessels weighing thousands of tons into Slipspace.

The Covenant have a very finely tuned version of this technology, far superior to the UNSC Shaw-Fujikawa Slipspace Drive. Instead of simply tearing a hole into Slipspace, Covenant Slipspace drives cut a very fine hole in the fabric of space time and slips into Slipspace with precision (much like a scalpel compared to a butcher knife). It exits with the same pinpoint accuracy.

Because the superfine quantum filaments the UNSC use to compute paths are disrupted by gravity, Human vessels are incapable of transitioning while in any significant gravitational field. The Covenant's technology, though, is more than capable of computing Slipspace paths in gravitational fields, meaning that they are able to transition while in a gravity well. Indeed, while using the captured Ascendant Justice to make a Slipspace jump within Threshold's atmosphere, Cortana remarked that 'It was as if she was blind before'. After observing this innovation, a Covenant AI managed to leak the data out to the rest of the Covenant in a transmission. During the First Battle of Earth, the Prophet of Regret uses this newfound knowledge to transition to Slipspace while directly over New Mombasa in Earth's gravity well, destroying the city. These events are further proof that the Covenant are imitative rather than innovative.

Slipspace travel is dangerous due to the high level of radiation encountered during the trip, which can be extremely hazardous to the crew. This is negated by the use of Lead Foil in UNSC ships, which absorbs the radiation. Fissile materials also emit radiation (specifically Cherenkov radiation, emitted when particles travel through a medium at a faster rate than light travels in that same medium) upon exiting Slipspace; this is not harmful to humans, however it does make emerging from Slipspace very noticeable. It is not known how the Covenant deal with radiation, but it is presumed that either they also utilize lead, or with their improved Slipspace technology and energy shields, it does not affect them at all (Fissile materials are not used by the Covenant, therefore Cherenkov radiation is not emitted). During the beginning of the Civil War of the Covenant a flood-controlled In Amber Clad entered Slipspace and exited into High Charity. .

Velocities
Human slipspace drives are far slower than Covenant versions, only able to carry a ship at a speed of 2.625 lightyears per day, while Covenant drives can reach 8.15 lightyears per day. The capture of a Covenant slipspace drive by the Master Chief and survivors of the Battle of Reach and survivors of the events at Halo may increase the capabilities of human slipspace technologies.

Dangers
In addition to the radiation of slipspace, Cherenkov radiation is emitted by fissile materials upon entry and exit of the dimension, requiring all slipspace-capable craft to be lined with lead as radiation protection. The stress caused to small craft, such as a dropship, is considerable, one of the reasons only large ships are equipped with slipspace drives, and can tear a craft apart.

In addition, large concentrations of slipstream radiation can cause anything from unconciousness to death in life forms whose vessels intersect them. An occurence of this was once faked in order to trick a Covenant vessel into boarding a human freighter.

Communications
The Forerunner's were somehow capable of advanced message carrier waves in Slipspace. This way, messages could travel at great speeds throughout their empire. Cortana was able to use this technology to declare codes Bandersnatch and Hydra during The First Battle of Earth and The Battle of Installation 05.

The closest technology the UNSC has been able to create like this is the Slipspace COM Launcher. And even then this technology is limited as there were only three in existance before 2552: one on Reach, one on Onyx and one on Earth. As of the conclusion of the Human-Covenant war, both the devices on Reach and Onyx have been destroyed, with the fate of the Earth device unknown.