The Reaper (Alcubierre-White-Sierpinski-Reaper or AWSR) - Drive

"The AWSR Drive was not "discovered" in a singular effort: It was dwarves standing on the shoulders of giants, all the way down. And although I did the last step, I still am a dwarf compared to the genius of those who came before me. But here we are… the way to the stars is finally open. However in order to honor my predecessors I would insist not to call the drive the Reaper drive, which… allegedly has a nice martial sound I admit, which is why I presume that the press fell back on it so easily, but rather call it Alcubierre-White-Sierpinski-Reaper drive or AWSR Drive for short.   I know that is a tonguetwister, but I have to insist… deal with it."
— Lisbet Reaper, 29th November 2353
"Don't fear the Reaper"
— Well known pilot's proverb in the 30's Century.


The Alcubierre-White-Sierpinski-Reaper Drive is, as far as humanity knows, the only drive possible, which, for very short intervals of time, allows objects with mass to exceed the speed of light. It does that by creatingle" of spacetie wich separates the ship from "Spacetime-proper" and instead of moving the ship moving the bubble, while the ship remains perfectly still in it's center.   There are actually two types of drive: the "Cruise" or Sierpinski drive and the "Jump" or Reaper drive.   Sierpinski Drives are not actually superluminal but stay firmly in the region of 20 to 50% of the speed of light (0.2 to 0.5c), and are used for travel inside a star system.   Simple Cruise engines can very well come without the option to also engage in Reaper-Jumps, and these drives are known to be more optimized towards interplanetary travel rather than interstellar. They usually fall closer to the 0.5 c limit.   Modern Reaper Drives in contrast often come with two modes, a Reaper (Faster-than-light) Jump mode, and a Sierpinski "Cruise" mode. This necessitates them to support two different metrics, which usually results in a slower Cruise speed of "only" 0.2 to 0.3c at best.   Having both kinds of drive (a specialized Cruise and a Jump engine) on board is entirely possible, but due to space and weight reasons not really efficient, except in military craft designed for quick interstellar strikes.  

Disengage Distances and Fusion Drives

  The two drives do not suffice to facilitate interstellar travel on their own though, as they rely on the manipulation of spacetime by gravitational effects. Strong gravitational effects like planets, moons or asteroids, if close enough, threaten to destroy the craft by disturbing the metric at entry or exit, forcing ships to exit or enter cruise and/or jump in safe distances to an object and overcome the remaining distance to and from the object with traditional fusion drives.   Note though, that this does not affect ships which are inside cruise mode or even in a jump already, as they are causally disconnected from the universe. While a mass effectively prevents a ship from engaing or disengaging Cruise or Reaper drive, the same ship, once it enters "Cruise or Reaper space" could just move through a gravitational field and even a planet or sun without further harm.   Depending on the mass of the object that is targeted or left, these fusion bursts (and decceleration phases) could last from mere seconds (large asteroid space stations), over one hour with earth like planets up to almost a day for gas giants.   A good rule of thumb for a given stellar object is to take earth acceleration as a basis, multiply it with the number of earthmasses of the object, and assume the resulting number as the burst acceleration which has to be kept up for half an hour, followed by a brake with the same decceleration for the same amount of time. The resulting distance traveled is the distance at which cruise speed has to be disengaged / or can be engaged again when leaving. For Earth it is thus 2 times half an hour at 1 g, while for a planet like Jupiter this gives a cruise disengage distance of about 2 times 8.5 hours at 1g. (or 2 times half an hour with 317g, which is entirely theoretical if there are lifeforms on board of course)   Noticeable here is, that sufficiently homogenous fields, like the Gravity wells of stars, can be mitigated by a cruise drive through adapting the much more adaptable Sierpinski metric. Therefore, at least for cruise, these fields do not really play a role. This is fortunate, as it actually allows to use the cruise drive for cruising a system, rather than being stuck 70 Astronomical units or more from the planet one wants to reach, with only fusion dirves as an option to travel the distance.   The more elaborate, and much more fragile Reaper Metric however can not be easily adapted, which is why it has to be disengaged at distances much further from the star. In order to calculate the so called "Reaper disengage distance" one takes the rule of thumb and applies it to the star itself. Our sun for example would give a disengage distance of about 71 Astral units, which is more than twice the distance between the sun and Neptune. At 30% of Light speed a journey to the inner planets would then still take about 3 hours plus the time necessary to boost to the target with fusion drive, once cruise drive is disengaged.   Therefore a standard approach of a ship traveling to another system would look like this:   The ship engages its jump drive at a distance larger than or equal to the minimum Reaper disengage distance from the star it want's to leave. It chooses a star at most 7.819 Lightyears (1 Reaper) away and engages the Reaper drive to jump. It arrives in a distance larger than or equal to the Reaper disengage distance of that particular star, and engages its cruise drive in order to travel to the inside of the star system (if the star has one), disengaging cruise when approaching the cruise disengage distance of the object it want's to reach, and overcoming the remaining distance with it's fusion drives.  

Preventing Jump accidents

  The surface of the sphere with a radius of Reaper disengage distance is vast enough to prevent jump accidents (ships jumping into one another) by its sheer size and the laws of probability alone. This however disregards human nature, habit or just plain stupidity of using the same spot time and time again because it promises the shortest distance to cruise. Be it as it may, because it is definitely vast enough to prevent effective control structures, even at 0.5c cruise speeds, space travelers have to rely on protocol, which, if infringed upon and caught, often imples a hefty fee, followed, if not paid, by a criminal entry and time in prison. This of course only holds for systems which have the ressources to track these offenses.   The standard jump protocol demands the following:   Every system defines a "Jump mantle" which begins at Reaper disengage distance, and is about 1000 km thick. Ships trying to leave a system have to engage their reaper drive within these limits. Ships arriving in a system must arrive at the outer limit of the mantle and are requiered to immediately accelerate further inside. Once inside the mantle, they can remain stationary and charge their Reaper drive again (if they desire to jump further), or continue to travel further inside.   However, the region of the mantle and further out is not the only place from which it is physically possible leave or arrive in a system. There are also the Lagrange points (also called "Jump Points").  

Lagrange Points

As Lagrange Points are points where gravitational forces inside a system cancel each other out, it is possible to successfully form a Reaper spacetime metric at these points, allowing to directly jump to and from these points. While jumping from these points is comparatively easy, jumping to them provides a major navigational challenge and requires an experienced navigator with a good navigtional expert system and access to recent information about the targeted star system (not older than a day). Also it is usually forbidden for safety reasons, in order to prevent Jump accidents.   Of couse the navigation could effectively also be done from a classic arrival point at the Jump mantle, as the information necessary is present then, and the distances involved are much smaller. But the recharge rate of the jump capacitor, which provides the energy for the Reaper jump, and the comparatively high energy needs compared to cruising, mean that actually cruising towards any Lagrange point in a system is cheaper, easier and also quicker than plotting and executing an inner system jump.   The so called "Jump Room", which is the region of spacetime around a Lagrange point, which is "flat" enough to allow for a successful formation or dissolution of a Reaper spacetime metric without destroying the ship, forms a sphere of a diameter that is heavily dependent on the mass of the object to which the Lagrange point belongs to. (See: Rule of Thump: (Jump Room sizes))   Most Jump rooms around habitable planets range from diameters of about 100 m (Earth) to diameters of about 700 m (massive gas giants).   Ships larger than the jump room size cannot use it to perform (or end) a jump.   Jumping to a Lagrange point is also strictly forbidden in most systems, as it provides an exponentially higher chance of jump accidents than jumping to the Jump mantle. As a jump accident destroys both involved ships, star captains planning this kind of stunt better know what they are jumping into... leaving it to the realm of military maneuvers.  

Jump Interdiction

  A ship in jump or during cruise cannot effectively be interrupted. First because a jump takes at most 10012 Planck time intervals, which is as close to instantaneous as possible, but secondly, because ships in jump or cruise are causally separated from our universe. Nothing we do can affect them, as much as nothing they do can affect us until they disengage the drive.   HOWEVER it is still possible to prevent ships from engaging their jump or cruise drive if one is able to employ a strong enough gravitational field. It is expensive however. The reason for this is that, albeit humanity managed to control gravitational forces enough to allow for FTL, the energy requirements of forming spacetime are still enormous. A common trick which FTL drives employ to circumvent this, is shrinking the jump or cruise metric at entry point to a length of a few atoms, with the most advanced cruise drives (the 0.5c ones) even downsizing it to the size of a few thousand planck lengths. Because the inside of the metric is causally separated, it can remain as large as necessary, therefore posing no problem for the ship inside. The original size is reinstated at exit point.   Ships who want to prevent other ships from jumping can't employ this tactic however, but rather have to bend spacetime in large volume, and although the metrics of Interdiction fields are often a lot less complicated (they are usually nothing else but large gravitational sinks), the energy problem persists.   Modern Jump interdiction field generators can create an "interdiction bubble" of 2 km radius, which is enough to prevent a ship from jumping, **if** the generator is fired up close enough. However only capital ships, specialized large ships that sacrifice most of their other functionlities and space stations are powerful enough to support such a device.  

Warp Communication

"Foldings space is expensive."
— Any commander of a Warp Relay Station when asked why sending a message is so expensive
  In order to get a message from one point of the known space to the other, there are basically two ways to go about. Sending a messenger or sending it via Warp Relay Station. Warp relay Stations are space stations, usually located at or close to Lagrange Points, which take classical radiosignals and encode them in a gravitational deformation not unlike an Alcubierre-White metric. While these metrics, compared to the Reaper metrics, have the disadvantage that they can't   

Jump Stress. Refueling and the "Two Jump Limit"

  Although Jump stress sounds awefully like something that happens to the passengers during a jump, it is actually something that happens to the ship, or rather certain components of the ship. Jump stress affects the warp coils which create a Reaper metric.   Jump stress results in microscopic changes in the makeup of the warp coils, which, over distance traveled, turns the coils unusable, forcing them to be replaced or restructured. This effect scales relatively linear with the overall jump distance travelled rather than the number of jumps, yet despite this, it became known under the name "Two jump rule". This is due to the maximum distance, which a jump drive can traverse before it's coils become unusable, corresponding to almost extactly (up to a few km) 2 maximum distance jumps, or about 15,638 Light Years.   A Jump coil which is unusable for Reaper jumps can yet still be used for Cruise travel however, as the structure of the coils rather than the material begins to play a role only for FTL (Faster than Light) metrics. Also, dedicated Sierpinski coils would not suffer this effect, as it only appears with reaper metrics, allowing Sierpinski coils to, if not damaged due to other reason, work for decades, if not centuries.   The past has seen thousand's of tries to extend this "two jump rule", yet it was understood that restructuring warp coils to prevent those microscopic disturbances, also meant changing the reaper metric to suboptimal shapes, eventually leading to overall maximal distances of even less than 15,638 lightyears. Other materials also had no effect, because the effect is quantum in nature and hence chaotic and unpredictable. Independent of the material, microscopically small space time warps form at random places inside the warp coils and change their delicate structure. Material doesn't even factor in here.   Therefore, in the year 2948, the new "nothing can travel faster than the speed of light" has become "Nothing can travel further than 2 Reaper"   Because warp coils are relatively large and heavy parts of a Jump Drive, and need to undergo a costly and time consuming restructuring before being able to be used again, this gave rise to a warp coil recycling industry which also led to the standardisation of warp coils into medium, large and capital coils, that can each be used by ships of the same classification. Small would refer here to Sierpinski coils, which,as already mentioned, do not have to be replaced, at least not as frequent as true Warp coils. Warp coils in modern ships are installed in "Warp coil compartments", which are, once granted access, comparatively easily accessible from the inside and outside of a ship, easing the replacement of the coils. Emphasis on "comparatively", as large and capital warp coils cannot effectively be carried but have to be hauled from their compartments with cranes while medium coils "only" require the use of personal power loaders.   Ships with "spent" Reaper warp coils would thus travel into a system, land on a planet or station, and aqcuire (against a fee) new or restructured warp coils while leaving their old ones. The old coils would then be restructured in a restructuring facility, and, once this is done, sold to the next ship that needs them.   Because of the two Jump Limit, most ships rarely have more fuel aboard than they need for longer distances than an actual two Reaper jump (+ flying into the system). They refuel when they also need to replace their jump coils. An exception for this are military ships, or the highly independent Exploration ships, which not only sacrifice parts of their storage space for up to two sets of spare warp coils, (allowing them to operate a whopping 23 light years from civilized space and still return home), but also come equipped with fuel scoops that allows them to harvest hydrogen fuel from gas planets or in the vicinity of a sun.

Recharge rate

While Cruise speed can, energywise, relative comfortably be supported by a ships fusion engines, which at that point in time do not have to provide boosts, jumps need a lot more energy in a much shorter timeframe. A huge part of a jump drive are thus the so called "Jump capacitors". These massive capacitors are designed to store the huge amounts of energy and release it almost instantly, when the jump drive is engaged.   In order for this to work however they have to be charged first. Standard jump capacitors of any jump capable shipsize (medium, large or capital) are able to be recharged in about a day, provided it is done from the ships fusion drives, which burns fuel, with the fuel consumption scaling with the ships size.   There are also "quicker" (military) jump drives which can facilitate the recharge in half the time (at four times the fuel consumption) or a third of the time (at nine times the fuel cost). Standard civilian vessels can "achieve these speeds" only by removing some safety limiters, allowing them to "overclock" their standard reactors, which, additional to the heightened fuel costs, comes with threat of overheating the reactor, which can lead to its destruction (and the destruction of the ship). This might be be prevented by slowly venting the ships air supply for cooling. Given the situation, it might be worth it.   Ancient ship designs in comparison came with giant solar shields, which could be unfolded and folded back, that allowed them to use the energy provided by the central star to charge their jump. This process however was far slower. Charging a jump drive of a medium ship solely with solar power takes about 4 weeks. Charging a large ship takes about 4 months, and charging the capacitors of a capital ship would take about a year. Hence. Most ships do not come with this option equipped anymore, except some exploration vessels which use it to save fuel on their travels.

Access / Availability

  Wherever humanity has settled, Reaper drives are known. They might not be easily replaced though, or even acquired.

Civilized space (from Core space to the Outer Rim).

This covers all systems which provide jump coil restructuring and manufacturing facilities. Spaceships and Jump drives can relatively easily be aqcuired here. They still have a pricetag though, but having one does not necessarily ruin you.  

Fringe Systems

  Given the "Two jump Rule", systems on the outer fringe of civilized space, which do not produce their own warp coils yet, and also have no warp coil restructuring facilities, represent dead ends, except for military craft or exploration vessels.   This is because a ship can travel there, but if it ever wants to return to "civilized space", it cannot travel further, and has to leave towards a system which provides these facilities. Settled systems might be close enough to each other for one system to cover for it's neighbors with it's coil restructuring facilities, but for the systems "truly out there" this is no option.   Having these facilities erected thus becomes a major focus to support further colonization efforts.   That is after:   Breathing, food and water production, energy needs, housing, relative security of the settlers, establishments of mining outposts, establishment of basic technologies... etc..etc....   ALSO the restructuing of warp coils is complicated, takes a lot of refined ressources, which first have to be aqcuired, and is based on several key technologies which first have to be available.   This is why the colonization of space happens in waves.

Outer Colonies

  Next to the fringe systems, there are also further systems, which can only be traveled to in military craft, exploration vessels, or other vessels who sacrifice large parts of their cargo space for warp coil replacements. These are the Outer Colonies, with little to almost no contact to the central systems and highly self sufficient government.   They often have a military craft or another vessel with enough warp coil replacements in its cargo bay to make the journey to and back from "civilzed space", which it usually performs once or twice a year to transport messages and limited amounts of goods.   Having a ship jump into system in these outer colonies is therefore an occasion truly worthy of raising eyebrows. Thus, Jump travel, at least on a regular basis, is not present... and if your jump drive breaks, you are stuck, until the "Postal ship" makes it's annual journey.

Isolated systems.

  Some systems were colonized not with the intention of coming back. Here live Dropouts and Adventurers. (Or lunatics, as they are also sometimes called).   They are >3 to 6 Reaper distances (>23,5 to 47 ly) out from any system which provides warp coil restructuring or manufacturing facilities, and coming here is a one way trip. These systems usually still have database cores and also expert systems which theoretically, once all basic colonization is done, allow for the construction of Warp coils and Jump drives. But given how all the other things have to be there first, this can take years, decades or even centuries, if the inhabitants are not in a hurry to reconnect with the rest of humanity.   Which they usually aren't.   Jump tech is no issue here, except probably in museums to show where the people of the system came from. And why they decided to drop out.
In the year 1994 a physicist, Miguel Alcubierre, proposed, inspired by a vintage television series (note to the reader: Television was a purely visual predecessor of our modern VR) the so called Alcubierre “Warp”metric. This metric, meant as a thought experiment at first, was still a far shot of the spacetime metrics we use today and necessitated negative mass particles with more energy than the universe contained.   Nevertheless it laid the theoretical foundation of the works of Harold "Sonny" White, who started to work on the subject almost ten years later as part of his job at the so called Eagleworks Laboratories. He perfected the metric in so far that, by oscillating the metric and using more than one torus to control the "Warp -Bubble", he was able to, at least theoretically, scale the energy need down to 700kg matter and get rid of negative mass altogether.   However, it still took 173 Years, until Ralf Sierpinski and his team were able to create a working warp drive which achieved 0.1 % of Lightspeed in 2187.   Humanity had spread over the inner planets of the solar system already, building first outposts on Mars, the Earth Moon, Ceres, the Inner Asteroid belt and the Saturn Moon Titan when the one man capsule performed the very first "Warp" Flight, with what we today call "Cruise Speed”.   This opened up the entire Solar System and also gave hope to the colonization of close Star systems, which, albeit fiendishly far still, at least were able to be reached within the span of a single human life now.   Nevertheless, although theoretically able to achieve any possible speed, the drive had severe theoretical issues which prevented it from exceeding the speed of light, first and foremost the so called Exit Nova, when the Warp bubbles front, during it's flight, collects so much matter and radiation (which, at superluminal speed, can't be emitted) that exiting the warp and releasing the energy would immediately create a nova or even a micro black hole directly in front of the ship as it left warp space, inevitably destroying the ship at exit point, albeit not the target Star system as was originally expected, as the energy is directed in all directions and not just one, which, if the ship exited far enough from the target system, would limit the effect.   This problem was solved in 2317, when Topologist Lisbet Reaper came up with the idea of the "Double-Klein” Alcubierre metric, which today is called the Reaper Metric.   This metric, although containing a volume on the inside, didn’t have a well defined outside, allowing it to be put over the stored energy during exit, somewhat like “pulling over Bertlman's sock” as Lisbet preferred to explain it to layman listeners. This would allow to trap the Nova in a separate Alcubierre Space at exit point, effectively removing it from spacetime proper.   The major downside to the drive was, that the Reaper Metric would remain stable only for a few Planck time intervals, during which the whole travel had to be performed, effectively turning the Warp Drive into a Warp Jump drive.   The original metric was further perfected and the optimal shape could be found, keeping the metric stable for up to 10012 Planck time intervals. Also it was proven that metrics of the type of the Reaper metric were not only one possible type of superluiminal metric, but the **only** type of metric which satisfied all requirements of warp travel, most importantly that of actually staying alive.   The first actual prototype of a Jump Drive was tested 2353, and it was theorized to be able to cover distances of about 9.6 Astral units, yet, to play it safe, the test was performed between the Lagrange points L4 and L5 of Earth. Although,at this point in time, it was already known that more optimized shapes of the Reaper metric existed, the necessary founding was only released after successfully completing the jump.   This test was also the occasion when Lisbet gave her famous “dwarves on the shoulders of giants” speech which coined the official name ASWR-Drive, that, much to her chagrin, didn’t catch on.   Today we know that the optimal “Reaper-Shape”, which is the basis of all modern jump drives, allows for jumps of 7.819 Light Years, the so called Reaper Distance, or RD for short, which, next to light years, has become one of the standard units of distance in colonized space.   Sadly Lisbet Reaper succumbed to a tragic laboratory accident in her lab on Titan in 2359 and thus never saw the first interstellar jump between colonized star systems, namely Sol and Alpha Centauri A in 2365.

Rule of Thumb: (Disengage Distance)

    When calculating the disengage distance of a stellar object one takes the Mass of the object in Earth masses and multiplies this with g (9.81 m/s²), which gives the acceleration that has to be kept up for 30 minutes, before breaking for 30 minutes with the same decceleration. The distance traveled during this time gives the disengage distance.   Due to field smoothness reasons, cruise drives can ignore the disengage distance of a star almost up to it's surface. (Which is heavily advised against to be approached with a starship). The disengage distance of stars is therefore often called "Reaper disengage distance" as it only affects the reaper drive, while the disengage distance of smaller objects like planets, moons and asteroids is called "Cruise disengage distance"

Rule of Thumb: (Jump Room Size)

  In planetary systems, Starships can use Lagrange points to jump closer to a star, exploiting the balance of gravitational forces that govern these points. Because these points change over time, and need to be targeted precisely, Star ships trying to exploit this are reliant on recent information about the star system (not older than a day).   The region of relatively flat spacetime around a Lagrange point which is able to support a Reaper jump (the so called Jump Room) is dependent on the mass of the celestial object to which the respective Lagrange point belongs to, with larger objects also creating larger Jump rooms. Ships larger than a specific Jump room in any spatial direction cannot use it to initiate or end a jump.   In order to calculate the Jump room size of a Lagrange point, one takes the diameter of jump rooms at earth Lagrange points (Spheres with 100m diameter) and multiplies it with the cubic root of the weight in earth masses of the celestial object to which the Lagrange point belongs to. The Jump room of a Jupiter (317 Earth masses) Lagrange Point would thus be a sphere with a diameter of 6,81 (cubic root of 317) * 100 = 681 m, which is sufficient to allow many large and all medium sized ships to use it.   A Lagrange point of the Earth moon (0.012 earth masses) in comparison would have a Jump room of 0.23 *100m = 23m diameter.

Warp coils and the "Two Jump Limit"

  A Reaper drive can perform jumps with a maximum accumulated distance of 2 times the maximum jumpdistance (1 Reaper = 7,819 Light years) before the warp coils become unusable for further Reaper jumps (Cruise still works) and have to be replaced.   Warp coils can be replaced at all major stations, planets or moons in systems which provide warp coil manufacturing or warp coil restructuring facilities. Ships leave their old warp coils (which can be restructured) and pay a fee to receive newly installed, warp capable coils. The "spent" coils which were left by the ship can then be restructured and sold again to other ships.   Reaper capable warp coils come in three standard sizes: medium, large and capital, which can be installed in ships of the same size classification. Small warp coils are pure Sierpinski-cruise coils, due to the energy needs of a Reaper jump, which a small ship like a fighter or shuttle simply can't sustain (except long range heavy fighters which are actually medium sized ships)   Due to this standardisation, warp coils now are located in Warp coil compartments, which, once access is granted, can relatively easily be accessed from the inside and outside of a ship to replace the coils. In order to replace large or capital warpcoils, it is necessary to use cranes, while for medium sized warpcoils at least a Personal Power Loader is necessary to handle them.   It is possible for ships to sacrifice large parts of their cargo space to store up to two sets of spare warp coil sets, before the accumulated mass of a third set would carry them out of their size classification and prevent actually using the jump drive. Ships also often do not have enough storage space to even sustain a third set.   Having spare warp coils on board is usual for long range military craft or exploration vessels, which also usually come equipped with crane extensions (in order to change the coils) and a fuel scoop in order to sustain their extended times outside civilized space.   It is hovever entirely possible for standard civilian vessels to stack their storage space with spare warp coils too. Just almost thrice as expensive as simply buying the ship and remaining content with the warp coils installed.... (Yes... military ships and exploration vessels are expensive...)

Cover image: by Fan Gao


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25 Jun, 2020 22:36

I really enjoyed this article. Lots of hard tech and crunchy scifi. As a fan of Dune, Statgate, and Battletech/Aerotech this hits a very sweet spot for me!

Featured Articles in the Shadow War across Creation by Graylion

26 Jun, 2020 08:21

Well... the influence of Battletech is surely felt here. Odd as it may sound, Dune played a much larger role as an inspiration during the conceptphase of my fantasy campaign (Ardu, which you are also following i believe, see Link here: My players still have to find out how though....   This is atmospherewise planned as somewhat more Elite with Battletech aspects + the Expanse + Cyberpunk + sprinkles of Transhumanism .   Also i am trying to include more players for development here while Ardu, due to the many campaign relevant secrets of which they already discovered the first, i keep closer to my chest.   Not entirely selfless from me, as it is a: less work and b: i will be able to play in this as a player...