The construction of a Death Star battle station must have been a phenomenal feat of engineering and logistics. A quantity of metal equivalent to the mass of a small moon would have to be mined and refined, and eventually brought together. No mere handful of planets could supply enough raw materials and components for a Death Star. The fact that the Galactic Empire was able to commit to several such undertakings without any noticeable effect on its economy signifies of the enormous scope of that institution and its territory. This would only be possible with something like the Empire's twelve million inhabited systems [according to Dark Empire] and the roughly tens of thousands of times more numerous uninhabited but potentially exploitable systems of a spiral galaxy.
Even with the benefit of droid labour, the amount of human and alien effort involved is almost incomprehensible. Without automation and droid labour, the assembly of a Death Star within a year would probably require trillions of technical overseers. To finish a battle station within a reasonable time using mere billions or millions of living sentient beings implies very sophisticated automation.
Massive automated construction droids performed much of the work, similar to those lumbering machines which continually demolish and extrude buildings in Imperial City [Jedi Search, ITW:SWT]. The irregular, fractal-like fringes of the incomplete Death Star II suggest that construction is locally organised and performed by self-replicating automata. The station's feathery, fractal growth provides the machines with a maximum possible working area, keeping mutual obstruction to a minimum. Whenever a feathery promontory is built beyond a certain size, a newly made constructor can be set to work there. On the largest scales, the automata must conform their work to a grand plan. On the smallest, human scales, sentient overseers might check the installation of local life-support, power and computer systems [ANH novel refers to construction crews who left the corridor near trash compactor].
The Hutt Clans' Darksaber private Death Star was primarily built by taurill, semi-intelligent hairy four-armed simians who possessed a communal awareness and owed allegiance to Durga the Hutt. Thus they serve as a living substitutes for Imperial construction droids. The taurill life cycle must be short enough for rapid population doubling to keep pace with the available construction work. Although the taurill were a well-coordinated and dispensable workforce, their poor understanding of the technology and the low quality of taurill workmanship vexed designer Bevel Lemelisk.
During the Clone Wars, the Confederacy of Independent Systems secretly began development and construction of a moon-sized battle station with superlaser prime weapon. Geonosians already had plans for an Ultimate Weapon before their world was overrun [AOTC]. Three years later, Archduke Poggle the Lesser had dubbed the secret project as the Great Weapon. After the Battle of Coruscant the war had apparently reached a stalemate, but the Separatist leaders knew that they could win eventually if they could prolong the conflict until the Great Weapon's completion. According to Shu Mai (in a pessimistic mood on Utapau), this might have taken "years" [Reversal of Fortune #112].
At some unknown time after the Separatist Council's demise and Lord Vader's recuperation as a cyborg, an incomplete battle station fell into the hands of the Galactic Empire. Emperor Palpatine, Lord Vader and Moff Tarkin inspected this prize [Revenge of the Sith]. This may have been the unfinished remains of the Great Weapon. The framework is almost exactly spherical (whereas Tarkin's later, operational Death Star was oblate) and the superlaser dish is proportionally smaller. Therefore they are not the same object. The earlier device must have remained secret. In their ignorance, Princess Leia and the Rebel Alliance wrongly believed that the Death Star was a novelty. Development of prototypes started much earlier than the Alliance suspected.
Tarkin's experts could reverse-engineer and improve the secret, captured Separatist technology at their leisure. This opportunity may have been a vital inspiration and practical boost to the later Death Star research programme. (Similarly, German rockets and engineers captured at the end of World War 2 greatly advanced the USSR's and USA's efforts to develop space travel.)
The construction of moon-sized starships remains a novelty at the end of the Clone Wars. How, specifically, did the Empire exploit what it learned from its studies of the Great Weapon? Where was it hidden; when and how was it eventually discarded? Was there any continuity between the Separatist project and Tarkin's later programme in the Maw? Did the research effort pause or halt when mundicidal weapons were no longer needed, during the years of peace between the Clone Wars and the eruption of rebellion? How many more intermediate prototypes were built and tested? What were their flaws and inefficiencies? Did any of the prototypes fail catastrophically or explode? These stories remain untold.
Intruiguingly, the initial design of Ultimate Weapon differs from the Great Weapon. The Ultimate Weapon's dish is shaped more like the eventual Death Star's. Perhaps the Ultimate Weapon was only one of several idealised concept designs presented to Count Dooku, and not the first one to begin practical development?
Measurements: As shown here in the movie, the axis of the Great Weapon was oriented at about 4.9° (tangent 10/116) to the horizontal (plane of the ship carrying Palpatine). After rotating to the frame of the construction, we can measure the polar diameter as 119±0.5 pixels (interval 11≤Y≤130 in the attached image). The equatorial radius is 59±0.5 pixels (pixel columns 109 to 168), implying an equatorial diameter 118±1 pixels. Thus the polar and equatorial axes are equal, to within the uncertainties of measurement. The core of the station is in pixel row 70.5±1; while the parallels of the top and bottom of the dish are at rows 36 and 61. Thus the Great Weapon's dish spans latitudes 9.2° to 35.6° north (approximately).
Applying the same methods to Tarkin's Death Star reveals that the polar and equatorial diameters are approximately in the ratio 678:730 (aspect ratio 0.929). The dish of this operational battle station spans latitudes 5° to 39°. In angular terms, this is approximately 28% wider than the dish of the Great Weapon, or about 63% more angular area.
Emperor Palpatine and Lord Vader survey the site of the incomplete Great Weapon. It is more perfectly spherical than the Death Star, and has a smaller prime weapon. [ROTS movie & comic]
Archduke Poggle the Lesser discusses the sensitivity and security of his superweapon plans [AOTC]. At the start of the Clone Wars, the Geonosians are planning to build an “Ultimate Weapon”, which would eventually be called Great Weapon [in Reversal of Fortune]. The Ultimate Weapon is shaped more like the Death Star than the Great Weapon
Count Dooku receives a copy of the plans of at least one Death Star predecessor, for safekeeping. [AOTC]
The Maw is a tight and seemingly unstable cluster of black holes. At least one Death Star prototype was constructed at a secret and isolated research facility situated within the perilous Maw black hole cluster near the Kessel system [JS, DA].
The cluster's stability is something of a mystery; such a collection ought to have ended in collision and coalescence of the holes long ago. Some astrophysicists had speculated that the Maw's improbable stability was due to deliberate design and assembly by an advanced, vanished civilisation. The Maw's interior is a virtually unnavigable cauldron of deadly radiation and plasma streams contorted by the holes' gravity. The Maw has long been avoided as a peril to hyperspace travel near the planet Kessel. Safe passages around or through the Maw are extremely difficult to calculate; approaching the black hole cluster is considered suicidal. Along with the secret discovery of a gravitationally stable zone hidden inside the Maw, this remoteness and inaccessibility made it an ideal site for Grand Moff Tarkin's secret superweapons research facility.
A Death Star prototype lurks near the research station in the Maw. [Jedi Search; Jedi Academy Sourcebook]
The first fully functional Death Star battle station was built using convict labour in orbit around the tropical penal world of Despayre in the Horuz system. [DSTC] The construction took less than two years. [SWTJ] After construction finished, the planet was destroyed in an early test firing, as a precaution to ensure the Death Star's secrecy. The military forces previously stationed on Despayre apparently were redeployed as detention guards aboard the Death Star. The fate of the convicts is less certain.
A mere few years elapsed between the initiation of the Death Star project at the secret Maw Installation and the time when the first operational Death Star destroyed Alderaan. Tarkin's enumerated journal entries [in DSTC] indicate a schedule of less than 2 years. The total duration of the project, from the gathering of Tarkin's project team until the demonstration at Alderaan, has been reported as 3 years [The Essential Chronology]. The speed and efficiency of this research effort is astonishing, as is the accomplishment in logistics and construction.
It has sometimes been suggested that Tarkin's Death Star project strained the resources of the Empire, but this couldn't be literally true, considering the quick construction of the Death Star II (about 178 times as voluminous) over Endor. What excuses can we make for Tarkin's construction time of months rather than days? Novelty is probably the most important factor. The initial research effort needed to prove and develop the superlaser concept may have cost more than the actual construction of a battle station. The need to conceal the project from the Imperial Senate would also be a handicap; four years later the Emperor could act openly. It is also possible that the first Death Star was delayed because it was only Tarkin's own local project, supported by a small fraction of the Empire's resources.
Lord Vader motivating convict labourers at Despayre. At first, the battle station's north pole appears closest to the planet, unlike the alignment of the DS2 over Endor's moon. [Death Star Technical Companion, Essential Chronology]
Grand Moff Tarkin, Bevel Lemelisk and their great design. [The Essential Chronology]
“...and the Emperor, pleased with the concept, ordered construction to begin. An unoccupied and isolated sector of space was chosen as the construction site. For nearly two years, every resource of the Empire was directed toward the completion of the project.” — Star Wars Technical Journal, p.100.
The second Death Star was built hovering above a point on the surface the forest moon of Endor, in a remote region nominally governed by Quanta Sector's Moff Jerjerrod. [SWAJ#6] Starting after the Battle of Hoth, the 900km wide sphere was approximately 60% complete within 6 months [SOTE, ROTJ]. This implies a construction rate on the order of 38 million km³ per month, or 458 million km³ per year.
If it had been finished, the volume of this battle station would have been about 178 times that of the original. In order to avoid overburdening regular naval supply systems, the Emperor partly outsourced shipping of raw materials to the XTS corporation owned by courtier Prince Xizor [SOTE]. Nevertheless, the scale of the project was insignificant compared to the Imperial economy, and its funding was disguised under the Ministry for Energy [SWAJ]. The project remained secret until it was deliberately leaked to Bothan spies.
If the radius of the moon was about 5200km then the Death Star was situated approximately 2000km above its surface [rebel tactical hologram, ROTJ]. There it would subtend about 27° on the Endorian sky above the garrison [which is consistent with views in the film].
The Death Star hovered directly above the generator of its protective deflector shield. Therefore its orbital period matched the spin period of the Moon. In other words, it behaved as if it were in a synchronous orbit. However a naturally stable orbit at this altitude requires a high velocity that implies an orbital period of about 2.5 hours. If the Endorian day were this brief then the daylight would change visibly during scenes. If the Endorian rotation takes a normal day, then the Death Star needs to be higher in order to orbit synchronously. How then does the construction stay aloft without overtaking the garrison? The Death Star's equilibrium position must have been controlled by more than just the moon's gravity. A supplementary repulsive force was needed to prevent the Death Star from falling from the Ewoks' sky. An artificial force of about one third of Earth's surface gravity is required.
The Endor surface facility projected up an immensely powerful repulsorlift field, in conjunction with the deflector shield [ITW:SWT]. This might actually be a subtle clue regarding the nature of deflector shields and/or repulsorlift fields in STAR WARS. Are deflector and repulsor technologies directly related? Why does the repulsorlift field not appear to affect the pressure balance of the air between the projector and the Death Star?
The weight applied by the repulsorlift support beam and the intrinsic gravity of the Death Star II must both exert tidal effects on the Endorian surface, and this should be obvious to coastal ewok communities. The magnitude of this effect depends on the mass/energy of the station and its fuel. At the very least, the empty density of the station must exceed 10 kg / m³. Endorian lakes may rise by nine metres or more. Depending on how the physics of repulsorlift works, the tidal effects may be offset in large part by the station's repulsortlift support field. Because the battle station stays above one region, the deformation of the moon's crust and displacement of surface waters are a static effect unlike the daily tides of an asynchronous moon. The distortions increase gradually as the Death Star's mass is assembled. Ewoks and yuzzum would notice lakes and waterways gradually creeping from their normal positions. Severe quakes are likely as the crust is deformed by the station's weight. (What happens when this pressure is relaxed after the station is gone?)
The transport and redistribution of the mass and energy to the Death Star's construction site must have had a slight but appreciable effect on the orbital mechanics of the Endor system. The mass, angular momentum and orbital energy are not insignificant compared to the natural configuration of the system. The moon's distance from its binary suns probably changes very little. However there must be subtle changes to the long-range resonant gravitational interactions with the parent planet Endor and its other moons. If the Endor moon had any subordinate moons of its own, then their orbits could have been perturbed severely.
Death Star II hangs serenely in low orbit above the sanctuary moon.
One of the great dishes of the Endor surface facility. It is probably an important extension of the underground machinery, but its identification with the shield and the repulsor remains uncertain because the dish doesn't point at the battle station.
After arriving with the Emperor, Executor led the construction site's security cordon. Devious rebels gaze out into the majestic construction site from a stolen shuttle.
An image from Coruscant taken at around the time of the Battle of Endor (or perhaps shortly afterwards), shows the construction of twin Death Stars above the planet [TISWU]. The fates of these battle stations are unknown, although they were gone by the time the Rebel Alliance captured the capital planet, three years after the Endor debacle [X-Wing: Wedge's Gamble].
It seems likely that they fell victim to the collapse of governmental and military authority which followed the Emperor's death at Endor.
Perhaps the Emperor's courtiers and admiralty were too preoccupied with the succession struggles, the Empire's fragmentation into warlordism, and fending off the New Republic forces. In those desperate and chaotic circumstances, two unfinished Death Stars might seem like an extravagance, especially after the concept was discredited by the embarrassement at Endor. With years of hindsight [Heir to the Empire], Captain Pellaeon recalls that the Admiralty had long held misgivings about the Death Star project, viewing it as an attempt by Palpatine to centralise naval power, just as he'd assumed total political power by dissolving the Imperial Senate. Perhaps the humiliating loss of another Death Star gave the skeptical admirals an excuse to abort its younger siblings.
It seems likely that construction of Coruscant's two Death Stars was halted and the raw materials recycled into millions of conventional warships. Using the same resources to build starships allows a wider dispersal of forces throughout volatile sectors of the galaxy. A Death Star can only threaten one system at a time, and its intimidation value was seriously debased by the Endorian debacle. With insurrection and mutiny erupting across the entire galaxy following Palpatine's fall, the Death Star concept had lost its strategic value.
Alternatives:
The incomplete twin Death Stars under construction around Coruscant.
A Golan battle station (right side) over Coruscant. This non-spherical structure looks completely different from either of the unfinished Death Stars. [The Essential Chronology]
The Hoth system is particularly rich in asteroids, much to the detriment of the security of the Rebel Alliance base on the sixth planet. Asteroids strayed across the planet's orbit or even crashed as meteorites with such a frequency that sensor crews could never be sure of distinguishing approaching starships from the natural rocky debris.
Many years after the Battle of Hoth, this abundance of asteroids was a boon to the mining activities of Orko SkyMine Corporation, controlled by former Black Sun official Durga the Hutt. Employing the genius of the original Death Star engineer Bevel Lemelisk, massive automated mineral extraction drones were designed and set to the task of refining and accumulating the material for a privately-owned superlaser weapon.
Using a stolen duplicate of his original Death Star designs, Lemelisk devised the Darksaber. This vessel was structurally much simpler than its Imperial forerunners. Appealing to Durga's thrift, Lemelisk deleted most of the original design's spherical superstructure, leaving a cylindrical form centred around the superlaser itself. Thus the power needs of support systems were reduced (though the weapon always must have been the most power-consuming component). The Darksaber is probably slower and more cumbersome than a Death Star. Lemelisk also dispensed with the superlaser's "eye" structure, emitting the final beam directly from an axial shaft. This simplification may have improved yield (as Lemelisk emphasised), but it eliminates the tributary beam system that allowed the Death Stars to aim precisely.
Collective-minded taurill creatures in Durga's thrall performed the actual construction work. These beings, which individually are semi-intelligent simians, had a very poor technical aptitude. Their poor workmanship and construction flaws caused Lemelisk such great anxiety that he feared that the station might misfire.
The Darksabre construction site among the Hoth asteroids, surrounded by taurill workers. [The Essential Chronology]
Appearance of a taurill [Essential Guide to Alien Species].
Durga the Hutt, chief patron of the gangster-funded Darksabre project. Amazingly, Durga has the same shape of broken nose as the late Jabba. [New Essential Guide to Characters]
Rebel starfighters at the Battle of Yavin exploited a small thermal exhaust port in a minor surface trench near one of the poles of the Death Star. The vent was equipped with ray shielding, which precluded the use of laser cannon fire. Only the absence of particle shielding permitted damage by proton torpedo.
The rebel fighters made their attack runs by flying within the trench, from a starting point several dozen kilometres from the port. This attack pattern provided shelter from most of the surface guns outside the trench, during the time when target computers sought to lock on the exhaust port. Flying above the rim of the trench may have entailed a suicidal exposure to enemy fire while the rebels' targeting computers require an abonormally straight, non-evasive flight path.
After Red Leader's first (unsuccessful) attack run, the Imperial battle analysts guessed the purpose of the rebel tactics. Chief Bast attempted to alert Grand Moff Tarkin to the station's vulnerability. Tarkin was heedless and irritated by the interruption, but Bast must have been sufficiently convinced of his analysis to make his own escape. He survived and reappeared a year later in Lord Vader's fleet [in the STAR WARS Holiday Special]. (For further information refer to: Death Star Survivors.) Bast was seen lingering hesitantly in the Overbridge until half a minute before the cataclysmic explosion, at the point when Tarkin gave the order to commence the firing sequence. This proves that a suitable shuttle hangar or other escape facility was within easy running distance of the command centre.
When Luke Skywalker's two fire-linked proton torpedoes detonated inside the shaft, they set off a chain-reaction which propagated and grew for several seconds until it reached the main reactor core, detonating the entire battle station.
The explosion of the Death Star was not symmetric, but in real life very few explosions are. The explosion first erupted near the north pole, possibly because this part of the station was already more heavily damaged by the lesser chain of explosions started by the proton torpedoes. Otherwise, the asymmetries of the final explosion may have been guided by non-uniformities in the Death Star's internal structure: weaker regions allow the fireball to propagate faster. The explosion may be inherently unstable as well: if it momentarily goes further in one direction then it weakens that part of the structure, which promotes faster eruption at the same place. In these ways, an initially spherical explosion inside the complicated artificial structure was able to erupt unevenly on the surface.
The explosion did not completely annihilate the material of the Death Star. A substantial amount of wreckage was left in orbit around Yavin. Much of the debris was soon acquired by the scavenging Ugor species, including some immense fragments with surprisingly mild damage. In at least one section corridors and chambers remained intact enough for exploration [Scavenger Hunt]. In the following months an Imperial Security Bureau salvage station under the command of a Major Reskik was placed in a nearby orbit, in order to deter unauthorised scavenging and analyse the remains [Galaxy Guide 2]. However, the explosion's expansion velocity apparently exceeds the escape velocity for Yavin orbit, and therefore much of the material would exit the system.
Polar trenches displayed on a global view of the Death Star. The desired entry point to the meridional trench vicinity is highlighted.
Interior details of the trench, simulated as a wireframe animation from the viewpoint of a rebel pilot approaching the thermal exhaust port (highlighted at the end).
Bast hurries to report his dreadful analysis.
A starfighter releases a proton torpedoes, and they enter the exhaust port. Proton torpedoes entering the exhaust port.
The torpedoes detonate in the shaft. An explosive chain reaction propagates down towards the core, until the chain reaction reaches the main reactor and the station explodes.
Once the Endorian security deflector shield fell, rebel starfighters were able to swarm about and inside the incomplete Death Star II. Dedicated anti-starfighter laser cannons on the surface and pursuing TIE fighters were unable to eliminate the rebel menace.
A rebel X-Wing and freighter were able to fly directly into the main reactor chamber. Their first target was a power regulator on a tower which sprouted off the northern end of the reactor. Damage to this component destabilised the reactor and sent a flaming explosion circling around the central toroidal region. Further hits at the point of the axial spike below the reactor bulb were dramatically effective, exacerbating the reactor's destabilisation and filling the whole chamber with a horrific conflagration. The incandescant plasma was a yellow/amber hue, implying that the outer surface attained temperatures of several thousand degrees K. (The obscured inner regions of the explosion may have been hotter.)
A roiling fireball grew at the core of the battle station. Gaseous outburst erupted through the tunnels connecting the reactor to the surface. Some minutes later, a flash of light from the deep regions illuminated the incomplete parts of the station from within. Further eruptions appeared at weak points on the surface, and then within a second the entire battle station was consumed in its own blastwave. The gaseous fireball of evaporated material expanded in the normal decelerating manner, proportional to a small power of time. Solid particles up to several tens of km wide were hurled in all directions, and continued in ballistic trajectories. A peculiar luminous ring effect appeared about the equatorial plane and expanded much faster than the other components. Its substance and effect are a mystery, but it may be related to some mechanism of the Death Star that had a preferred axis (perhaps the onboard shield distributors).
The destruction of the second Death Star would have cataclysmic consequences for life on the forest moon of Endor. The exact results depend on how well the battle station was fragmented when it exploded. Pieces of metal debris larger than a few metres would be likely to make noticeable impacts on the surface, as meteorites. Smaller pieces would burn completely upon entering the atmosphere, but must eventually recondense as dust.
Larger impactors, over a hundred metres wide, are violent enough to compare with the violence of nuclear detonations or natural impacts like the Tunguska event in Siberia in the early Twentieth Century. Each fragment wider than a kilometre or tens of kilometre will inflict devastating environmental effects like that which caused the dinosaurs' mass-extinction event on Earth 65 million years ago. Several projectiles of this size are visible in the Death Star II's explosion.
About half of the Death Star's mass must eventually enter the moon's atmosphere, and ultimately settle on the surface. Small meteoroids and the vapour mass from the fireball will become atmospheric dust. The weight of large quantities of dust may cause convection throughout the atmosphere, until it is all deposited on the ground. Lighter quantities of airborne dust will produce a "nuclear winter" effect by reflecting sunlight back to space. Indeed the Endorian winter effect is likely to be much greater than that which killed the dinosaurs, because it involves orders of magnitude more dust (the Death Star may be a hundred times wider than Earth's K-T asteroid or comet). Global wildfires ignited by the larger meteoric strikes may enhance the winter by adding smoke to the dust and impact debris. (However the total biomass available to generate smoke is far exceeded by the likely dust mass injected from the explosion.)
Now let us consider the detailed consequences of the winter. Fallout dust would concentrate in the upper atmosphere, blocking sunshine and cooling the moon's surface. The lack of sunlight would cause most plants to die or go dormant. This would cause starvation of herbivores, which would eventually starve those creatures which are higher in the food chain. At best, the Endor moon would experience a serious mass-extinction event. At worst, the chemistry of the atmosphere might be irrevocably altered by the metallic debris, possibly killing all animal life.
Endor would become uninhabitable within a period of no longer than a few months but the "winter" effect could last for years. It is probable that the Ewoks became extinct on their homeworld. Remnant populations may survive if they were evacuated by the Rebel Alliance, along with those few individuals (like Joh Yowza) who had boarded the infrequent trading vessels which visited the system before the establishment of the Imperial base. Those ewoks seen among rebels in Dark Empire are probably among only a few thousand lucky survivors.
The demise of the Ewoks was noted in a historical display about the Battle of Endor in The Galactic Museum on Coruscant [described in X-Wing: Wedge's Gamble]. The display blamed the extinction of the adorable and innocent Ewoks on callous exploitation by the Rebel Alliance. The suggestion of premeditated genocide may be misleading or deceitful. Although the rebel attack indirectly resulted in the near-extinction of ewoks, it is not clear that the Alliance planners knew that the moon had intelligent natives. In the absence of sapients, biocide is arguably an acceptable price for the elimination of another Death Star in a desperate galactic war. Once the mistake became known, the Alliance might have assisted and relocated the few Ewoks who could be gathered into ships in the days after the explosion. Nevertheless, the tragic fate of the Ewoks seems to have been the subject of a New Republic cover-up.
[For further commentary, refer to Endor Holocaust.]
Schematic of Endor moon, Death Star II and the security deflector shield.
Rebel fighters weave through scaffolding, evading turbolaser fire.
Millennium Falcon enters a reactor tunnel. TIE Interceptors valiantly pursue the rebel pests into the superstructure.
One of the culprits of the growing conflagration races from the main reactor chamber.
Rebel technicians monitor the chain-reaction of explosions and meltdowns within the doomed battle station.
Holes in the superstructure allow the explosion consuming the inner regions to illuminate some outer sections, just prior to full detonation.
The explosion as seen from space and then the vicinity of the ruined deflector shield facility. Note the immense fragments which are falling towards the atmosphere. [Topps Widevision cards]
For detailed discussion of contuity and the precedence of sources, refer to Continuity, Canon and Apocrypha.
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