The origins of the second Death Star are outlined on p.45 of Galaxy Guide 5: Return of the Jedi, by Michael Stern, West End Games, 1990.
The designer of both projects was a man named Bevel Lemelisk, a well-respected architect and designer of many of the Empire's most sophisticated space stations. The original concept for the Death Star came from Grand Moff Tarkin, a man of brilliant vision but almost no grasp of engineering. Lemelisk, along with a virtual army of subordinate architects and engineers, transformed Tarkin's vision into reality.
After the first Death Star was destroyed, Lemelisk went into hiding. Knowing the price of failing the Emperor, he feared for his life. When Imperial Intelligence agents tracked him down at his remote retreat on Hefi, he thought surely he was doomed. He was quite surprised to discover that the Emperor did not want his head, but rather what was in it.
Specifically, the Emperor wanted him to design a new, more powerful Death Star battle station, this time without even the most minute design flaw. Amazed at his good fortune, Lemelisk went to work with a will. He would not disappoint the Emperor a second time.
The solution to the thermal exhaust port problem was rather simple. In place of one large port, Lemelisk included millions of millimeter-wide heat dispersion ducts. These ducts would serve the same function as the exhaust port, carrying the excess heat from the reactor core to the station's surface. But these ducts were equipped with emergency baffles, designed to muffle any high pulse of energy before it reached the core.
With that problem solved, Lemelisk set out to improve the main weapon of the Death Star, or “super laser” as Lemelisk called it. The laser was quite strong enough already — Lemelisk couldn't conceive of any need to increase the power of a weapon which could vaporize a planet — but there was room for improvement in the weapon's targeting systems and rate of fire. At this, Lemelisk was highly successful. The powerful beam could now be focused much more finely and quickly, allowing it to fire at a moving target, such as a capital ship.
Lemelisk also increased the overall size of the station. This allowed much larger Imperial vessels to dock within the station; the previous Death Star had been able to accommodate nothing larger than a cruiser, bigger vessels being required to orbit the station.
To handle the possibility of attack by small, fast starfighters, Lemelisk increased the number of light anti-ship batteries nearly threefold, creating a nearly impenetrable blanket of anti-starship fire. The battle station's increased size allowed Lemelisk to add dozens of TIE fighter bays as well. If this Death Star were to fall, it would not be at the hands of a few lucky Rebel X-wings.
In fact, Lemelisk didn't believe that anything could defeat the new Death Star. When presenting the new design to the Emperor, Lemelisk boldly claimed that the only way the new Death Star could be destroyed would be if it were attacked while still under construction — once completed, it would be invulnerable.
Apparently, the Emperor believed him. So did Mon Mothma and Alliance Command. This, as we know, set the stage for the great battle of Endor and the destruction of the Death Star, the Emperor, and the New Order.
This passage contains several key revelations:
p.100 (of the combined volume):
“...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.”
This passage is interesting as it shows that the Death Star commanded by Tarkin took less than two years to build. This observation, combined with the fact that the frame differs from the skeletal Great Weapon in ROTS, proves that they were different structures.
The Hammertong story [by Timothy Zahn] is one of the Tales from the Mos Eisley Cantina, [ed. Kevin J. Anderson, Bantam, 1995]. This story has some relevance to the chronology of the Death Stars. A group of Mistryls (amazon mercenary women) were hired as security to transport an experimental device (called the “Hammertong”) from an Imperial research facility in a system near Tatooine. The base's troops turned hostile, and two of the women stole a hollow “Strike Cruiser”, which they crashed into the dunes of Tatooine. The Hammertong, in the ship's hold, is a 200m-long cylindrical object. A plaque on its side attributes the design to Eloy and Lemelisk. It is supposed to be a segment of a superlaser prototype. The device is annotated as “Mark 2”.
Some fans, in open correspondence, interpret the Hammertong as part of the Death Star II in ROTJ. This cannot possibly be true.
Galaxy Guide 5 and the Movie Trilogy Sourcebook state that Lemelisk's redesign of the battle stations and weaponry didn't occur until after he fled to Hefi, and was subsequently caught by Imperial Intelligence. He didn't flee until he heard news of the Battle of Yavin. The Battle of Yavin hadn't happened at the time of the Hammertong adventure, because the women crashed their stolen ship (containing the superlaser components) into the Tatooine dunes about an hour before Devastator and Tantive 4 appeared above the same planet [pp.82,95].
Tatooine is an obscure planet, distinguished only by the secret residence of Obi-Wan Kenobi. It is a remarkable coincidence that the Mistryls took their stolen superlaser to the same place as Princess Leia, R2-D2 and the Death Star plans. Their arrival was almost simultaneous. Are these events linked by a hidden conspiracy? Did one of the Mistryls have secret contact with Kenobi or the Rebel Alliance? Was the Imperial research base deliberately insecure? Was it linked to the base where rebel spies stole the Death Star plans? Was the “Hammertong” was a diversion or a trap?
The Hammertong probably is a genuine, working superlaser component (as indicated in Spectre of the Past) but it wasn't built to be part of the Death Star II, the Tarkin or any other specific battle station. Rather, it must be a prototype piece invented as part of a broad and ongoing superlaser research program. It may only be a workbench test model. However the Mistryls' adventure proves that (at least for the sake of appearances) Eloy's weapons research was continuing at the time when the first Death Star became operational.
“Hard to tell through all the sand, but I think there's a battle going on up there. An Imperial Star Destroyer against something about the size of a bulk freighter.”
“— wait a minute, there's a break. It's a Corellian Corvette.”
“He said he'd picked up something sneaking in toward the Dune Sea an hour or so before that Star Destroyer showed up and all these Imperials dropped in on us. Something just about the size of a Strike Cruiser.” Riji lifted his eyebrows. “Interesting, wouldn't you agree?”
He looked up at her, his face pasty-white. “Do you know what you have here?” he whispered. “Do you have any idea?”
“Not really,” she said warily. “Do you?”
“Look here,” he said, pointing to a plate. “See? ‘D.S. Mark Two. Module Seven, Prototype B. Eloy/Lemelisk.’ ”
“I see it,” Shada said. “What does it mean?”
Riji straightened up. “It means this is part of the prototype superlaser for the Death Star.”
“What's a Death Star?”
“The Emperor's latest grab for power. Like nothing you've ever seen.” Riji looked back along the Hammertong's length. “And we've got a piece here of its main weapon.“
“A piece?” Shada frowned. following his gaze. A solid two hundred metres of laser — “You mean this isn't all of it?”
Deefour, with a complete technical readout on the Hammertong .... “No,” Shada told her, smiling in spite of herself at Riji's ingenuity. “No, it's all right. we owe him that much. And if he's right, he and his friends are going to need all the help and information they can get.”
Her smile faded. “D.S. Mark 2” the plate on the Hammertong had said. Death Star, Mark 2, perhaps? A second generation of the thing Riji was so afraid of?
It could be. And if so, the Mistryl might have to seriously consider that offer to join up with the Rebel Alliance.
A.Gehrls kindly provided the following excerpt from Spectre of the Past, Timothy Zahn, pp.314–315. W.Poe ennumerated the pages. In this scene, Shada, one of the Mistryls involved in the “Hammertong” incident [TFTMEC], is attempting to establish her credentials with some important persons from the New Republic.
She looked back at Solo. “So do your people, though you might not know it,” she said. “Nineteen years ago on Tatooine I helped get you the technical readout for a prototype component of the second Death Star's superlaser.”
Another ripple of surprise ran through the room. A ripple that, to Shada's own mild surprise, didn't seem to touch Solo himself. “Really,” he said. “Tell us how.”
“A friend and I stole the component from an Imperial research base,” she said, trying to read his face. Suddenly the one who'd been pushing her the most seemed almost to be on her side. “It was code-named the Hammertong. We flew the ship it was mounted aboard to Tatooine —”
“What kind of ship?” Solo interrupted.
“Loronar Strike Cruiser,” Shada said. “Heavily modified — the interior had been gutted so the thing would fit inside. We half buried the ship in a dune and went to the Mos Eisley cantina to find a freighter pilot with a ship who could transport a segment of it for us.”
This passage reveals that Shada still believes that the Hammertong was a genuine superlaser module. Perhaps this conclusion was supported by the Mistryls' analysis of the recovered Hammertong segments? The Hammertong was a prototype component, and not a final product. Even while the first Death Star neared completion, the Empire supported a continuing programme of basic superlaser weapons research. This programme apparently yielded Hammertong as one of its intermediate results.
Shada's reference to the Death Star II is made in hindsight. The Empire didn't decide to design and construct a newer Death Star until long after the Hammertong theft [GG5]. As a prototype, the Hammertong was not made for incorporation in the Death Star II itself. The Hammertong tale does not imply any commencement of construction at Endor before the Battle of Yavin.
Tales of the Bounty Hunters [ed. Kevin J. Anderson, Bantam, 1996] provides glimpses of a remarkable relationship between the assassin droid IG-88 and the Death Star II. Following the Battle of Hoth, the droid was summoned by Lord Vader to hunt the Millennium Falcon. While aboard the Executor, IG-88 hacked into Vader's personal files, and thus discovered the Death Star II project [p.49]. The battle station's construction may have commenced by this time, but the semantics are inconclusive.
The IG-88 droids were already preparing to substitute the Death Star II computer core before the Millennium Falcon arrived at Bespin [p.53]. At this stage, the battle station lacked its computer core, reinforcement girders and the superlaser; these were marked as future developments in the stolen plans [pp.50-51]. Without reinforcement girders — effectively the frame of the battle station — it appears that the construction must have been at a very early stage. Later, the computer core that was infected with an IG-88 mind remained inert for at least a month after its arrival at Endor [p.66]. Moff Jerjerrod's construction schedule lasted “several months” [p.66]. Thus the Death Star II construction process was meant to take less than a year from start to finish.
Not only was Vader concerned with his flagship and the Imperial fleet under his iron command — he also knew of the Emperor's pet project, a second, larger Death Star under construction in orbit around the sanctuary moon of Endor.
As IG-88 digested the information, he had another flash of intuition. Some might have called it a delusion of grandeur, but IG-88 — who had already been copied into three identical counterparts, his personality moved into separate droid bodies — saw no reason why he could not upload himself into the huge computer core of the new Death Star!
With their optical sensors tuned to peak performance, the four IG-88s studied the shimmering classified plans of the second Death Star. The perfect curves of the armillary sphere indicated where reinforcement girders were to be installed, where the central superlaser would be aligned . . . where the new and precise computer core would be attached.
The Death Star computer core had not yet been installed. It had not even arrived at the sanctuary moon — but now IG-88 had the schedule and the destination. According to Vader's plans stolen from Executor, IG-88 knew how the computer core would be guarded, what path it would take as it entered and left hyperspace. It was all the information he needed.
“The solution is obvious.” IG-88A said. The others agreed.
“We must create a duplicate computer core, which we will inhabit.”
“We will secretly make the exchange. An identical core will be delivered to Endor.”
As preparations for the assault on the Death Star computer core proceeded with all the speed the droid manufacturing droid could muster, an imperative transmission from one of IG-88B's smart microtracers shot towards Mechis III.
Boba Fett had found Han Solo.
Fett's ship, Slave I, was currently en route to Bespin, where Solo was heading toward a gas-mining metropolis known as Cloud City.
[Jerjerrod] stood in his smart olive-grey uniform, watching the new stormtroooper escorts. “Attention!” he snapped. “Get that computer core installed as soon as possible. For the next several months our schedule is exceedingly tight, with no tolerance for delay. We must redouble our efforts. These orders come directly from Lord Vader.”
The blackness of sensor deprivation was distressing, but unavoidable. Humans would have called it “unconsciousness” — but when IG-88 finally reawoke after a month or so of stasis, he found himself in an immense new world of data input.