Base Delta Zero

Written: 2001-12-10
Last Updated: 2002-03-07

Base Delta Zero is the Imperial codename for what is often referred to as "burning off" a world. As described in the Imperial Sourcebook, "it is the systematic complete destruction of all 'assets' of production, including factories, arable land, mines, fisheries, and all sentient beings and droids." This operation has been referred to as reducing "a civilized world to slag"¹, reducing "a planet's surface to smoking debris in a matter of hours"², and "the Imperial code order to destroy all population centres and resources, including industry, natural resources and cities."³ The timeframe is known to be less than a day, although it is not known how much less.

The order to perform a Base Delta Zero on a populated world is one of the most grave orders an Imperial commander can receive. While no Imperial officer would have any qualms about obliterating a Rebel base of operations or a pirate outpost, it is not uncommon for Academy cadets to express reservations about the wisdom of such operations when performed on non-military, heavily populated worlds such as Camaas. This underscores the importance of the psychological conditioning aspects of our training program, since we could not afford to have officers balking at any orders, regardless of whatever private concerns they may have. There are always extenuating factors beyond the knowledge of the individual starship captain, and without respect for the chain of command, our military forces simply could not function.

A more serious problem with the Base Delta Zero is the wholesale destruction of potentially useful assets. Conventional military operations are generally geared toward the liberation of territory from hostile forces, but a Base Delta Zero removes all possible value from a planet, rendering it utterly worthless to anyone. It is quite literally "scorched Earth", and ultimately, the total destruction of industry, arable land, fisheries, and non-combatant population is of more use as a terror tactic than a legitimate military operation. It is the fear of a Base Delta Zero more than the actual operation itself which is of use to us.

Historical BDZ operations

Caamas: records are sketchy about this operation, but it has been established that it was performed shortly after the Clone Wars by forces loyal to Emperor Palpatine. There were no living witnesses to the attack⁴, which means that there were no survivors anywhere on the entire planet (not even animals, plants, or people in buried shelters, according to the official records). This meant that the only surviving Caamasi were those who had been off-world during the attack. It is also known that the attack took less than a day⁵, although we don't know how much less, and the size and composition of the attacking force is still unknown. Moreover, we also learned that the environmental devastation was so great that even after 40 years, it would have actually been easier to terraform a barren planet to Caamas's original specifications than it would have been to restore Caamas itself⁶! This suggests that Caamas was massively irradiated, or that so much of its surface material was blasted up into the upper atmosphere that it rendered normal terraforming operations impractical. It was effectively destroyed⁷ as a habitable world, although not as literally or permanently as Alderaan.

Dankayo: in Scavenger Hunt, three star destroyers attacked Dankayo and reduced the Rebel base to slag. They blasted the atmosphere off the planet and atomized its topsoil⁸, pounding the planet with such violence that only a "deep planet shelter" could provide protection.⁹. The surface of the planet was left in an evenly cratered state, which indicates the blanket use of indiscriminate high-yield ground-burst explosions.

Emberlene: the homeworld of the Mistryls was apparently attacked and devastated around the same time as Caamas¹⁰. However, it turned out that the Empire was not responsible. The Mistryls had apparently been terrorizing their neighbours, and their neighbours had hired mercenaries to do the job¹¹. This is an indication of the ease with which such an operation can be performed, since freelancers can do it without the resources or knowledge of the galactic government.

Meridian: a once-powerful civilization was apparently wiped off this planet through some kind of bombardment which left its surface a radioactive wasteland¹². This happened centuries before the rise of the Empire, and unfortunately, there is no information on the size and composition of the naval force involved.

Bothawui: this planet was targeted for a BDZ by three star destroyers, but not successfully attacked. They had planned to wait until warring fleets of lesser vessels destroyed each other, and then they were to eliminate the survivors and depopulate the planet. Like Caamas, this attack was intended to leave no survivors (in fact, this was a crucial mission requirement because they were trying to frame the warring forces for the attack and fan the flames of civil war in the New Republic). Unfortunately, a stroke of ill fortune led to their early detection, whereupon they were set upon by both fleets and forced to withdraw before commencing the operation¹³. The use of three star destroyers in this incident as well as the attack on Dankayo may indicate that when it is necessary to eliminate all witnesses, three vessels are required. Given a single ship's inability to fire on ships leaving from the opposite side of the planet, this is not surprising.

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Tactical Considerations

Given the great speed at which reinforcements can arrive and the fact that historical BDZ operations have never been interrupted in progress, it seems likely that if necessary, a Star Destroyer should be capable of accomplishing a Base Delta Zero in a period of an hour or less.

Baseline energy level

It is possible to generate a conservative energy estimate by assuming a dry planet (no oceans) and assuming that this devastation will be caused by the melting of surface material to a depth of one metre (note that this would be insufficient to kill military personnel in deep underground bunkers). Using these conditions and a planet of roughly Earth-like dimensions, the Base Delta Zero operation would melt 5.1E14 m³ of surface material. The crust of a typical planet is composed mostly of silicates, so the thermodynamic properties of silicon dioxide can be used as a reasonable basis for estimating the characteristics of planetary crust material. The melting point of silicon dioxide (quartz microstructure) is 1883K, its density is 2220 kg/m^3, and its specific heat is roughly 1050 J/kgK at high temperatures¹⁴. The energy required to heat 5.1E14 m³ of rock from 300K to melting point is therefore 1.9E24 J. The latent heat of fusion for SiO2 is at least 250 kJ/kg¹⁵, thus raising the total to over 2E24 J. Given a 1 hour timeframe, the power requirement would be well over 500 million TW.

Other requirements

Realistically, the baseline energy requirement would be insufficient to accomplish a true Base Delta Zero for many reasons. Unlike most planetary bombardment scenarios, in which only military or industrial targets such as major cities and bases are targeted, a full Base Delta Zero operation is all-encompassing. It seeks not only to depopulate the planet and wipe out its military capability, but also to render it utterly useless for future generations. The explicit requirement for destroying all "arable land, mines, fisheries, and all sentient beings" as well as all "natural resources" goes far beyond the minimum requirements for planetary neutralization. The destruction of all animal life, both on land and at sea, is a truly massive undertaking. Indeed, Gholondreine-ß's punishment¹⁶ was arguably an extravagant waste of resources, and so is a Base Delta Zero. But if the Emperor decides that it is necessary to make an example out of a dissident world, such actions can become necessary despite their shortcomings.

The realistic energy requirements for this kind of all-encompassing destruction are much larger than a naïve observer might initially assume. The destruction of all edible sea life (ie- "fisheries") requires the boiling of large quantities of the planetary oceans, and the destruction of all mines (which are underground structures by nature) and underground bunkers requires much deeper ground penetration than is possible with a 1 metre melt depth. A BDZ also requires the melting of all cities, and the kind of urban agglomeration seen in typical Republic worlds would require a great deal of energy to melt in such a manner. It is obvious even without detailed analysis that a 400 metre tall skyscraper requires much more energy to melt than the one metre thick layer of rock upon which it once stood, yet we know from the example of Milagro¹⁷ (where entire cities were reduced to shimmering glassy lakes) that such complete melting is not unusual.

These added concerns are not trivial, nor is the difference between killing most or all of a planet's inhabitants. The energy requirement for destroying the fisheries alone can easily exceed the baseline by orders of magnitude! For example, given an Earth-like planet, one might hope to destroy all edible sea life by boiling the top 100 metre thick layer of the oceans (which is over-conservative; edible sea life is found at depths much greater than 100 metres). However, the specific heat of water is 4180 J/kgK, and its latent heat of evapouration is roughly 2.5 MJ/kg, so it takes roughly 2.8 MJ to boil 1 kg of water from room temperature. If 70% of an Earth-like planet is covered with ocean, there are roughly 350 million square kilometres of ocean surface, so a 100 metre thick layer would be 35 million cubic kilometres of water. There are roughly 1E12 kg of water in one cubic kilometre, so it would take roughly 1E26 J to boil off enough water to exterminate all the fisheries. If we wanted to achieve total extermination of all edible sea life (thus fully meeting the BDZ criteria), we would probably want to kill everything down to 1000 metres depth rather than 100 metres, thus increase the energy requirement again, to 1E27 J.

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Popular Objections

Some have claimed that surface melting is an overly optimistic figure. In fact, semantic debates have raged for years about the precise meaning of the term "slag", with naysayers claiming that the term might have been used in the colloquial sense rather than the technical sense. If the only evidence for this capability were the quote about reducing "a civilized world to slag", they might actually have a point. Any argument based solely on the choice of a particular word is highly suspect (although I note with some cynicism that the people who angrily point this out for Star Wars often hypocritically turn around and use dialogue semantics as "proof" in Star Trek). However, the devastation of Milagro serves as mute testimony to the fact that when Imperials decide to slag something, they literally reduce it to a molten puddle.

In any case, some still deny that a BDZ involves enough energy to melt 1 metre of surface layer, obviously because they have no idea how many conservative assumptions were used in the derivation of the resulting energy figures. It has been suggested that the objectives of a BDZ are to "merely" wipe out a planet's population and destroy all military targets, despite the rather explicit requirements for annihilating any and all means of production on that planet, including energy-intensive targets such as ocean fisheries and mines. They make these claims in order to cast doubt upon the 2E24 J figure. But if we humour those claims, what happens? Does the energy requirement decrease, as they claim? Or does it remain the same, thus demonstrating how conservative the original figures were in the first place?

Some have suggested that a large number of 1 megaton airbursts could achieve the objectives of a Base Delta Zero. However, this claim is quite frankly laughable. Even a group of megaton-class explosions in and around a metropolitan city such as New York or London would not cause 100% fatalities, and those are purely civilian targets, nowhere near as difficult to destroy as military targets. While thermal radiation, shockwave, prompt ionizing radiation, fallout and firestorm can all cause massive casualties, there would still be survivors, particularly in military bunkers, buried facilities, underwater installations, and armoured vehicles with NBC protection. Contrary to popular belief, exposed civilians can survive within the blast radius of a nuclear warhead¹⁸. Remember that a BDZ, unlike a typical nuclear attack, leaves zero survivors, unless someone builds a specialized deep-planet shelter (which would presumably be several kilometres deep, considering that ordinary mines are already hundreds of metres deep and they are destroyed). Indeed, hardened military installations would easily shrug off nuclear explosions unless they are in immediate proximity to the blast (thus ruling out airbursts).

This means that even if we accept the Federation cultists' greatly diminished definition of a BDZ, the energy requirements for a dispersed airburst attack are much higher than they may realize. First and foremost, one megaton airbursts would be woefully inadequate. At optimum burst height, a one megaton explosion has a blast radius of approximately 7.4 kilometres. In order to blanket the entire planet's surface with the blast radii of one megaton airbursts, one would need to fire more than 4.6 million shots!¹⁹ The total energy would be 2E22 J instead of 2E24 J, but there are many problems with this figure. First and foremost, even if we assume that a Star Destroyer can fire 50 shots per second continuously for hours, with zero downtime for cooling or service (a rather questionable assumption to say the least), it would take more than a full day to accomplish this task. That is a ridiculously long timeframe for an operation which can and has been carried out without leaving any witnesses. Even if we disregard the possibility of reinforcements arriving, the chance of random travellers simply happening to arrive during such a period is far too great, especially considering the cheap availability of interstellar craft.

A more reasonable timeframe is one or two hours, which requires that we dramatically increase the per-shot yield. According to conventional scaling laws²⁰, the blast radius of a 20 megaton bomb at optimum height is approximately 20 kilometres. The area of a 40 kilometre wide circle is approximately 1250 km², and the Earth's surface area is slightly over 500 million km², so a naïve observer might conclude that one could therefore use 630,000 such blasts (5E22 J instead of 2E24 J) in order to execute a Base Delta Zero. The number of shots is not unreasonable; given 15% downtime for cooling and service, with a firing rate of 50 shots per second, a Star Destroyer could accomplish this task in roughly 4 hours.

However, this is where we run into yet another problem. This analysis, while not as preposterous as the previous one (based on one megaton blasts) is still an enormous underestimate because like the previous one, it is based on conventional blast radii. Conventional blast radii are calculated based on a mere five psi of atmospheric overpressure, which is so low that the unprotected human body can easily survive!

Blast radii are calculated for 5 psi overpressure because that is the overpressure required to demolish most civilian structures, but it is totally inadequate for destroying hardened military targets. In Earth's twentieth century, American Atlas missile silos were designed to withstand two hundred psi of overpressure, not five! Are these people arguing that an Imperial BDZ would be useless against 1960s-era American missile silos? Given the requirements of a BDZ (not to mention the effects of past BDZ operations), that is patently ridiculous. If we use the destruction of all surface targets up to and including missile silos as a baseline, and assume that their protection technology is no greater than that of the 1960s-era United States, we would need to blanket the entire surface with 200 psi overpressure instead of 5 psi. This raises the yield requirement by a factor of forty²¹, so instead of 630,000 20 megaton blasts, we would need 630,000 eight hundred megaton blasts. The energy yield adds up to a total of roughly 2E24 J, which (coincidentally enough) is precisely the figure that the naysayers are attempting to debunk!

But of course, it gets better. Modern nuclear attack simulations often use blast overpressure figures as high as 2000 psi, to ensure destruction of hardened targets (remember: this is a zero-survivor mission). That raises the figure by another order of magnitude, so we need 630,000 8 gigaton blasts. And while this would undoubtedly exterminate all surface life, it still wouldn't destroy the fish!

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Conclusions

The Imperial Base Delta Zero operation serves as a useful benchmark for Imperial firepower estimates, with energies on the order of 1E24 to 1E26 J and time-averaged firepower on the order of 1E22 to 1E24 watts. Their power generation systems are more than capable of supplying energies on these scales (so they are obviously not a limiting factor), and scaling of a minimum-yield Death Star blast²² down to a single Star Destroyer (dividing by roughly 20 million to account for the size difference) generates a lower limit of 1E25 J, which is entirely consistent with this estimate. Moreover, given the fact that a Death Star blast is equivalent to a firepower somewhere between half the Imperial starfleet and the entire Imperial starfleet²³, this may actually be an underestimate, unless the entire Imperial starfleet consists of 40 million ships, or incorporates a large number of smaller superweapons (which is also possible, given that superlaser technology was undoubtedly developed and deployed on a smaller scale before the Death Star was built).

Federation cultist objections tend to revolve around gross underestimates of the scope of a BDZ (ie- ignoring the requirement to destroy 100% of the mines, arable land, animals, humans (both civilian and military) and fisheries so they can hit the major cities and declare the operation over), ignorance of the nature of nuclear blast radii (ie- assuming that 5 psi overpressure blast radii will achieve total destruction of all life), and semantic nitpicks (eg- debating about whether "slag" should be used in its colloquial sense or its technically correct sense, even though Milagro demonstrated that when Imperials decide to slag something, they melt it). As with the Death Star's firepower, it is quite obvious why they would seek to ignore or diminish the implications of the BDZ. However, as with the Death Star, the BDZ serves as evidence for the sizable tactical superiority of Imperial Star Destroyers over the Federation's diminutive warships, and the best efforts of Federation cultists to attack this evidence are fruitless.

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Addendum

This section contains numerous notes and pieces of information on real-life nuclear attack and asteroid impact scenarios, as well as global environmental catastrophe information.

Regarding the effects of megaton-class explosions in and over cities:

The 1979 OTA report "The Effects of Nuclear War" (see "Suggested Reading", below) described nuclear attacks on Detroit, a metropolitan city with a population numbering somewhere around 4.3 million at the time. For a 1 megaton ground burst, projected short-term casualties were roughly 220,000 dead and 420,000 injured, with a 95% chance of surviving the blast for civilians 5 to 8 km away from its epicentre, with heavy radioactive fallout and a large crater. For a 1 megaton air burst, projected short-term casualties were roughly 470,000 dead and 630,000 injured, with no fallout, no crater, and some reinforced structures surviving even directly under the blast. For a huge 25 megaton air burst, projected short-term casualties were roughly 1.84 million dead and 1.36 million injured, with no fallout.

In short, even a massive 25 megaton air burst at optimum altitude directly over the city of Detroit would still leave a million survivors! And this is for civilians, not military personnal in hardened installations, bunkers, or armoured vehicles. Moreover, the same report described a projected Soviet attack with 80 1-megaton weapons, hitting various cities across the continental United States. Total casualties were roughly 5 million.

There is no question that nuclear weapons are devastatingly powerful, but their short-term effects have been somewhat exaggerated over the years. You will not kill everyone in a major metropolitan city with a 1 megaton bomb, or even a monstrous 25 megaton bomb.

Regarding radioactive fallout:

Radioactive fallout is a prime component of nuclear attack scenarios, but it is not a critical factor in asteroid impacts. The primary source of radioactive fallout from a nuclear device is radioisotopes with long half-lives, and those materials come from the fission trigger of the weapon itself. Irradiation of surrounding material is a strictly secondary source of fallout, and it occurs due to neutron capture rather than electromagnetic radiation, so a weapon must emit significant neutron radiation in order to irradiate surrounding material²⁴. Moreover, such isotopes often have short half-lives (from seconds to minutes), and do not represent anywhere near the long-term environmental threat posed by fissionable materials and/or fission products such as cesium.

We are currently unsure as to how much radioactive fallout will be produced by a turbolaser blast, although we can state definitively that it will be much lower than the amount of radioactive fallout produced by a thermonuclear weapon of similar yield, and that it will be short-lived.

Regarding so-called "nuclear winter" effects:

Some casual observers assume that a nuclear winter is an "on/off" scenario, ie- you either don't get a nuclear winter and the biosystem survives, or you get a nuclear winter and the entire biosystem dies. That is not the case. Only the most extreme and devastating nuclear winter scenario would result in the extermination of all advanced forms of life on a planetary scale.

Computer simulations of large-yield asteroid impacts (a worst-case scenario for atmospheric particle ejection) show that global climate changes occur with yields of 1E5 megatons and above. Such simulations have shown that an impact of 3E5 megatons would create nuclear winter effects leading to the deaths of more than 25% of the Earth's human population²⁵. This would be devastating for any planetary civilization, but with a 75% survival rate, it is completely inadequate for a Base Delta Zero operation.

From the same source, mass extinction events are projected to occur with yields of 10 million megatons and above. The so-called "Dino-killer" asteroid struck the Earth 65 million years ago with approximately 100 million megatons yield, creating a 200 km wide crater and hurling some 1E16 kg of dust into the atmosphere. This darkened the atmosphere, dramatically lowering global temperatures and triggering a mass-extinction event in which some three quarters of the Earth's living species were wiped out. However, even this kind of global catastrophe is not comparable to a BDZ. The biosystem did survive (obviously, since we are here), and a BDZ does not allow for one quarter of a planet's species to survive (even without technological means of environmental protection, such as humans would have).

Global catastrophes severe enough to threaten the survival of all advanced forms of life (ie- what we generally consider "sentient life forms", as opposed to bacteria and insects) occur with yields of 1 billion megatons and above (4E24 J). This is somewhat larger than the BDZ energy yield estimate (2E24 J). Keep in mind, however, that even such a global catastrophe still relies largely upon long-term environmental effects, while a BDZ operation exterminates all forms of animal and plant life, including humans in artificial shelters or hardened military facilities, in less than a day.

One might argue that these figures are not directly applicable to a BDZ operation, which would presumably involve a widely dispersed attack rather than a localized attack. However, the amount of dust and soot thrown into the atmosphere would be the same. The significant differences between asteroid impacts and nuclear war are the widespread multiple shockwave centres of nuclear war (tidal wave and shockwave are regional in a high-energy asteroid impact), the selective targeting of nuclear explosions (which obviously increases the human casualty rate dramatically), and the effects of radioactive fallout and smoke from the burning of man-made materials such as plastics and petroleum products in major cities (which obviously didn't exist during ancient asteroid impacts). Keep in mind that burn effects (as opposed to blast shockwaves) are global in both scenarios; the K-T mass-extinction asteroid impact was so violent that it most likely ignited fires all over the entire planet²⁶. However, these are long-term indirect environmental effects, and inapplicable to BDZ. Moreover, a BDZ will not involve the kind of radioactive fallout produced by thermonuclear weapons, and it is highly doubtful that the Star Wars civilization relies as heavily upon petroleum products as we do today.

Clearly, not only are long-term environmental "nuclear winter" effects inapplicable to a BDZ operation because of its short timeframe, but even if a BDZ exclusively employed groundbursts in order to apply the maximum possible energy to the creation of atmospheric soot and dust, the energy requirement for global extermination of sentient life would still remain at its current level or above. In this scenario, not only would blast/burn effects be reduced (because of diminished efficiency in propagation of both effects from ground bursts as opposed to air bursts), but the largely environmental effects would lengthen the depopulation timeframe from hours to weeks or months, which is obviously well beyond the parameters of a BDZ. Moreover, they would be ineffective against hardened military targets or even civilian bomb shelters, both of which could easily preserve survivors long enough for rescue and evacuation.

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Suggested Reading

• The Nuclear Weapons FAQ, hosted by the Federation of American Scientists, as well as numerous other mirrors. This is a good general source of information.

• Effects of Nuclear Weapons and Nuclear Wars, by the United States Department of Defense, 1977. Hosted by the Federation of American Scientists. This is the definitive unclassified text on nuclear weapons effects. It deals very specifically with the physical effects of nuclear explosions.

• The Effects of Nuclear War, by the American Office of Technology Assessment, 1979 (Library of Congress Catalog Card Number 79-600080). Digitized and hosted by the Federation of American Scientists. This text is the most useful source in some ways, because it contains projections of the effects of air and ground bursts over Leningrad and Detroit.

• Hazards Due to Comets and Asteroids, by T. Gehrels ISBN 0-8165-1505-0 (sorry, there's no online version that I'm aware of). Strictly speaking, this is not a nuclear explosion effects source. However, it deals with the effects of extreme high yield groundbursts and nuclear winter effects, so it is still applicable (and you should keep in mind that a turbolaser is not a nuclear weapon). It's also a fascinating read, if you don't mind paying for it.

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Footnotes

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