Research Associate, The James Martin Center for Nonproliferation Studies
Proliferation Pathways to a North Korean Intercontinental Ballistic Missile
The December 2012 Launch of a Satellite into Orbit Aboard an Unha-3 Rocket, Korean Central News Agency (KCNA)
On 17 December 2013 a South Korean official announced that North Korea was preparing to conduct a nuclear test.  This followed a February 2013 nuclear test, and the successful December 2012 launch of a satellite into orbit. It is widely believed that North Korea's satellite launch vehicle program is a guise for developing an Intercontinental Ballistic Missile (ICBM) with the capability to deliver a nuclear warhead. 
Assuming this is Pyongyang's intention, the country has three possible pathways for doing so: (1) North Korea could build on its current technology and convert the Taepodong-2 (TD-2)/Unha space launch vehicle (SLV) into an intercontinental ballistic missile (ICBM), using the Sohae and Tonghae launching sites as deployment bases for the missile; (2) Pyongyang could use existing TD-2/Unha rocket technology, but develop new ways to deliver the missile, such as road-mobile systems or ICBM silos; and/or (3) North Korea could opt to develop an entirely new missile based on new technologies and rocket engines/motors.
This issue brief examines these three potential pathways, and the probable consequences of each for policymakers. What are the assets and liabilities of each pathway for North Korea? Conversely, what advantages and disadvantages does each pathway offer to policymakers in the international community hoping to prevent North Korea from acquiring an ICBM capability? How easily, and by what methods, could the international community detect North Korean progress along each pathway? How easily could the international community detect and monitor the deployment of a completed ICBM? How would each pathway affect monitoring and verification options for any potential missile deal between the international community and North Korea? Finally, if North Korea acquired an ICBM using one of these pathways, how much strategic and tactical warning of planned use of the system would the international community be able to obtain using imagery intelligence and measurement and signature intelligence?
Brief History of the DPRK's Missile Development
The North Korean ballistic missile program reportedly began in 1972, when the DPRK acquired the R-17 (Scud-B) from the Soviet Union. While this transfer remains unconfirmed, the DPRK did acquire the Scud-B in 1976 from Egypt. North Korea's entire arsenal is based on modified Scud designs. A complete history of the DPRK's missile program can be found on North Korea's Country Profile.
I. Alternative Pathways to an ICBM
North Korea will have to overcome certain obstacles regardless of which pathway it ultimately pursues toward acquisition of an ICBM. First, Pyongyang has not yet proven that it has the ability to miniaturize a nuclear weapon to fit on a warhead, although many experts believe it either has this capability or will in the near future.  Second, the DPRK must develop a reentry vehicle that can withstand the intense heat and pressure of atmospheric reentry. However, the development requirements for these two capabilities will be similar regardless of the selected pathway. What, then, are the benefits and drawbacks of the three alternative pathways?
Pathway 1: Utilize current technology and launch infrastructure
Theoretically, using its current technology and infrastructure would provide North Korea with the quickest pathway to an ICBM capability. The Taepodong-2 (TD-2)/Unha space launch vehicle is currently North Korea's longest range rocket, and the only candidate in Pyongyang's arsenal for possible transformation into an ICBM. North Korea has done significant work to develop the Taepodong-2/Unha space launch vehicle, having conducted four tests, including the successful launch of a satellite into orbit.
Despite being potentially the quickest route to an ICBM, Pathway One is not without numerous liabilities for North Korea. First, even with a warhead and reentry vehicle, it is not certain that the Unha could serve as an effective ICBM. In its current configuration, rocket expert Markus Schiller notes that the TD-2/Unha's second stage has a low thrust and a long burntime.  David Wright adds that this "is exactly what you would design for a satellite launcher, since you want a long boost phase to allow the satellite to reach high altitude before inserting the satellite into orbit. For a ballistic missile, on the other hand, such a design would cost you more than 1,000 km in range compared to using a Nodong engine in this stage." 
To date, the TD-2/Unha's largest payload was a 100 kg satellite launched into a 500 km orbit. In order to launch a heavier payload to ICBM ranges (such as a nuclear warhead), significant modifications to the second and third stages would be needed. If North Korea's intentions are to develop the Unha into an ICBM, it may find additional efforts from this point forward a major liability. If needed modifications turn out to be impossible, Pyongyang may find itself at a "no-go" decision point where it must return to the drawing board and develop a new system altogether.  
A second liability is the TD-2/Unha's poor utility as a weapon. The TD-2/Unha is a three stage, liquid propellant rocket. Liquid propellant rockets take days to weeks to assemble, and hours to days to fuel prior to launch.  The launch process is tedious and easily detected by satellite imagery analysis. Nick Hansen, an imagery expert, outlines the launch process for the 2006, 2009 and 2012 launches: For each launch, preparations, assembly, and fueling were detected 10-26 days before the launch occurred, providing plenty of advance warning. Moreover, Hansen utilized limited resources and commercial satellite imagery; undoubtedly, U.S. intelligence is more easily able to detect and monitor launch preparations, and will not be surprised by a North Korean launch. Should the DPRK attempt to use the Unha as an ICBM, it would not be able to launch a surprise attack, and prior to launch the missile would be extremely vulnerable to a preemptive strike.
In addition to the liability posed by the Unha's liquid propellant, North Korea's launch infrastructure is disadvantageous to an ICBM program. North Korea has two launch sites, the Tonghae Satellite Launching Ground and the Sohae Satellite Launch Center. Each contains one horizontal assembly building capable of holding two Unha-sized rockets at a time, or one larger single rocket. It is unknown how long the assembly and checkout times take at either facility.
At each site, once a rocket leaves the assembly building, it takes 10 to 26 days to prepare it for launch. In that time, the assembly and checkout processes for additional rockets may begin at each assembly building. North Korea is limited to two Unha-sized missiles ready for launch, two assembled and awaiting transportation to the launch pad, and two in the assembly process. 
Following a first launch at each site, North Korea could begin moving the additional missiles to the launch pad. However, the new missiles would require the same 10 to 26 days to stack and fuel. North Korea's launch capacity is therefore limited to two launches every 10 to 26 days. In summary, the TD-2/Unha, with the current launch infrastructure, has very low military utility. A second strike is not possible, and even a first strike could not be launched without significant warning and detection time. 
Pathway 2: Develop new delivery methods for existing rocket technology
North Korea's second option is to utilize the existing TD-2/Unha rocket technology and develop a new launch system. The same assets and liabilities associated with the TD-2/Unha are applicable here; however, North Korea may mitigate many of the final assembly and launch liabilities associated with above ground launch pads by developing either underground launch silos or a road-mobile version of the TD-2/Unha. Either option still requires that Pyongyang first make the modifications necessary for the TD-2/Unha to be an effective ICBM.
Silos would offer North Korea the advantage of being able to hide launch preparations. North Korea could assemble and store the TD-2/Unha in silos semi-ready for launch for an indefinite period of time. Once ready to launch, fueling would be shielded from satellites, and the international community would have minimum warning of an impending launch. While launch preparations may not go completely undetected by imagery intelligence (IMINT),  the likelihood of detection by satellite imagery would be reduced. In addition, silos, like launch sites, are stationary, and thus vulnerable to a military strike.
An alternative for North Korea is to develop a road-mobile ICBM. Road-mobile ICBMs are difficult to track. A launch can occur from nearly any location, and the number of launches is limited to the number of missiles and launch vehicles, not to launch sites such as a launch pad or silo. During the Gulf War, Coalition Forces had an extremely difficult time tracking and targeting Iraq's road-mobile Scud missiles. Coalition Forces conducted 4,750 anti-Scud sorties that resulted in 1,460 air strikes.  Many strikes targeted fixed launch sites and support structures, and it is unclear how many targeted transporter erector launchers (TELs). A 2001 report by RAND states that, of the "42 occasions during the war when orbiting strikers visually sighted mobile TELs, in only eight instances were they able to acquire the targets sufficiently well to release ordnance."  Following the war, it was revealed that Iraq had used decoy launchers in addition to active ones, and it remains unclear how many, if any of the sorties and ground operations eliminated active launchers. While the ability to detect, monitor, track, and strike mobile launchers has only improved with advancements in technology, there is no precedent of the United States or another country detecting, tracking, and eliminating road-mobile missiles with a high success rate.
While a road-mobile Unha can theoretically be launched from anywhere, the use of liquid propellant remains a liability. Liquid propellant is highly corrosive and combustible, and cannot be stored in the missile or support vehicles for significant amounts of time. The missile and its support vehicles are limited to deployments in a given radius around missile bases to which they can return quickly. The limited mobility decreases the ability of North Korea to "hide" the launchers.
A Note on the KN-08
In April 2007 and July 2013, North Korea paraded the Hwasong-13 (KN-08) road-mobile missile, which appears to be an ICBM. Since first displayed, there has been significant debate as to whether the missile is fake or a mock-up of an actual missile design. In either case, the KN-08 cannot be viewed as an operational missile. North Korea has not proven the ability to produce a missile engine with the thrust needed to launch a significant payload over ICBM ranges, a miniaturized nuclear warhead, or a reentry vehicle. Until these technologies and the KN-08 are tested, the KN-08 is in essence no more than Schrodinger's Cat, and we cannot know the missile's status until the box is opened.  Furthermore, once the box is opened and the missile is tested, it still will not equate to a reliable ICBM capability until it is successfully tested numerous times.
Rockets and missiles are complex systems that require advanced systems engineering to coordinate across multiple departments and laboratories, and to integrate a plethora of rocket parts into one working system.  We know little of North Korea's systems engineering process; however, we can assume that North Korea is bound by engineering processes, and that flight testing is the conclusion of a successful systems engineering process. Without adequate testing, a system cannot be deemed reliable. A perfect example of this is Russia's RSM-56 Bulava ICBM, which has failed in at least eight of its first 20 flight tests.  The failures were due to manufacturing and production problems rather than design flaws.   The Bulava program highlights an important factor in missile development; flawless designs do not necessarily translate into workable missiles. This is why a typical missile program will undergo numerous flight tests in the design and production phases of development, to ensure the success of both the design and production. In the case of the Bulava, Russia has approximately 60 years of experience developing rockets and ICBMs, yet still struggles with the design to production transfer of technologies. North Korea has never produced an ICBM, and therefore requires testing to prove not only manufacturing and production, but design as well.
A separate research project the author is currently conducting compares and contrasts North Korea's missile test record to the test records of the United States, Russia, China, India, and Iran. While the research is ongoing, Table 1 summarizes the initial findings for comparing test records leading to an ICBM.
While North Korea does not have to have an identical test record to any other country, it cannot ignore engineering fundamentals and bypass testing altogether. No country has ever developed a reliable ICBM capability without a strong test record.
Pathway 3: Develop new rocket technologies
The third option for acquiring an ICBM and launch capability is to develop an entirely new missile that is designed with ICBM ranges and payloads in mind from the start.
A new rocket design with ICBM performance characteristics in mind from the design phase would prove more formidable than the Scud-based TD-2/Unha. Two designs North Korea could pursue are a new liquid propellant missile that uses cryogenic fuel, or a solid propellant missile. The use of a cryogenic liquid propellant will decrease the preparation time to launch a missile, as propellant can be stored in the missile for a slightly longer amount of time. However, if launched from above ground launch pads, the cryogenic propellant missile will have the same assembly and stacking liabilities mentioned above for the TD-2/Unha, and the use of cryogenic fuels will only eliminate the hours needed for fueling. It is unlikely that a cryogenic fueled missile could serve as a road-mobile ICBM, as the nature of the propellant requires cooling before fueling. A solid fueled missile, on the other hand, would entirely eliminate the need for fueling, as the propellant could be stored in the missile indefinitely. The missile could be assembled and fueled inside of assembly warehouses, and launched with minimum notice.
However, a new missile design, especially if the solid fuel route is chosen, would essentially mean starting from scratch. North Korea has no experience developing solid fueled, long-range missiles, and could not quickly design, assemble and test a system. Table 2 outlines the solid propellant missile programs of the United States, the USSR, China, and India.
While North Korea does possess a solid fueled missile, the KN-02, it is a 140 km short-range ballistic missile, and an exact copy of the Soviet OTR-21 Tochka. Unlike liquid fueled missiles, solid fueled missiles cannot easily be modified to steadily increase their ranges. With its liquid fueled missiles, North Korea was able to scale-up engine designs and stretch propellant tanks to increase their ranges, but this cannot be done with solid fueled missiles. To jump from 140 km to ICBM ranges, North Korea must develop a new design.  Given that North Korea has never developed a solid fueled motor, this would take a significant amount of time. Furthermore, it is unknown if North Korea possesses the manufacturing know-how and materials needed for a solid rocket motor. The infrastructure and manufacturing equipment used to develop liquid fueled missiles may not be fungible to solid fueled technologies.
The United States, the Soviet Union, China, and India all had significantly more resources and experience with rockets than North Korea, yet each took a significant amount of time from the beginning of a solid propellant program to the deployment of a solid fueled ICBM. While a solid fueled ICBM offers military advantages, North Korea could not reasonably develop and deploy such a missile in the short to medium-term.
II. International Community and Detection, Monitoring, Verification
During the Clinton Administration, the United States and North Korea came extremely close to concluding a "Missile Deal" that would have halted North Korean development, production, and testing of increasingly longer-range missiles. However, the deal never came to fruition, and under the Bush Administration it was scrapped completely. One of the primary issues for both the Clinton and Bush administrations was monitoring and verification. The United States sought a comprehensive monitoring and verification regime that would have permitted U.S. inspectors on-site access to rocket and missile facilities, while North Korea believed that the United States could accomplish verification through imagery analysis and other national technical means.  It is therefore likely that any future missile deal negotiations will focus heavily upon verification.
Detection and Monitoring
Any advances in rocket technology using the three pathways described above will require numerous tests before the missile can be accepted into service and deployed. Given North Korea's limited geographical size, all long-range missile tests will result in debris falling into international waters. For the December 2012 Unha-3 launch, the rocket's first stage fell into the Yellow Sea, and the second fell off the coast of the Philippines. By recovering the first stage debris, South Korea was able to confirm some facts about the Unha, while discovering new data that indicated progress in the Unha's design. The debris demonstrated continued areas of struggle and primitive design elements, such as in the propellant, airframe, and welding, while also showing program advancements and new design elements, such as the use of steering engines in place of jet vanes for orientation.  It is reasonable to assume that over the course of a testing program, debris will be recovered to enlighten the world on the progress of North Korea's missile program.
New deployment methods, such as the use of silos or road-mobile launchers in pathways two or three will not necessarily be detected. While the construction of silos could be detected by satellite imagery analysis, it is not guaranteed that the international community would detect every silo. Iran's Shahab silos went unnoticed in the open source until displayed on Iranian media during the Great Prophet 6 military exercises.  A road-mobile TD-2/Unha would seemingly go undetected unless paraded or displayed publically. The KN-08 was unknown in the open source until it was displayed at the April 2012 military parade in Pyongyang. Deployments and launches of silo-based or road-mobile TD-2/Unha's would be very difficult to detect and monitor.
The issue of verification is complex, and any missile deal will undoubtedly cover the entirety of North Korea's missile production, from battlefield and short-range ballistic missiles to space launch vehicles and ICBMs. However, this brief will only address the relationship between a missile deal and the three pathways to an ICBM. For the purpose of this section, the author assumes that a future missile deal will either aim to prevent or reverse a missile program in four key areas: development; manufacturing and production; acquisition; and deployment. The question becomes for each of the three pathways to an ICBM, can the international community verify that North Korea is abiding by a deal that prevents or reverses 1) development; 2) manufacturing and production; and 3) deployment of an ICBM?
Development: Development launches, no matter the pathway, can and will be detected. If a missile deal with North Korea results in prevention of further development of a system or limits the range of a system, any violation will be detected by monitoring launches and recovering debris from them. Even if North Korea designs a missile with a given range and tests it to a shorter range,  debris recovered would indicate the missile's true range and payload potential. No matter the pathway, it would be relatively easy to verify whether development is taking place.
Manufacturing and Production: If a design is tested and proven, or untested but entered into service nonetheless, it would be nearly impossible to verify manufacturing and production constraints without on-site inspections, no matter the pathway chosen.
Deployment: Deployment is where the three pathways begin to diverge. For pathway one, the TD-2/Unha cannot be deployed in a traditional sense, as it requires significant and time-consuming launch preparations. National technical means would provide adequate intelligence to verify that no missiles were being prepared for launch. Furthermore, satellite intelligence would alert the international community to any construction of new launch sites and launch pads.
Pathway two would entail significant hurdles to verifying deployments. Although the international community could theoretically know where all silo bases were located, it is equally plausible that some locations or silo bunkers would remain unknown and be undeclared. In order to prevent the possibility that North Korea could fail to declare a silo and deploy a missile in violation of a missile deal, the verification regime would require a mechanism that allowed on-site inspection of suspected sites without geographical limitations. Should North Korea deploy a mobile ICBM, verification of a freeze on deployments and/or reductions in deployments would be virtually impossible. It would be difficult to prevent North Korea from obtaining the transporter-erector launchers (TEL) needed for a road-mobile ICBM. The TEL for the KN-08 is a converted lumber transporter imported from China.  North Korea could easily import and convert a number of lumber or other heavy-load vehicles into TELs and deploy missiles across the country. It would be relatively easy to station the TELs around the country in warehouses, tunnels, underground bunkers, or forests, or camouflage them in the open. On-site inspections of suspected TEL bases would do little, as by definition the launcher would be mobile and therefore easily moved.
The exception to this rule would be a liquid propellant road-mobile missile. Liquid propellant is highly corrosive and combustible, and has a short life. It cannot be stored in the missile or in mobile storage tanks for a significant period of time, and therefore the road-mobile missile must remain relatively close to its base to ensure quick fueling before launch. The limited range of a liquid propellant road-mobile missile decreases the geographical area in which the missile can be deployed. While this does not guarantee that a verification mechanism could verify deployment, it does decrease the area which the international community would need to monitor if the site is known. If the verification mechanism allowed for on-site inspections at suspected sites, it could uncover deployment violations of the missile deal.
Pathway three poses some interesting obstacles with regards to verifying constraints. First, it should be stated that any new missiles deployed in silos or on road-mobile launchers face the same obstacles mentioned above for pathway two. Where pathway three differs is with a solid fueled missile. Solid fueled missiles can be stored indefinitely with the propellant, and can therefore be ready to launch. Even without a road-mobile launcher, if any silos or launch pads are intact in the country, then theoretically the missile could be launched on short notice. Such a scenario only requires that a fully assembled and fueled missile be stored in the country. It could then be transported to a launch site and quickly prepared for launch. The international community would have a difficult time verifying that no such missiles and propellant were being stored secretly within the country.
III. Strategic and Tactical Warning
Strategic warning considers broad security threats in order to affect policy decisions on preparedness and defense. North Korea's missile program and pursuit of an ICBM is a strategic warning challenge. Tactical warning addresses specific and imminent threats where the enemy "has probably made the decision to attack but that decision may be tentative, conditional, or revocable, and in any case the attack has not yet been initiated."  All source intelligence is used in providing strategic and tactical warning analyses. Although all source intel is used to provide strategic and tactical warning, some intelligence, such as human and signals intelligence, cannot be guaranteed, and therefore is not under consideration here. The two primary sources of intelligence that collect intel independent of people are imagery intelligence (IMINT) and measurement and signature intelligence (MASINT). How does each pathway to an ICBM affect the IMINT and MASINT collection that shapes strategic and tactical warning?
North Korea claims that the Unha rocket is a space launch vehicle intended for civilian purposes. All four TD-2/Unha launches had a satellite payload, and the Unha design is indicative of a satellite launcher. Furthermore, North Korea's launch infrastructure is inadequate for a military weapon. However, it is unclear if the limitations in the Unha and North Korea's rocket program are due to intentions, or technical and resource limitations. Looking at the TD-2/Unha and launch facilities alone, it is difficult to ascertain strategic warning apart from additional intelligence sources.
As noted above, all launches of the TD-2/Unha have been detected well in advance by open source, civilian experts/analysts, and by the U.S. intelligence community. The time-consuming nature of assembling and fueling an Unha rocket, and the use of above ground launch pads leaves a North Korean launch vulnerable to detection and a preemptive strike if an adversary deems such necessary. North Korea may lessen the preparation time by bypassing some safety protocols; however, it is unlikely that a launch could occur in less than a few days. With current missile technology and launch infrastructure, the United States and the international community will likely have adequate tactical warning before any launch, and could preemptively strike before one occurs.
Deploying a modified Unha in silos or on road-mobile launchers would clearly indicate that North Korea's intentions are not to use the rocket for civilian purposes, but as a military weapon. Only one country, Russia, currently launches space vehicles from silos. The United States previously launched Titan 23G SLVs from silos. Russian Dnepr and Rokot SLVs were converted from R-36M and UR-100N ICBMs, while the Titan 23G was converted from the Titan II ICBM. For both Russia and the United States, a combination of rockets nearing the end of their service lives, and arms control agreements that limited missile arsenals, resulted in excess stockpiles of ICBMs and related infrastructure. No country has developed underground silos with the intention of using them for SLVs. For North Korea, the development of Unha silos could only be interpreted as intended for missile deployments, and not for space use.
Similarly, no country has launched a space vehicle from a road-mobile launcher. A road-mobile version of the Unha would clearly indicate North Korea's intention of using the rocket as an offensive weapon.
By employing silos or road-mobile systems to launch the TD-2/Unha, North Korea would greatly decrease the probability of a launch being detected in advance. The Unha could be assembled and stored in silos in advance, and fueling could go undetected prior to a launch. Road-mobile missiles, as noted above, are very difficult to track, and imagery intelligence can be distracted by the use of dummy launchers. Without additional intelligence from human or signals sources, it is unlikely that a pathway two launch would provide adequate tactical warning.
The development of a new missile utilizing either liquid cryogenic or solid propellants would not in and of itself indicate North Korea's intentions. The United States, Russia, China, and others have utilized cryogenic liquid propellant engines and solid propellant motors in space launch vehicles. There are numerous benefits to using either cryogenic liquid or solid propellants in an SLV over the basic liquid propellant North Korea currently uses in the Unha. However, while neither new design would necessarily indicate an active ICBM program or intention, the dual-use nature of rockets and missiles would indicate a capability that, should it be used in a missile, would equal a decreased launch time, and conversely an increased threat. Therefore, any developments in new engine/motor technologies must increase the threat analysis associated with strategic warning.
The ability to provide tactical warning for a pathway three missile depends entirely on the launch platform used. An above ground launch of either a cryogenic or solid fueled missile could be detected in advance. Although neither provides the "days" warning that the Unha currently does, the transportation of a missile from an assembly building to the launch pad would be detected. However, the time between transportation to the launch pad and launch could be extremely short, and any attempt to negotiate down a launch or to strike preemptively would have to be made immediately. Apart from additional source intelligence, tactical warning could be provided, but with a small response window. Should a Pathway Three missile be deployed in either a silo or on a road-mobile launcher, the United States would have little warning, apart from human or signals intelligence, of an impending launch.
North Korea does not currently have an intercontinental-ballistic missile capability, and faces many obstacles to obtaining one. North Korea lacks the proven capability of a miniaturized warhead, reentry vehicle, and rocket efficient enough to lift a nuclear payload to ICBM ranges. Significant testing would be required before the TD-2/Unha, KN-08 or a new design could be deemed a reliable ICBM and deployed.
Despite the obstacles North Korea faces, each rocket and missile test conducted takes it one step closer to an ICBM capability. Should North Korea obtain an ICBM, the pathway chosen will greatly affect the international community's ability to detect and monitor missile advancements, and verify any potential future missile deal. Absent any missile deal, it is likely that North Korea will continue to pursue an ICBM through each pathway, first through the TD-2/Unha, and then through new technologies, until its strategic objective is met.
 "N. Korea shows signs of nuclear test preparations: lawmaker," Yonhap News, 16 December 2013, english.yonhapnews.com.kr.
 Michael Elleman, "Prelude to an ICBM: Putting North Korea's Unha-3 Launch Into Context," Arms Control Association, www.armscontrol.org.
 David Albright, "North Korean Miniaturization," 38 North, 13 February 2013, www.38north.org.
 Markus Schiller and Robert H. Schmucker, "The Unha-3: Assessing the Successful North Korean Satellite Launch," Federation of American Scientists: The FAS Blog, Winter 2013, Volume 66 Number 1, blogs-cdn.fas.org.
 David Wright, "Markus Schiller's Analysis of North Korea's Unha-3 Launcher," Union of Concerned Scientists, 22 February 2013, www.allthingsnuclear.org.
 A "go, no-go" point refers to a key decision point by which a project or course-of-action is allowed to proceed forward or is cancelled. It is used both in systems engineering as a checkpoint in a project, and for space launch vehicles prior to launch.
 The development of complex systems requires expert tacit knowledge. Tacit knowledge is hands-on experience working on a project or in a laboratory, oftentimes developed under a supervisor. Tacit knowledge differs from explicit, codified knowledge. Tacit knowledge is difficult to transfer and must be obtained via experience. Any design, production or test failures are not complete losses, as North Korea gains valuable tacit knowledge through the process.
 Launch preparation varies depending on technologies and propellants. The "days to weeks" assembly, and "hours to days" to fuel is representative of North Korea's current technology.
 North Korea is currently constructing a new assembly building at Tonghae which would increase its capacity to assemble and prepare additional rockets for launch. "Construction at Tonghae Resumes: No Tests Likely in 2013," 38 North, 29 November 2013, www.38north.org.
 A first strike, when equipped with a nuclear warhead, is a significant threat and of high military utility. The author's intention is to show that 1) a first strike will likely be detected in advance and counter-actions could be taken to eliminate the threat, and 2) the overall launch capacity is low, and if a surprise launch were to occur, unlike the cases of the United States and the Soviet Union during the Cold War, additional strikes would not be possible.
 Intelligence satellites are not limited to visible imaging, but also include infrared, thermal, and radar sensors that may detect launch preparations.
 Lt. Colonel Mark E. Kipphut, "Crossbow and Gulf War Counter-Scud Efforts: Lessons from History," Air War College, April 1996, pp. 32; 50.
 William Rosenau, "Special Operations Forces and Elusive Enemy Ground Targets: Lessons from Vietnam and the Persian Gulf War," RAND, 2001, p. 34.
 Schrodinger's Cat is a thought experiment or paradox that illustrates the problem of superposition in quantum theory. The illustration revolves around a cat that is placed in a box with a chemical substance or apparatus that may kill the cat. The paradox centers on the cat's status. Until the box is opened one cannot know whether the cat is dead or alive, and therefore it is in a state of quantum superposition of pertaining to both states, dead and alive.
 Systems engineering is a process that focuses on the design, development, and testing of complex systems throughout a program's life cycle. Rockets are inherently complex requiring the collaboration across numerous laboratories and professions. For example, different laboratories will develop the electronics, guidance systems, propulsion system, airframe, etc. A Systems Engineering Process (SEP) is used to implement the system's life cycle and coordinate design, development, and testing across all laboratories and expertise.
 "Timeline of Bulava Missile Launches," Ria Novosti, en.ria.ru.
 Причина нового неудачного запуска "Булавы" – неисправность механизма ракеты [Prichina novovo nyeudachno zapuska "Bulavi" – nyeispravnost myekhnizma rakyeta, [The Reason for the Failed Bulava Launches – Failure of Mechanism of Rocket], Itar TACC, 5 December 2013, itar.tass.com.
 "Комиссия не нашла конструкторских недоработок в "Булаве" [Kommissiya nye nashla konstrucktorskix nyedorabotok v "Bulavye", The Commission found new flaws in the design of the Bulava"], Ria Novosti, 20 November 2013, ria.ru.
 It is extremely difficult to extend the range of solid propellant missiles without integrating new designs. France developed the M1 solid propellant missile with a range of 2,500 km in 1967, the M4 with a range of 4,000 km in 1980, and the M51 with a range of 10,000 km in 2010. With significantly more resources, expertise and know-how, and starting with a 2,500km solid fueled missile, France took 40 years to develop an ICBM range solid fueled missile from a starting point of a 2,500km missile. France had significantly more resources and experience with solid fuel than North Korea currently has.
 Joel S. Witt, Andrew Hood, Jeffrey Lewis, Leon Sigal, "Missile Negotiations with North Korea: A Strategy for the Future," US-Korea Institute at SAIS, October 2011.
 In flight dynamics, a vehicle's attitude refers to its orientation or position along three axis: pitch (y), roll (x), and yaw (z). Thrust vectoring is a way of controlling or manipulating rocket engine thrust, thereby affecting attitude. One method is by inserting jet vanes into the path of the exhaust plumes exiting the rocket's nozzle. The vanes redirect the thrust and change the rocket's orientation. The use of jet vanes is a simple technique; however, they lower the efficiency of the rocket's engine by redirecting the much needed thrust. Steering engines are a more efficient mechanism for thrust vector control. A steering engine, or vernier thruster, is a small, low-thrust rocket engine located on the side(s) of a vehicle for attitude control. Steering engines increase a rocket's overall thrust.
 William J. Broad, "Iran Unveils Missile Silos as It Begins War Games," International Herald Tribune, 27 June 2011, www.nytimes.com.
 Such was the case when India tested the Agni-V to 5,000 km.
 Melissa Hanham, "North Korea's Procurement Network Strikes Again: Examining How Chinese Missile Hardware Ended Up in Pyongyang," Nuclear Threat Initiative, 31 June 2012, www.nti.org.
 Edmund Brunner Jr., "Perception and Strategic Warning," RAND, November 1979, www.rand.org, p. 1.
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