Concept art of a laser-armed aircraft destroying a missile. Photo Credit: Defense One.
North Korea remains a clear threat to American security. Despite demonstrating a willingness to carry out major diplomatic spectacles and “dismantle” satellite launch sites such as the Sohae facility, North Korea continues to develop its ballistic missile and nuclear arsenal. The Kim regime remains committed to developing its ballistic missile program in at least 16 hidden bases and moves ever closer to possessing a nuclear warhead capable of striking the US homeland.[i] Despite the best efforts of the international community, Kim Jung-un is determined to develop a nuclear deterrent directed against the United States. Consequently, it is becoming increasingly critical to enhance US missile defense technologies to protect the U.S. from a possible North Korean ICBM.
Multilayer Missile Defense
The optimal missile defense system requires a layered defense that is capable of intercepting enemy missiles in all three stages of their trajectory: boost (when the missile launches and ascends in the atmosphere), mid-course (when the missile travels beyond the atmosphere), and terminal (when the warhead reenters the atmosphere and descends on its target). One clear benefit of having multiple opportunities to successfully intercept incoming missiles is the requirement for fewer interceptors per attacking object.[ii] If one’s goal is to eliminate all incoming missiles, it behooves one to engage across all three phases because this enables a controlled reduction of the threat. By reducing the number of interceptors required, one also minimizes cost. Conversely, if one were to engage solely during the terminal phase, one would be forced to target the incoming warheads with more interceptors than necessary because it is the “last chance” to ensure a kill. Current missile defense systems, such as Aegis and THAAD, operate in the mid-course and terminal phases only.
Boost-phase missile defense is seen as the “holy grail” of missile defense, as it targets enemy missiles in the earliest stages of flight when they are most vulnerable. Missiles are ideal targets at this point because they are much larger and slower than in later stages. Their burning engines generate a significant heat signature, making them easy to track and, because they are full of flammable propellant, boost phase missiles become very vulnerable to explosive warheads and high energy lasers.[iii] Moreover, enemy missiles cannot deploy countermeasures such as decoys, flairs, and debris during the boost phase, making them ripe for interception. The concept of boost phase defense is nothing new. It was prominently featured in the Strategic Defense Initiative (SDI) launched by President Reagan in 1983. But to this day, a viable boost phase defense system remains elusive.
Disabling ICBMs in the boost phase is made complicated by important geographic and engineering obstacles. The main challenge is the short window of opportunity between launch detection and the missile reaching terminal velocity. When an ICBM is launched, it spends approximately three to four minutes burning fuel in the boost phase, but a realistic window of interception is substantially shorter than the duration of the burn.[iv] Even systems with state-of-the-art tracking sensors require at least 45 to 65 seconds to detect the launch of a rocket, determine whether it is hostile, and calculate its trajectory well enough to reliably fire an interceptor.[v] One must also factor in human “decision time,” which includes any additional time required for communication between system elements and human decision makers, estimations of the performance characteristics of the attacking missile, the missile’s trajectory, the resolution of uncertainties in the performance of the defense system, and other operational factors.
Kinetic interceptor systems must therefore either be placed very close to the interception point or travel well beyond current maximum velocities. A terrestrial kinetic interceptor would have to be approximately 400 to 1,000 kilometers away from the interception point for a successful intercept, while an Airborne Laser would need to be between 300 to 600 kilometers away.[vi]An ICBM launched from North Korea toward the continental United States would travel northward, since the shortest distance between the two points is over the Arctic. Based on this trajectory, a boost phase interception point would almost certainly occur over Chinese or Russian airspace. There are simply no allied countries or international waters in which one could place a land-based defense system that could hit the missile before it exits the atmosphere.
Airborne Laser 2.0
To overcome this limitation, the United States should instead deploy HALE UAVs equipped with high-energy lasers to the international airspace around North Korea. A HALE UAV is an aircraft capable of operating at altitudes of 20 km for considerable periods of time. Mounting direct energy weapons on HALE UAVs in the region would allow the U.S. to deal a concentrated energy blow to a DPRK missile at the speed of light, overcoming the range and time constraints that confront kinetic interceptors. Unfortunately, previous attempts to mount a laser on an aircraft have been unsuccessful.
In 2014, the Department of Defense discontinued the YAL-1 Airborne Laser project, which mounted a megawatt-class chemical oxygen iodine laser (COIL) on a modified Boeing 747 with an altitude of 12 km.[vii] According to former Secretary of Defense Michael Gates, their were fundamental concerns about the project’s practicality and operational costs. The project required a laser 20 to 30 times more powerful than was available and, if operationalized, would require 10 to 20 747s, at a billion and a half dollars apiece and costing $100 million a year to operate.[viii]
Since the cancellation of the YAL-1 ABL, the scientific community has seen significant advancements in UAV and directed energy technology, which has renewed interest in the ABL. With advanced optical and radar capabilities, UAVs are becoming increasingly integrated into military operations. Today’s HALE UAVs, such as the RQ-4 Global Hawk, are capable of flying much higher, far longer, and for significantly less than the gas guzzling four-engine Boeing 747s that carried the YAL-1 ABL.[ix] At the same time, directed energy technologies have continued to evolve into much smaller and lighter solid-state laser technologies that use electricity instead of chemicals for energy. Today’s solid-state lasers are safer and easier to maintain than the unstable chemical-based lasers of the previous generation.[x] Highly dynamic tactical laser systems are also increasingly incorporated into combat aircraft such as gunships, high-performance fighters, and attack helicopters.[xi]
Combined, these two technologies eliminate many of the obstacles that faced ABL in the past. With a 20km flight ceiling, HALE UAVs such as the Global Hawk and Phantom Eye possess much longer lines-of-sight and lower beam distortion due to the thin atmosphere, giving them the ability to deliver a concentrated energy beam capable of disabling an enemy ICBM.
More to Be Done:
Still, more R&D needs to be done before HALE UAV high energy lasers are deployable. For example, according to a business solicitation posted on FedBizOpps.gov in June 2017, the Missile Defense Agency (MDA) is interested in a HALE UAV that can carry a payload capacity of between 5,000 and 12,500 pounds, which is something that platforms like Global Hawk currently cannot do.[xii] To help reach these requirements, the MDA has also contracted with the Defense Advanced Research Projects Agency (DARPA) to make their 150 kW High Energy Liquid Laser Area Defense System (HELLADS) lighter and more compact. The goal is to scale down the HELLADS to the size of a large refrigerator while producing one kW of energy for every 5 kg of weight.[xiii] Further efforts will result in a similar 500-kilowatt laser by 2021 and a “best-of-breed” 1-megawatt laser capability by 2023 that could be coupled with a HALE UAV capable of carrying the load.
Producing a more powerful laser beam is critical to realizing the ABL dream. Lower power energy beams are less effective against solid fueled missile engines, whose hulls are designed with significant heat tolerance. Thankfully, North Korea’s current ICBM arsenal is entirely liquid fueled. But considering how quickly the DPRK developed its liquid ICBM, it is reasonable to expect it to diversify its ballistic arsenal to include solid fuel rockets relatively soon.[xiv] Additionally, countries can deploy countermeasures to increase their missiles’ survivability against laser beams in the boost phase. For example, spinning missiles after take-off can prevent lasers from concentrating enough energy on one location to achieve a kill.
Despite the R&D costs associated with further developing laser technology, successfully mounting a condensed megawatt laser on a HALE UAV could be the “holy grail” of boost phase missile defense that the U.S. has been looking for. Having an effective means of disabling a hostile ballistic missile will provide the U.S. with a complete and effective layered missile defense system that increases the United States’s ability to defend the homeland from North Korea or any ballistic missile-equipped nation hostile to the U.S.
Estimated Costs for Boost Phase Defense Options:
Surface to Air: $15 – $25 billion
- No credible cost estimates have been advanced for converting an Aegis-equipped ship, for example, to the boost phase mission.
Airborne Laser: $1.5 billion per unit + $100 million a year to operate
- The discontinued YAL-1 ABL cost over $5 billion in R&D and would have required a fleet of 10 – 20 YAL-1s, would have cost $1.5 billion apiece, and would have demanded $100 million a year to operate.[xv]
- The Army Space and Strategic Defense Command estimated that the ABL would cost $6 billion in a 10-year life cycle for the ABL.[xvi]
- Congress has already spent over $4.5 billion on the ABL thus far
Satellite Kinetic: > $40 billion
- “Roughly 1600 satellites orbiting at an altitude of 300 km would be needed to have at least one, and typically two, in position to intercept an ICBM from North Korea. The total mass in orbit would be about 2,000 tons.[xvii]
- 2,000 tons ≈ 1,800,000 kg
- Launching costs to low Earth orbit are about $20,000/kg
- $20,000 x 1,800,000 kg = Astronomical costs
- And all that is on top of the cost of the satellites
HALE UAV: $500 million – $1 billion
- Boeing’s Phantom Eye or Global Hawk would range between $20 – $200 million per unit but would require a smaller deployed fleet because the platforms’ flight endurance is at least twice as long as the YAL-1
[i] David Sanger, Willian Broad, “In North Korea, Missile Bases Suggest a Great Deception,” The New York Times, November 12, 2018.
[ii] Erick Larson and Glenn Kent, “A New Methodology for Multi-Layered Defenses,” RAND, 1994, pp xii.
[iii] John Pike, “Boost Phase,” Global Security, July 2011. https://www.globalsecurity.org/space/systems/boost-phase.htm.
[iv] David Barton, “Report of the American Physical Society Study Group on Boost-Phase Intercept Systems for National Missile Defense: Scientific and Technical Issues,” Reviews of Modern Physics, 2004, p xxviii.
[vii] Nathan Hodge, “Pentagon Loses War to Zap Airborne Laser From Budget,” The Wall Street Journal, February 11, 2011. https://www.wsj.com/articles/SB10001424052748704570104576124173372065568.
[viii] Michael Gates, “Missile Defense Umbrella?” Center for Strategic and International Studies, January 11, 2011. web.archive.org/web/20110111093235/http://csis.org/blog/missile-defense-umbrella.
[ix] “RQ-4 Global Hawk Fact Sheet,” U.S. Air Force, October 27, 2014. https://www.af.mil/About-Us/Fact-Sheets/Display/Article/104516/rq-4-global-hawk/.
[x] Thomas Higgins, “The three phases of lasers: solid-state, gas, and liquid,” Laser Focus World, July 1, 1995. https://www.laserfocusworld.com/lasers-sources/article/16553578/the-three-phases-of-lasers-solidstate-gas-and-liquid.
[xi] Tyler Rogoway, “This Is Northrop Grumman’s Idea Of A Sixth-Generation Fighter, But Is It Feasible?” Jalopnik, December 12, 2015. https://foxtrotalpha.jalopnik.com/this-is-northrop-grummans-idea-of-a-sixth-generation-fi-1747680825; Tyler Rogoway, “Lockheed’s New Laser Super Turret Could Change Air Combat Forever,” Jalopnik, September 16, 2014. https://foxtrotalpha.jalopnik.com/lockheeds-new-laser-super-turret-could-change-air-comBa-1635210849; Tyler Rogoway, “The AH-64 Apache Will Get A Laser Cannon To Play With This Summer,” The Warzone, May 27, 2016. https://www.thedrive.com/the-war-zone/3700/the-ah-64-apache-will-get-a-laser-cannon-to-play-with-this-summer?iid=sr-link1.
[xii] Missile Defense Agency, “High Altitude Long Endurance (HALE) unmanned aircraft,” FedBizOpps, Solicitation Number: HQ0147-17-BAA-RFI_HALE, June 13, 2017. https://www.fbo.gov/index?s=opportunity&mode=form&id=ad7b678ce54e0cc5324a529ebac8e84c&tab=core&_cview=0.
[xiii] Jen Judson, “Space-based laser weapons could ultimately take out missile threats in boost phase,” Defense News, August 14, 2018. https://www.defensenews.com/digital-show-dailies/smd/2018/08/14/space-based-laser-weapons-could-ultimately-take-out-missile-threats-in-boost-phase/.
[xiv] Missile Defense Project, “Missilnes of North Korea,” Missile Threat, Center for Strategic and International Studies, June 14, 2018, last modified June 15, 2018. https://missilethreat.csis.org/country/dprk/.
[xv] Michael Gates, “Missile Defense Umbrella?” Center for Strategic and International Studies, January 11, 2011. web.archive.org/web/20110111093235/http://csis.org/blog/missile-defense-umbrella.
[xvi] Pamela Hess, “USAF Questions Army Plan to Use UAVs for Boost-Phase Intercept Mission,” Inside Missile Defense, October 11, 1995.
[xvii] Daniel Kleppner, Frederick Lamb, David Mosher, “Boost-Phase Defense Against Intercontinental Ballistic Missiles,” Physics Today, 57, no. 1 (January 2004). https://physicstoday.scitation.org/doi/full/10.1063/1.1650067.