Strategic Capabilities of SM-3 Block IIA Interceptors (June 30, 2016)

In two previous posts, I made estimated projections forward in time of the number of U.S. Navy ballistic missile defense (BMD) capable ships and the number of SM-3 BMD interceptors.[1]  These projections reached two main conclusions: (1) The number of BMD capable ships would reach the upper seventies (77) by 2040; and (2) The number of SM-3 Block IIA interceptors (including possible more advanced version of the missile) would be in the hundreds, possibly 500-600 or more, by the mid-to-late 2030s.

Several developments since those posts were written illustrate the uncertain nature of such projections.  In February 2016, it was revealed that the Navy had decided to upgrade three additional Flight IIA Aegis destroyers to the full advanced BMD capability (under the previous plan these three ships would have had no SM-3 BMD capability).[2]  In addition, it is still unclear how long the five Aegis BMD cruisers will remain in service, although this makes no difference to the longer term projections..

Later in February it was reported that the Navy was reducing the number of SM-3 Block IB missiles it would procure from FY 2017 to FY 2020 from 52 per year to about 35 per year in part due to ongoing problems with the missile’s third stage booster.[3]  However, the impact of this reduction is likely to be more than mitigated by recently announced plans to extend the service life of Block IA interceptors from eight years to twelve.[4]    More significantly, an April 2016 GAO report stated the United States planned to procure 351 SM-3 Block IIA missiles.[5]  This number is above my low projection of about 280 missiles, but also well below my medium projection of about 520 missiles.  However, it is unclear what this 351 number really means, given that United States has apparently not yet even decided on how many Block IB interceptors it intends to buy.[6]  Nevertheless, it seems low, as it less than twice the 182 SM-3 Block IIA missiles the United States intends to buy just for the four ships and two Aegis Ashore sites in European Phased Adaptive Approach (EPAA) system, leaving on average just 2 Block IIA missiles for the other 73 Aegis BMD ships currently requested by U.S. regional Combatant Commanders.[7]

Thus these recent developments do not significantly affect my long term projections: that by mid-to-late 1930s, the United States will likely have about 80 BMD capable ships and hundreds, possibly 500-600 or even more, of Block IIA (or more advanced) missiles.


Strategic Capabilities of SM-3 IIA Missiles

Several published analyses have argued that Block IIA missiles have little in the way of strategic capabilities, in particular, that they will have little or no capability to intercept Russian ICBMs launched toward the United States.[8]   However, these studies only consider Block IIA deployments as part of the EPAA system in Europe and its surrounding waters (such as the North Sea).  They do not consider the deployment scenarios in which the Block IIA interceptors would have potentially significant capabilities against intercontinental-range missiles – when the ships carrying the interceptors are deployed close to U.S. territory.

U.S. Navy ships equipped with Block IIA interceptors will be distributed globally.  For example, the four Aegis destroyers forward deployed to Europe as part of the EPAA are only 12% of the United States’ current 33 BMD capable ships, a figure that will fall to 10% by 2020 and ultimately to only 5% as more BMD capable ships become operational.  The majority of U.S. BMD capable ships are and will be based at U.S. ports.  Moreover, BMD ships can be rapidly deployed to new locations.  As stated in April in Congressional testimony about U.S. regional missile defenses: “Our focus is on developing and fielding missile defense capabilities that are mobile and relocatable, which allow us to address crises as they emerge.”[9]  All of these ships can be supported by the global sensor network of United States’ Ballistic Missile Defense System (BMDS) that spans the entire northern hemisphere, as shown in Figure 1.  According to the Missile Defense Agency (MDA), BMDS sensors have coverage in 20 of the world’s time zones.[10]

BlockIIA - sensors

Figure 1. The land-based radar sensor network for the U.S. BMDS spans the northern hemisphere.  Aegis radars on ships and at Aegis Ashore sites are not shown.  Missile Defense Agency figure.[11]

In the discussion below, the capability of the Block IIA missiles to defend the United States against ICBMs is broken down into two aspects; coverage — the portion of U.S. territory the Block II missiles have the kinematic capability to attempt to defend; and kill capability – the ability of the Block IIA interceptor to actually home in on and destroy intercontinental ballistic missile (ICBM) warheads.


It has long been known, although perhaps not as widely understood as it should be, that if Block IIA interceptors were deployed close to U.S. territory and supported by the BMDS system’s sensors, they could provide coverage of the entire United States.

Figure 2 below shows a rough coverage “footprint” of a SM-3 Block IIA-like interceptor (then known as the Navy Upper Tier interceptor) against an ICBM flying over the North Pole produced by myself and several colleagues in 1994.[12]  It shows that the contiguous 48 states could potentially be covered from a few off-shore launch sites.

BlockIIA - footprint 1

Figure 2.  Rough footprints for SM-3 Block IIA-like interceptors deployed off the coasts of the United States.  The interceptor speed is 4.5 km/s, the speed typically assumed for the Block IIA.  Interceptors are assumed to be launched based on a then-planned (but never built) space-based tracking system.  If the launches were instead based on the current Upgraded Early Warning Radars (the orange pentagons in Figure 1), the footprints would likely be somewhat smaller in the forward (northern) direction, giving footprints more like that shown in Figures 3 and 4.

Unknown to us at the time, Strategic Defense Initiative Organization (SDIO) had already produced a similar figure.  Figure 3 below shows a SDIO chart from 1992 (which appears to have been publicly released in 2005).  It shows the coverage against an ICBM of a naval Block IIA-like interceptor, then known as the Navy Upper Tier interceptor.  Figure 3 shows the entire contiguous states could be covered from five ATBM (anti-tactical ballistic missile) sites – four just offshore and one in the Great Lakes.  Today, basing a ship in the Great Lakes would not be necessary, as the central United States site (if needed) could be provided by an Aegis Ashore (AA) site similar to the ones already deployed in Romania and Hawaii and planned for Poland.

BlockIIA - footprint2

Figure 3.  1992 SDIO figure showing coverage of the United States by a Block IIA – like interceptor.  Source: Rear Admiral A. Brad Hicks, “Aegis Ballistic Missile Defense (BMD) System,” Washington Roundtable of Science and Public Policy, George C. Marshall Institute, December 19, 2005.  Available at:

Figure 4 below shows a similar “footprint” for a single ship, explicitly with SM-3 Block IIA interceptors, located off the U.S. East Coast.

BlockIIa - footprint3

Figure 4.  Coverage of the eastern half of the United States against an ICBM from a single ship just off the coast.  Source: Sydney J. Freedberg, Jr., “Aegis Ashore: Navy Needs Relief from Land”, July 2, 2015, available at:  The image is attributed to retired VADM J.D. Williams and is described as being based on analysis by M.I.T.’s Lincoln Laboratory.

Figure 5 below provides a different perspective on the coverage of U.S. territory by Block IIA interceptors by showing potential intercept geometries against Russian ICBMs.

BlockIIA - foorprint4

Figure 5.  Intercept geometries for Block IIA-like interceptors against Russian ICBMs.  Image from: Yousaf Butt and Theodore Postol, “Upsetting the Reset: The Technical Basis of Russian Concern over NATO Missile Defense, Federation of American Scientists Special Report Number 1, September, 2011, p. 24.  Online at: Block IIA interceptors will likely have a speed of about 4.5 km/s.

These above figures make it clear that the entire contiguous United States could be covered by no more than three or four ships equipped with Block IIA interceptors, perhaps supplemented by a single Aegis Ashore (AA) site.  An additional ship or AA site would be needed for Alaska; Hawaii already has an experimental AA site that could be converted to an operational site.  According to one estimate, the experimental AA site in Hawaii could be converted into an operational site for $41 million.[13]


Kill Capability

Given the ability of Block IIA interceptors to cover the country from a small number of launch sites, the only thing that could prevent them from having a potential capability (leaving aside for now the problem of countermeasures that plagues any exo-atmospheric defense) against Russian and Chinese intercontinental ballistic missiles (ICBMs) would be if the Block IIA kill vehicles were not capable of homing in on and hitting the ICBM warheads.[14]

ICBMs (missiles with ranges greater than 5,500 km) have higher burnout speeds than shorter-range missiles, and intercepting them will thus often involve higher closing speeds than against shorter-range missiles, in turn requiring more capable kill vehicles.  Official descriptions of the SM-3 Block IIA credit it with being able to intercept intermediate-range ballistic missiles (IRBMs, ranges between 3,000 and 5,500 km) and shorter range missiles and “some ICBMs.”[15]  However, there is little doubt that the Block IIA kill vehicles will be able to home in on and intercept ICBM warheads.

In February 2008, the United States used an SM-3 interceptor to destroy a malfunctioning satellite, specifically targeting a fuel tank on the satellite.[16]  The satellite was travelling at a speed of greater than 7.6 km/s, a speed comparable or greater than that of an ICBM.  Three years later, the United States demonstrated that an SM-3 missile can intercept an IRBM in a successful intercept test in April 2011.[17]

Both of these intercepts involved only a first-generation Block IA interceptor.  The Block IIA kill vehicle will be two generations in capability beyond the Block IA kill vehicle used in these intercepts.  Relative to the Block IA kill vehicle, the next-generation Block IB kill vehicle adds a two-color seeker with improved optics and an advanced signal processor.  The Block IB kill vehicle also has a new, “more flexible” throttleable divert and attitude control system (TDACS), which improves its divert capabilities.[18]  According to reports, the TDACS is able “to dynamically vary its thrust and operating time” and provides higher thrust levels using continuous thrust management to give a greater divert capability than does Block IA kill vehicle.[19]  The Block IIA interceptor will further improve on the Block IB kill vehicle by adding a “large diameter” kill vehicle with an “advanced discrimination seeker” and a “high divert DACS.”[20]  [Added 7/7/2016: Relative to the SM-3 Block IB, the SM-3 Block IIA has “more than doubled seeker sensitivity” and “more than tripled divert capability.” (FY 2017 President’s budget, MDA, RDT&E, vol. 2a, p. 2a-891)

Official figures make it clear that the Block IIA is expected to be able to intercept full-range ICBMs.  Figure 6 below is from a 2008 Missile Defense Agency slide which shows that the Block IIA is able to intercept ICBMs with a full ICBM range of about 10,000 km in the descending phase of their flights – precisely the scenario illustrated in Figures 2, 3, 4 and 5.

 BlockIIA - footprint5

Figure 6.  MDA slide from 2008 showing Block IIA interceptors can intercept ICBMs with ranges of 10,000 km during the ascending and descending phases of their flights.  Source: Missile Defense Agency, “Aegis Ballistic Missile Defense: Status, Integration and Interoperability,” May 6, 2008.  Online at:  Note that, as another figure in this briefing shows, in 2008 the Block IIA was expected to begin deployment in 2015.

A similar figure in a 2012 National Academy of Sciences Report shows the Block IIA being able to intercept an ICBM over an even greater fraction of its trajectory.[21]

The proposed plan to convert the Hawaii Aegis Ashore experimental site into an operational site also assumes an SM-3 capability against ICBMS, as Honolulu is about 7,000 km from North Korea, and thus could only be reached by an ICBM-range missile.

More generally, DOD and MDA officials have stated that they have at least considered the use of SM-3 interceptors as substitutes or supplements for the Ground Based Interceptors (GBIs) of the current U.S. Ground-based Midcourse Defense (GMD) national missile defense system.  In April 2013, in response to a question about a possible East Coast GBI interceptor site, the Chairman of the Joint Chiefs Of Staff General Martin Dempsey told Congress that: “The only thing I would add, Mr. Secretary and Congressman, is that the environmental impact study shouldn’t be taken to assume that we will, in fact, establish an East Coast missile field for the ground-based interceptor, because we have other options.  We have other options, to include sea-based.”[22]

Three months later, in response to similar question, MDA Director Vice Admiral James Syring told the Senate that: “As Chairman Dempsey has testified, that will be one of the capabilities that will be evaluated. The Aegis system, as you known, is a fantastic system.  We would have to get into a classified discussion in terms of what coverage and what capability that could provide in defense of the homeland, which I’d rather not go into here in an unclassified setting.  But, yes, sir, it will be a capability that we examine in conjunction with examining the third site.”[23]  Note that both Dempsey’s and Syring’s statements were made after the cancellation of the SM-3 Block IIB interceptor program.

Ultimately, the GBI and the SM-3 Block II interceptors may even end up using the same kill vehicle.  The MDA is in the early stages of developing a Multiple-Object Kill Vehicle (MOKV), which would enable deploying multiple, small kill vehicles on a single GBI interceptor beginning in the mid-2020s or later.  As figure 7 below illustrates, these same or similar MOKVs could also be deployed on SM-3 interceptors (although perhaps only one per missile).

Block IIA -CKV

Figure 7. The Ground-Based Interceptors (GBIs) of the U.S. GMD national missile defense system and SM-3 interceptors may eventually both use a similar or identical kill vehicle.  Slide from Richard Matlock (MDA Program Executive for Advanced Technology), presentation to 2013 Space and Missile Defense Symposium, August 15, 2013.  Available at:



For the United States and Russia (Soviet Union), any discussions of the consequences of the deployment of strategic-capable BMD systems have been largely hypothetical, since they have always taken place in the context of very large existing deployments of long-range ballistic missiles. The end of the Cold War, the United States’ withdrawal from the ABM Treaty, and the negotiation of the New START Treaty have so far not fundamentally changed this situation. Even after the implementation of New START, each country will retain nearly 1,500 nuclear ballistic missile warheads, dwarfing the 44 Ground-Based Interceptors (GBIs) planned for the United States’ GMD national missile defense system by the end of 2017, and even the nearly 100 GBIs that the U.S. could end up deploying if it builds an additional interceptor launch site in the eastern United States.

However, the large-scale deployments of strategic-capable SM-3 Block IIAs (or successor missiles) could greatly change the balance between offensive warheads and strategic-capable interceptors.  By the late 2030s, the U.S. could have very roughly 350 – 650 strategic-capable interceptors either based in or near U.S. territory or capable of being relocated there on short notice.[24]  Although the United States might have no intention to ever relocate these interceptors in such a way, it seems very unlikely that it would be willing (or possibly even able) to provide Russia and China with any credible assurance that it would never undertake such a step – a step that could directly undermine their nuclear deterrents.

After New START goes into effect in February 2018, Russia will likely have about 1490 deployed ICBM and SLBM warheads (based on the limit of 1,550 accountable warheads minus about 60 bombers).  If we assume that about half of these warheads are survivable at any given time, then Russia would have about 750 survivable strategic ballistic missile warheads.  This number is roughly comparable to, although likely somewhat larger, than the number of strategic-capable ballistic missile interceptors the United States would likely have by the late 2030s.  Whether such a situation would be acceptable to Russia is unclear; at a minimum it would be much less acceptable than the current situation, which Russia is already complaining about.

Perhaps more significantly, even relatively modest future reductions below New START levels, say to a level of 1,000 strategic warheads, could then see the number of Russia’s survivable ICBM and SLBM warheads fall below the number of U.S. strategic-capable interceptors.  A direct comparison between the number of country’s strategic missile warheads and the number of adversary’s strategic-capable BMD interceptors may not be the best way for the country to assess the adequacy of its nuclear deterrent.  Nevertheless, the point at which the number of  survivable warheads falls below the number of interceptors seems likely to be  a significant symbolic barrier to further reductions in the number of ballistic missile warheads.

On April 7, 2010, the day before the New Start Treaty was signed, Russia made a (non-binding) unilateral statement that, in its view, the Treaty “… may be effective and viable only in conditions where there is no qualitative and quantitative build-up in the missile defense capabilities of the United States.”[25] At that time, the United States had thirty deployed strategic interceptors – GBIs in Alaska and California.  That Russia felt it necessary to make such a statement despite the then lop-sided ratio of New START warheads to U.S. strategic-capable interceptors — at that time nearly fifty to one — does not bode well for it agreeing to further cuts in the face of expanding U.S. missile defenses that could bring the ratio its survivable warheads to U.S. strategic-capable interceptors close to or below one to one.

In addition, Russia is significantly modernized its strategic nuclear forces, and the number of missile warheads it is capable of deploying is expected to continue to grow at least into the mid-2020s, and it may well have to eliminate some missile warheads to get under the New START limits.[26] Thus Russia no longer has the incentive to agree to lower numbers simply to maintain parity with the United States in numbers of strategic warheads, an incentive that helped it agree with the New START limits.

The implications of U.S. SM-3 Block IIA deployments are even more severe with respect to China.  Today, the number of Chinese survivable nuclear warheads capable of reaching at least the U.S. West Coast is roughly comparable to the number of U.S. strategic-capable interceptors.[27] Although the number of Chinese strategic warheads is expected to slowly increase, this anticipated increase falls far short of keeping pace with the rapid increase in the number of U.S. strategic-capable warheads that will begin in the 2020s.

There are already indications that U.S. missile defense deployments are affecting Chinese decision making on their strategic nuclear forces. In 2015 the United States announced that China had begun to deploy MIRVed warheads (multiple, independently-targeted warheads) on some of its silo-based DF-5 ICBMs.[28] China has been capable of MIRVing its missiles for decades, but had refrained from doing so, and this recent development of MIRVs is widely viewed as being at least in part a response to the U.S. BMD program.[29] A second, road-mobile, MIRVed ICBM is also under development, and was first flight tested in August 2015.[30]  U.S. officials attribute at least part of China’s motivation for MIRVing to concerns about U.S. ballistic missile defenses.[31] In addition, in 2016 the U.S. Department of Defense stated that it expected the first deterrent patrol of a Chinese ballistic missile submarine to take place later that year.[32]  Chinese military officials have stated that the primary reason for their increased emphasis on sea-based missile forces was the expanding U.S. missile defense program.[33]  Thus the U.S. BMD program already appears to be influencing China to build up its land-based long-range nuclear ballistic missile forces faster than it otherwise would have.[34]  The much larger-scale deployment of Block IIA interceptors in the 2020s and 2030s can only be expected to lead to even greater buildups.  Indeed, unless China is willing to see its number of strategic retaliatory warheads reduced to a fraction of the number U.S. strategic-capable missile defense interceptors, its strategic nuclear forces will have to be several to many times their current size.

Many U.S. officials and analysts are already expressing great concern about new Chinese conventionally-armed ballistic missiles, the DF-21D and the DF-26C. These so-called “carrier killer” missiles are believed to be equipped with a maneuvering warhead with terminal guidance, and both are believed to be conventional variants of nuclear-armed missiles. The deployment of such missiles raises the prospect of an offense-defense competition as China deploys more regional missiles and the U.S. expands its missile defense capabilities in Asia. Such a competition could then feed back into Russian and Chinese strategic force concerns if it leads the United States to deploy significantly larger numbers of naval SM-3 Block II interceptors which could be rapidly redeployed to defend U.S. territory.

By 2017, the United States will have twelve Aegis ships based in Japan, seven of which will be BMD capable – nearly twice as many as the four BMD ships deployed as part of the EPAA.[35]  Moreover, three of these ships will then have the most capable “advanced” Baseline 9 Aegis BMD capability – compared to none in the EPAA. Japan currently has six Aegis destroyers, four of which are currently BMD-capable, with the other two expected to become BMD-capable by FY 2018 and 2019 respectively.[36]  Japan also plans to build two new Aegis ships, which would give it a total of eight BMD-capable ships.

While the United States does not intend its BMD systems as a counter to Russia and China’s strategic forces, neither does it seem to take Russian and Chinese concerns about missile defenses seriously. Unless this changes, the likely outcome is that the United States will simply continue to build up its missile defense system in spite of their objections until it provokes a strong reaction from one, or more likely both, countries. Some of the most obvious forms such a Russian reaction could take are refusing to go below New Start levels, refusing to extend the Treaty and building up its forces, or deploying its own national missile defense system. Moreover, by the time the reaction occurs, U.S. BMD deployments may be at or approaching a level that would preclude Russian reductions much below New Start levels for the indefinite future and thus would be a severe and likely long-lasting setback for any efforts to reduce U.S. and Russian nuclear arsenals. Such reactions, and similar ones from China, would only reinforce the connection between strategic missile defenses and strategic offensive missile forces, and thereby raise the prospect of nuclear offense-defense competitions.


[1] This post is based on part on a working paper for Cornell University’s Judith Reppy Institute for Peace and Conflict Studies’ Project on A Stable Transition to a New Nuclear Order: George Lewis, “Prompt Global Strike Weapons and Missile Defenses: Implications for Reductions in Nuclear Weapons,” January 2016.  Online at:

[2] Sam LaGrone and Megan Eckstein, “FY 2017 Navy Budget Adds 3 More Aegis Combat System Modernizations Over Next Five Years,” USNI News, February 11, 2016.  Available at:

[3] Jason Sherman, “MDA Scraps Plan for $1.8B Block Buy of Raytheon Missile, Slashes Procurement,” Inside Defense SITREP, February 22, 2016.

[4] MDA Director Vice Admiral James D. Syring, written statement, Strategic Forces Subcommittee, House Armed Services Committee, April 14, 2016, p. 12.  Available at:

[5] U.S. Government Accountability Office, “Missile Defense: Ballistic Missile Defense System Testing Delays Affect Delivery of Capabilities,” GAO-16-339R, April 18, 2016, p. 45 (slide 32).  Available at:

[6] At the April 14, 2016 HASC Strategic Forces Subcommittee hearing, MDA Director Vice Admiral Syring, discussing the number of Block IA and Block IB interceptors, stated that “I do not have an end inventory objective yet for Aegis.

[7] As discussed in my post of December 13, 2015, the number of Aegis BMD ships requested by U.S. Regional Combatant Commanders has increased from 42 in 2014 to 77 in 2016.  The United States is unlikely to have enough BMD ships to meet these requests until at least the late 2030s.

[8] Joan Johnson-Freese and Ralph Savelsberg, “Why Russia Keeps Moving the Football On European Missile Defense: Politics,” Breaking Defense, October 17, 2013.  Online at:  Jaganath Sankaran, “Missile Defense Against Iran Without Threatening Russia,” Arms Control Today, November 2013.  Online at:

[9] Brian P. McKeon, Principal Deputy Under Secretary of Defense for Policy.  Written statement, Subcommittee on Strategic Forces, Senate Armed Services Committee, April 13, 2016.  Available at:


[10] James D. Matthewson Jr., “Missile Defense Agency, Small Business Programs Conference, Sensors Directorate Overview,” August 14, 2015.  Online at:

[11] Matthewson Jr., “Sensors Directorate Overview.”


[12] Lisbeth Gronlund, George Lewis, Theodore Postol and David Wright, unpublished footprint, 1994.

[13] Andrea Shalal, “Exclusive: U.S. Weighs Making Hawaii Missile Test Site Operational – Sources,” Reuters, January 22, 2016.

[14] This conclusion would also apply to Russian and Chinese submarine launched ballistic missiles that were launched from close to their national territory.

[15] RDML Joe Horn, “Aegis BMD Overview to the National Defense Industrial Association,” July 13, 2010,   slide 13.  Available at:

[16] Thom Shankar, “U.S. Missile Strikes Spy Satellite from its Orbit,” New York Times, February 21, 2008.

[17] U.S. Missile Defense Agency, “Sea-based Missile Defense Flight Test Results in a Successful Intercept,” News Release, April 15, 2011.  Available at:

[18] MDA, “Second-Generation Aegis Ballistic Missile Defense System Completes Successful Intercept Flight Test,” News Release, May 9, 2012.

[19] Zachary M. Peterson, “Raytheon, ATK Hope To Start Advanced SDACS Flight Tests This Year,” Inside Missile Defense, August 30, 2006; “Raytheon and Aerojet demonstrate SM-3 Throttling Divert and Attitude Control System,” PR Newswire US, August 15, 2006.

[20] Ballistic Missile Defense Review Report, p. 20.

[21] Figure 1-2 on page 27 of Committee on an Assessment of Concepts and System for U.S. Boost-Phase Missile Defense in Comparison to Other Alternatives, National Research Council of the National Academies, Making Sense of Ballistic Missile Defense: An Assessment of Concepts and System for U.S. Boost-Phase Missile Defense in Comparison to Other Alternatives, 2012, shows SM-3 Block IIA missiles are able to intercept ICBMs over most of their descending trajectories. Available at:

[22] Defense Subcommittee, House Appropriations Committee, April 16, 2013.

[23] Defense Subcommittee, Senate Appropriations Committee, July 17, 2013.

[24] The 350 figure is based on the GAO’s figure of 351 SM-3 Block IIAs + 44 GBIs – 24 to 48 Block IIAs deployed on land in Europe.  The 650 figure is based on my medium projection of 580 Block IIAs + 100 GBIs – 24 to 48 Block IIAs on land in Europe.  (Note: the environment impact materials produced by MDA for a possible East Coast deployment sites indicate up to 60 GBIs might be deployed at that site.)

[25] U.S. Department of Defense, “New Start: Article-by-Article Analysis Unilateral Statements,” no date. Available at:

[26] Hans M. Kristensen and Robert S. Norris. “Nuclear Notebook: Russian Nuclear Forces,” Bulletin of the Atomic Scientists, May/June, 2015.  Online at:

[27] The best publicly available estimate is that China currently has about 64 ICBM warheads capable of reaching at least as far as the U.S. West Coast, about half of which are deployed in vulnerable land-based silos. Hans M. Kristensen and Robert S. Norris, “Nuclear Notebook: Chinese Nuclear Forces, 2015,” Bulletin of the Atomic Scientists, Vol. 71, No. 4 (2015), pp. 77-84.  Online at:

[28] David E. Sanger and William J. Broad, “China Making Some Missiles More Powerful,” New York Times, May 16, 2015. Available at:

[29] Sanger and Broad, “China Making Some Missiles.”

[30] Statement of Admiral C. D. Haney, Commander, U.S. Strategic Command, before the Senate Armed Services Committee, March 19, 2015. Available at: Bill Gertz, “China Tests New Long-Range Missile with Two Guided Warheads,” Washington Free Beacon, August 18, 2015.

[31] Office of the Secretary of Defense, Annual Report to Congress: Military and Security Developments Involving the People’s Republic of China 2015, April 2015, p. 31.  Online at:

[32] Office of the Secretary of Defense, Annual Report to Congress: Military and Security Developments Involving the People’s Republic of China 2016, April 2016, p. 26.  Online at:

[33] Julian Borger, “China to send nuclear-armed submarines into Pacific amid tensions with US; Beijing risks stoking new arms race with move although military says expansion of the US missile defence has left it with no choice,” The Guardian, May 26, 2016.  Online at:

[34] The MIRVing of these missiles does not immediately allow China to greatly increase the number of its missile warheads, since the limited payloads of these missiles means that each one can carry at most only two or three warheads. See David Wright, “Groundless Claims about Chinese MIRVing,” All Things Nuclear blog, October 9, 2015. Available at:

[35] The 11 current Aegis ships homeported in Japan are listed at:  The USS Milius will be added in 2017.  The USS Barry, USS Benfold, and USS Milius have the advanced Baseline 9 BMD capability. The other BMD capable ships are the USS Curtis Wilbur, USS John S. McCain, USS Fitzgerald, and the USS Stethem.

[36] Statement of Brian P. McKeon, Subcommittee on Strategic Forces, Senate Armed Services Committee, April 13, 2016.  Online at:

Leave a comment


  1. Paul Austin

     /  June 7, 2017

    I read your posting with interest. I worked in missile defense for some years but have not done so, again for years.

    Proposing Aegis as a general BMD system, tasked with ICBM engagements as you discuss have several major flaws. They mostly stem from inadequate kinematics of the Standard Missile interceptor family. I will discuss that below.

    What Aegis has going for it as a general BMD system is system maturity. The base Aegis system software as well as the BMD functions have been trialed more extensively that any other missile and air defense system in existence. That’s a major strength. System software and hardware maturity raises the confidence level of Aegis, confidence that competing systems can only buy with time in operation and numbers of tests run.

    Aegis does have one major flaw, that all the Standard Missile family airframes must be compatible with the Mk41 VLS. The SM-3 Block II uses the maximum available cell volume to increase the terminal velocity of the missile to about the maximum that can be achieved with the constraints of the Mk41 VLS.

    A rule of thumb in missile defense world says that an exo interceptor needs a velocity of the same order as its target. That’s to that the intercept engagement can begin at something like apogee of the target. As your figure 5 shows, SM-3s will engage an ICBM-class target very late in it’s trajectory and will do so with a very adverse engagement geometry, late in time and with very high crossing velocities. Improvements in KV performance can’t make up for either challenge. Engagement late in time means there are very few shots available (in shoot-shoot-look-shoot terms) for any single target and the crossing velocity makes intercepts -much- more difficult; think the difference between shooting skeet and shooting trap.

    The GBI interceptors are large for a reason; to increase engagement velocity and initiate intercepts for far out along the incoming trajectory. If the Navy wishes to have a serious ICBM-killer, it needs to build launch tubes that can accommodate a (notionally) Trident C-1 sized airframe. Such a launch tube will not fit in a cruiser/destroyer hull but will fit in what the Navy calls a “deep draft” hull like amphibious ships, large auxiliary ships and aircraft carriers.

    Why can’t a further-developed KV solve these problems? Because the enemy will not remain passive. There are a number of strategies, some not doubt currently in place, that can make a late exo interceptor non functional. You touch on decoys, the favorite topic of BMD critics. Exo-atmospheric detonated nuclear weapons are very effective in defeating a defense system. Having a warhead detonate in space creates a number of artifacts that interfere with defense systems: RADARs and visual/IR sensors are blinded for long periods, communications are disrupted and last but not least, unless the interceptors themselves are as radiation-hardened as the RVs themselves, an exo-atmospheric burst will disrupt or destroy the KVs themselves. Any or all of these things will protect RVs following or accompanying the detonated warhead. RVs -are- supremely radiation hardened. They are very simple compared to a KV and so it is simpler to make them very, very radiation hardened.

  1. A Comprehensive Guide to American Ballistic Missile Defense Systems -

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