The Sea-Based Terminal Program and the SM-6 Dual Interceptors (July 25, 2016)

Sea-Based Terminal

Most of the attention given the US Navy’s Aegis Ballistic Missile Defense (BMD) program focuses on its various versions of the SM-3 anti-missile interceptor.  These missiles, the SM-3 Block IA, the SM-3 Block IB and the forthcoming SM-3 Block IIA, intercept their targets above the atmosphere and are intended to provide coverage over large areas (particularly the Block IIA).  However, this post discusses the Missile Defense Agency’s and the Navy’s Sea-Based Terminal (SBT) program, which is developing and deploying lower-altitude, within-the atmosphere ballistic missile defense interceptors.

An SBT capability offers several possible benefits.  First, it provides a second layer of ballistic missile defense for Navy ships and nearby areas, thereby potentially increasing the overall effectiveness of the Aegis BMD system.  SBT interceptors operate in a completely different way than the SM-3 interceptors.  The SBT interceptors home in on their target using radar, maneuver using atmospheric forces, and kill with a high-explosive fragmentation warheads, while SM-3 interceptors use infrared homing, maneuver using rocket thruster (divert thrusters), and kill using direct high-speed collisions.  These differences in operating principles may make it less likely that a countermeasure (or other circumstance) that defeats an SM-3 interceptor can also defeat an SBT interceptor.  Second, SBT interceptors can potentially intercept shorter-range missiles, such as Scuds (or longer range missiles on depressed trajectories) that do not leave the atmosphere (that is, rise above about 100 km altitude) and thus cannot be intercepted by SM-3 interceptors.  Third, SBT interceptors are likely to be much less expensive, by a factor of three or more, than SM-3 interceptors.  Finally, SBT interceptors can also be used to intercept aircraft (and soon ships), allowing more efficient use of the limited number of vertical launch tubes on Navy ships.

SM-2 Block IV, Block IVA, and Block IV (modified)

In the 1990s, the Ballistic Missile Defense Organization and the U.S. Navy planned to develop a terminal phase ballistic missile defense system known as Navy Lower Tier.  (In parallel, BMDO was developing the Navy Upper Tier interceptor, which was renamed Navy Theater Wide, and eventually evolved into the current SM-3 Aegis BMD interceptors.)  This program, which was renamed Navy Area Defense in 1996, was based on a new version of the Navy’s existing extended-range air defense missile the SM-2 Block IV.  The SM-2 Block IV operates within the atmosphere, uses semi-active radar homing and has a high-explosive fragmentation warhead.

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THAAD Radar Ranges (July 17, 2018)

A central element of the debate surrounding the recent decision by South Korea to allow the United States to deploy a Terminal High Altitude Area Defense (THAAD) missile defense system on its territory is the range of the THAAD’s radar. China argues that the THAAD radar will be able to look deep into its territory; supporters of the deployment counter that the radar will be configured so that its range will be limited.

The radar used with a THAAD battery is the X-band AN/TPY-2.  The TPY-2 radar has two configurations.  It can be configured as Terminal Mode (TM) radar, in which it operates as the fire control radar for a THAAD battery.  Alternatively, it can be set up as a Forward-Based Mode (FBM) radar, in which it relays tracking and discrimination data to a remote missile defense system, such as the U.S. Ground-Based Midcourse (GMD) system.  If THAAD is deployed to South Korea, The United States has stated that its TPY-2 radar would be in the shorter-range TM configuration.  Since in the TM mode, the radar reportedly only has a range of 600 km, supporters of the THAAD deployment argue that while its range is adequate to cover N. Korea, it cannot look deeply into China.  Critics of this argument point out that in the FBM mode the radar has a much greater range, and that the radar can be converted from TM to FBM (or vice versa) in only eight hours or less.  According to a U.S. Army manual, “The hardware used by the two modes is identical, but their controlling software, operating logic, and communications package are different.”[1]  In addition the radar is highly mobile: it can be transported by air and can be operational with four hours of reaching its deployment site.

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THAAD Flight and Intercept Tests Since 2005 (July 10, 2016)

Flight tests of the Terminal High-Altitude Area Defense (THAAD) system since developmental testing resumed in 2005 and planned future tests.

THAADTests-07-2016

Figure 1. THAAD intercept tests since 2005. In April 2012, the Director of Operational Test and Evaluation stated that “due to budget constraints within the agency, MDA had decided to slow the pace of THAAD testing to about one test every eighteen months.[1] 

FTT-01 (November 22, 2005:  First launch of an operationally-configured THAAD interceptor.[2]  The launch, conducted at the White Sands Test Range (WSMR), successfully demonstrated the operation of missile and kill vehicle, although no target was used and thus no intercept was attempted.  The THAAD TPY-2 radar does not appear to have participated in this test.

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SM-3 Block IIA Testing Chronology (July 7, 2016)

SM-3 Block IIA Testing Chronology

SCD PTV-01 (October 2013): SM-3 Cooperative Development (SCD) Propulsion Test Vehicle (PTV)-01. A test of the Block IIA booster rocket and canister, reportedly successful, intended to demonstrate that The Block IIA could be launched from the Vertical Launching System used on U.S. Navy Aegis ships and at Aegis Ashore sites.

SCD CTV-01 (June 6, 2015): SCD Controlled Test Vehicle (CTV)-01.  First flight test of SM-3 Block IIA.  It was not an intercept test and no target was present.  The Missile Defense Agency stated that the test “successfully demonstrated flyout through nosecone deployment and third stage deployment.”[1]  According to the Government Accountability Office (GAO), the test was delayed by about 5 months.[2]

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