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♞ Erman Douglas - 🕔 May 26, 2020


ICBM-T2 Target Missile

During the third quarter of 2020, the Missile Defense Agency (MDA) confirmed it will conduct an inter-continental ballistic missile (ICBM) intercept test with the Aegis Ballistic Missile Defense SM-3 Block IIA (RIM-161D) missile.

 This will be the first time an SM-3 Block IIA will attempt to intercept an ICBM-class target missile. The test is extremely important as it has been theorized for some time that the Block IIA version of the SM-3 may have the capability from a kinematic perspective to intercept an ICBM both in the post-boost exo-atmospheric phase of flight as well as the pre-terminal descent phase. The Block IIA would not have the burnout velocity necessary for a midcourse intercept - the Block IIA has a maximum velocity of 4.5 km/s while many ICBMs achieve velocities greater than 8 km/s - this limits the intercept altitude to a maximum of 1450 kilometers for the Block IIA missile while the ICBM may achieve altitudes of 2,000+ km. However, much of a theoretical ICBMs flight would still be potentially susceptible to an SM-3 Block IIA exoatmospheric interception. In the following paragraphs we will review the components of the weapon system and ICBM target test missile.




ICBM-T2 Target Missile

ICBM-T2 Target Missile

The ICBM will likely be simulated by a ICBM-T2 target launched from Meck Island at the Reagan Test Site at the Kwajalein Atoll in the Marshall Islands. The T2 uses a Trident-C4 solid rocket booster (SRB) for its first stage and two Pegasus-based second and third stages in a similar configuration to the T1 IRBM target also manufactured by Northrop Grumman Innovation Systems (NGIS). It is believed to have a separating reentry vehicle. It is undisclosed whether the test vehicle will be engaged by Aegis in a post boost-phase exoatmospheric intercept or after the target missile's midcourse coast. Many potential ICBM systems would have already engaged in their bus operations having ejected all Multiple Independently-targetable Reentry Vehicles (MIRV) warheads in preparation for terminal phase reentry. This would lead one to believe that it would be more desirable to conduct and intercept during ascent. However, a descent phase test might also provide data which may be helpful in the event the system is deployed as a backstop for reentry vehicles that avoid destruction by the ground based midcourse defense (GMD) interceptor.


ICBM-T2 Target Missile

Standard Missile SM-3 Block IIA (RIM-161D)

The very first form of the Standard missile was the RIM-24 Tartar. The RIM-24 was abandoned due to reliability problems, but the airframe was reused in order to ease use with existing launchers and automated magazine delivery systems. While the missiles shared the same appearance, the RIM-66A/B missile was an entirely new internal design. The Standard MR (SM-1MR Block I to V) was in service during the war in Vietnam. The missile's autopilot was programmed to fly the most efficient path to the target and would receive course corrections from the ground. Target illumination for semi-active homing was needed only for a few seconds in the terminal phase of the interception. This capability enables the Aegis combat system to time share illumination radars, greatly increasing the number of targets that could be engaged nealy simultaneously. Later, the rail launcher with automated delivery from the ship's magazine was replaced with the Mk 41 Vertical Launch System (VLS). The RIM-66C/D, designated Standard Missile 2 (SM-2), was first deployed aboard the USS Bunker Hill, a Ticonderoga-class cruiser. The RIM-66L (SM-2MR) is the current version of the SM-2 still in service.

ICBM-T2 Target Missile

The SM-3 (RIM-161) evolved from the proven SM-2 Block IV design. To support the extended range of an exo-atmospheric intercept, additional missile thrust is provided in a new third stage for the SM-3 missile, containing a dual pulse rocket motor for the early exo-atmospheric phase of flight. It possesses not only an anti-ballistic missile capability, but may also be employed against satellites. The ship's AN/SPY-1 radar locates the ballistic missile and the Aegis weapon system calculates an intercept solution.

When the missile is launched, the Aerojet MK-72 solid-fuel rocket booster launches the SM-3 out of the ship's Mark-41 vertical launch system (VLS). After booster burn out, staging occurs and the Aerojet MK-104 solid-fuel dual thrust rocket motor (DTRM) continues endoatmospheric propulsion (centric dual thrust rocket motors have a fast burning booster propellant at their core and slower burner sustainer propellant mixture which surrounds the core). The missile continues to receive mid-course guidance information from the AN/SPY-1 radar/Aegis with GPS data updates. The MK-136 solid-fueled third-stage rocket motor fires after the second stage burns out. The third stage motor is pulse-fired and provides propulsion for the SM-3 until 30 seconds before intercept. Pulse-fired solid rocket motors overcome the solid propellant motor constraint which prevents easy shut down and reignition. The pulse rocket motor allows the motor to be burned in segments that burn until completion of that segment. The pulsed rocket motor is constructed with propellant molded in individual segments. Each segment is separated by a barrier (Pulse Separation Device, or PSD) which prevents additional segments from burning until ignited. In this way, the solid rocket motor may deliver calibrated energy to achieve a specific flight profile by delivering variable delta-V depending upon the required final intercept altitude and speed.

ICBM-T2 Target Missile

Lightweight Exo-Atmospheric Projectile (LEAP) kinetic kill warhead (KW)

Before separation from the third stage, the multi-spectrum IR seeker/telescope located in the forward area of the LEAP-KW interceptor begins to track the target object field. When the warhead is released via a low-energy separation mechanism, the on-board multi-axis throttleable divert and attitude control system (TDACS) begins employing precise thrust vectoring to maintain alignment with the intercept window. The TDACS utilizes a electically-controlled extinguishable solid propellant (ESP) motor combined with a mechanism that can vary the nozzle throat area. This mechanism is in the form of a tapered plug called a pintle which can be translated in and out of the nozzle throat causing the annular throat area to increase or decrease thrust output. The material for the nozzle and pintle must be capable of surviving ultrahigh temperature thermal, chemical, and mechanical environments (an example of such a material is melt infiltrated carbon fiber-reinforced zirconium-silicon carbide (Zr Si C) matrix composite) in order to prevent any change to the geometry of the nozzle-pintle due to erosion. The LEAP-KW has built in warhead discrimination which augments the radar data transmitted from the SPY-1 radar to analyze the target field in an attempt to distinguish the target warhead from delivery vehicle clutter or penetration aid (PENAID) countermeasures. Upon interception of the target, the kinetic energy of impact provides 130 megajoules (96,000,000 ft·lbf, 31 kg TNT equivalent). Intercept velocities may take place in excess of 10 kilometers per second (by way of comparison, the average muzzle velocity of a .308 WIN rifle round is 0.8 km/s Рthe closure velocity of 2 such projectiles being no greater than twice that velocity).

Aegis Combat System (ACS)

The Aegis Combat System is an advanced command and decision (C&D) and weapon control system (WCS) that uses powerful computers and radars to track and guide weapons.

The ACS is composed of the Aegis Weapon System (AWS), the fast-reaction component of the Aegis Anti-Aircraft Warfare (AAW) capability, along with the Phalanx Close In Weapon System (CIWS), and the Mark 41 Vertical Launch System. The empty weight for a Mk-41 8-cell module is 32,000 lb (for the strike version) which incorporates anti-submarine warfare (ASW) systems and Tomahawk Land Attack Cruise Missiles (TLAM). Torpedo and naval gunnery systems are also integrated.

ICBM-T2 Target Missile

AWS is comprised of the AN/SPY-1 Radar, the MK 99 Fire Control System, the WCS, the Command and Decision Suite, and SM-2/3/6 Standard Missile family of weapons. These include the basic RIM-66 Standard, the RIM-67 extended range missile, and the newer RIM-161 designed to counter ballistic missile threats. A further SM-2 based weapon, the RIM-174 Standard ERAM is also in service (SM-6) - the multirole SM-6 also provided terminal endoatmospheric intercept capability. The Aegis Combat System is controlled by an advanced, automatic detect-and-track, multi-function three-dimensional passive electronically scanned array radar, the AN/SPY-1. The SPY-1 is a 6 megawatt radar that is able to perform search, tracking, and missile guidance functions simultaneously with a tracked object capacity of well over 100 targets at more than 100 nautical miles.

ICBM-T2 Target Missile

The Aegis system communicates with the Standard missiles through a radio frequency (RF) uplink using the AN/SPY-1 radar for mid-course update missile guidance during engagements and uses the AN/SPG-62 radar for terminal guidance - a large number of targets can be simultaneously engaged. The Aegis Ballistic Missile Defense System (BMD) program is intended to enable the Aegis system to act in a sea-based ballistic missile defense platform.

The Multi-Mission Signal Processor (MMSP) provides Anti-Air Warfare (AAW)/Ballistic Missile Defense (BMD) multi-mission capability as part of the Aegis Open Architecture Modernization Program. MMSP modifies transmitters of the SPY-1D radar to enable dual-beam operation for reduced frame times and better reaction time.



This capability, if successfully demonstrated, will be a very important milestone for U.S. ballistic missile defense. Aegis BMD can offer a significant new layer to defend against low volume ICBM attacks – particularly those most associated with rogue state actors.

I will update this article after the test takes place with whatever data is publicly released.


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