The height-of-burst (HOB) sensor provides fusing to the warhead at the proper height to ensure maximum lethality. The weapon is initialised in the vertical launch system (VLS) with the target co-ordinates, GPS initialisation data, and initial position, velocity and attitude of the missile prior to launch. The basic guidance concept is inertial navigation, using a three-axis inertial measurement unit (IMU) to measure the missile acceleration and angular rate components that result in velocity, spatial position and attitude being used by the guidance laws. The latter are designed to fly to the target in minimum time, with desired flight path, body attitude and velocity for maximum warhead effectiveness against a target. Inertial navigation is aided using position measurements from a GPS receiver.

LASM-1 flight test
In preparation for LASM's first flight test, a standard missile-2 BLK IIIA Tartar configured round was obtained from the navy's existing inventory. The RF seeker head, associated electronics and semi-active homing guidance algorithms were replaced with a spare GAINS unit from the Terrier LEAP demonstration programme. In addition, the terminal phase of the command points guidance software was redesigned to accept GPS data in lieu of board inertial reference unit data. These modifications to existing Tartar configured hardware allowed the LASM-1 mission to be flown as a 'wooden' round with no communication from the land-based fire control system.

On 21 November 1997, the LASM-I round was launched at White Sands Missile Range (WSMR) after being initialised with the target GPS co-ordinates and GPS ephemeris data. The round flew over 70 miles downrange and impacted within the intended aimpoint. The flight profile matched closely with the six-degree-of-freedom simulation predictions and the accuracy was within the required limits.

Warhead arena test 1
It was determined that the MK125 AAW warhead could provide a highly lethal land attack capability while reducing total missile weight and extending the operational range of LASM. The Naval Surface Warfare Center Dahlgren Division (NSWCDD) performed detailed warhead simulations and JTCG/ME approved missile system effectiveness analyses that confirmed the concept.

On 18 November 1997, a modified MK-125 warhead was placed on a stand, approximately 10 feet above the ground in the centre of the test arena and detonated. Various targets were arrayed around the warhead within expected stand-off ranges, including a cruise missile, TEL launcher, radar van, various trucks, an artillery piece and mannequins. Fragmentation witness plates were emplaced to measure the fragment pattern.

All of the targets received extensive damage sufficient to meet JMEM kill criterion standards. The high velocity, high density and large fragment size provided penetration capability against lightly armoured targets. Fragments in the arena test penetrated engine blocks, the artillery breach mechanism, critical engine components, and other critical target components rendering functional kills.

LASM-2 flight test
The goal of the second LASM flight test was to demonstrate approach angle control and verify warhead burst height predictions using a production-based target detection device (TDD). A standard missile production surveillance round (PSR) was utilised. The WSMR fire control system received software modifications to enable LASM-2 to fly in an up-and-over trajectory approaching the target area in a near-vertical configuration. On 18 March 1998, the LASM-2 round was launched from the WSMR. The round flew a near-perfect trajectory and approached the target pole with a near-vertical trajectory. The existing TDD provided fusing on the ground and detonated the warhead at the required distance above the ground.

Warhead arena test 2
The objective was to characterise the warhead fragmentation pattern resulting from minor modifications made to compensate for the MK-125's downward velocity. The initiation system was repackaged and installed near the forward end. When combined with the missile velocity, this results in a near-horizontal fragment pattern. In addition, the shroud fragment assembly was modified to ensure a more uniform distribution of fragments. Analysis of the data collected from this test resulted in a warhead characterisation model nearly identical to model predictions.

LASM-3 flight test
The objective of the final test was to validate the warhead's fragmentation pattern in a dynamic missile flight environment. An SM-2 BLK IIIA round was integrated with a forward-initiated MK-125 warhead. The TDD was modified in order to achieve the required burst altitude.

The fire control software was also modified to cause the missile to fly in an up-and-over trajectory. The LASM-3 round was launched from the VLS at WSMR and flew over 50nm downrange. The missile approached the target arena with the intended velocity and approach angle. The warhead detonated at the required height. The fragment pattern on the witness plates matched closely with the NSWCDD warhead lethality simulations.

Summary