понедельник, 12 марта 2012 г.

LOSAT: Line of sight antitank

Soldier Armed

Throughout the changing political and military global landscapes of the last two decades, there are few system needs that have remained constant. One example is the need to provide U.S. Army early entry/light forces with a vehicle-based capability to defend themselves against heavy modern armored vehicles. Contingency planning in the 1980s to meet this need focused largely on the venerable but obsolescent M551 Sheridan. Even into the early 1990s, it was the M551 that was called upon to make the anti-armor vehicular contribution to the first stages of Operation Desert Shield. The mid-1990s saw the identification of a successor to the M551 in the M8 105 mm armored gun system before budget tradeoffs curtailed that effort. Current development efforts on the 105 mm mobile gun system variant of Stryker are seen by some as the 21st-century step in this evolutionary capability path.

Meanwhile, during much of this period, Army and industry scientists have continued working to refine the design concepts for what some see as the ultimate antitank weapon. Called line of sight antitank (LOSAT), the system is based on the general concept of a large rocket wrapped around a long rod penetrator that goes incredibly fast, simply destroying any armor that it hits. No known or projected armor packages can stop it.

Program participants note that LOSAT's technical challenge is not so much in the manufacture of a hypersonic missile but more in the development of its guidance to allow the missile to consistently hit its target. LOSAT designers employed a guidance system that includes a C02 laser with two functions: determining range to the target and providing updates to the missile. In its simplest sense, the fire unit transmits target location information through a series of laser pulses. The pulses are received through the aft looking receiver at the rear of the 174 pound, 6.4 inch diameter x 113 inch long kinetic energy missile (KEM) which is traveling at approximately 5,000 feet per second. Based on that pulsed information, the missile's guidance electronics fire a series of small squibs on the forward attitude control motor to push the missile into the correct azimuth to impact the target.

Designers acknowledge essential similarities between LOSAT's terminal guidance and the-design used on the PAC-3 air defense missile. Although the KEM design has remained largely unchanged for the past 15 years, the combat packaging has seen the entire spectrum of chassis configurations. Early notional designs, for example, featured LOSAT variants of both heavy and medium chassis versions of the Army's armored family of vehicles. With the dissolution of that concept, planners resolved to put kinetic energy missiles on an Abrams tank chassis. From there the program evolved into hardware prototypes, with vehicle engineers and missile engineers integrating the system onto both a stretched Bradley chassis and an armored gun system chassis. LOSAT's chassis roulette finally ended with the sixth variant concept, one based on the M1114 "Heavy" Humvee.

Missile changes during the same period have been relatively minor, focusing primarily on improvements to the electronics in the fire unit. Advances to the missile itself have been made in areas like new guidance and electronics circuit cards. Approximately 50 LOSAT missile test firings have been made over the developmental period. After several years of no live-fire activity, the most recent shots were made in May and July 2001 and involved testing of a new inertial measurement unit with its related software.

Emerging from the tech base arena, LOSAT officially entered an Advanced Concept Technology Demonstration (ACTD) program in April 1998. Approximately two years later, it was figuratively accelerated into what participants describe as an "ACTD+." Goals of the program acceleration include moving directly from ACTD into production with all of the activities that would normally take place under systems development and demonstration (formerly engineering and manufacturing development) now taking place under ACTD.

Work is beginning on modification of the first dozen M1114s to LOSAT firing unit configuration. Modification of this initial company-sized element will be completed over the next year, with these vehicles slated for delivery to a company in the XVIIIth Airborne Corps (Alpha, 5/11) during the summer of 2003. That unit will then conduct the necessary testing to allow the program to proceed into full production.

Along with the fire units, the system includes a missile resupply trailer that will be towed by a separate resupply Humvee. In addition, the current contract includes an option for 144 go-to-war LOSAT KEMs for potential use by the first company (12 fire units).

Service funding currently projects fielding five battalion-sized (36 fire units) LOSAT units, with the first battalion going to the 82nd Airborne Division. Additional battalions will be fielded to the 10th Mountain (Light Infantry), the 25th Infantry (Light), the 29th Infantry and the 101st Airborne (Air Assault) Divisions. Projected LOSAT fielding runs through fiscal year 2012.

"This will provide the light forces with a ground-to-ground antiarmor capability that they severely need," says Randy Tatum, LOSAT Business Development Manager for Lockheed Martin Missiles and Fire Control. "When the XVIIIth Airborne Corps retired their Sheridans, and then the Armored Gun System program went away, they were left with a severe deficiency in antiarmor capability for the U.S. Army's light forces. This fills that gap.

"[It] is a system that absolutely overwhelms any known or projected armors out through the foreseeable time frame," he continues. "The momentum and the energy it imparts onto its targets are so overwhelming that it just overmatches anything that you can pile onto a vehicle to keep it out. It moves so fast that the computing capability of the active protection systems that are out there can't keep up with it. And it has a large mass with the long rod penetrator, not to mention the large rocket engine that's wrapped around it. We say that LOSAT puts 40 + megajoules of energy onto a target. Contrast that with an M829 tank sabot round that puts somewhere between seven and 10 megajoules of rod energy onto a target. This will be a pretty devastating capability in the hands of the soldiers who truly need it."

The same technologies that make LOSAT such a devastating weapon will likely evolve to support Future Combat Systems capabilities, including the desire by service planners to obtain and field a future compact kinetic energy missile.

Engineers are reportedly looking at the physics behind such a missile, which would be capable of defeating the most modern battlefield armor suites at just over half the size and weight of the current LOSAT design.

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