SLAM ER – An Innovative Update to a Premier GPS Guided Weapon

Robert Kuhlmann, Dennis Gerth,Ken Heckroth, John Nielson

Abstract:	The U.S. Navy/Boeing Standoff Land Attack Missile Expanded Response (SLAM ER) (see Figure 1) is a premier air-launched, adverse weather, standoff weapon. Its role in the U.S. Navy arsenal is to allow carrier-based F/A-18 aircraft to attack high-value targets from a safe distance, with a high probability of success. SLAM ER uses its GPS/INS for precise navigation along a pre-programmed trajectory to a data link transmit point, at which time an infrared image is broadcast to the F/A-18. System specifications require the pre-programmed target to be in the seeker staring field-of-view at this time. The aircraft pilot then designates the desired impact point (via data link) and commands the missile to estimate the coordinates of and steer towards the designated target until impact. SLAM ER, based on its predecessor, the Standoff Land Attack Missile (one of the first GPS-aided weapons), is a major retrofit effort. Only the turbo-jet engine, fuel tank, fin actuators, IIR seeker, and GPS receiver antennas remain. New for SLAM ER is its Guidance Navigation Unit (GNU) (derived from the Honeywell H-764), which integrates a R4700- based mission computer, existing Collins GPS Embedded Module III (GEM III) receiver, and NDI Honeywell Air Data System, Honeywell GG1320 Ring Laser Gyros and Allied Signal QA2000 ISO accelerometers, into a tightly-coupled GPS/INS subsystem. Other new equipment includes a video/control data link and antenna, nose fairing, planar wings, warhead, control fins, and mission planning system (see Figure 2). The benefits gained from this retrofit are increased range, lethality, and target coverage, with a much-improved pilot interface. This paper will document the challenges and innovation involved in the GPS/INS integration phase of the SLAM ER GNU development. The GEM III and navigation Kalman filter in the Mission Computer make special provisions for severe shock (100s of Gs) encountered during launch and warhead arming. Long-term storage requirements drove a unique approach allowing frequency calibration terms to be output by the receiver, stored in mission computer non-volatile memory, then passed-back to the receiver for reuse (possibly many years later) during the next SV acquisition. This approach allows input of test calibration terms simulating the effects of frequency standard aging. The Navigation software allows GPS acquisition/ track at any phase in the mission: on the aircraft carrier deck, during ingress, or post-launch. This drives the need for: 1) fast but highly probable SV acquisition times (using a pre-launch aircraft mask), 2) an air data reference (used if launched prior to SV track), 3) adaptive azimuth calibration (improves seeker pointing), and 4) a cost-effective null steering anti-jam antenna system using a dual antenna system (omni-directional and fixed jammer null) with embedded logic to switch antennas in the presence of jamming. Three highly successful flight test phases will be discussed. The first was a SLAM ER guidance equipment captive carry test, using a Beechcraft Super King Air test-bed. Following were numerous missile captive carry tests using preliminary software builds. A highly successful free-flight test phase is nearly complete, with eight missile flight successes in eight attempts.
Published in:	Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998) September 15 - 18, 1998 Nashville, TN
Pages:	583 - 589
Cite this article:	Kuhlmann, Robert, Gerth, Dennis, Heckroth, Ken, Nielson, John, "SLAM ER – An Innovative Update to a Premier GPS Guided Weapon," Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998), Nashville, TN, September 1998, pp. 583-589.
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