AGM-158 Joint Air to Surface Standoff Missile (JASSM)
The JASSM is a conventionally armed, low observable cruise missile designed to destroy the enemy's high-value targets from aircraft that can be launched from outside the area defenses. The missile has automatic target recognition, autonomous guidance, precision accuracy, and a J-1000 warhead optimized for penetration and carrying a new high-yield explosive. These characteristics give JASSM capabilities against heavily defended hard targets such as aircraft shelters and underground command posts, as well as soft targets such as rail yards.
The JASSM Penetrator concept was a P3I to the Joint Air-to-Surface Standoff Missile (JASSM) to replace the baseline warhead with an advanced penetrator that meets or exceeds the objective penetration requirement specified in the JASSM Operational Requirements Document (ORD) and to add a synthetic aperture radar (SAR) seeker for adverse weather precision attack capability. The warhead concept was a 1000 pound dense or ballasted penetrator. The warhead would either be designed with a dense metal case or contain dense metal ballast for maximum penetration. The warhead would be filled with advanced insensitive explosive to compensate for the reduced charge weight. This concept used the Hard Target Smart Fuze (HTSF), an accelerometer based electronic fuze, which would allow control of the detonation point by layer counting, distance or time. The accelerometer senses G loads on the bomb due to deceleration as it penetrates through to the target. The fuze can distinguish between earth, concrete, rock and air.
The production JASSM contains the WDU-42/B (J-1000), a 1000-pound class, penetrating warhead with 240 pounds of AFX-757. AFX-757 is an extremely insensitive explosive developed by the Air Force Research Laboratory/High Explosives Research and Development Facility, Eglin AFB, Florida. The fuze is the FMU-156/B employing a 150-gram PBXN-9 booster. The warhead includes vents in the aft closure and a proprietary Thermally Re-active Retaining ring. The retaining ring releases at approximately 290 degrees Fahrenheit. This, in combination with the vents, provides for the expulsion of the main charge, which precludes excess pressure buildup and any reaction other than burning when exposed to hazardous stimuli.
The Air Force/Navy Joint Air to Surface Standoff Missile (JASSM) program was established in the FY96 budget, following cancellation of the Tri-Service Stand-off Attack Missile (TSSAM), to develop a replacement for that system at the earliest possible date. In light of the urgent need for the operational capability that would have been provided by the TSSAM, the Secretary of Defense established a joint program in the Air Force and the Navy for development of a replacement for TSSAM, canceled for escalating program cost, that would meet the requirements of both services. After the termination of the TSSAM, the Services continued to reiterate the need for a high survivability standoff weapon capable of attacking a variety of deep interdiction type targets. The Joint Requirements Oversight Council revalidated the need for the weapon in an August 1995 mission need statement.
JASSM was designed to be a precision cruise missile designed for launch from outside area defenses to kill hard, medium-hardened, soft, and area type targets. The threshold integration aircraft were the F-16, B-52, and F/A-18 E/F, and the airframe design was to be compatible with all intended JASSM launch platforms: the B-52H, F-16C/D, F/A-18E/F, F-15E, F-117, B-1B, B-2, P-3C and S-3B.
The weapon was required to attack both fixed and relocatable targets at ranges beyond enemy air defenses. After launch, it would be able to fly autonomously over a low-level, circuitous route to the area of a target, where an autonomous terminal guidance system would guide the missile in for a direct hit. The key performance parameters for the system were Missile Mission Effectiveness, range, and carrier operability.
JASSM's midcourse guidance was provided by a Global Positioning System (GPS)-aided inertial navigation system (INS) protected by a then new high, anti-jam GPS null steering antenna system. In the terminal phase, JASSM was guided by an imaging infrared seeker and a general pattern match-autonomous target recognition system that provides aim point detection, tracking and strike. It also offered growth potential for different warheads and seekers, and for extended range.
The passive IR sensor on JASSM is a medium wavelength sensor using a 256 x 256 focal plane array with an IFOV of 12 degrees. The Sensor is turned on with approximately 8 seconds to go to impact with a sampling rate of 5 Hz. There are normally about 10-15 good IR pictures to put into the automatic target correlating algorithm once the sensor comes up and stabilizes. Sensor is mounted below the waterline, but on centerline axis of the vehicle (i.e. it looks out the IR window on the lower forward portion of the munition).
Normal dive angles for the vehicle range from 40-70 degrees nose-low from horizon (40 for soft targets, 70 for hard targets requiring penetration), which is in that range for JASSM targets for which targeteers would want to airburst the warhead.
The JASSM P-LOCAAS-DM P3I concept integrated powered LOCAAS submunitions with dual mode LADAR and MMW seeker. LOCAAS had a multimode warhead and a maneuvering airframe to produce a high performance submunition. The warhead could be detonated as a long rod penetrator, an aerostable slug, or as fragments based on the hardness of the target. The LADAR allowed target aim point and warhead selection to be determined automatically. The powered LOCAAS uses a small turbojet engine, which was capable of powering the vehicle for up to 30 minutes. JASSM would provide the delivery platform for LOCAAS thus increasing the range and operational flexibility of LOCAAS.
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