6-DOF Enhancement of Precision Guided Munitions Testing

Enemy threats during Operation Desert Storm drove many Allied ground attack aircraft to medium altitude to deliver their weapons. Although many Precision Guided Munitions (PGMs) proved to be highly accurate at increased heights, the majority of bombs dropped from medium altitude were low-drag general purpose bombs (LDGP). The aircraft carrying the LDGPs traded accuracy for altitude in order to reduce the risk to aircraft and crews. This event helped highlight the need to drop LDGP weapons more accurately. Additionally, there are environments where even many current PGMs are ineffective. During the Gulf War, for example, smoke from the Kuwaiti oil fires obscured the skies, prohibiting the use of laser guided bombs. Currently there is a program in testing that is designed to fill these operational gaps. The Joint Direct Attack Munition (JDAM) is being developed to convert our inventory of LDGPs into PGMs and modeling/simulation is playing a vital role in its design.

JDAM is a strap-on tail kit assembly that uses a Global Positioning System (GPS) and an Inertial Navigation System (INS) for navigation. The tail kit has one stationary and three movable tailfins that deflect to steer the weapon to the programmed target and lift-producing strakes that increase weapon range. The GPS/INS aided tail kit can be connected to standard MK-84, MK-83 or BLU-109 bomb bodies, effectively turning dumb bombs into precision guided munitions. Early test results have indicated that JDAM is achieving the required circular error of probability (CEP) of 30 meters for INS-only aided deliveries and 13 meters for GPS-aided deliveries. One of the reasons for this success is the use of a six degree of freedom (6-DOF) model that accurately predicted the weapon trajectory.