Joint Direct Attack Munition
The Joint Direct Attack Munition (JDAM) is a guidance kit that converts existing unguided gravity bombs, or "dumb bombs", into all-weather "smart" munitions. JDAM equipped bombs are guided to their target by an integrated inertial guidance system coupled with a Global Positioning System (GPS) receiver for enhanced accuracy, giving them a published range of up to 15 nautical miles (28 km) from the release point. The program's approach was in contrast to earlier laser-guided bomb and imaging infrared technology, both of which can be hindered by adverse ground conditions; however, laser designators are now being fitted to some JDAMS as well, because of their suitability for attacking certain types of targets. The JDAM is a joint United States Air Force and United States Navy program.
Overview
The JDAM is not a weapon; rather it is a "bolt-on" upgrade for unguided gravity bombs, installed during build up of the munition by Naval Ordnancemen or Air Force Munition Systems Specialists. JDAM-equipped bombs range in size from 500 pounds (230 kg) to 2,000 pounds (910 kg), by nominal bomb weight. A JDAM kit consists of a tail section with aerodynamic control surfaces, a strake kit, and a combined inertial guidance system and GPS guidance control unit. When installed on a bomb, the JDAM kit is given a GBU (Guided Bomb Unit) nomenclature, superseding the Mark 80 or BLU (Bomb, Live Unit) nomenclature of the bomb to which it is attached. Thus, the gravity bomb on which the kit is installed becomes the warhead for a precision guidance system.
History and development
The bombing campaign in the initial phase of Desert Storm highlighted a shortfall in air-to-surface weapon capability in the US Air Force. Limited visibility of the ground caused by smoke, fog, dust, and cloud cover limited the employment of precision guided munitions, and also degraded the accuracy of unguided weapon delivery from medium and high altitudes. Research, development, testing and evaluation (RDT&E) of an "adverse weather precision guided munition" began in 1992. To solve this problem, several concepts were submitting utilizing seekers, and one radical concept proposing the use of the GPS. Although the GPS concept was the most attractive, at the time, there were few GPS satellites and the idea of using satellite navigation for real-time weapon guidance was untested and controversial. To identify the technical risk associated with an INS/GPS guided weapon, in early 1992, a rapid response Air Force High Gear program designated the “JDAM Operational Concept Demonstration” (OCD) was created at Eglin Air Force Base. A Government-industry team consisting of Honeywell, Interstate Electronics Corporation, Sverdrup Technology, the USAF 46 Test Wing, and McDonnell Douglas were tasked to demonstrate the feasibility of a GPS weapon within 1 year. The OCD program modified an inventory GBU-15 guided bomb airframe with an INS/GPS guidance kit and on February 10, 1993, the first INS/GPS weapon was dropped from an Air Force F-16 and made a direct hit on the target 88,000 feet downrange. This flight was followed by five additional weapon tests in various weather conditions, altitudes, and ranges. The OCD program demonstrated an 11 meter CEP.
The first JDAM kits were delivered in 1997, with operational testing conducted in 1998 and 1999. During testing, over 450 JDAMs were dropped achieving a system reliability in excess of 95% with a published accuracy under 10 metres (33 ft) Circular Error Probable (CEP). In addition to controlled parameter drops, the testing and evaluation of the JDAM also included "operationally representative tests" consisting of drops through clouds, rain and snow with no decrease in accuracy from clear weather tests. In addition, there have been tests involving multiple weapon drops with each weapon being individually targeted.
JDAM and the B-2 Spirit stealth bomber made their combat debuts during Operation Allied Force. The B-2s, flying 30-hour, nonstop, round-trip flights from Whiteman Air Force Base, Missouri, delivered more than 650 JDAMs during Allied Force. An article published in a military acquisition journal in 2002 cites that "[d]uring Operation Allied Force ... B-2s launched 651 JDAMs with 96% reliability and hit 87% of intended targets...". Due to the operational success of the original JDAM, the program expanded to the 500 pounds (230 kg) Mark 82 and 1,000 pounds (450 kg) Mark 83, beginning development in late 1999. As a result of lessons learned during Operation Enduring Freedom and Operation Iraqi Freedom, the Navy and Air Force are both pursuing enhancements to the kits such as improved GPS accuracy as well as a precision seeker for terminal guidance for use against moving targets.
JDAM bombs are inexpensive compared to alternatives such as cruise missiles. The original cost estimate was $40,000 each for the tail kits, but after competitive bidding, contracts were signed with McDonnell Douglas (later taken over by Boeing) for delivery at $18,000 each. Unit costs have since increased to $21,000 in 2004 and are expected to reach $31,000 by 2011. For comparison, the newest Tomahawk cruise missile, dubbed the Tactical Tomahawk, costs nearly $730,000 a piece.
Operational use
Guidance is facilitated through a tail control system and a GPS-aided inertial navigation system (INS). The navigation system is initialized by transfer alignment from the aircraft that provides position and velocity vectors from the aircraft systems. Once released from the aircraft, the JDAM autonomously navigates to the designated target coordinates. Target coordinates can be loaded into the aircraft before takeoff, manually altered by the aircrew in flight prior to weapon release, or entered by a datalink from onboard targeting equipment, such as the LITENING II or "Sniper" targeting pods. In its most accurate mode, the JDAM system will provide a minimum weapon accuracy CEP of 13 meters or less when a GPS signal is available, though Boeing and the Air Forces report less than 10 meters CEP in testing. If the GPS signal is jammed or lost, the JDAM can still achieve a 30 meter CEP or less for free flight times up to 100 seconds.
The introduction of GPS guidance to weapons brought several improvements to air-to-ground warfare. The first is a real all-weather capability since GPS is not affected by rain, clouds, fog, smoke, or man-made obscurants. Previous precision guided weapons relied on seekers using infrared, visual light, or a reflected laser spot to “see” the ground target. These seekers were not effective when the target was obscured by fog and low altitude clouds and rain (as encountered in Kosovo), or by dust and smoke (as encountered in Desert Storm).
The second advantage is an expanded launch acceptance region (LAR). The LAR defines the region that the aircraft must be within to launch the weapon and hit the target. Non-GPS based precision guided weapons using seekers to guide to the target have significant restrictions on the launch envelope due to the seeker field of view. Some of these systems (such as the Paveway I, II, and II) must be launched so that the target remains in the seeker field of view throughout the weapon trajectory (or for lock-on-after-launch engagements, the weapon must be launched so that the target is in the field of view during the terminal flight). This requires the aircraft to fly generally straight at the target when launching the weapon. This restriction is eased in some other systems (such as the GBU-15 and the AGM-130) through the ability of a Weapon System Operator (WSO) in the aircraft to manually steer the weapon to the target. Using a WSO requires a data link between the weapon and the controlling aircraft and requires the controlling aircraft to remain in the area (and possibly vulnerable to defensive fire) as long as the weapon is under manual control. Since GPS-based flight control systems know the weapon current location and the target location, these weapons can autonomously adjust the trajectory to hit the target. This allows the launch aircraft to release the weapon at very large off-axis angles including releasing weapons to attack targets behind the aircraft.
The third advantage is a true “fire-and-forget” capability in which the weapon does not require any support after being launched. This allows the launching aircraft to leave the target area and proceed to its next mission immediately after launching the GPS guided weapon.
Another important capability provided by GPS-based guidance is the ability to completely tailor a flight trajectory to meet criteria other than simply hitting a target. Weapon trajectories can be controlled so that a target can be impacted at precise headings and vertical angles. This provides the ability to impact perpendicular to a target surface and minimizing the angle of attack (maximizing penetration), detonating the warhead at a the optimum angle to maximize the warhead effectiveness, having the weapon fly into the target area from a different heading than the launch aircraft (decreases the risk of detection of the aircraft). GPS also provides an accurate time source common to all systems. This allows multiple weapons to loiter and impact targets at preplanned times and intervals.
In recognition of these advantages, most weapons including the Paveway, GBU-15, and the AGM-130 have been upgraded with a GPS capability. This enhancement combines the flexibility of GPS with the superior accuracy of seeker guidance.
Despite their precision, JDAM employment does not come without risk. On December 5, 2001, a JDAM dropped by a B-52 in Afghanistan nearly killed Hamid Karzai, while he was leading anti-Taliban forces near Sayd Alim Kalay alongside a US Army Special Forces (SOF) team. A large force of Taliban soldiers had engaged the combined force of Karzai's men and their American SOF counterparts, nearly overwhelming them. The SOF commander requested Close Air Support (CAS) to strike the Taliban positions in an effort to stop their advance. A JDAM was subsequently dropped, but instead of striking the Taliban positions, it struck the Afghan/American position. An investigation of the incident determined that the U.S. Air Force Combat Controller attached to the Special Forces team had changed the battery in the GPS receiver at some point during the battle, thereby causing the device to return to "default" and "display its own coordinates." Not realizing that this had occurred, the combat controller relayed his own coordinates to the delivery aircraft.
Upgrades
U.S. military experience during Operation Enduring Freedom and Operation Iraqi Freedom highlighted the need for additional capability in one package, resulting in ongoing program upgrades to place a precision terminal guidance seeker in the JDAM kit. The Laser JDAM (LJDAM), as this upgrade is known, adds a laser seeker to the nose of a JDAM equipped bomb, giving the ability to engage moving targets to the JDAM. The Laser Seeker is called Precision Laser Guidance Set (PLGS) by Boeing and consists of the Laser Seeker itself, now known as DSU-38/B and a wire harness fixed under the Bomb body to connect the DSU-38/b with the tailkit. During FY2004, Boeing and the U.S. Air Force began testing of the laser guidance capability for JDAM, with these tests demonstrating that the system is capable of targeting and destroying moving targets. This dual guidance system retains the ability to operate on GPS/INS alone, if laser guidance is unavailable, with the same accuracy of the earlier JDAM.
On 11 June 2007, Boeing announced that it had been awarded a $28 million contract by the U.S. Air Force to deliver 600 laser seekers (400 to the Air Force and 200 to the Navy) by June 2009. According to the Boeing Corporation, in tests at Nellis Air Force Base, Nevada, Air Force F-16 Fighting Falcons and F-15E Strike Eagles dropped twelve (12) 500 pounds (230 kg) LJDAMs that successfully struck high-speed moving targets. Using onboard targeting equipment, the launch aircraft self-designated, and self-guided their bombs to impact on the targets. In addition to the LJDAM kits, Boeing is also testing under a Navy development contract, an anti-jamming system for the JDAM, with development expected to be completed during 2007, with deliveries to commence in 2008. The system is known as the Integrated GPS Anti-Jam System (IGAS). Boeing announced on September 15, 2008, that it had conducted demonstration flights with the LJDAM loaded aboard a B-52H.
On July 24th, 2008 Germany signed a contract with Boeing to become the first international customer of LJDAM. Deliveries for the German Luftwaffe will begin in mid-2009. The order also includes the option for further kits in 2009.
Integration
JDAM is currently compatible with:
•AV-8B Harrier II
•A-10C "Warthog"
•B-1B Lancer
•B-2A Spirit
•B-52H Stratofortress
•F-117 Nighthawk
•F-14A/B/D Tomcat
•F-15E Strike Eagle
•F-16C Fighting Falcon
•F/A-18C/D Hornet
•F/A-18E/F Super Hornet
•F-22 Raptor
•F-35 Lightning II
•Panavia Tornado
Follow-on integration efforts are currently underway or planned to evaluate compatibility with:
•S-3 Viking
•MQ-9 Reaper
•Eurofighter Typhoon
Export
The U.S. Government has approved the JDAM for export sale under the Arms Export Control Act, though in limited numbers to only a few countries. Outstanding requests for purchase are under review.
Export customers
• Australia
• Belgium
• Chile
• Denmark
• Germany (first international customer of LJDAM)
• Israel
• Italy
• Netherlands
• Norway
• Pakistan
• Poland
• Saudi Arabia
• Singapore
• South Korea
General characteristics
•Primary function: Guided air-to-surface weapon
•Contractor: Boeing
•Length: (JDAM and warhead) GBU-31 (v) 1/B: 152.7 inches (3,880 mm); GBU-31 (v) 3/B: 148.6 inches (3,770 mm); GBU-32 (v) 1/B: 119.5 inches (3,040 mm)
•Launch weight: (JDAM and warhead) GBU-31 (v) 1/B: 2,036 pounds (924 kg); GBU-31 (v) 3/B: 2,115 pounds (959 kg); GBU-32 (v) 1/B: 1,013 lb 1,013 pounds (459 kg)
•Wingspan: GBU-31: 25 inches (640 mm); GBU-32: 19.6 inches (500 mm)
•Range: Up to 15 nautical miles (28 km)
•Ceiling: 45,000 feet (14,000 m)
•Guidance system: GPS/INS
•Unit cost: Approximately $21,000 per tailkit (FY 01 dollars)
•Date deployed: 1999
•Inventory: The tailkit is in full-rate production. Projected inventory is approximately 240,000 total, 158,000 for the US Air Force and 82,000 for the US Navy. (As of October 2005)
•2,000 lb (900 kg) nominal weight
oGBU-31(V)1/B (USAF) Mk-84
oGBU-31(V)2/B (USN/USMC) Mk-84
oGBU-31(V)3/B (USAF) BLU-109
oGBU-31(V)4/B (USN/USMC) BLU-109
•1,000 lb (450 kg) nominal weight
oGBU-32(V)1/B (USAF) Mk-83
oGBU-32(V)2/B (USN/USMC) Mk-83
oGBU-35(V)1/B (USN/USMC) BLU-110
•500 lb (225 kg) nominal weight
oGBU-38/B (USAF) Mk-82,(USN/USMC)Mk-82 and BLU-111
oGBU-54/B LaserJDAM (MK-82)
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