The Joint Direct Attack Munition gets a lot of the press these days because of how precise and lethal it is. Its GPS guidance, however, is actually just one of three general approaches to precision-guided weapons. Outside of GPS guidance systems, ordnance is directed by lasers and television. All of these approaches have their pros and cons — here's the run-down:
This was the first guidance system to be widely used as a weapon. The Paveway bombs first made their impact in the Vietnam War, where they took down the Paul Doumer bridge. These bombs were the stars during Desert Storm.
Pros: Accuracy. Bombs guided by lasers hit within three feet of the aiming point. They can also engage moving targets, like ships or trucks, or change targets when necessary.
Cons: Laster guidance doesn't work in bad weather or when there's a lot of smoke and dust. The target must be consistently "painted" with the laser, limiting a plane's maneuverability.
Aviation Ordnancemen assigned to the "Swordsmen" of Fighter Squadron Three Two (VF-32) prepare to load 500-pound laser guided bombs (GBU-12) to an F-14B Tomcat aboard the Nimitz-class aircraft carrier USS Harry S. Truman (CVN 75). Carrier Air Wing Three (U.S. Navy photo by Photographer's Mate 2nd Class Danny Ewing Jr.)
This system also made its debut during the Vietnam War with the GBU-8 HOBOS. As the name implies, this guidance system uses a television camera to send images back to the launch station. There, an operator can offer corrections to the missile or bomb's course, ensuring it hits the intended target. Later versions, like the GBU-15, allow the pilot to control the bomb all the way in.
Pros: This type of guidance can be used to hit a moving target and, when necessary, change targets altogether. The system also features very good battle damage assessment, telling operators exactly what was hit based on the last image transmitted before impact.
Cons: These systems are pretty expensive. Additionally, the need for a pilot to control some versions can be a fatal distraction in combat. This guidance system is best used from two-seat planes, meaning the F-22 and F-35, which currently may not be able to use these weapons effectively.
The GBU-15 uses a TV camera to allow the pilot (or weapon systems officer) to get a bomb's-eye view of the target. (USAF photo)
In the War on Terror, the Joint Direct Attack Munition has become the precision-guided weapon of choice. In some ways, it is arguably the simplest of the systems — with a tail kit and guidance package. It places the bomb within about 30 feet of the target and is responsible for ruining the days of plenty of Taliban, al-Qaeda, and ISIS thugs.
Pros: This is a fire-and-forget system — there's no need to guide the bomb manually. It's also the cheapest system.
Cons: Currently, GPS guided systems aren't very good at handling moving targets. Additionally, its use is restricted to land-based targets.
U.S. Air Force F-15E Strike Eagles, from the 335th Expeditionary Fighter Squadron, drop 2,000 pound Joint Direct Attack Munitions on a cave in eastern Afghanistan, Nov. 26, 2009. (U.S. Air Force photo by Staff Sgt. Michael B. Keller)