Air Weapons: Viper Strike Gets Work


April 20, 2012: After over a decade of rejection the Viper Strike laser guided bomb is getting some work. The U.S. Army now uses Viper Strike on its' Hunter UAVs. The 727 kg (1600 pound) Hunter can only carry up to 91 kg (200 pounds) of sensors and weapons. That makes it marginal for using the 47 kg Hellfire but perfect for the 20 kg Viper Strike.

Viper Strike was originally designed as an anti-tank weapon and the warhead contains only 1.8 kg (four pounds) of explosives. But this made it an excellent weapon for fighting in urban areas, as the bomb is very accurate and less likely to cause injury to nearby civilians. Viper Strike is a 914mm (36 inch) long unpowered glider that is 130mm in diameter (with the wings folded). You have to be within a thousand meters of the target before dropping it but that has proved to be no problem. 

Recently, Viper Strike was also used from the new KC-130J transports equipped with a modified rear door (the Derringer Door) that enables missiles to be fired and the missile launcher reloaded without first depressurizing the aircraft and lowering the rear ramp.

The KC-130J is the latest, and largest, USMC version of the C-130 transport used for aerial refueling. But the KC-130J can also carry cargo and weapons (bombs and missiles) hung from the wings. This last item is the Harvest Hawk version of the KC-130J. This "instant gunship" system enables weapons and sensors to be quickly rolled into a C-130 transport and hooked up. This takes a few hours and turns the C-130 into a gunship (similar in capabilities existing AC-130 gunships). The sensor package consists of day/night vidcams with magnification capability. The weapons currently consist of ten Derringer Door launch tubes and four Hellfires hanging from the wings. The first U.S. Marine Corps "instant gunship" arrived in Afghanistan two years ago. Since then Harvest Hawk aircraft have fired hundreds of Hellfire and Griffin missiles, as well as spotting lots of enemy activity. Now Viper Strikes are being used as well.

The one problem was the need to lower the rear door to fire missiles and reload the launchers. Since the aircraft usually operated at high altitude (6,400 meters/20,000 feet) the crew had to put on oxygen masks and it took time to depressurize the cargo bay and lower the rear ramp. The new Derringer Door has ten launch tubes that can be used (for firing or reloading) while the ramp is closed.

Initially, the Griffin missile was used in these launch tubes. Griffin weighs 20.5 kg (45 pounds) and has a 5.9 kg (13 pound) warhead. Griffin has a greater range (15 kilometers) than Hellfire because of pop-out wings that allow it to glide after launch. Griffin uses laser, GPS, and inertial guidance. The Hellfire II missile has been around a lot longer, weighs 48.2 kg (106 pounds), carries a 9 kg (20 pound) warhead, and has a range of 8,000 meters.

The big thing with gunships is their sensors, not their weapons. Operating at night the gunships can see what is going on below in great detail. Using onboard weapons gunships can immediately engage targets. But with the appearance of smart bombs (GPS and laser guided), aerial weapons are more available to hit any target that is found. So Harvest Hawk would be able to hit targets that were "time sensitive" (had to be hit before they got away) but could also call on smart bombs or laser guided missiles for targets that weren't going anywhere right away. Most of what Harvest Hawk does in Afghanistan is look for roadside bombs or the guys who plant them. The marines want to track the bomb planters back to their base and then take out an entire roadside bomb operation.




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