Boeing and Saab’s ground-launched glide bomb is quite possibly a brilliantly cost-effective supplement to close air support.

The defense trade press has devoted a flurry of coverage over the past two days to Boeing and Saab’s announcement that it recently tested a ground-launched version of the GBU-39B Small Diameter Bomb (SDB). The 250-pound unitary is a clean replacement of the cluster munitions on the end of the M26 rocket in the M270 Multiple Launch Rocket System. With quite a few countries that own MLRSs now signatories to the Cluster Munitions Convention, many of those M26s must be scrapped—unless their warheads can be replaced with something that doesn’t potentially litter battlefields with duds. That’s the marketing pitch, though the biggest potential customer, the United States, is just fine with its future, smarter cluster bombs. What’s really interesting about this ground-launched bomb is how a treaty limitation spurred an military innovation that has nothing to do with the original political intention. For while we all argue over the A-10C, this ground-launched SDB might prove a very cost-effective supplement to close air support.

Because the SDB glides on pop-out wings after boost, Boeing and Saab claim a 93-mile range for the new rocket-launched version. Because the SDB navigates by an integrated GPS-inertial system, the circular error probable is probably close to that of its air-launched cousin—roughly five meters—and at that maximum range. Better yet, the SDB offers what Boeing calls “all-angle, all-aspect attack”, meaning the bomb can double-back as it glides, and attack troops on a reverse slope. That’s something at which artillery (other than comparatively short-range mortars) doesn’t typically excel.

This begs a question about why we get particular about how a bomb kills its target. When an SDB comes off an airplane, we call that close air support. If it comes out of a rocket launcher, we call that artillery fire. The biggest gap, Boeing and Saab assert, is in the cost: the ground-launched bomb is much cheaper, once we factor in the cost of building and flying the fixed-wing jets that would deliver the air-dropped version. A glide-bomb is also difficult to intercept, and in any case doesn’t present to air defenses the lucrative target of a jet-powered bomber.

Fairly, artillery can’t mass as quickly as aircraft can. It can’t range around the battlefield, picking out targets of opportunity. It must move forward with the infantry—indeed, closing within not more than 93 miles of the front to be useful. That’s not appealing to the political leadership these days—except perhaps in Tehran—when thinking about how to fight Abu Bakr al-Baghdadi’s faction around Tikrit.

In other scenarios, though, this cost-effective support will matter a lot. As Beth Kluba, Boeing’s vice president of weapons and missile systems, stressed to Valerie Insinna of National Defense, assigning close support missions to missile artillery will allow commanders to reprioritize jets towards longer-ranged attacks. Why is this important? Because as we all know by now, the US Air Force wants to dump its A-10Cs, even if its F-35As “will initially lag older aircraft in close air support”. So the stealth jets can go deep, while the gunships and the artillery work the lines.

In both Sweden and the United States, military requirements are supposed to be satisfied by modifications to existing equipment before wholly new developments are launched. Tricking out something on-the-shelf for an 80 percent solution is usually more cost-effective than launching another exquisite new start. That’s why the US Navy is enthusiastically refurbishing Boeing’s F-18Es (and much faster than it’s buying Lockheed’s F-35Cs) extending the their life expectancy from 6,000 to 10,000 flying hours. It’s why the US Marine Corps podded out a bunch of its KC-130J tankers as Harvest Hawk gunships. It’s why, back in 2001, the USAF matched an AH-64’s Hellfire missile to an MQ-1 Predator to make a killer drone. It’s why the US Army might just get enthused about this all-aspect flying-bomb artillery. And it’s why a bunch of other cash-strapped armies could potentially seize the opportunity to keep some otherwise surplus rockets in service. Anyone want to try out a few over Donetsk?

James Hasík is a senior fellow at the Brent Scowcoft Center on International Security.