The Devastating Impact of Sensor Fuzed Weapons

March 1, 1998
The United States Air Force late last year carried out the first operational deployment of the CBU-97/B Sensor Fuzed Weapon when it dispatched two SFW-equipped B-1B bombers to Bahrain. The Bahrain deployment marked a coming out event for a weapon that is expected to drastically alter the ability of airpower to engage and stop moving ground targets.

The SFW is the Air Force’s newest wide-area cluster munition, the first of that breed smart enough to find its target after it has been released. The SFW is considered 10 times more effective than Vietnam-era cluster munitions, which had only a small chance of hitting their targets.

The SFW, in fact, has a proven all-weather, 24-hour operational capability. This new anti-armor munition is projected to go a long way toward meeting the Air Force’s goal to be able to find, fix, track, target, and engage any moving ground target anywhere on the surface of the Earth.

Acquisition of the SFW has generated new visions of what future combat will be like. Air Force planners foresee B-1B heavy bombers taking off from bases in the continental United States, flying halfway around the world, and then delivering a full load of SFWs against large columns of advancing enemy armor. Each SFW released by the bombers would be able to cover an area the size of 20 football fields with 40 top-attack projectiles. Because each B-1B could carry 30 of these SFWs, one heavy bomber would be able to deliver 1,200 projectiles over a huge battle area.

Instant Paralysis

The Air Force doesn’t expect to achieve a hard kill from each projectile, but service officials are confident that little, if anything, would remain on the move after such an attack.

Maj. Jeff Latas, USAF’s SFW requirements officer at the Pentagon, said the ability of an aircraft using SFWs to engage several targets at the same time is “something we’ve never had before.” He added, “In one pass, I can drop a whole array of weapons in an optimum fashion, so I can go out and kill many targets with one airplane.”

That concept represents “a potentially revolutionary capability,” said David Ochmanek, a defense analyst for the Rand Corp. in Washington. He said that the B-1B/SFW combination shapes up to be the cornerstone of the new Air Force concept that calls for engaging the enemy’s main armored force decisively in the halt phase of major theater war, a time when USAF would strive to slow, break up, and finally stop an attack.

“This kind of capability [the SFW] is key to the halt,” he said. “Without it, you just don’t get enough kills, given the kill capacity of the small number of attack platforms you would have available on short notice.”

Because of the numerical drawdown of Air Force aircraft during the past decade and the high operational tempo troops are experiencing, the SFW’s ability to reduce the number of sorties needed to stop an enemy is considered a significant force multiplier.

Each SFW comprises an SUU-66/B tactical munitions dispenser with an FZU-39 fuze. Each tactical munitions dispenser contains 10 BLU-108/B submunitions, and each submunition contains four projectiles that, upon being thrown out, seek out their target and deliver a warhead. Thus, each SFW can deliver a total of 40 lethal projectiles.

Col. William Wise, Air Force system program director in charge of area-attack munitions at Eglin AFB, Fla., outlined for Air Force Magazine how the SFW functions in both the low-altitude and high-altitude attack profile. The area covered in both scenarios is similar. Each CBU-97/B can cover an area of about 500 feet by 1,200 feet, Wise said.

Low altitude. The engagement would begin with the bomber making a drop at an altitude ranging from 200 feet to 3,000 feet above ground level, with a typical mission altitude of 300 feet, said Wise. For any attack commencing below an altitude of 1,500 feet, the dispenser would use a preset timed release.

Wise said that, although the time is variable, it would be about one second after a drop at 300 feet, meaning the dispenser would release the 10 BLU-108/B submunitions at about 280 feet. Each of the 10 submunitions then would hang on a parachute for about eight seconds, during which time the projectiles are spun up and finally ejected at about 100 feet above ground level.

Each of the hockey puck­shaped projectiles then uses an infrared sensor to rapidly locate a hot target, such as a tank or armored vehicle. The projectile locks on to its target and fires a self-forging, high-velocity slug, which strikes and immobilizes the target.

Medium-to-high altitude. Here the engagement would begin with the aircraft releasing the SFW anywhere above 15,000 feet, with the fuze set in its proximity mode. At about 1,500 feet, the tactical munitions dispenser throws out the 10 submunitions. They glide on a parachute for 20 seconds, spinning up the projectiles as they descend. Once a submunition reaches an altitude of 100 feet, the weapon operates the same as in a low-altitude engagement.

Better Versions

Even as the SFW is being fielded, the Air Force is working on improved versions of the weapon. The service already has moved forward with the first of two Product Enhancement Programs to reduce the price of the munition. The first program, called PEP 1, reduced the cost of each SFW. With full-rate production just beginning, the Air Force has been able to reduce the cost of SFWs from $360,000 to $260,000 per copy. Still in the works is PEP 2, which is expected to save another $5,000 per unit. That effort will enter production in about two years.

More significant is an operational improvement that has already entered the test phase. Projectiles would be dispensed at a greater altitude with a different look-angle, thereby expanding the area covered by an SFW to about 600 feet by 1,800 feet.

This preplanned product improvement is expected to double the effectiveness of a regular SFW at a 20 percent premium.

In addition, the Air Force will add a laser range finder to the projectile to allow the SFW to detect a target by its height as well as by its infrared signature. That capability will provide a better aim point for the slug.

Finally, USAF is modifying the slug itself. In the new configuration, the SFW will fire a smaller center slug and an outer ring of shards. Those shards will improve the weapon’s performance against soft targets, such as unarmored vehicles. Because the center slug is fired at a higher velocity than before, it is expected to remain as lethal as the larger slug on the regular SFW.

No one expects each SFW slug to destroy a target. The goal is to stop the vehicle in its tracks. Latas noted that “the goal is a mobility kill, not a catastrophic kill.” He added, however, that “a mobility kill is just as good as anything else, when you can cover that kind of area and affect that many targets per sortie.”

USAF has postulated three levels of mobility kill, differentiated by how quickly a target stops functioning. Latas said the SFW achieves the highest-level mobility kill currently measured by the Air Force.

The SFW’s kill probability is classified, but Latas said, “We’ve seen in testing that, with the current threat, this is going to be a pretty devastating weapon.” The Air Force has run more than 111 SFW tests so far and, Wise noted, it has exceeded its requirements.

Many of USAF’s current and near-future inventory of smart weapons resulted from the experience of Desert Storm in 1990­91. However, the idea for SFWs considerably predates the Gulf War.

Choked Up

Originally, the Air Force envisioned the SFW as a Cold War weapon system useful in a “Fulda Gap” scenario, whereby large numbers of heavy Warsaw Pact tanks would concentrate to try to punch through NATO defenses at specific choke points and then race through Western Europe to the Atlantic. The SFW was going to be one of the weapons that kept the choke points choked with the blazing, burned-out hulks of Soviet tanks.

The end of the Cold War not only removed the original wartime scenario but also opened up new ways of delivering such weapons. With the end of the Cold War, USAF’s heavy, long-range bombers were withdrawn from their nuclear orientation and revamped as conventional delivery systems. Thus, the number of potential SFW carriers increased dramatically.

Initially, the Air Force judged the primary delivery means to be F-16, F-15, and A-10 fighter-attack aircraft. Now added to the mix are the B-52, B-1B, and even B-2 bombers. All will be able to carry the SFW in large numbers.

One of the ironies of this dramatic turn of events, Air Force officials remarked, is that the SFW, a quintessential Cold War weapon, may well end up having even greater significance in the post­Cold War world. “If we had had something like this in Desert Storm, it would have significantly reduced the number of sorties we would have had to fly,” said Wise. Latas went further. He said that, had the SFW been on hand in August 1990 and had Washington demonstrated the political will to respond immediately to Iraq’s troop and tank movements around Kuwait, Iraqi forces never would have made their way into the desert sheikhdom in the first place.

The Air Force’s analysis of the Gulf War produced a key lesson that had a direct effect on subsequent development of the SFW. In most cases, Air Force pilots had to deliver their ground-attack weapons at medium-to-high altitude so as to stay out of the range of enemy air defenses. USAF saw immediately that, at those altitudes, the performance of the SFWs could be hampered or undercut by the force of winds.

Into the Wind

The search for an answer to that problem led directly to something called Wick-Mid, for the acronym WCMD. It stands for Wind-Corrected Munitions Dispenser. Eventually, all SFWs will be equipped with special WCMD tail-kit assemblies that will turn them into WCMDs. New ones will be built that way. Those SFWs already fielded–the Air Force had about 500 SFWs in inventory at the beginning of the year–will be retrofitted with the new system. The SFW/WCMD combination will carry the designation CBU-105. The first SFWs are to be mated to the WCMD tail-kit system later this year.

The main benefit of using WCMD comes during releases at medium-to-high altitude. There, it ensures the tactical munitions dispenser does not get blown off target, However, the SFW can benefit from the WCMD tail-kit even in a low-altitude scenario.

Wise noted that the WCMD provides “increased flexibility as far as your launch region is concerned.” Without WCMD, a fighter or bomber has to overfly a target area so that the tactical munitions dispenser drops ballistically over the target vehicles. With WCMD, the aircraft can approach away from the center of the target, deploy the SFW, and let WCMD take care of bringing the tactical munitions dispenser into its proper location.

The SFW can be targeted three different ways.

  • The simplest way, self-targeting, requires the pilot of an aircraft with SFWs to fly over the battlefield, find the target using the airplane’s sensors, and then engage the target with the weapon. That scenario is less likely to involve bombers than fighters or A-10 attack aircraft, Latas noted.
  • The second approach, third-party cuing, entails use of an off-board sensor, such as a Joint Surveillance Target Attack Radar System, to tell the pilot of the SFW aircraft where to go to find the target.
  • The third and most challenging approach is third-party targeting. In that scenario, an outside sensor “tells” the weapon where it needs to go. The pilot flying the SFW aircraft never has to see the target.

The B-1B is turning into the main SFW delivery vehicle, largely because of its ability to project power from the United States and its ability to carry a large load of SFWs. But other aircraft are also going to use SFWs. The likely operational load of SFWs is four for the F-16, 12 for the F-15E, 10 for the A-10, 16 for the B-52, and potentially 34 for the B-2.

Air Force and outside analysts see little chance for the enemy’s military leaders to be able to avoid devastation by SFW, short of completely dispersing their forces. “I don’t see how the Red Force can at the same time evade the SFW tactically and still achieve its objectives,” said Rand analyst Ochmanek. The result, he went on, is that SFW could “render obsolete large-scale armored advances.”

Current plans call for the Air Force to buy 5,000 weapons, about half of which will be in the improved configuration. That represents a significantly lower number than the almost 17,000 SFWs the Air Force once planned on buying. To many analysts, the lower number appears certain to pose a major problem, particularly in light of the US national strategy of being able to fight and win two Major Theater Wars at more or less the same time. They said that 5,000 is enough for a single Major Theater War, but two of them would require a far larger number.

Weapon Characteristics

Munition

Submunition

Projectile

Weight

927 pounds

63 pounds

8 pounds

Length

92 inches

31 inches

3.75 inches

Diameter

16 inches

5.25 inches

5.25 inches

Operational envelope

200 feet­–20,000 feet (above ground level)

250 knots–­650 knots

Guidance

None (except on WCMD)

Control

Parachute-retarded submunitions

Propulsion

Dual-nozzle rocket motor (per submunition)

Fuze

Proximity sensor, timed release

Targets

Tanks, armored vehicles, support vehicles

Source: US Air Force

Robert Wall is the Pentagon reporter for Aerospace Daily, a Washington-based defense and commercial aviation periodical. His most recent article for Air Force Magazine, “The Electronic Triad,” appeared in the January 1998 issue.