The Munitions Directorate conducted five proof-of-concept guided flight tests of the Small Smart Bomb with the Range Extension (SSBREX) wing kit (see Figure 1). The directorate conducted the SSBREX program to demonstrate the maturity and operational utility of a joined, folding wing (Diamond Back™), Global Positioning System/Inertial Navigation System (GPS/INS) guided glide weapon. The performance goals were multiple-mile standoff downrange and crossrange, controlled highly accurate impact conditions, and sufficient impact energy to penetrate concrete. The SSBREX, based upon the Miniature Munitions Technology Demonstrator program, uses miniaturized GPS navigation integrated with an INS to achieve accurate guidance performance. Also, this program was the first United States flight demonstration of the lattice fin concept. Researchers used lattice fins, which have a grid or lattice pattern cut through the fins, because they require smaller and less power-consuming control actuators, thus freeing space in the miniaturized munition tail kit.
Alenia Marconi Systems, Inc. of California, developed the Diamond Back wing kit while the Boeing Phantom Works was responsible for the design and fabrication of the remaining components and integration of the complete SSBREX weapon. In addition, Boeing designed and fabricated a smart multiple ejector rack (SMER) to carry four small smart bombs (SSBs) (see Figure 2). Ground crews can load the SMER in any location where an individual guided bomb can fit. It uses a single connector to the aircraft and contains internal avionics, which will ultimately control, target, and release each of the SSBs singly or at intervals selected by the pilot.
Captains Sean Jackson, a flight test engineer, and Mike Tarlton, a project pilot for the 40th Flight Test Squadron (FTS), worked with Mr. Ken Lockwood, the directorate's original program manager, to conduct a series of tests on the ground and over the water ranges at Eglin Air Force Base, Florida. According to Lockwood, the program began with captive flight tests and proceeded to drops of test shapes (simulated bombs) from the SMER. "A total of four SMER drop tests were conducted: two were individual releases, one was a ripple release of two weapons, and the last test was a ripple release of four drop shapes. Release conditions varied from 25,000 to 40,000 ft with airspeeds up to 0.9 Mach," he explained. All of the ejections produced stable clean separation from the aircraft.
Directorate researchers conducted the first SSBREX free-flight test in May 2000 over one of Eglin's water ranges in the Gulf of Mexico to demonstrate the test vehicle's extended flight range (see Figure 3). According to Lockwood, "The SSBREX separated cleanly from the F-16 launch vehicle and began normal flight, but due to an error in the guidance algorithm, the test goals were not completely met. Objectives that were met included a successful folding wing deployment and lattice fin control effectiveness." Researchers conducted a detailed posttest review of the air vehicle design, guidance system design, and software to identify the error. They performed rigorous analyses along with extensive simulations to verify the guidance algorithm correction.
The directorate conducted a second SSBREX flight in August 2000 over the same water range to demonstrate a medium-range flight with a crossrange component. Additional objectives of the test included navigation accuracy assessment of the SSBREX tail kit INS/GPS navigation system. "The SSBREX separated cleanly from the F-16 launch vehicle and successfully entered into the mid-course guidance mode. After a 25 nm flight, the vehicle entered into a terminal dive and impacted at the planned target point," Lockwood said.
The directorate conducted the final two proof-of-concept flight tests at White Sands Missile Test Range, New Mexico. Captain Colin Ireton, 40th FTS, released two inert guided weapons from an F-16 fighter during two test flights conducted in December 2001. According to Captain Ken Germann, 40th FTS flight test engineer, "The most recent testing added the Multi-Event Hard Target Fuze (MEHTF), which uses accelerometers to measure the penetration of the warhead and decide the best time to detonate the weapon." Both tests demonstrated the standoff capability of the weapons with a downrange and crossrange trajectory. These were also the first flight tests of the MEHTF.
First Lieutenant John Mehrman, Munitions Directorate program manager for the last two flight tests, reported, "The first SSBREX impacted a concrete target to validate penetration capabilities of the warhead. The second SSBREX impacted a layered target to demonstrate the void sensing capability of the fuze. Both weapons were recovered and are being analyzed to investigate the effect of the wing kit on the impact event. Acceleration data from the fuze is also being analyzed to evaluate how well it measured and made decisions during the penetration event."
Figure 1. SSBREX
Figure 2. SSBREX mounted on the SMER
Figure 3. Integrated system mounted on an F-16 wing
Lt John Mehrman, Mr. Ken Lockwood, and Mr. Rex Swenson (Madison Research Corporation) of the Air Force Research Laboratory's Munitions Directorate wrote this article. For more information contact TECH CONNECT at (800) 203-6451 or place a request at http://www.afrl.af.mil/techconn/index.htm. Reference document MN-02-06.
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