OPTIMIZING M&S APPROACHES FOR PENETRATING PLATFORM SURVIVABILITY TESTING
by CPT Maxim Olivine
U.S. Air Force Photo by MSgt Donald R. Allen
Analysts have generally assessed aircraft combat survivability, particularly in the electronic warfare domain, through a series of scientific analyses, as well as developmental and operational testing (including laboratory and flight test events) during the design, development, and fielding stages of a particular weapon system [1]. More recently, with the help of advanced computer processing power, modeling and simulation (M&S) has begun to play a larger role in aircraft survivability test approaches by allowing mathematical approximations to examine survivability characteristics in ways not possible in traditional laboratory, ground, and flight test (and often at a fraction of the cost). The traditional survivability model has been a customized software set, based on proven mathematical algorithms, created for each unique test article and data analysis requirement. Unfortunately, custom-built software and computation tools often require a large amount of resources to generate and can serve as an exercise in “re-inventing the wheel” for each respective acquisition program. This article presents a modular approach to M&S that could serve as a universal “go-to tool” for analyzing aircraft survivability in many diverse applications.
THE TEST SPECTRUM
From an engineering perspective, one of the key aspects of improving survivability in the radio frequency (RF) domain can be described as the act of minimizing the RF signature of an aircraft, also known as the radar cross section (RCS). A smaller, “stealthier” RCS improves aircraft survivability by making the platform not able to be detected easily or consistently by enemy integrated air defense systems (including RF early warning, target acquisition, and target tracking radars), especially at longer ranges [1]. Developers attempt to reduce RCS by using various RF dampening methods such as specialized paint coatings, exotic materials, and clever airframe designs, to name a few [1]. A major aspect of the testing of these stealth aircraft to determine if the signature reduction techniques were successful/sufficient is by examining the aircraft RCS using representative threat systems.
As shown in Figure 1, the testing spectrum ranges from a controlled laboratory environment to an open-air, combat-realistic environment. Overlapping those two, and spanning the entire spectrum, is M&S. In the past, flight testing would be conducted directly after laboratory testing, often leading to an enormous number of required sorties, taking valuable time and carrying greater cost and risk. M&S has not replaced laboratory or flight testing, and likely never will, but it can bridge the uncertainty gap between the two while reducing the cost and risk of both.
The laboratory/scientific approach to survivability testing deals with various tests in microenvironments traditionally located in laboratories. These methods are intended for specific analyses and generally prevent the types of interference from outside agents that occur when an aircraft is flying in an operational environment. This approach results in a clean, repeatable, pure measurement, though not necessarily a realistic one.
While useful from a preliminary design perspective, such laboratory test methods are incapable of representing the complex survivability scenarios a weapon system might encounter in combat. What laboratory testing does well is to analyze specific, critical aspects such as materials, air vehicle design, software programming, and electronics in a consistent and controlled environment, thus laying the groundwork for transition into less controlled, more operationally representative assessments.
The operational test approach provides the most realistic and accurate survivability assessment environment, shown in Figure 2. In a typical operational test scenario, operational users operate a production-representative system in an operationally representative combat environment on various ranges throughout the world. The testers gather data on the threats and test article, along with all anomalies, including weather, noise, electromagnetic interference, etc. If the test team executed the event successfully and generated sufficient data for statistically valid analysis, the testers will be able to provide an accurate assessment of weapon system survivability.
Unfortunately, while being the most effective approach, operational testing is also by far the most expensive and, due to test asset and test range availability, can take months to years to generate sufficient data for a valid evaluation. Open-air range missions for an operational test can easily cost $1 million or more per sortie. Creating a perfect operational assessment of an aircraft, which can require dozens of range missions, might prove cost-prohibitive for most Department of Defense (DoD) programs.
Even more importantly, modern platforms are encountering more and more severe open-air range limitations. For example, around 50% of operational test points for modern weapon systems are not executable on today’s open-air ranges. Coupled with issues such as resource limitations, technological plateaus, and the inability to keep up with the continually evolving threat systems, these limitations are forcing the test community toward M&S as the best supplement to lacking capabilities.
After microenvironments in laboratories and costly flight test events, the third option for aircraft survivability testers is the M&S approach. Using modern computing power, we are able to simulate an operational environment with extreme precision. We are capable of emulating a realistic environment by using random number generators to provide distributions of performance,
Figure 1 Test Spectrum
red and blue system data, and mathematical algorithms proven to reflect actual performance through rigorous analysis and comparisons between M&S results and flight testing [1]. These scenarios include the system under test and other blue forces executing operational mission actions in the presence of integrated air defense systems that are representative of threats the system will encounter in combat around the world.
The downside is most M&S packages typically in use today are proprietary and have been custom-built over many months or even years by development/ contractor teams. The complexity of the proprietary design forces the inefficiency of the development and drives the modeling tool to be more expensive and take more time than the program leadership desires.
THE WAY FORWARD
The proposed solution is to blueprint a design for a portable, easy-to-use, one-stop-shop software suite that packs all of the tools necessary to simulate or model any aircraft in any survivability scenario—almost like having a Microsoft Office-like toolkit for M&S. With such a tool, a user would select his/her parameters for the test article and the test environment from a list of available threat environments; no expensive and time-consuming coding or customization would be required.
Moreover, plugins and scripts should be available as options if unique tasks need to be performed, such as hardware or man-in-the-loop tests. Because the vast majority of aircraft M&S software packages use the same methods and techniques, combining their solvers into a single, universal package through a common medium, such as the Distributed Interactive Simulation standard [2], should be manageable. A personal computer (PC)-based graphical user interface will serve as the medium through which users customize their simulations, and it will be able to add an adequate number of functions that could provide ample modification options.
The Air Force Operational Test and Evaluation Center (AFOTEC) is one of the major drivers of such a universal platform—namely, the Joint Simulation Environment (JSE), a government-owned M&S battlespace setting that is undergoing initial phases of development at the Naval Air Systems Command in support of the F-35 Lightning II Joint Strike Fighter program. The JSE is being developed at Naval Air Station Patuxent River, MD, and future expansion will be to an M&S campus at the Virtual Warfare Center at Nellis Air Force Base, NV.
Currently, the JSE is being built to support a man-in-the-loop, multisecurity caveats operational test of the F-35. However, the system’s modular capabilities should allow for future integration of fifth-generation platforms—namely, the F-22 Raptor, the B-2 Spirit, and the B-21 Raider.
Ultimately, the environment should allow for integration (such as illustrated in Figure 2) of most DoD air systems, including command and control, intelligence, surveillance, and reconnaissance assets, as well as fourth-generation platforms (F-16s, F-15s, B-1s, etc.). What the JSE is intended to provide is a universal, real-time, effects-based environment where any test team can bring an operational flight program (OFP) cockpit representation of its system to test with other blue assets in operationally representative threat environments.
The current prototype at Navy Pax is not designed with personal device (PC, laptop, tablet, etc.) portability in mind, nor is it controlled through a single user-friendly interface. The system must be operated by a team of personnel with hardware-in-the-loop mock-up cockpits of the F-35 to create the most realistic scenario possible for the upcoming operational test. Admittedly, this is a long shot from Microsoft Office running on one’s tablet. However, the use of the JSE to support the operational test of the F-35 will provide the M&S community with the building blocks of the universal simulation environment. The ideal solution will build from the JSE to a more mobile product (a disc-carried distribution, for example) that can potentially link and run with any representation of a blue system under test, from an all-digital model to a high-fidelity hardware/ operator-in-the-loop cockpit, and test together with other blue assets in combat-representative environments.
CONCLUSION
To assess an aircraft’s survivability in an electronic warfare environment accurately, we need to test its survivability against threat systems. We do so through a consortium of a scientific laboratory-based approach, an open-air range test approach, and M&S. Unfortunately, laboratory testing provides fundamental and controlled data but not necessarily real-world characterization. Operational flight test events can be far too expensive, take too much time, and, as the threat evolves, may not be able to reflect the intended environment on its own. And unique M&S packages can take excessive amounts of time to produce and are not as cost-effective as desired.
Figure 2 U.S. Air Force Fourth-/Fifth-Generation Enterprise Operational View 1 (OV-1)
The proposed universal M&S suite or toolkit approach described herein has the potential to revolutionize the way we test for RF survivability by minimizing resources required for the process via the leveraging of a common suite while providing a solution as accurate as traditional M&S. The future of M&S lies in this realm as current proprietary approaches are unsustainable in the modern defense world of low-density, high-value assets.
ABOUT THE AUTHOR
CPT Maxim Olivine is the Director of Engineering for the Air Force Operational Test and Evaluation Center, Detachment 5, at Edwards Air Force Base, CA. He provides oversight, technical guidance, and analytical expertise to test new weapon systems in realistic, combat-oriented environments. He also serves as the Deputy Division Chief for the Detachment Test Support Division. CPT Olivine holds a B.S. in computer engineering from the University of California, Davis and an M.B.A. from Wright State University. He is currently pursuing a Ph.D. in systems engineering from Colorado State University.
