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Next Generation Toolsets for Weapons Separation Evaluations to Enable Enhanced Strike Capabilities


OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Advanced Computing and Software

OBJECTIVE: Develop a next generation software package to simulate and assess multiple weapons’ trajectories after release from tactical aircraft to ensure safe and effective separation.

DESCRIPTION: As adversary aircraft detection and surface-to-air strike capabilities increase, the need for long-distance, over-the-horizon strike capabilities intensifies. The difficulty in simulating accurate pre-flight trajectories increases drastically as more conventional air-to-ground strike capabilities like Small Diameter Bomb Increment IIs (SDB-IIs) continue to become smaller and lighter, allowing aircraft to deploy more assets. Air-launched weapon systems are highly stressed during aircraft separation and terminal phases. Common design traits of effective long-range weapons, such as high maneuverability, low observability, and aerodynamic efficiency, often exacerbate this problem. During separation, modern air-to-ground stores can dissipate more than 10% of their energy arresting forces and moments imparted by the aircraft environment. This level of energy loss can have profound impacts on the maximum range of the weapon. For smaller and lighter stores, the influence of the aircraft during the separation phases produces large body rates on the store, often in excess of 1000 degrees per second, which affects the ability of the assets to complete their mission.

The current Six-Degree-of-Freedom (6DOF) trajectory solver, NAVSEP, is a FORTRAN-based toolset, which originated in the 1970s. Unfortunately, the use of FORTRAN makes it difficult to maintain or increase NAVSEP’s abilities to better predict and understand the relationship between the aircraft and the multiple assets during separation phases. As a result, NAVSEP lacks modern data analytics methods such as data handling and interpolation methods, workflow automation approaches, and the ability to handle complex autopilots featured in many modern weapon systems. These deficiencies can significantly increase analysis time required to assess weapon separation performance, especially between test flights. Late identification of store separation and controllability issues during flight test can result in reduced flight envelopes or asset redesign causing significant fielding delays.

A novel toolset with a core 6DOF equation-of-motion solver, an integrated visualization tool/workflow, and an efficient miss distance calculator for generating proximity data between the aircraft and store is sought. The core 6DOF solver will synthesize freestream aerodynamic information, aircraft influence data, and other external forces such as rocket motor thrust, bomb rack ejection forces, and so forth to produce store trajectories across given employment or jettison envelopes. The core 6DOF solver will report diagnostic data for trouble shooting purposes. The computed store trajectories are paramount to understanding separation dynamics to assess safety and weapon system controllability which are critical to system performance.

This integrated visualization tool will use computer-aided design (CAD) geometries of representative aircraft and stores to produce animations of body trajectories output by the core 6DOF solver. Visualizations will quickly assess potential areas of concern during release.

An integrated miss distance calculator will provide the means for quantitatively assessing the safety of a given separation using trajectory data from the core 6DOF solver and CAD geometries from the visualization tool. Minimum miss distance is the most direct measurement of safety that exists, but it comes at a high-computational cost, which limits its utility. An efficient calculator that identifies the location of this key metric will enable expanded utilization and ultimately enhance Naval Air Warfare Center Aircraft Division’s (NAWCAD) organic separation assessment capability.

The resulting flexible software package will be able to handle aerodynamic input data from legacy and modern wind tunnel testing methods, along with Computational Fluid Dynamics simulation data, to generate high-confidence weapons’ trajectories near the tactical aircraft. This capability is necessary to ensure stores separate safely from the aircraft before their design is finalized. In addition, the novel software tool will assess separation dynamics, which are critical to weapon controllability and performance.

PHASE I: Develop workflow, explaining a novel approach for simulating store trajectories using Next Generation 6DOF equation-of-motion solver. Approach must include interpolation schemes and be compatible with Windows 10. The preferred solution is Operating System independent. For example, the proposed tools/process could use webapps, function in platform-independent environments (such as python scripts), or be compiled to run on modern versions of Windows (version 10), Mac OS (version 12), and RedHat Linux (version 8) operating systems with no special environments or libraries. Concept software designs for integrated visualization tool and miss distance calculator will be generated with performance estimations or simple demonstrations of capabilities showing time to compute. The Phase I effort will include prototype plans to be developed under Phase II.

PHASE II: Produce prototype toolset based on the Phase I results. Develop and refine toolset workflow assuring accurate and efficient calculation and user interaction with computed data. Validate core 6DOF calculations with relevant inputs simulating known trajectories. Demonstrate entire workflow and applicability with Navy Information Technology (IT) systems.

PHASE III DUAL USE APPLICATIONS: Complete validation and verification of Next Generation toolsets. Speed of code performance, as well as accuracy of calculation comparisons to existing tools (where applicable), workflow and compatibility with Naval Air Systems Command (NAVAIR) systems will be evaluated.

The resulting 6DOF computational modeling capability can be utilized for optimization and evaluation of airdrop separation from commercial aircraft, ensuring safe separation and delivery of packages for commercial and humanitarian relief applications. Because the core dynamic equations are derived from general equations of motion, coupled with integration algorithms to yield a trajectory, the product is able to calculate the dynamics of several types of vehicles in motion, such as general aircraft, orbital launch vehicles, and so forth [Ref 2].


  1. Zipfel, P. H. (2000). Modeling and simulation of aerospace vehicle dynamics. American Institute of Aeronautics and Astronautics.
  2. Zipfel, P. H. (2014). Advanced six degrees of freedom aero sim and analysis in C++. American Institute of Aeronautics.

KEYWORDS: Store Separation; Six-Degree-of-Freedom; 6DOF; analysis toolset; trajectory; calculation; visualization

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