OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Trusted AI and Autonomy; Hypersonics The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the statement of work (SOW) tasks intended for accomplishment by the FN(s) in accordance with the Announcement. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws. OBJECTIVE: The objective of this topic is to develop a hardware-in-the loop scene simulator that captures both aero-optical and thermal-structural impact to wave propagation through optical windows on high-speed airframes. Numerous aero-optical tools exist for predicting image artifacts due to propagation through flow-field shock and boundary layers. These tools have transitioned to real-time (30 to 1000 frames per second) image processing capabilities that impart image distortion and energy distribution onto a simulated image. The additional impact of optical propagation through heated and deformed windows has typically been assumed to be relatively small. Recent results have shown window effects to be a predominant source of image degradation in some designs. Availability of real-time models that can impart the window induced degradation in closed-loop trajectory simulations is the technology gap intended to be addressed by this topic. DESCRIPTION: Hardware-in-the-loop (HWIL) simulations of autonomous weapons are intended to allow avionics software to fly a mission with simulated sensor feedback. These simulations allow analysts to assess performance in a low-cost, repeatable laboratory environment, reducing risk prior to flight testing or operational deployment. The technical challenges associated with HWIL simulation often center around the simulators of sensor stimulus, which must represent complex phenomena without introducing significant latency into the guidance and control systems. An imaging seeker must receive an image representative of what it would see in flight, as a function of position, orientation, velocity, and environmental phenomena. The environmental impacts may include atmospheric optical propagation, transmission through shock and boundary layers, and heating of a sensor window, along with the associated lensing and index of refraction changes. Systems currently exist for real-time scene generation that rely on state-of-the-art GPU technology to generate images of targets and backgrounds. Environmental effects have previously been implemented by taking perfect, over-resolved images and applying polynomial distortion functions and convolution kernels to capture the effect of energy spreading in the boundary layer. The resultant down-sampled images can be used in a focal plane model for scene injection or to drive optical projection systems. For scene projection, the scene generation system performs floating point calibration and non-uniformity correction functions prior to sending data to the scene projector. The scene generation hardware typically includes an engineering workstation with a real-time operating system, a high-end graphics card to run a sensor/scene model, e.g., FLITES, and an FPGA personality board to control output interface protocols and time synchronization. The intent of this SBIR is to leverage existing approaches and add to them innovative high-performance approaches that provide window heating and distortion effects into the image generation. Challenges include 1) surrogate modeling to capture thermal forcing functions on the window surface, 2) surrogate modeling for structural deformation and temperature distribution, 3) data transfer between multiple GPU's (if necessary) and between GPU, CPU, and output interface, 4) combining multiple optical effects associated with propagation through the flowfield, deformed window, and index variations within the window, 5) data interface flexibility and variable rate frame synchronization with an external source, 6) real-time interface with 6DOF simulation computer (~1200 Hz), 7) data throughput encompassing oversampled input generation (e.g., 5x5) to output with 16bit gray scale images (1kx1k) at 1kHz, 8) User Interface for FLITES configuration, timing verification, and system initialization. PHASE I: Phase 1 will establish the feasibility of the approach taken and a final design approach. A generic Use Case will be defined for which a CFD data set will be generated for baseline aero-optical parameters, and heat transfer coefficients. Structural and thermal models will be generated based on window geometry, and material characteristics. Databases will be generated to drive computational processes as a function of Mach, altitude, attitude, temperature, etc. Modeling approaches for each stage of processing and physical process modeled will be defined and implemented for establishing approach feasibility. Subsystems challenges and lessons learned will be documented for Phase II implementation. Based on subsystem designs and preliminary performance results a hardware configuration will be defined for final Phase II implementation. An interface control document will be created to establish interface requirements associated with buffering and output communication, timing control/synchronization, and 6DOF simulation communication. The flexible output communication personality card will be selected to interface with the design configuration selected and a nominal set of output protocols for scene injection and scene projection test systems. PHASE II: Phase II will perform any additional software iteration and testing necessary to reduce risk in the final implementation. Subsystems will be integrated together, and integrated timing benchmarks will be collected prior to finalizing hardware specifications and ordering system components. System software will be developed, verified, documented, and placed under configuration management. A set of acceptance test conditions will be documented as prototype targets. The graphical user interface (GUI) design and development will take place. The GUI should allow configuration of different combinations of functions, depending on test requirements (FLITES passthrough, scene injection, scene projection). The GUI will establish paths to sensor model parameters for scene injection and paths to sensor calibration data for projection mode. FPGA programming and verification will take place for selected test cases. Databases will be fully populated over the flight envelope of interest. Surrogate models for heat transfer and structural response will be finalized for the Use Case defined in Phase I. The Use Case will be sufficiently document for the end user to be able to implement models for an alternative Use Case of their choosing. A Test Plan will be established for acceptance testing for both a signal injection and a scene projection test case. At the end of Phase II, testing will take place at the AFRL KHILS facility. PHASE III DUAL USE APPLICATIONS: For specific applications, surrogate structural and thermal models will be generated for real-time implementation. CFD data will be generated with the flight envelopes expected to be encountered for system of interest. A fully populated database of optical distortion parameters will be generated for the system of interest. Specific interfaces required for test configuration required will be programmed into the personality interface if not already implemented. The GUI will be modified based on end user requirements. Host computer hardware will be ordered, and the final system integrated for verification testing prior to delivery. The system will be delivered and acceptance tested. Optimization and further development based on new requirements, new technology availability, or lessons learned will take place in Phase III as required. REFERENCES: 1. Crow, Dennis R., Charles F. Coker and Wayne Keen. Fast line-of-sight imagery for target and exhaust-plume signatures (FLITES) scene generation program. SPIE Defense + Commercial Sensing 2. Crowell, Andrew R., and Jack J. McNamara. "Model reduction of computational aerothermodynamics for hypersonic aerothermoelasticity." AIAA journal 50, no. 1 (2012): 74-84. 3. Hudson, Douglas J., Manuel Torres, Catherine Dougherty, Natesan Rajendran, and Rhoe A. Thompson. "Prediction methodologies for target scene generation in the aerothermal targets analysis program (ATAP)." In Technologies for Synthetic Environments: Hardware-in-the-Loop Testing VIII, vol. 5092, pp. 295-306. SPIE, 2003. 4. Jumper, Eric J., and Stanislav Gordeyev. "Physics and measurement of aero-optical effects: past and present." Annual Review of Fluid Mechanics 49 (2017): 419-441. 5. 5. Ewing, Craig. The Advanced Guided Weapon Testbed (AGWT) at the Air Force Research Laboratory Munitions Directorate. (2009). KEYWORDS: FLITES; Scene Generation; Aero-optical; Aerothermal Image Generation; Distortion; Surrogate Modeling; Deformation; Transmission
