The progression of hypersonic vehicle research and development has presented a challenge to modern missile defenses. These attack vehicles travel at speeds of Mach 5+, have low trajectories that result in late radar detections, and can be highly maneuverable. To counter this, new interceptors must be developed. This work explores using machine learning for the guidance of these interceptors through applied steering commands, with the intent to improve upon traditional guidance methods. Specifically, proximal policy optimization (PPO) was selected as the reinforcement learning algorithm due to its advanced and efficient nature, as well as its successful use in related work. A framework was developed and tuned for the interceptor guidance problem, combining the PPO algorithm with a specialized reward shaping method and tuned parameters for the engagements of interest. Low-fidelity vehicle models were used to reduce training time and narrow the scope of work towards improving the guidance algorithms. Models were trained and tested on several case studies to understand the benefits and limitations of an intelligently guided interceptor. Performance comparisons between the trained guidance models and traditional methods of guidance were made for cases with supersonic, hypersonic, weaving, and dynamically evasive attack vehicles. The models were able to perform well with initial conditions outside of their training sets, but more significant differences in the engagements needed to be included in training. The models were therefore found to be more rigid than desired, limiting their effectiveness in new engagements. Compared to the traditional methods, the PPO-guided interceptor was able to intercept the attacker faster in most cases, and had a smaller miss distance against several evasive attackers. However, the PPO-guided interceptor had a lower percent kill against nonmaneuvering attackers, and typically required larger lateral acceleration commands than traditional methods. This work acts as a strong foundation for using machine learning for guiding missile interceptors, and presents both benefits and limitations of a current implementation. Proposals for future efforts involve increasing the fidelity and complexity of the vehicles, engagements, and guidance methods. / Master of Science / Hypersonic vehicles are advanced threats that are difficult to intercept due to their low trajectories, maneuverability, and high speeds. Machine learning is used to have a model learn to intelligently guide an interceptor against an attack vehicle, with the goal of protecting a target. A framework is developed and tuned to address the specifics of this problem space, using an existing advanced algorithm. Various case studies are explored, with both maneuvering and non-maneuvering attackers. The non-maneuvering cases include supersonic, constant velocity engagements with one or more targets as well as ones with hypersonic attackers and an initially stationary interceptor. The evasive methods include preplanned weaving maneuvers and dynamic evasion. The test results from these guidance models are then compared to traditional methods of guidance. Although the performance varied by case, the machine learning models were found to be fairly rigid and did not perform well in engagements that significantly differed from what they were trained on. However, some performance benefits were observed, and additional strategies may be required to increase adaptability. This work provides a foundation for proposed future work, including improving the fidelity of the models and the complexity of the engagements.

International Telemetering Conference Proceedings / October 25-28, 1993 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Given the small size of hit-to-kill interceptor test vehicles currently under development, volumetric limitations mandate using the experimental vehicle's telemetry system during vehicle ground level acceptance and environmental testing to gather performance data, in addition to the primary function of successfully gathering and transmitting data during the test flight. In small, lightweight test interceptors, volume and mass become major telemetry system design considerations. In this paper we describe a system engineering approach to determine the key requirements and calculate some of the critical design parameters necessary for the successful design and development of a high data rate wide band FM Pulse Code Modulation (PCM) airborne telemetry system.

The Cougar Creek / Northeast Interceptor Canal watershed is located within the Corporation of Delta and the City of Surrey. Urbanization has been affecting the natural dynamic and environmental conditions of this watershed. This study was conducted to provide a preliminary evaluation of the health of the Cougar Creek, which includes physicochemical and biological aspects of water quality, and to serve as the basis for the design of a more complex water quality monitoring program. A three-tiered methodological approach, which included a literature review, field measurements and statistical analyses, was used. The stream was monitored from Fall 2010 to Fall 2011 at Westview Drive and at Nicholson Road. Chemical constituents were monitored monthly and benthic macroinvertebrates were sampled in Spring 2011. Physical parameters were recorded continuously using automated samplers. Concentrations of constituents did not exceed the BC criteria for the protection of aquatic life, except for total cadmium. Parameters such as dissolved oxygen and temperature at Nicholson Road, and streamflow at both locations during the dry season were recorded at levels that can harm aquatic life. Statistic analysis indicated that differences in streamflow are associated with concentration changes in some of the constituents between the two sites. Analysis of the benthic community indicated that only tolerant organisms were present at the sites. Differences in habitats between the sites were identified which limited the stream’s health comparability. The study identified the need for collecting first flush events data in future research and recommends BMP that could enhance the stream’s environmental condition.

Master of Science / Department of Mechanical and Nuclear Engineering / J. Kenneth Shultis / A program which calculates the radiation dosage to a predetermined set of components inside of a kill vehicle as a result of natural or artificial radiation sources has been developed for use within the confines of a parent external simulation. This dose can then be used to determine if a critical component has malfunctioned or failed completely, thereby rendering the interceptor unable to finish its mission. Knowledge of system and component performance as a function of incident high-energy particles leads to better battle management planning, CONOPS, and potentially a more efficient shielding design to achieve a higher probability of mission success.

The joint European Space Agency and Japan Aerospace Exploration Agency mission Comet Interceptor seeks to perform a flyby of a Small Solar System Body (SSSB), through use of a multi-element spacecraft. It comprises a primary spacecraft and two subspacecraft, the latter of which will encounter the intercepted object at a small enough distance that its end-of-life might occur at an impact of either the object itself or its potential coma. The Optical Periscopic Imager for Comets (OPIC) is an instrument implemented on one of these small probes which will generate monochromatic images during the encounter. Given a limited data budget before the possible impact, there is a need for data prioritization to ensure that only the most scientifically relevant data is collected. To enable this, algorithms for autonomously cropping an object nucleus from an image were developed during this thesis work. As the computational capabilities of OPIC are limited, the algorithms were required to be of low computational complexity. Additionally, given that the close environment of SSSB in general and comets in particular often exhibit considerable quantities of gas and dust which can generate cluttering in images, the algorithms developed were required to be resistant to noise. Three image cropping algorithms were developed with varying computational complexities. These were tested for cropping accuracy and relative execution times on data from both previous space missions as well as simulated photorealistic images. All three algorithms were able to properly find a bounding box of an object nucleus and any of its significant plumes. The accuracy in cropping correctness of the region borders generated increased with the computational complexity of the algorithms.

Nonlinear stabilization and control autopilots are capable of sustaining nominal performance throughout the entire fight envelope an interceptor missile may encounter during hostile engagements and require no gain scheduling to maintain autopilot stability. Due to non minimum phase conditions characteristic of tail controlled missile airframes, a separation of time scales within the dynamic equations of motion between rotational and translational differential equations was enforced to overcome unstable effects of non minimum phase. Dynamic inversion techniques are then applied to derive linearizing equations which, when injected forward into the plant result in a fully controllable linear system. Objectives of the two time scale control architecture are to stabilize vehicle rotational rates while at the same time controlling acceleration within the lateral plane of the vehicle under rapidly increasing dynamic pressure. Full 6 degree of freedom dynamic terms including all coriolis accelerations due to translational and rotational dynamic coupling have been taken into account in the inversion process. The result is a very stable, nonlinear autopilot with fixed control gains fully capable of stable nonlinear missile control. Several actuator systems were also designed to explore the destabilizing effects second order nonlinear actuator characteristics can have on nonlinear autopilot designs.

In this thesis the cubic spline guidance law and its variants are derived. A detailed analysis is carried out to find the initial conditions for successful interception. The results are applied to three dimensional guidance design and for solving waypoint following problems. The basic cubic spline guidance law is derived for intercepting a stationary target at a desired impact angle in a surface-to-surface engagement scenario. The guidance law is obtained using an inverse method, from a cubic spline curve based trajectory. For overcoming the drawbacks of the basic cubic spline guidance law, it is modified by introducing an additional parameter. This modification has an interesting feature that the guidance command can be obtained using a single cubic spline polynomial even for impact angles greater than π/2, while resulting in substantial improvement in the guidance performance in terms of lateral acceleration demand and length of the trajectory. For imparting robustness to the cubic spline guidance law, in the presence of uncertainties and acceleration saturation, an explicit guidance expression is also derived. A comprehensive capturability study of the proposed guidance law is carried out. The capturability for the cubic spline guidance law is defined in terms of the set of all feasible initial conditions for successful interception. This set is analytically derived and its dependence on various factors, such as initial engagement geometry and interceptor capability, are also established. The basic cubic spline guidance and its variants are also derived for a three dimen- sional scenario. The novelty of the present work lies in the particular representation of the three dimensional cubic spline curve and the adoption of the analytical results available for two dimensional cubic spline guidance law. This enables selection of the boundary condition at launch for given terminal boundary condition and also in avoiding the singularities associated with the inverse method based guidance laws. For establishing the feasibility of the guidance laws in the real world, the rigid body dynamics of the interceptor is presented as a 6 degrees-of-freedom model. Further, using a simplified model, elementary autopilots are also designed. The successful interception of the target in the presence of the rigid body dynamics proves practical applicability of the cubic spline based guidance laws. Finally, the theory developed in the first part of the thesis is applied to solve the waypoint following problem. A smooth path is designed for transition of vehicle velocity from incoming to outgoing direction. The approach developed is similar to Dubins’ path, as it comprises line–cubic spline–line segments. The important feature of this method is that the cubic spline segments are fitted such that the path curvature is bounded by a pre-specified constrained value and the acceleration demand for following the smooth path obtained by this method, gradually increases to the maximum value and then decreases. This property is advantageous from a practical point of view. All the results obtained are verified with the help of numerical simulations which are included in the thesis. The proposed cubic spline guidance law is conceptually simple, does not use linearised kinematic equations, is independent of time-to-go es- timates, and is also computationally inexpensive.

No description available.

The Comet Interceptor is a joint mission by European Space Agency (ESA) and Japan Aerospace Exploration Agency (JAXA) which seeks to perform a flyby over a Long Period Comet using a multi-element spacecraft. The Comet Interceptor comprises three spacecrafts- A, B1 and B2. All three spacecrafts will observe and map the comet at three different points on the coma of the comet, thereby making this mission the first ever multipoint mission dedicated to study a Long Period Comet. Out of the eleven instruments aboard the Comet Interceptor, the work done for this thesis aims to help the team designing the instrument-Optical Periscope Imager forComets (OPIC). The team designing OPIC uses the imaging simulation software Space Imaging Simulator for Proximity Operations (SISPO) to render images of theoretically modelled dust and gas densities of the coma of a comet to obtain prerequisite knowledge of the images which is to be taken by OPIC during its flyby. Using the theoretical model of the coma, a 3D model was created as part of the thesis which shall be later implemented in SISPO. The structure of the coma was made with the help of a sparse volumetric data manipulation tool OpenVDB, which was coded and run in Python. The generated data was imported in Blender to visualise the volumetric data with the help of Blender’s rendering engine-Cycles. To visualise the 3D model with utmost physical realism as the software Blender allows, a study on the scattering properties of the dust and gas model was done. Also, a motion blur was implemented in Blender to simulate the high relative velocity between the instrument and comet. Multiple approaches of varying complexities and time consumption were considered for importing and visualising the volumetric data. The final render images were brightness-matched with reference to images from previous cometary missions. Finally, a qualitative analysis was done by visually comparing the render images to the images from previous missions. With the help of this qualitative analysis, several features and characteristics were identified which were analogous to the real life images, thus establishing the correctness of the renders produced.

The study presents a numerical investigation about the hydrodynamic characteristics of a transom mounted interceptor on the Oliver Hazard Perry class frigate (FFG-7), in order to assess the potential of propulsion power reduction in a wide range of speeds. This study is aimed to design a stern interceptor with optimal efficiency not only at top speed, but also cruising/transfer speeds, by a simple regulation of its variable geometrical characteristics (from a construction and operational standpoint). A high fidelity numerical model is developed in the open source CFD suite OpenFOAM for the prediction of the longitudinal dynamic equilibrium at speed and the total resistance characteristics of the bare hull. The Reynolds Averaged Navier-Stokes Equations are solved using interDyMFoam, a multiphase volume of fluid solver which allows for a dynamic mesh. The numerical model is validated using the results of the experimental model tests conducted on a 1/80th scale model at the United States Naval Academy Hydromechanics Laboratory (NAHL). The validated numerical model is used to predict the hydrodynamic characteristics of the transom mounted interceptor at different interceptor settings and speeds. The results show that the interceptor reduces the amount of resistance, the running trim, and the sinkage of the ship at high speeds. For a speed of 0.392 Froude number (Fr), a drag reduction of 3.76% was observed, as well as a significant reduction in trim. / Master of Science / The drag acting on the hull is an important component that has to be considered during the process of designing the ship. An interceptor is a device that has been developed to improve the performance of hulls by reducing the drag. This research studies the influence of the interceptor on the resistance and motion of the ship across a range of speeds. The geometrical characteristics of the interceptor are varied in order to identify the geometry that would provide optimal performance across the speed range tested. This study is conducted using the Computational Fluid Dynamics (CFD) software OpenFOAM as well as model tests that were conducted on a 1/80th scale model.