Research
  • A Distributed Relative Attitude Sensor for Proximity Operations and Rendezvous (DRAPOR) (formerly the Docking Guidance Sensor)
    DRAPOR is a system for determining the relative attitude and position of one spacecraft with respect to another in close proximity for the purpose of performing Autonomous Rendezvous and Docking (ARD) maneuvers and other spacecraft proximity operations (prox-ops). Its fundamental operating premise is really quite simple. The maneuvering, or chase spacecraft emits four laser beams which diverge from a common axis at a small angle (approximately 2 degrees). These beams strike a target plane on the non-maneuvering target spacecraft. Since the diverging beams in space define a unique cone, their points of incidence (POIs) on a plane define a conic section (an ellipse, to be precise), and any three of these POIs may be used to calculate the exact ellipse. Then, the various properties of that ellipse may be used to calculate the relative attitude and position.

    Virginia Space Grant Consortium under the supervision of Dr. Chris Hall and continues to this day.

    A number of papers and presentations are available:

    1. Semi-Autonomous Spacecraft Docking Control
         (Interim Presentation 11/2003, 117k)
    2. Semi-Autonomous Spacecraft Docking Control
         (Final Presentation 12/2003, 246k)
    3. A Semi-Autonomous Terminal Phase Spacecraft Docking Attitude Determination and Control System Simulator
         (Interim Report, 12/2003, 264k)
    4. Semi-Autonomous Terminal Phase Spacecraft Docking Attitude Determination and Control
         (VSGC Conference Report, 3/2004, 643k)
    5. Semi-Autonomous Spacecraft Docking
         (Conference Poster 3/2004, 183k)
    6. A Distributed Ranging and Relative Attitude Determination Sensor for Spacecraft Docking
         (Presentation at the CoE Undergraduate Research Conference 10/2004, 2.3MB)
    7. A Distributed Ranging and Relative Attitude Determination Sensor for Spacecraft Docking
         (Interim Presentation 11/2004, 8.6MB)
    8. A Distributed Ranging and Relative Attitude Determination Sensor for Spacecraft Docking
         (Final Presentation 12/2004, 8.0MB)
    9. A Distributed Ranging and Relative Attitude Determination Sensor for Spacecraft Docking
         (Final Report, 12/2004, 2.9MB)
  • The Distributed Spacecraft Attitude Control System Simulator (DSACSS)
    DSACSS is a project to provide a testbed environment for multiple experiments requiring fully functioning air bearing spacecraft simulators. An attitude determination and control system (ADCS) is under development to provide absolute and relative attitude determination along with high precision, three axis control using multiple actuators, including three custom-built momentum wheels, a custom-built control moment gyroscope (CMG), and a set of cold gas thrusters.

    This project is an ongoing effort. The principal investigator is Dr. Chris Hall and more than two dozen graduate and undergraduate students, including myself, have contributed to the research. Multiple theses, conference papers, and journal articles about the simulators, their ADCS, hardware, development, and onboard experiments have been published, most of which should be available here.

  • Reflection Plane Test Platform
    The Virginia Tech Subsonic Stability Wind Tunnel is one of the largest university wind tunnel facilities in the US, with a full 6' by 6' square test section. Current test platforms are all center mounted, however, limiting the size of semi-span wing models to 3 feet or less. With a wall-mounted reflection plane test platform, semi-span models just under the full 6 feet in length could be tested in this facility. This project seeks to develop such a platform, completely self-contained with all load measurement devices, and equipped with dynamic pitch control.
  • High Order Simulation-Based Optimization of Geostationary Orbit Maintenance Maneuver Strategies
    Under a grant from the VA-based aerospace contractor, Applied Defense Solutions, Inc. (ADS), we analyze an algorithm to iteratively compute optimal orbital maneuvers using the very high order force model orbit propagators in the commercial simulation package Satellite Tool Kit (STK). As the precision of on-orbit maneuvering is limited by hardware, conventional maneuver planning is typically based on an initial burn calculated from the closed form solutions obtainable from low order models and a potential followup burn calculated from the same models after the first post-burn orbit determination. This series is potentially costly to the operator both in terms of satellite downtime and inefficient fuel usage.

    The simulation-based approach allows for the use of arbitrarily complex force models (STK includes the complete JGM-2 and EGM-96 gravity models, among others) which avoid introducing additional uncertainty into the computed solution. Existing writings concerning this commercial solution will become available shortly after its presentation at AGIUC 2005.