Using IDOS to Develop EAGLE into “Real” Flight Software to Support Responsive Missions

1. Using IDOS to Develop EAGLE into “Real” Flight Software toSupport Responsive Missions David Chen Universal Space Lines 1501 Quail St., Suite 100 Newport Beach, CA 92660 2nd Responsive Space Conference Apr. 19-22, 2004 Los Angeles, CA

2. Overview • IDOS • Entry Guidance Problem • EAGLE Guidance Algorithm • Implementation in MAVERIC • Implementation in IDOS • Comparison • Results • Conclusion 2nd Responsive Space Conference

3. IDOS Objectives • Reduce Vehicle Development Cost • Develop efficient Flight Mechanics Analysis Tools for vehicle development • Develop efficient requirements definition and systems engineering processes • Develop efficient processes to develop and test advanced GN&C systems to a TRL of 6 or 7 • Ensure Flight Mechanics technologies are available to all potential vehicle developers • Reduce Operational Cost • Develop GN&C systems that require little or no mission specific software updates or pre-flight verification • Reduce effort for trajectory planning, GN&C system verification I-load generation and sustaining flight software engineering for new missions or anomaly resolution • Contribute to Department of Defense Operational Needs • Advanced GN&C enables short notice “on demand” mission planning to adapt to new missions without the need for extensive ground planning 2nd Responsive Space Conference

4. IDOS in the Life-cycle • IDOS is designed around 3 fundamental workflows • Some or all are useful during each phase of the life-cycle Design & Develop Validate Operate IDOS Workflow GN&C capabilities assessment Monte Carlo Analysis Mission plans Requirements flowdown Mission iloads Collaborative reviews via Web IDOS Products Mission optimization and DRMs Real-time execution metrics System evaluation through simulation Mission validation Avionics requirements Advanced GN&C algorithms Flight software IDOS is an Integrating Environment designed to support the flight software life cycle needs of aerospace vehicles 2nd Responsive Space Conference

5. z + 1 z 2 - 1 z z - 1 How does IDOS work? • A design environment provides: • highly productive development tools (industry standard Matlab/Simulink) • Standardized and automated interfaces • A central, web-accessible database manages common: • vehicle configuration data • simulation and validation tools • mission planning and optimization tools • Advanced GN&C algorithms • A real-time test environment provides: • Automatic generation of prototype flight control software from GN&C developer’s models • EARLY identification of software defects and avionics requirements Flight Control Software (FCSW) Development System Real Time Test Environment (RTTE) Database Web Web IDOS Management System (IMS) 2nd Responsive Space Conference

6. Entry Guidance Problem • Compute feasible entry trajectory • Boundary conditions on longitude and latitude & other state variables (i.e., TAEM and entry interface) • Path constraints • dynamic pressure • heating rate • acceleration • Control constraints • max and min limits on angles of attack and bank • rate limits on angles of attack and bank • acceleration limits on angles of attack and bank • Track computed entry trajectory • Command angle of attack and bank based on reference trajectory and measured errors • Nullify disturbances and uncertainties 2nd Responsive Space Conference

7. EAGLE Guidance Algorithm • Trajectory length sub-problem • Determine an appropriate trajectory length to satisfy downrange: • Determine a drag profile according to trajectory length: • Trajectory curvature sub-problem • Cross range angle: • Heading angle: 2nd Responsive Space Conference

8. EAGLE Guidance Algorithm • Successive approximation approach • Initialize trajectory length to great circle arc distance • Solve trajectory length sub-problem • Solve trajectory curvature sub-problem using drag profile from previous step • Revise trajectory length according to the downrange error • Repeat steps 2-4 until error tolerances are satisfied 2nd Responsive Space Conference

9. EAGLE Guidance Algorithm • Feedback linearized controller • Drag tracking • Follows reference drag profile to achieve range requirements • Commands L/Dcoss • Heading tracking • Follows reference heading profile to achieve cross range requirements • Commands L/Dsins • Angle of attack modulation 2nd Responsive Space Conference

10. Implementation in MAVERIC • Written in C Code • Developed on UNIX platform • gcc • EMACS • dbx • EAGLE implementation • Euler integration • Bisection search for drag profile • Finite number of bank reversal points • Development time ~ 1 year 2nd Responsive Space Conference

11. Implementation in IDOS • Written in Matlab/Simulink • Accepts S-functions or Simulink blocks • Graphical output • Integrated debugger • Developed on a PC platform • EAGLE implementation • Runge-Kutta integration • Gradient search for drag profile • Continuous bank reversal points • Development time < 3 months 2nd Responsive Space Conference

12. MAVERIC Text output Command line based debugger Non real-time simulation Supports C IDOS Graphical plots GUI based debugger Non real-time and real-time simulation Supports multiple languages Comparison 2nd Responsive Space Conference

13. X-33 suborbital entry FCSW-DS Capsule entry from orbit CAV Entry Results 2nd Responsive Space Conference

14. Conclusion • IDOS capabilities demonstrated • Rapid implementation of EAGLE to IDOS • Integrated environment for design, development, implementation, testing, and validation • Greater flexibility for implementing advance guidance algorithms • EAGLE successfully tested in real-time • Brings new design and implementation issues to light • Not possible with MAVERIC 2nd Responsive Space Conference