Flight-dynamics Simulation Tools 2 nd ESA Workshop on Astrodynamics Tools and Techniques ESTEC, September 13-15, 2004 Erwin Mooij
Introduction (1) Areas of interest (not complete): Load analysis and impact-area determination free-falling objects Conceptual design of flight vehicles Design and/or verification of GNC systems of space planes (ascent/descent) Design and/or verification of AOCS of satellites Mission design and requirements verification Aero-elasticity versus control-system performance... Traditionally different tools for different problem areas More important: new tools for new projects! 1
Introduction (2) Sänger ascent trajectory with HORUS stage separation 2
Introduction (3) AURORA: Mars Sample Return 3
Overview Simulation Tool for Ascent and Re-entry Trajectories (START) Introduction Architecture Modelling capabilities Simulation loop Post processing User Interface Applications Generic AOCS simulator Architecture Applications 4
START Introduction Development started at ESTEC in 1991 for the simulation of reentry trajectories in Earth and Titan Atmosphere Mission analysis Huygens Project: entry and descent until landing (1991) Extension to software: 7 dof parachute model, shadow engineering Huygens Project (1992) Implementation of deorbit-burn manoeuvres and related study (ESA contract, 1993) Implementation of powered ascent flight, GNC systems, postprocessing facilities (1993-1998) Many more extensions and applications (1998-present) 5
START Architecture 6
START Modelling capabilities 7
START Simulation Loop (1) 8
START Simulation Loop (2) 9
START Post processing 10
START User Interface (1) 11
START User Interface (2) User-defined subroutines with Batch initialisation Run initialisation Integration-step execution Subroutines available for: Atmosphere model Wind model Aerodynamics External forces and moments Navigation, Guidance and Control (three separate subroutines) Output variables Performance criteria for sensitivity analysis (MC, Taguchi, etc.) 12
START Applications (1) Validation versus RATT software: open-loop entry of Apollo Huygens mission analysis (open-loop entry and parachute descent) Controllability study of Hyperion-1 Conceptual design and mission analysis Hyperion-2 LQR design and verification HORUS-2B re-entry vehicle Performance analysis and adaptive control of Winged Cone Configuration EXPERT flight-mechanics support 13
START Applications (2) Huygens 14
START Applications (3) Hyperion-2 15
START Applications (4) Cross-range command Winged Cone Configuration 140 120 reference ascent trajectory 14: circularisation 100 13: coast altitude (km) 80 60 40 20 take-off 2 3 4 5 6 7 8 9 12: pull up 11 10 max. dyn. pressure max. heat flux 0 0 1 1000 2000 3000 4000 5000 6000 7000 8000 9000 velocity (m/s) Trajectory performance improvement 16
START Future work Implementation of JPL Ephemerides Sun (and other planets) as central body, including (dynamic) change during integration Interface with Earth/Mars GRAM-99 atmosphere Windows User Interface Integrated 2D/3D visualisation... 17
Generic AOCS Simulator Originally developed as satellite AOCS simulator Extended with US76 atmosphere model For re-entry simulation, accurate modelling of aerodynamics Per guided and controlled application, implementation of GNC system But: once this is done, EuroSim simulator can be built automatically, and can serve as platform to test GNC on-board software 18
GAOCS Architecture (1) 19
GAOCS Architecture (2) Flight Dynamics Core 20
GAOCS Architecture (3) Actuators and aerodynamics 21
GAOCS Architecture (4) Control-surface aerodynamics 22
GAOCS Architecture (5) Elevon aerodynamics implementation 23
GAOCS Architecture (6) Guidance: trim commanding 24
GAOCS Architecture (7) Attitude Control system 25
GAOCS Application (1) Entry control modes HORUS-2B 26
GAOCS Application (2) reference trajectory 150 entry interface altitude (km) 100 TAEM interface 50 #2 bank reversal #1 #3 #4 0 0 1000 2000 3000 4000 5000 6000 7000 8000 velocity (m/s) attitude angle (deg) 100 bank reversal #1 #3 50 0 angle of attack -50 bank angle #2 #4-100 0 200 400 600 800 1000 1200 1400 time (sec) control history 27
GAOCS Application (3) bank-reversal analysis yaw moment (Nm) angle of sideslip (deg) rudder deflection (deg) 1 0-1 -2-3 -4 0 5 10 15 20 25 30 35 40 time (sec) 1 x 104 plant 0.5 0-0.5-1 0 5 10 15 20 25 30 35 40 time (sec) 40 20 0-20 reference model plant reference model reference model plant -40 0 5 10 15 20 25 30 35 40 time (sec) bank angle (deg) aileron deflection (deg) 100 50 0-50 -100 0 5 10 15 20 25 30 35 40 time (sec) 5 0-5 reference model plant reference model plant -10 0 5 10 15 20 25 30 35 40 time (sec) 28
GAOCS Application (4) bank-reversal analysis angle of attack (deg) 40.2 40 39.8 39.6 reference model plant 39.4 0 5 10 15 20 25 30 35 40 time (sec) elevator deflection (deg) 2 1.5 plant 1 0.5 0 reference model -0.5 0 5 10 15 20 25 30 35 40 time (sec) 29
Concluding remarks Two software environments presented: START: fast FORTRAN simulator for all mission phases GAOCS re-entry tool: still under development Further development of GAOCS version based on START models Detailed validation of GAOCS version based on START results Documentation 30