Flight-dynamics Simulation Tools

2nd ESA Workshop on Astrodynamics Tools and Techniques

ESTEC, September 13-15, 2004

Erwin Mooij

1

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!

2

Introduction (2)

Sänger ascent trajectory with HORUS stage separation

3

Introduction (3)

AURORA: Mars Sample Return

4

Overview

Simulation Tool for Ascent and Re-entry Trajectories (START)Introduction

Architecture

Modelling capabilities

Simulation loop

Post processing

User Interface

Applications

Generic AOCS simulatorArchitecture

Applications

5

START Introduction

Development started at ESTEC in 1991 for the simulation of re-entry 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, post-processing facilities (1993-1998)

Many more extensions and applications (1998-present)

6

START Architecture

7

START Modelling capabilities

8

START Simulation Loop (1)

9

START Simulation Loop (2)

10

START Post processing

11

START User Interface (1)

12

START User Interface (2)

User-defined subroutines withBatch 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.)

13

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

14

START Applications (2)

Huygens

15

START Applications (3)

Hyperion-2

16

START Applications (4)

0

20

40

60

80

100

120

140

0 1000 2000 3000 4000 5000 6000 7000 8000 9000

velocity (m/s)

altit

ude

(km

)

max. heat flux

max. dyn. pressure

13: coast

12: pull up

14: circularisation

take-off2

45

3

6 798

1011

reference ascent trajectory

1

Cross-range command

Trajectory performance improvement

Winged Cone Configuration

17

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

......

18

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

19

GAOCS Architecture (1)

20

GAOCS Architecture (2)

Flight Dynamics Core

21

GAOCS Architecture (3)

Actuators and aerodynamics

22

GAOCS Architecture (4)

Control-surface aerodynamics

23

GAOCS Architecture (5)

Elevon aerodynamics implementation

24

GAOCS Architecture (6)

Guidance: trim commanding

25

GAOCS Architecture (7)

Attitude Control system

26

GAOCS Application (1)

HORUS-2B

Entry control modes

27

0 1000 2000 3000 4000 5000 6000 7000 80000

50

100

150

velocity (m/s)

altit

ude

(km

)

0 200 400 600 800 1000 1200 1400-100

-50

0

50

100

time (sec)

attit

ude

angl

e (d

eg)

bank angle

angle of attack

entry interface

TAEM interface

bank reversal #1 #2 #3 #4

bank reversal #1

#2 #4

#3

GAOCS Application (2)reference trajectory

control history

28

GAOCS Application (3)

0 5 10 15 20 25 30 35 40-4

-3

-2

-1

0

1

time (sec)

angl

e of

sid

eslip

(de

g)

0 5 10 15 20 25 30 35 40-1

-0.5

0

0.5

1x 10

4

time (sec)

yaw

mom

ent (

Nm

)

0 5 10 15 20 25 30 35 40-40

-20

0

20

40

time (sec)

rudd

er d

efle

ctio

n (d

eg)

plant

reference model

plant

reference model

plant

reference model

0 5 10 15 20 25 30 35 40-100

-50

0

50

100

time (sec)

bank

angle

(deg)

0 5 10 15 20 25 30 35 40-10

-5

0

5

time (sec)aile

ron d

efle

ctio

n (

deg)

plant

reference model

reference model

plant

bank-reversal analysis

29

GAOCS Application (4)

0 5 10 15 20 25 30 35 4039.4

39.6

39.8

40

40.2

time (sec)

an

gle

of

att

ack

(d

eg

)

0 5 10 15 20 25 30 35 40-0.5

0

0.5

1

1.5

2

time (sec)

ele

vato

r d

efle

ctio

n (

de

g)

reference model

plant

reference model

plant

bank-reversal analysis

30

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