1. valerio.rossi@astos.de, sven.shaeff@astos.de, sven.weikert@astos.de
ASTOS MULTIBODY FEATURE FOR SIMULATIONS OF FLEXIBLE LAUNCHER DYNAMICS

2. Outline Company presentation ASTOS & Multibody feature overview
Launcher flexibility
Sloshing dynamics
Stages separation
Engine propulsion oscillations
Conclusions
© 2018 Astos Solutions GmbH
ICATT November

3. Company presentation Astos Solutions © 2018 Astos Solutions GmbH
ICATT November

4. Astos Solutions Overview
SME with sites in Unterkirnach (DE), Stuttgart (DE), Oradea/Sibiu (RO)
Spin-Off of the Univ. of Stuttgart, standalone company since 2006
Roots of Astos Solutions go back to 1989
Office in Stuttgart
© 2018 Astos Solutions GmbH
ICATT November

5. Astos Solutions’ Expertise
Trajectory Optimization
Multi-Disciplinary Vehicle Design
Mission Analysis
System Concept Analysis
GNC
Launch
Structure & Tanks
Navigation Analysis
Thermal Control Sys.
Launcher GNC Design
Re-entry
Propulsion System
Link Budget Analysis
Power System
Robotics
Low-thrust transfer
Aerodynamics
Coverage Analysis
Data Systems
Test beds
Interplanetary
Reference Trajectories
Launch & Re-entry Safety
Camera & Lidar Simulation
Suborbital
Asteroid Trajectory Propagation
Magnetic Cleanliness Identification
Pointing Error Engineering
© 2018 Astos Solutions GmbH
ICATT November

6. Astos Solutions’ Releveant Expertise
Trajectory Optimization
Multi-Disciplinary Vehicle Design
Mission Analysis
System Concept Analysis
GNC
Launch
Structure & Tanks
Navigation Analysis
Thermal Control Sys.
Launcher GNC Design
Re-entry
Propulsion System
Link Budget Analysis
Power System
Robotics*
Low-thrust transfer
Aerodynamics
Coverage Analysis
Data Systems
Test beds
Interplanetary
Reference Trajectories
Launch & Re-entry Safety
Camera & Lidar Simulation
Suborbital
Asteroid Trajectory Propagation
Magnetic Cleanliness Identification
Pointing Error Engineering
© 2018 Astos Solutions GmbH
ICATT November

7. Product Portfolio Spaceflight Design & Analysis Optimisation Testbed
Visualization
VESTA
(OSS)
ASTOS
GESOP
Camera/Lidar Simulator
Vehicle Design
ODIN
MT-Aerospace
DCAP
SOS
AMA Inc
dSPACE
HIL-Unit
Exploration
Asteroid Trajectory Propagation
LOTOS
WORHP
SFZ
GRAVMOD-2
POINT
MIDACO
Schlueter
Magnetic Cleanliness Identification
Pointing Error Engineering
PEET (OSS, ESA)
GAMAG
© 2018 Astos Solutions GmbH
ICATT November

8. Applicable Product Portfolio
Spaceflight Design & Analysis
Optimisation
Testbed
Visualization
VESTA
(OSS)
ASTOS
GESOP
Camera/Lidar Simulator
Vehicle Design
ODIN
MT-Aerospace
DCAP
SOS
AMA Inc
dSPACE
HIL-Unit
Exploration
Asteroid Trajectory Propagation
LOTOS
WORHP
SFZ
GRAVMOD-2
POINT
MIDACO
Schlueter
Magnetic Cleanliness Identification
Pointing Error Engineering
PEET (OSS, ESA)
GAMAG
© 2018 Astos Solutions GmbH
ICATT November

9. ASTOS & MULTIBODY FEATURE OVERVIEW
Astos Solutions
ASTOS & MULTIBODY FEATURE OVERVIEW
© 2018 Astos Solutions GmbH
ICATT November

10. ASTOS software
Built-in trajectory and multi-disciplinary design optimization
Performance and system concept analysis
Simulink and dSPACE interfaces for closed-loop simulations, HIL and SCOE applications
Trajectory optimization
Vehicle design optimization
Wide range of mission analysis features
Launch and re-entry safety analysis
Built-in plotting and animation tools
Built-in batch-processing engine and configuration tool
NEW preliminary assessment of the needs relevant to the on-board Flight Termination System (FTS), including localization, tele-command, and neutralization
© 2018 Astos Solutions GmbH
ICATT November

11. DCAP software
DCAP is a no-frills, rational, fast multi-body software tool, designed for assessing space systems and devices.
Symbolic order(n) dynamic formulation
Rigid and flexible bodies
Analytic flexible beam model
Transitions of hinge DOF state
Variable body properties
Gravity gradient
Contact and friction dynamics
Built-in space sensors and actuators
Non-linear devices
© 2018 Astos Solutions GmbH
ICATT November

12. Multibody feature overview
The new multibody feature is design to address complex launcher simulations.
A launcher vehicle is a typical multibody system composed of several components.
The link ASTOS/DCAP is realised through ASCII files and dynamic libraries.
EoM are generated as auto-coded Fortran subroutines.
EoM are then compiled and linked for a fast interface with ASTOS.
© 2018 Astos Solutions GmbH
ICATT November

13. Multibody feature overview
DCAP computes the system dynamics and the state derivatives.
ASTOS provides the external forces such as:
gravity acceleration of each body;
aerodynamic forces;
actuators and engines output.
ASTOS finally performs the numerical integration.
The user never interacts directly with DCAP.
The post-processing is completely managed in ASTOS.
© 2018 Astos Solutions GmbH
ICATT November

14. LAUNCHER flexibility Astos Solution © 2018 Astos Solutions GmbH
ICATT November

15. Flexible launcher structure
A launcher structure is a very long flexible slender beam.
Considering the components flexibility improves the overall launcher simulation reliability.
Structural deformations and deflections can alter the aerodynamic forces acting on the rocket.
The GNC system needs to handle those disturbances
Each component can be defined as flexible
© 2018 Astos Solutions GmbH
ICATT November

16. Flexibility model
A linear Euler-Bernoulli flexible beam model is used as flexibility model (no external FEM software)
Different mass distribution for liquid and solid propellant
Geometrical parameters automatically computed by ASTOS
The user inputs are:
Young modulus
Damping ratio
Number of flexible modes
© 2018 Astos Solutions GmbH
ICATT November

17. Mode shapes export
A dedicated export allows to compute the global mode shapes and frequencies at different point in time
This knowledge is crucial for the design of the GNC controller which takes into account also rocket deformations.
Third mode shape of a flexible rocket model
© 2018 Astos Solutions GmbH
ICATT November

18. Sloshing dynamics Astos Solution © 2018 Astos Solutions GmbH
ICATT November

19. Sloshing effect
The lateral dynamic force resulting from the motion of liquids in tanks is known as the sloshing effect.
Possible coupling between the sloshing effect, the mechanical structure and the control system leading to unstable dynamics
Computational Fluid Dynamics (CFD) model are not suitable for multibody simulation because of the high computational burden
Credits Flow Science
Equivalent mechanical models are much more convenient for these applications
© 2018 Astos Solutions GmbH
ICATT November

20. Mechanical sloshing model
Spring-mass mechanical system
Fuel is split into:
a static mass rigidly attached to the tank
one or more sloshing masses attached to the tank through spring-damper elements
One sloshing mass accounts for two flexible modes
In the ASTOS GUI, the user is required to provide only three high level inputs:
tank shape (cylindrical or spherical);
number of sloshing masses;
kinematic viscosity of the propellant.
Static mass
Sloshing mass
© 2018 Astos Solutions GmbH
ICATT November

21. Sloshing model damping
Sloshing effect is minor when tank is almost empty
Damping coefficient depends on the tank geometry
Cylindrical tank
damping
Spherical tank
damping
© 2018 Astos Solutions GmbH
ICATT November

22. Stages separation Astos Solution © 2018 Astos Solutions GmbH
ICATT November

23. Stages separation
The separation starts with the disconnection of two components (explosive bolts, pneumatic latches or explosive shaped charges)
A later process involves the actuators which actually separate the components (retrorockets, pneumatic thruster or elastic spring elements)
© 2018 Astos Solutions GmbH
ICATT November

24. Stages separation
The detachment process is achieved by a reconfiguration of the mechanical system (hinge releasing)
Separation devices:
hard-stop springs;
clamp bands;
actuators.
Clamp band separation device has been developed for payload release
Several linear springs are placed along a circumference
Payload
Upper stage
Clamp band
© 2018 Astos Solutions GmbH
ICATT November

25. Clamp band separation device
High level settings
Springs misalignment and separation delay by using different mechanical properties for each spring (input table)
Simulation results of stage separation have been benchmarked with a commercial clamp band data sheet
© 2018 Astos Solutions GmbH
ICATT November

26. Engine pressure oscillations
Astos Solution
Engine pressure oscillations
© 2018 Astos Solutions GmbH
ICATT November

27. Engine pressure oscillations
The complex feedback mechanism involving vortex shedding and acoustic resonant mode produces pressure oscillations in solid rocket engines
Data available in literature shows a typical frequency around Hz
Complex coupled CFD and FEM simulations are needed in order to estimate the frequencies involved
No equivalent mechanical models are available for multibody applications
© 2018 Astos Solutions GmbH
ICATT November

28. Time domain engine disturbances
Experimental or simulation data can be used in ASTOS as disturbances
Pressure oscillations contribution is added to the average engine thrust profile by superimposing a time domain signal
The signal is directly added to the average time domain
Total engine thrust
Pressure oscillation (time domain)
Average thrust
© 2018 Astos Solutions GmbH
ICATT November

29. Frequency domain engine disturbances
The propulsion disturbances spectrum is associated by the user to a coloured noise and then superimposed to the average engine thrust
A red noise signal is converted into the time domain during the simulation and then added to the average thrust
Total engine thrust
Pressure oscillation (red noise)
Average thrust
© 2018 Astos Solutions GmbH
ICATT November

30. Conclusions
The implementation of new EoM in ASTOS has improved the capability of the software to answer the need of aerospace engineers during the preliminary design of the vehicle.
The funding by ESA through multi-year projects made possible a comprehensive implementation in the most important areas of the vehicle design: structure and propulsion.
The dynamic coupling with DCAP opens a multitude of possibilities to use ASTOS for simulations (spacecraft with flex appendages, docking, towing, robotic arms, landing,...)
ASTOS is therefore an efficient simulation infrastructure to design launchers up to the phase B1.
This software is commercially available to all interested entities worldwide.
© 2018 Astos Solutions GmbH
ICATT November

31. © 2018 Astos Solutions GmbH
ICATT November