ariane5 coupled loads analysis - nafems · estec, october 9, 2003 ariane 5 coupled loads analysis 1...

ESTEC, October 9, 2003 Ariane 5 Coupled Loads Analysis 1

ESTEC Structures Section TOS-MCSAtos Origin Engineering Services B.V.

ArianeAriane 5 Coupled Loads Analysis5 Coupled Loads Analysis

FENET Technology WorkshopsFENET Technology WorkshopsMultiMulti--Physics and Analysis ProgrammePhysics and Analysis Programme

ESTEC, October 9, 2003ESTEC, October 9, 2003Hermann Fischer AOES, ESA/ESTEC Structures Hermann Fischer AOES, ESA/ESTEC Structures

SectionSection



Table of ContentsTable of Contents

IntroductionObjectives

Launcher Ariane5 Launcher FEM Model

Methods Software Tools

Payload FEM ModelLoadcases

Example PLResults

Concluding Remarks



IntroductionIntroduction• Dynamic coupled loads analysis (CLA) is carried out as part of the mission

analysis study and is used as verification tool for payload dimensioning.• CLA predicts responses of launcher (LV) & payload (PL) caused by dynamic

and quasi-static loads such as

– Liftoff from launch table – Gravity loads– Engine startup and shutdown – Engine thrust (constant)– Blastwaves from solid rocket ignition – Stage separation loads– Aerodynamic loads, gust at Transonic and Qmax– Internal acoustic modes in solid rockets

• Results are used to design or to verify the design of the payload, its qualification test plan including a notching procedure if applicable, to verify the final in-flight loads, and to make sure that the PL does not affect the behaviour of the LV or its stability.



ObjectivesObjectives

• Internal quick & preliminary assessment of spacecraft early projects and studies

• Assessment of merits of alternative designs• Robustness of loads• Preliminary CLA for satellite project teams• Maintain CLA expertise within TOS-MCS

• The TOS-MCS CLA tool is not meant to replacelauncher authority intermediate or final CLA



Launcher Ariane5Launcher Ariane5

Europe’s heavy launcher

Height from 45 to 56 mDiameter 5.4 m / 3.0 mLiftoff mass 710 - 790 t

Thrust at Liftoff 10,600 kNPerformance in GTO 6 - 10.5 t



Launcher Ariane5 (continued)Launcher Ariane5 (continued)

EPS (Upper stage)Height 3.35 m

Diameter 3.96 mDry mass 1.2 t

EPC (Cryogenic stage)Height 30.525 mDiameter 5.458 mDry mass12.5 tPropellants 132.37 t of LOX

25.84 t of LH2Structure Aluminum AZ 2219 Engine VulcainThrust 1,114 kNCombustion duration 590 s

EAP (SRB)Height 31.605 m

Diameter 3 mDry mass 40 t each

Propellants 237 t eachStructure Steel

Engine MPS with flexible nozzle

Thrust at lift off 6,709 kNeach

Combustion duration 129 sSeparation altitude between

55 & 70 km Propellants 3.2 t MMH, 6.5 t N2O4Engine AestusThrust 29 kNCombustion duration 1,100 s



Launcher FEM ModelLauncher FEM Model

• Features, Assumptions

– Dynamic effects up to about 100 Hz– 3D FE models of EPC, EAP, UC– Structure/fluid interaction– Incompressible or compressible fluid models for liquid propellants – Nearly incompressible SRB solid propellant modeling– Pressure and stress effects on launcher stiffness– Flexible interfaces between modules and LV-PL

interface (1, 16 or 36 node I/F)– SRB propellant and DIAS structural damping

evaluated for major modes (equivalent viscousdamping ratios used in direct transient or frequency response analysis)



• Models

EPC EAP

H158 H173

Launcher FEM Model (continued)Launcher FEM Model (continued)




• Propellant ModelsEPC LOX and LH2 liquid propellant BEM models

SRB propellant models for different flight events




• UpperCompositeModels

ESC-A

EPS



MethodsMethods• For accurately and efficiently performing CLA a number of methods are used

– Modal synthesis (Craig-Bampton method)– Prestress effects in tanks– Substructuring techniques – BEM for slosh and coupled structure/fluid modes of LV with liquid propellant– Efficient direct transient analysis for systems with changing boundary conditions– OTMs for accurate and efficient recovery of physical responses in the PL (mode

acceleration method, modal truncation augmentation method)

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Software ToolsSoftware Tools

• A number of different tools are used to perform specific computations, execute repetitive tasks, avoid error through editing, visualisation of results and pre- and postprocessing

– MSC.NastranTM (DMAP)– Fabe (Fluid Analysis with Boundary Elements)– MSC.PatranTM

– DynaWorks® (software package for managingand analysing dynamic environmental data, suchas vibrations, shocks, acoustics and thermalmeasurements)

– Fortran routines– UNIX scripts

Module

Mf,Kf

δ K

CB M,D,K

CB F

Flight event

f90



Payload FEM ModelPayload FEM Model

• Smart-1 (Small Missions for Advanced Research in Technology)

– mass 370 kg– Lunar exploration, technology

demonstrator– launched by Ariane5 Generic 10 days

ago, flight V162– ~50000 physical DOFs– 292 DOFs reduced model

• 192 DOFs interface to LV• 100 modal DOFs

(both physical or CB models can behandled)



LoadcasesLoadcasesFlight event Forcing functions Liftoff SRB thrust build-up, detachment from launch

table, blast waves, gimballing* Transonic (Mach 1.05) Aerodynamic gust pitch and yaw, buffeting on

nozzle*, gimballing* Maximum Dynamic Pressure Qmax (Mach 2.00)

Aerodynamic gust pitch and yaw, gimballing*

Maximum Acceleration SRB pressure oscillations in-/opposite-phase, 1st/2nd acoustic mode, gimballing*

End of Flight SRB Separation of SRBs from EPC End of Flight EPC Thrust tail-off and engine shut-down (chugging)

* currently not considered



• SRB ignitionBlastwave

Duct over pressure wave

LoadcasesLoadcases (continued)(continued)

EAPP

EAPM

3.00 3.15 3.30 3.45 3.60 3.75 3.90 4.05 4.20 4.35 4.500.

1.000+06

2.000+06

3.000+06

4.000+06

5.000+06

6.000+06

7.000+06



LoadcasesLoadcases (continued)(continued)

• SRB pressure oscillations / EPC chugging

SRB internal acoustic modes excited by vortices

Shutdown of Vulcain engine

0. .10 .20 .30 .40 .50 .60 .70 .80 .90 1.0

-13500.

-9000.

-4500.

0.

4500.

9000.

13500.

time 580 sec +

force

z=-4.7095 m

z=-29.406 m

+ - ∆pressure + -

+

∆pressure



Example PLExample PL

• CLA analysis steps

– Mass, stiffness, damping and load matrices in CB format from LV lower composite (LC) library

– Assembly of FE models, and generation of mass, stiffness, damping and load matrices in CB format for LV upper composite (UC)

– Verification and preparation of PL model, and OTMs

– Definition of loadcases to be analyzed– Performance of CLA for all selected loadcases

using scripts– Postprocessing of results

geometric stiffness fluid matrices

save CB model

plotting of modes

transformation of forces

damping matrix

modal selection

clamped normal modes

static I/F modes CB&ERD

read fluid/geometric stiffness

assembly of substructure



Example PL (continued)Example PL (continued)

definition of CB model

EPC CB model UC CB model

EAP- CB model P/L CB model

EAP+ CB model

plot modeshapes

modal analysis transient response frequency response

equivalent sine

plot responses

min/max responses

post-processing of I/F response

plot responses

min/max responses

internal PL

store in database

recovery PL

assembly of substructures

• CLA



Example PL (continued)Example PL (continued)

• Results are obtained directly from response analysis in time or frequency domain or after postprocessing

– Time histories of accelerations, forces and displacements– Min/max values accelerations, forces and displacements– Quasi-static load factors (equivalent to low frequency dynamic loads,

accelerations at CoG)– Equivalent sine– Stresses inside PL– MPC forces inside PL

• At the PL base, CoG and at other specific locations within the PL



ResultsResultsLoadcase

x y z Rx Ry Rz lateralpitch yaw roll

LO symmetric 1.13 4.36 12.66 0.68 0.17 0.59 4.36N121

LO non-symmetric 7.17 2.53 12.43 0.41 2.12 0.48 7.17N122

TR pitch/perpend max -0.10 1.43 19.79 0.30 0.02 -0.01 1.43N202 min 0.09 -0.43 -0.26 -0.02 0.44

TR yaw/parallel max 0.95 -0.11 19.79 -0.03 0.27 0.01 0.95N212 min -0.66 0.10 0.03 -0.24 0.67

MP pitch/perpend max -0.38 3.24 22.73 0.63 0.06 0.02 3.25N501 min 0.35 -1.56 -0.56 -0.05 1.60

MP yaw/parallel max 2.39 -0.36 22.74 -0.07 -0.59 -0.02 2.39N511 min -1.92 0.29 0.06 0.46 1.94

EBP 1st mode in-phase 0.15 0.20 3.59 0.22 0.14 0.21 0.25N301 f [Hz] 24.30 24.30 19.30 24.30 24.30 24.00 24.30

EBP 1st mode opposite-phase 1.63 0.85 0.08 0.39 0.46 0.10 1.65N302 f [Hz] 17.10 18.50 20.10 24.40 22.60 24.10 17.10

EBP 2nd mode in-phase 0.27 0.88 0.48 0.18 0.06 0.30 0.90N311 f [Hz] 47.00 48.00 48.00 48.00 47.00 47.80 48.00

EBP 2nd mode opposite-phase 2.15 0.45 0.20 0.10 0.32 0.05 2.19N312 f [Hz] 48.00 47.80 47.20 48.00 48.00 48.00 48.00

EBS symmetric 7.14 6.29 44.77 6.49 1.97 6.99 7.60N602

EBS non-symmetric long. 23.31 12.76 22.75 6.07 8.71 6.78 23.42N612

EBS non-symmetric lateral 22.46 6.86 28.41 4.82 8.47 -6.93 22.58N622

EE 1.26 2.90 1.63 1.00 0.27 0.19 2.96N401

maximum 23.31 12.76 44.77 6.49 8.71 6.99 23.42

[ACCE/ACCL,XDDA/XDDL] [ms-2] [ms-2] [ms-2] [rads-2] [rads-2] [rads-2] [ms-2]

Degree of Freedom (Launcher System)

• ModeshapesMin/max response



Results (continued)Results (continued)

• Accelerations at PL base



Results (continued)Results (continued)

• Forces at PL base



Concluding RemarksConcluding Remarks

• For CLA a number of phenomena are taken into account

– Elastic behaviour of a structure– Sloshing in large tanks including fluid-structure interaction– Aerodynamic and acoustic loading

– Gimballing of nozzles (SRB, cryogenic stage, considered by QSL factor)

– Aeroelasticity: interactions between structural dynamics and airloads– Effects of buffeting: excitation of nozzle pendulum modes– Loading generated by control system: loads ⇒ f (control law)

• CLA needs a ready-for-use LV model to respond quickly to project request

ariane5 coupled loads analysis - nafems · estec, october 9, 2003 ariane 5 coupled loads analysis 1...

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