Multidisciplinary Design Optimisation Strategy in Multistage Launch Vehicle Conceptual Design

1
Multi-disciplinary Design Optimisation Strategy
in Multi-stage Launch Vehicle Conceptual Design
2

• Introduction to Launch Vehicle (LV) conceptual
  design process
• Literature survey on Multi-disciplinary Design
  Optimisation(MDO) in LV design
• Proposed research work
• Preliminary work done

3
Introduction to LV Conceptual Design Process

• Design of Launch Vehicle
• Making appropriate comprises to achieve balance
  among many coupled objectives.
• Objectives
• High performance
• Safety
• Simple operation
• Low cost
• Conceptual design
• To reveal trends and allow relative comparison
  among alternatives, while design flexibility
  exists.

4
Introduction to LV Conceptual Design Process

• Outcome of conceptual design
• Number of stages
• Type of stage/propellant
• Mass split of stages
• Thrust levels and propulsive system details
• External layout

5
Mission Requirements
Propulsion Options design
Layout Surface geometry
Vehicle sizing
Weight C.G
Structural, Control Thermal Analyses
Trajectory Analyses
Vehicle Configuration Dimensions Steering rate
history
Aerodynamic Analysis
Launch vehicle conceptual design process
6
Introduction to LV Conceptual Design Process

• Determining the optimum configuration
• The evaluation of the interaction between the
  vehicle systems
• The impact of this system upon the vehicles
  ability to perform the desired mission.

7
Introduction to LV Conceptual Design Process

• Optimum values of design parameters
• Vehicle performance will be carried out to
  examine the value of each parameters by fixing
  the values of remaining parameters.
  one-variable-at-a-time approach

8
Introduction to LV Conceptual Design Process

• Conceptual design of Advanced Manned Launch
  System
• Ref Stanley, D.O., Talay, A.T., Lepsch, R.A.,
  Morris, W.D., Kathy, E.W. Conceptual Design Of
  A Fully Reusable Manned Launch System. Journal
  of Spacecraft And Rockets, Vol 29, No.4, pp
  529-537, July-August, 1992
• Reference vehicle geometry is chosen after all
  discipline analyses were carried out.
• After finalising the reference vehicle, a series
  of parametric trade studies were performed to
  determine the major vehicle parameters.

9
Introduction to LV Conceptual Design Process
10
Layout Surface geometry
Vehicle Concept options
Aerodynamic analysis
Mission Requirements
Trajectory analysis
Structural, Control, thermal Propulsion analyses
Propulsion option
Configuration, Weights and sizing
Technology options
Cost Analysis
Operational analysis
Operational options
Rethink/modify requirements and options
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Introduction to LV Conceptual Design Process

• The limitations associated with conceptual design
  are
• Conceptual design is carried out with low
  fidelity models
• The relationships among design and the conceptual
  design parameters are often not well modeled or
  understood.
• In one-variable-at-a-time approach, the impact
  of simultaneously considering all variables is
  not considered Result in near optimum
  configuration.

12
Introduction to LV Conceptual Design Process

• These limitations result in probably inefficient
  final design - Leaving room for significant
  improvements in performance and reduction in life
  costs.

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Introduction to LV Conceptual Design Process

• To improve results during conceptual design
• Improvement of disciplinary analysis, modelling
  and tools that capture, with sufficient fidelity,
  the major relationships among design variables
  and system objectives.
• The development of methods for coordinating the
  engineering analysis and optimising the total
  launch vehicle system.
• (iii) All-at-same-time approach is to be
  adopted.

14
Introduction to LV Conceptual Design Process

• All these can be achieved by design of all
  systems together should be iteratively refined
  together, with sufficient fidelity models, by
  MDO scheme.
• This was not practical earlier because of high
  computational expenditure associated with
  numerical prediction methods.
• Now, with availability of various methods and
  computational capabilities an MDO based
  conceptual design can be made.

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Introduction to LV Conceptual Design Process

• MDO based conceptual design will allow system
  engineers to systematically explore the vast
  trade space and consider many more
  configurations during the conceptual design phase
  before converging on the final design.

16
Literature Review on MDO Works Related to Launch
Vehicle Design
17
Literature Review on MDO Works on LV Design

• Performance optimisation of launch Vehicle
• System design Vehicle characteristic and
  parameters like number of stages engine sizing.
• Trajectory optimisation - Control vector that
  optimises the performance for the chosen
  configuration.
• Ideally, design of the vehicle and propulsion
  system and trajectory shaping should be
  iteratively refined together by a coupled MDO
  scheme to obtain solution.

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Literature Review on MDO works on LV design

• MDO approaches in LV design
• To optimise vehicle performance is collect
  all elements of the trajectory control vector and
  system design variables in one vector of
  optimisation parameters to be manipulated by an
  appropriate algorithm.
• This approach has been applied successfully
  to ascent mission of Rocket powered
  single-stage-to-orbit.
• (I) Iterative loop MDO strategy
• (ii) Sequential compatibility constraint
  solution
• (iii) Collaborative Optimization

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Literature Review on MDO works on LV design

• References
• Braun, R. D., Powell, R. W., Lepsch, R. A..
  Stanley, D. 0., and Kroo, 1. M., "Comparison of
  Two Multidisciplinary Optimization Strategies for
  Launch-Vehicle Design," Journal of Spacecraft and
  Rockets, Vol. 32, No. 3, 1995,pp.404-410.
• Braun, R.D. and Moore., Collaborative approach
  to launch vehicle design Journal of Spacecraft
  and Rockets, Vol. 34, No.4, pp 478-485,
  July-August,1997.

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Iterative-loop solution strategy
Optimizer Minimize Jdry weight Design
variables(40) Subject to inflight and terminal
constraints
Initial guess at GLOW, Sref Base diameter Landed
weight
propulsion
GLOWGLOWc SrefSrefc Landed wt Landed
wtc base diameter base diameterc
Inflight Terminal Constraints
Trajectory
N0
Delta (GLOWc-GLOW)2 (Srefc-Sref) 2
(Landed wtc-Landed wt) 2 (base diameterc-
base diameter) 2
Is Delta small
Weights Sizing
GLOWc, Srefc Base diameterc Landed weightc
Yes
Dry weight
Done
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Sequential compatibility-constraint solution
Optimizer Minimize Jdry weight Design
variables(40) Subject to inflight and terminal
constraints
propulsion
Trajectory
Inflight terminal constraints
Weights Sizing
Compatibility constraints GLOWc-GLOW
0 Srefc-Sref 0 Landed wtc-Landed wt 0 base
diameterc- base diameter 0
GLOWc Srefc Landed wtc base diameterc
Dry weight
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Literature Review on MDO works on LV design

• Advantages of sequential compatibility constraint
  approach
• i) being 3-4 times more computationally
  efficient
• ii) providing greater flexibility in the way
  in which consistency is maintained across
  disciplinary boundaries, and
• iii) a smoother design space.
• Disadvantage
• The compatibility constraint approach is in
  situations terminates without reaching the
  solution - Because multidisciplinary
  feasibility is only guaranteed at a solution in
  this approach, the design information could be
  invalid.

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Literature Review on MDO works on LV design

• Collaboration optimization
• A problem is decomposed into subproblems along
  domain-specific boundaries.
• Through subspace optimization, each group is
  given control over its own set of local design
  variables and is charged with satisfying its own
  domain-specific constraints.
• The objective of each subproblem is to reach
  agreement with the other groups on values of the
  interdisciplinary variables.
• A system-level optimizer is employed to
  orchestrate this interdisciplinary compatibility
  process while minimizing the overall objective

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Literature Review on MDO works on LV design
Collaborative optimization architecture for
launch vehicle design
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Literature Review on MDO works on LV design
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Literature Review on MDO works on LV design

• Ref Tsuchiya, T. and Mori. T.
  Multidisciplinary Design Optimization to
  future space transportation vehicle. AIAA
  2002-5171.
• MDO method to choose the best among the seven
  typical concepts of RLV.
• The design variables are representing geometry
  and shape of vehicles, flight performance
  parameters
• Similar to Sequential Compatibility Constraint
  Solution.

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Literature Review on MDO works on LV design

• Ref Hillesheimer, M., Schotlle, U. M. and
  Messerschmid, E., "Optimization of Two-Stage
  Reusable Space Transportation Systems with Rocket
  and Airbreathing Propulsion Concepts,"
  International Astronautical Federation Paper
  92-O863, Sept. 1992
• Though these MDO architectures has been applied
  successfully to the ascent mission of single
  stage vehicle, it has shown poor convergence
  properties even for less complex mission examples
  of an expendable multistage rocket launches, when
  major system design parameters such as the mass
  split of stages or engine sizing were included
  to optimize trajectory control and vehicle
  parameters simultaneously

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Literature Review on MDO works on LV design

• Proposed another approach that avoids this
  difficulty is a multistep sequential optimization
  procedure.

• Consists of a performance optimization cycle
  (inner loop) and a vehicle design cycle (outer
  loop).
• Inner loop uses the data of the latter to
  determine the control functions and major system
  parameters yielding the optimum performance -
  responds to varying vehicle size needs as long
  as the departure from the preset design (outer
  loop) remains small.

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Literature Review on MDO works on LV design
Multistep sequential procedure
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Literature Review on MDO works on LV design

• Otherwise, a vehicle redesign including system
  modifications and reevaluation of the aerodynamic
  coefficients (which are held constant in the
  inner optimization cycle) is performed in
  separate computations in the outer iteration
  loop.
• The latter requires manual interaction and is
  supported by graphic interface tools.
• This scheme outlined above is applied to enhance
  the performance of a reusable rocket launcher
  which is part of Ariane X family.

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Literature Review on MDO works on LV design

• Two design software based on the schemes similar
  to multistage sequential optimization process.
• FASTPASS (Flexible analysis for synthesis
  trajectory and performance for advanced space
  systems) developed by Lockheed Martin
  Astronautics and
• SWORD (Strategic Weapon Optimisation for rapid
  Design) developed by Lockheed Missile design and
  space Co. for solid motor missile.
• References
• Szedula, J.A., FASTPASS A Tool For Launch
  Vehicle Synthesis, AIAA-96-4051-CP, 1996.
• Hempel, P. R., Moeller C. P., and Stuntz L.
  M., Missile Design Optimization Experience And
  Developments, AIAA-94-4344,1994-CP

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Literature Review on MDO works on LV design

• Ref Rahn, M. and Schottle, U. M., "Decomposition
  Algorithm for Performance Optimization of a
  Launch Vehicle," Journal of Spacecraft and
  Rockets, Vol. 33, No. 2, 1996, pp. 214--221.
• Though Multistep sequential scheme was able
  to solve the optimization problem of a two-stage,
  winged rocket launch vehicle designed for
  vertical takeoff, severe convergence problems
  were encountered when it was applied to the more
  complex mission of an airbreathing launch
  vehicles.
• These difficulties were attributed in part
  to different performance sensitivities of the
  various flight phases, controls, and major system
  design parameters, and to scaling problems.

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Literature Review on MDO works on LV design

• Proposes a decomposition approach to solve
  the overall optimization problem of a Reentry
  launch system.
• Partitioning the trajectory into subarcs such
  that each mission segment can be optimized
  independently.
• These subproblems constitute the first level of
  optimization.
• A second-level controller is then used to
  optimize the entire mission.
• Hence, a two-level optimization procedure
  results, with the master-level algorithm
  optimally coordinating the solution of the
  subproblems.

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Literature Review on MDO works on LV design
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Literature Review on MDO works on LV design
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Literature Review on MDO works on LV design

• MDO methods may be divided into three groups
• i) Parameters methods based on design of
  experiments (DOE) techniques
• ii) Gradient or Calculus based methods
• iii) Stochastic methods such as genetic
  algorithm and simulated annealing.
• Parametric methods as well as gradient based
  methods are applicable at conceptual design
  phase.

37

Literature Review on MDO works on LV design

• Ref Stanley, D. O., Unal, R., and Joyner, C.
  R., "Application of Taguchi Methods to Dual
  Mixture Ratio Propulsion System Optimization for
  SSTO Vehicles," Journal of Spacecraft and
  Rockets, Vol. 29, No. 4, 1992, pp. 453-459.
• Taguchi design method to determine the thrust
  levels of a variety of engine and vehicle
  parameter for single-stage-to-orbit vehicle.
• This study considers five design parameters.

38
Literature Review on MDO works on LV design

• Ref Stanley, D. 0., Engelund. W. C., Lepsch.
  R. A., McMillin, M. L.Wt K. E.. Powell. R. W.,
  Guinta. A. A., and Unal, R. "Rocket-Powered
  Single Stage Vehicle Configuration Selection and
  Design," Journal of Spacecraft and Rockets,
  Vol. 31, No. 5, 1994. pp. 792-798 also AIAA
  Paper93-Feb. 1993.
• The configuration selection for rocket powered
  single stage vehicle configuration using RSM.
• Five configuration parameters considered for
  study.
• RSM was used to determine the minimum dry weight
  entry vehicle to meet constraints on performance.
  

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Literature Review on MDO works on LV design

• Ref Olds, J., and Walberg, G.,
  Multidisciplinary Design of a Rocket-Based
  Combined-Cycle SSTO Launch Vehicle using
  Taguchi Methods , AIAA 93-1096, Feb,1993.
• Taguchi method was used to evaluate the
  effects of changing 8 design variables (2 of
  which were discrete) in an "all at the same time"
  approach.
• Design variables pertained to both the
  vehicle geometry (cone half-angle, engine cowl
  wrap around angle) and trajectory parameters
  (dynamic pressure limits, heating rate limits,
  and airbreathing mode to rocket mode transition
  Mach number).

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Literature Review on MDO works on LV design

• Ref Anderson, m., Burkhalter J., and Jenkins R
  Multidisciplinary Intelligence Systems
  Approach To Solid Rocket Motor Design, Part I
  Single And Dual Goal Optimization. AIAA
  2001-3599, July, 2001.
• Investigated the potential of using a
  multidisciplinary genetic algorithm approach to
  the design of a solid rocket motor propulsion
  system as a component within overall missile
  system. Aerodynamics and trajectory performance
  disciplines were considered in this study

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Literature Review on MDO works on LV design

• A survey on literature reveals that MDO works
  related to conceptual design, that is,
  simultaneous optimization of system and
  trajectory are limited to
• Enhancement of an existing reference vehicle
  system
• Selecting one among canididate configurations
• Subsystem optimization with respect to vehicle
  performance.

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Literature Review on MDO works on LV design

• This may be attributed to the focused effort on
  the Advanced Manned Launch System (AMLS) activity
  since 1988. Two vehicles, single stage and two
  stages were used for this AMLS mission and all
  further design studies are to optimize the
  performance of these configuration.
• Also, other recently developed vehicles are
  designed by evolution strategy.

43
Proposed Research Work

• An MDO strategy with following capability would
  be useful in developing a new vehicle.
• That is, given the range of realizable mass
  fraction and specific impulse, the scheme should
  be able to decide number of stages, mass and
  propellant fraction and iterate this vehicle,
  propulsion system and trajectory shaping and give
  optimum configuration and trajectory that meets
  the specification.

44
Proposed Research Work

• This would be useful when no propulsion system or
  technological constraints are identified and the
  initial trade space is being defined.
• This scheme may come up with a design which is
  non- intuitive and much better than traditional
  design technique.
• Development of such scheme is the aim of present
  research effort.

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Preliminary Work Done
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Preliminary Work Done

• Aim
• To demonstrate the effect of bringing Mass
  estimation discipline into conceptual design
• Problem considered
• Choose a configuration with
  two-stage-to-orbit vehicle to inject 20t payload
  at 400km circular orbit.
• Assumptions
• ?V loss
• Structural factors (?1, ? 2 )
• Specific Impulse

47
Preliminary Work Done
48
Preliminary Work Done
Orbit Specifications Payload
Choice of propulsion Isp1, Isp2
ms1,mp1 ms2,mp2, mpf LOW
?Vtotal ? 1, ? 2
Ideal velocity calculations
Initialize ?V1
Assumptions ?V loss Structural factors (?1, ? 2 )
Optimum LOW Configuration
Is LOW minimum
Vary ?V1
Yes
No
49
Preliminary Work Done
Dy. Pressure Load factor Area ratios Fineness
ratios
mp1 mp2, mpf
Sizing of tanks
Weight estimation
ms1e,ms2e
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Preliminary Work Done
Dy. Pressure Load factor Area ratios Fineness
ratios
Orbit Specifications Payload
Choice of propulsion Isp1, Isp2
ms1,mp1 ms2,mp2, mpf LOW
?Vtotal ? 1, ? 2
Ideal velocity calculations
Initialize ?V1
Sizing of tanks ms1e,ms2e
Assumptions ?V loss Structural factors (?1, ? 2 )
Is ms1 ms1e ms2 ms2e
Weight estimation
No
Vary ? 1, ? 2
Yes
LOW
Optimum LOW Configuration
Is LOW minimum
Vary ?V1
Yes
No
51
Preliminary Work Done
52
Preliminary Work Done