Transcript Document

Multi-disciplinary Design Optimisation
Strategy in Multi-stage Launch Vehicle
Conceptual Design
 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
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.
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
Mission
Requirements
Vehicle
sizing
Propulsion
Options
& design
Layout &
Surface
geometry
Weight &
C.G
Structural,
Control & Thermal
Analyses
Vehicle Configuration
Dimensions
Steering rate history
Trajectory
Analyses
Aerodynamic
Analysis
Launch vehicle conceptual design process
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.
Resize
Vehicle
Vehicle
sizing
Vehicle
performance
Determine
Performance
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”
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.
Introduction to LV Conceptual Design Process
Vehicle
Concept
options
Mission
Requirements
Propulsion
option
Technology
options
Layout &
Surface
geometry
Aerodynamic
analysis
Trajectory
analysis
Structural,
Control, thermal
Propulsion
analyses
Configuration,
Weights
and sizing
Cost
Analysis
Operational
analysis
Operational
options
Rethink/modify
requirements
and options
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.
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.
Introduction to LV Conceptual Design Process
To improve results during conceptual design:
(i) Improvement of disciplinary analysis,
modelling and tools that capture, with
sufficient fidelity, the major relationships
among design variables and system
objectives.
(ii) 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.
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.
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.
Literature Review on MDO Works
Related to Launch Vehicle Design
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.
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
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, JulyAugust,1997.
Iterative-loop solution strategy
Optimizer
Minimize J=dry weight
Design variables(40)
Subject to inflight and terminal constraints
Initial guess at
GLOW, Sref
Base diameter
Landed weight
Inflight &
Terminal
Constraints
Trajectory
Weights & Sizing
GLOWc, Srefc
Base diameterc
Landed weightcDry weight
propulsion
GLOW=GLOWc
Sref=Srefc
Landed wt =Landed wtc
base diameter =base diameterc
N0
Delta
=(GLOWc-GLOW)2
+(Srefc-Sref) 2
+(Landed wtc-Landed wt) 2
+(base diameterc- base diameter) 2
Done
Is
Delta
small
Yes
Sequential compatibility-constraint solution
Optimizer
Minimize J=dry weight
Design variables(40)
Subject to inflight and terminal constraints
Trajectory
propulsion
Inflight & terminal
constraints
Compatibility constraints
GLOWc-GLOW =0
Srefc-Sref = 0
Landed wtc-Landed wt= 0
base diameterc- base diameter= 0
Weights & Sizing
GLOWc
Srefc
Landed wtc
Dry weight
base diameterc
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.
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
Literature Review on MDO works on LV design
Collaborative optimization architecture for launch vehicle design
Literature Review on MDO works on LV design
MDO
Architecture
Iterative
method
Combatiblity
Constraint
Collaborative
Function
Evaluation
Modification
time, month
Communication
Requirements
10482
4
66
3182
3
65
312524840
1
23
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.
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
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.
Literature Review on MDO works on LV design
Mass
Estimate
Opt
Loop
System
scaling
Verification
And valuation
Flight
simulation
Design
Aerodynamic
cycle Aerothermodynamic
Model
definition
Multistep sequential procedure
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.
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
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 twostage, 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.
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
optimize the entire mission.
then
used
to
• Hence, a two-level optimization procedure
results,
with
the
master-level
algorithm
optimally coordinating the solution of the
subproblems.
Literature Review on MDO works on LV design
Schematic diagram Decomposition of segments
Segment 3
h
Segment 1
Segment 2
Literature Review on MDO works on LV design
Master Problem:
Maximize upper-stage payload mass
Independent variables:
Staging Mach number
Longitude at staging
Load factor at pull-up
Time interval for pull-up
Subproblem 1:
Subproblem 1:
Subproblem 1:
Minimize: Booster stage
ascent propellant
Minimize: Booster stage
flyback propellant
Minimize: Orbiter ascent
propellant
Subject to:
Staging Mach no. (master
contr.)
Staging longitude(master
contr.)
Latitude at staging
heading staging
Independent variables:
flight heading after take-off
supersonic cruise flight
length
bank angle control
parameter determines the
length of the turn flight
Subject to:
Max flight acceleration
Max dynamic pressure
End head towards landing
site
Subject to:
Max long. Flight acceleration
Perigee velocity
Perigee altitude
Perigee path angle
Independent variables:
Angle of attack control
Bank angle control
Parameter determines the
length of the turn flight.
Independent variables:
Angle of attack control
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.
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
parameters.
considers
five
design
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
for study.
considered
• RSM was used to determine the minimum
dry
weight
entry
vehicle
to
meet
constraints on performance.
Literature Review on MDO works on LV design
Ref: Olds, J., and Walberg, G., ”Multidisciplinary
of a Rocket-Based Combined-Cycle SSTO
Vehicle using Taguchi Methods”
,
AIAA
Feb,1993.
Design
Launch
93-1096,
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).
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
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
reference vehicle system
• Selecting one
configurations
among
existing
canididate
• Subsystem optimization with respect
to vehicle performance.
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.
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.
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.
Preliminary Work Done
Preliminary Work Done
Aim:
To demonstrate the effect of bringing ‘Mass
estimation discipline’ into conceptual
design
Problem considered:
Choose a configuration with two-stageto-orbit vehicle to inject 20t payload at
400km circular orbit.
Assumptions:
V loss
Structural factors (1, 
Specific Impulse
2
)
m

m m
s
s
p
Preliminary Work Done
Preliminary Work Done
Orbit Specifications
Choice of propulsion
Payload
Isp1, Isp2
Vtotal
 1,  2
Initialize V1
Ideal velocity
calculations
ms1,mp1
ms2,mp2,
mpf
LOW
Assumptions
V loss
Structural factors
(1,  2 )
Vary
V1
No
Is LOW
minimum
Yes
Optimum
LOW &
Configuration
Preliminary Work Done
Dy. Pressure
Load factor
Area ratios
Fineness
ratios
mp1
mp2,
mpf
Sizing of tanks
Weight
estimation
ms1e,ms2e
Preliminary Work Done
Orbit Specifications
Choice of propulsion
Payload
Isp1, Isp2
Vtotal
 1,  2
Initialize V1
ms1,mp1
ms2,mp2,
mpf
LOW
Ideal velocity
calculations
Dy. Pressure
Load factor
Area ratios
Fineness
ratios
Sizing of tanks
ms1e,ms2e
Assumptions
V loss
Structural factors
(1,  2 )
Vary  1,  2
No
Is
ms1= ms1e
ms2= ms2e
Weight
estimation
Yes
LOW
Vary
V1
No
Is LOW
minimum
Yes
Optimum
LOW &
Configuration
Preliminary Work Done
Preliminary Work Done
Configurati LOW
on
(t)
Payload
Fraction
Without
Mass est.
C209+C85
366
5.5
With
Mass est.
C197+C55
299
6.7