2009 SEAri Annual Research Summit. Research Report. Design for Survivability: Concept Generation and Evaluation in Dynamic Tradespace Exploration

Transcription

1 29 Research Report Design for Survivability: Concept Generation and Evaluation in Dynamic Tradespace Exploration Matthew Richards, Ph.D. (Research Affiliate, SEAri) October 2, 29 Cambridge, MA Massachusetts Institute of Technology

2 Agenda Problem Statement Research Questions Methodology Overview Case Application: Satellite Radar Discussion Future Work PhD in Engineering Systems, June 29 Thesis Committee: Dean Daniel Hastings (Chair) Dr. Adam Ross Prof. Annalisa Weigel Dr. Donna Rhodes 29 Massachusetts Institute of Technology 2

3 Problem Statement Temporal system properties known as ilities (e.g., flexibility) are a critical design challenge for engineering systems Survivability is a critical challenge for aerospace system architecture Given limitations of survivability engineering for aerospace systems,* need design methodology that:. incorporates survivability as an active trade throughout design process 2. reflects dynamics of operational environments over entire lifecycle 3. captures path dependencies of system vulnerability and resilience 4. extends in scope to architecture-level survivability assessments 5. takes a value-centric perspective Opportunity to build on recent research on dynamic tradespace exploration (Ross 26) Application of survivability methodology may address critical issue for military space Satellite radar architecture development *Richards, M., Hastings, D., Rhodes, D., and Weigel, A., Systems Architecting for Survivability: Limitations of Existing Methods for Aerospace Systems, 6th Conference on Systems Engineering Research, Los Angeles, CA, April Massachusetts Institute of Technology 3

4 Research Questions. What is a dynamic, operational, and value-centric definition of survivability for engineering systems? 2. What design principles enable survivability? 3. How can survivability be quantified and used as a decision metric in exploring tradespaces during conceptual design of aerospace systems? 4. For a given space mission, how to evaluate the survivability of alternative system architectures in dynamic disturbance environments? 29 Massachusetts Institute of Technology 4

5 Definition of Survivability Ability of a system to minimize the impact of finite-duration disturbances on value delivery through (I) the reduction of the likelihood or magnitude of a disturbance, (II) the satisfaction of a minimally acceptable level of value delivery during and after a disturbance, and/or (III) a timely recovery V(t) value disturbance Epoch: Time period with a fixed context; characterized by static constraints, design concepts, available technologies, and articulated attributes (Ross 26) original state Type I disturbance duration T d Type III degradation V e emergency value threshold Type II recovery V x required value threshold Epoch a Epoch 2 T r permitted recovery time Epoch 3 Epoch b time 29 Massachusetts Institute of Technology 5

6 Survivability Metrics Need to evaluate ability of system to () minimize utility losses and (2) meet critical value thresholds before, during, and after environmental disturbances desirable attributes: value-based, dynamic, continuous time-weighted utility loss Difference between design utility, U o, and time-weighted average utility Internalizes lifecycle degradation Inspired by Quality Adjusted Life Years in health economics* U L U U ( t) T dl T dl = time of design life dt threshold availability Ratio of time above critical value thresholds (V x during baseline Epoch, V e during disturbance and recovery Epochs) to design life Accommodates changing expectations across contexts A T TAT T dl TAT = time above thresholds *Pliskin, J., D. Shepard and M. Weinstein (98). "Utility Functions for Life Years and Health Status." Operations Research, 28(): Massachusetts Institute of Technology 6

7 Multi-Attribute Tradespace Exploration (MATE) for Survivability Define Mission Elicit Attributes Enumerate Disturbances Specify Design Vector Model Baseline Performance Apply Design Principles Model Lifecycle Performance Monte Carlo analysis Calculate Utility Estimate Cost Calculate Survivability Legend MATE Explore Tradespace Evolved New 29 Massachusetts Institute of Technology 7

8 Phases of MATE for Survivability. Elicit Value Proposition Identify mission statement and quantify decisionmaker needs during nominal and emergency states. 2. Generate Concepts Formulate concepts that address decision-maker needs. 3. Characterize Disturbance Environment Develop concept-neutral models of disturbances in operational environment of proposed systems. 4. Apply Survivability Principles Incorporate susceptibility reduction, vulnerability reduction, and resilience enhancement strategies into design vector. 5. Model Baseline System Performance Model and simulate cost and performance of design alternatives to gain an understanding of how decisionmaker needs are met in a nominal operational environment. 6. Model Impact of Disturbances on Lifecycle Performance Model and simulate performance of design alternatives across a representative sample of disturbance encounters to gain an understanding of how decision-maker needs are met in perturbed environments. 7. Apply Survivability Metrics Compute time-weighted utility loss and threshold availability for each design alternative as summary statistics for system performance across representative operational lives. 8. Explore Tradespace Perform integrated cost, utility, and survivability trades across design space to identify promising alternatives for more detailed analysis. 29 Massachusetts Institute of Technology 8

9 Case Application: Satellite Radar Critical issue in national security space Unique all-weather surveillance capability Opportunity for impact given ongoing studies Rich multi-dimensional tradespace Unit-of-analysis: SR architecture Radar payload Constellation of satellites Communications network Availability of data Systems Engineering Advancement Research Initiative (SEAri) Case Application Goal (CBO 27) To assess potential satellite radar architectures for providing the United States Military a global, all-weather, on-demand capability to track moving ground targets; supporting tactical military operations; maximizing costeffectiveness; and surviving disturbances in the natural space environment. 29 Massachusetts Institute of Technology 9

10 Phase : Elicit Value Proposition Attributes: concept-neutral evaluation criteria specified by a decision maker Excluded Attribute Values single-attribute utility curve Utility Excess Attribute Values (typically assigned Utility = ) Attribute value satellite radar attributes k i =/8 k i =/8 k i =3/ number of target boxes k i =9/ target acquisition time (min) 5 5 minimum radar cross section (db) k i =3/ track life (min) number of target boxes minimum radar cross section (m 2 ) minimum detectable velocity (m/s) target acquisition time (min) track life (min) minimum detectable velocity (m/s) k i =/8 2 3 tracking latency (min) tracking latency (min) 29 Massachusetts Institute of Technology

11 Phase 2: Generate Concepts Design Value Mapping Matrix establishes traceability between valuespace and design-space DESIGN VARIABLES Minimum Target RCS Min. Detectable Velocity Tracking Variable Name Definition Range Peak Transmit Power.5 2 [KW] Radar Bandwidth.5 2 [GHz] Radar Frequency X UHF Physical Antenna Area 4 2 [m^2] Receiver Sats per Tx Sat Antenna Type Mechanical vs. AESA Satellite Altitude [km] Constellation Type 8 Walker IDs Comm. Downlink Relay vs. Downlink Tactical Downlink Yes vs. No Processing Space vs. Ground Maneuver Package x, 2x, 4x Tugable Yes vs. No Constellation Option none, long-lead, spare Total Number of Target Boxes Target Acquisition Time Target Track Life Mission Tracking Latency Resolution (Proxy) ATTRIBUTES Imaging Targets per Pass Field of Regard Revisit Frequency Imaging Latency Baseline Cost Programmatics Cost Schedule Actual Costs (Era) Baseline Schedule Actual Schedule (Era) Total Impact 29 Massachusetts Institute of Technology

12 Enumerate disturbances Orbital debris Signal attenuation Phase 3: Characterize Disturbance Environment Gather data on disturbance magnitude and occurrence NASA ORDEM2 debris model Space Surveillance Network Haystack and Haystack radar data Goldstone radar data Long-Duration Exposure Facility Hubble Telescope array impact data Space Shuttle impact data Mir impact data spatial density (objects/km 3 ) km/s 8 Spatial Density Debris Spatial Density (8 km circular, i=42.6º) ORDEM2 spatial density estimates fit (piecewise cubic hermite interpolating polynomial) debris size (cm) Average Orbital Velocity >um >um >mm >cm >cm >m Develop system-independent models of disturbance environment altitude (km) 29 Massachusetts Institute of Technology 2

13 Phase 4: Apply Survivability Principles disturbances Type II Type I T III Survivability Variable Mapping Matrix establishes traceability between environment and design-space atmospheric drag fluctuations arc discharging high-flux radiation micrometeorites / debris signal attenuation change in target characteristics failure of relay backbone loss of tactical ground node design principles concept enhancements design variables (units) prevention reduce exposed s/c area antenna area (m^2) mobility concealment deterrence preemption avoidance hardness redundancy margin heterogeneity s/c maneuvering V (m/s) 9 3 s/c servicing interface 9 ground receiver maneuverability mobile receiver 3 3 radiation-hardened electronics hardening (cal/cm^2) 3 9 bumper shielding shield thickness (mm) 9 duplicate critical s/c functions bus redundancy 9 3 on-orbit satellite spares extra s/c per orbital plan multiple ground receivers ground infrastructure level 3 9 over-design power generation peak transmit power (kw) over-design link budget assumed signal loss (db) 9 over-design propulsion system V (m/s) excess on-board data storage s/c data capacity (gbits) 3 3 excess constellation capacity number of satellites 3 9 interface with airborne assets tactical downlink multiple communication paths communications downlink tactical downlink distribution spatial separation of spacecraft orbital altitude (km) spatial separation of s/c orbits number of planes 3 9 failure mode reduction reduce s/c complexity bus redundancy 9 fail-safe autonomous operations autonomous control antenna type 3 9 flexible sensing operations evolution radar bandwidth (GHz) 9 3 retraction of s/c appendages reconfigurable 9 3 containment s/c fault monitoring and response autonomous control 3 replacement rapid reconstitution constellation spares 3 9 repair on-orbit-servicing s/c servicing interface

14 Phase 4: Apply Survivability Principles disturbances Type II Type I T III Survivability Variable Mapping Matrix establishes traceability between environment and design-space atmospheric drag fluctuations arc discharging high-flux radiation micrometeorites / debris signal attenuation change in target characteristics failure of relay backbone loss of tactical ground node design principles concept enhancements design variables (units) prevention reduce exposed s/c area antenna area (m^2) mobility concealment deterrence preemption avoidance hardness redundancy margin heterogeneity s/c maneuvering V (m/s) 9 3 s/c servicing interface 9 ground receiver maneuverability mobile receiver 3 3 radiation-hardened electronics hardening (cal/cm^2) 3 9 bumper shielding shield thickness (mm) 9 duplicate critical s/c functions bus redundancy 9 3 on-orbit satellite spares extra s/c per orbital plan multiple ground receivers ground infrastructure level 3 9 over-design power generation peak transmit power (kw) over-design link budget assumed signal loss (db) 9 over-design propulsion system V (m/s) excess on-board data storage s/c data capacity (gbits) 3 3 excess constellation capacity number of satellites 3 9 interface with airborne assets tactical downlink multiple communication paths communications downlink tactical downlink distribution spatial separation of spacecraft orbital altitude (km) spatial separation of s/c orbits number of planes 3 9 failure mode reduction reduce s/c complexity bus redundancy 9 fail-safe autonomous operations autonomous control antenna type 3 9 flexible sensing operations evolution radar bandwidth (GHz) 9 3 retraction of s/c appendages reconfigurable 9 3 containment s/c fault monitoring and response autonomous control 3 replacement rapid reconstitution constellation SEAri Annual spares Research Summit 3 9 repair on-orbit-servicing s/c 29 servicing Massachusetts interface Institute 9 of Technology

15 Type II Type I T III Phase 4: Apply Survivability Principles Survivability Variable Mapping Matrix establishes traceability between environment and design-space disturbances atmospheric drag fluctuations arc discharging high-flux radiation micrometeorites / debris signal attenuation change in target characteristics failure of relay backbone loss of tactical ground node design principles concept enhancements design variables (units) prevention reduce exposed s/c area antenna area (m^2) mobility concealment deterrence preemption avoidance hardness redundancy margin heterogeneity s/c maneuvering V (m/s) 9 3 s/c servicing interface 9 ground receiver maneuverability mobile receiver 3 3 radiation-hardened electronics hardening (cal/cm^2) 3 9 bumper shielding shield thickness (mm) 9 duplicate critical s/c functions bus redundancy 9 3 on-orbit satellite spares extra s/c per orbital plan multiple ground receivers ground infrastructure level 3 9 over-design power generation peak transmit power (kw) over-design link budget assumed signal loss (db) 9 over-design propulsion system V (m/s) excess on-board data storage s/c data capacity (gbits) 3 3 excess constellation capacity number of satellites 3 9 interface with airborne assets tactical downlink multiple communication paths communications downlink tactical downlink finalized design vector (n=3888) Orbit Altitude (km) 8 5 Peak Transmit Power (kw).5 2 Walker ID 5/5/ 9/3/2 27/3/ 66/6/5 Radar Bandwidth (MHz) 5 2 Antenna Area (m^2) 4 Comm. Architecture Direct Downlink Only Relay Backbone distribution spatial separation of spacecraft orbital altitude (km) spatial separation of s/c orbits number of planes 3 9 failure mode reduction reduce s/c complexity bus redundancy 9 fail-safe autonomous operations autonomous control antenna type 3 9 flexible sensing operations evolution radar bandwidth (GHz) 9 3 retraction of s/c appendages reconfigurable 9 3 containment s/c fault monitoring and response autonomous control 3 replacement rapid reconstitution constellation SEAri Annual spares Research Summit 3 9 repair on-orbit-servicing s/c 29 servicing Massachusetts interface Institute 9 of Technology

16 Type II Type I T III Phase 4: Apply Survivability Principles Survivability Variable Mapping Matrix establishes traceability between environment and design-space atmospheric drag fluctuations arc discharging high-flux radiation micrometeorites / debris signal attenuation change in target characteristics failure of relay backbone loss of tactical ground node design principles concept enhancements design variables (units) prevention reduce exposed s/c area antenna area (m^2) mobility concealment deterrence preemption avoidance hardness redundancy margin heterogeneity distribution s/c maneuvering disturbances V (m/s) 9 3 s/c servicing interface 9 ground receiver maneuverability mobile receiver 3 3 radiation-hardened electronics hardening (cal/cm^2) 3 9 bumper shielding shield thickness (mm) 9 duplicate critical s/c functions bus redundancy 9 3 on-orbit satellite spares extra s/c per orbital plan multiple ground receivers ground infrastructure level 3 9 over-design power generation peak transmit power (kw) over-design link budget assumed signal loss (db) 9 over-design propulsion system V (m/s) excess on-board data storage s/c data capacity (gbits) 3 3 excess constellation capacity number of satellites 3 9 interface with airborne assets tactical downlink multiple communication paths communications downlink tactical downlink spatial separation of spacecraft orbital altitude (km) spatial separation of s/c orbits number of planes 3 9 failure mode reduction reduce s/c complexity bus redundancy 9 fail-safe autonomous operations autonomous control finalized design vector (n=3888) Orbit Altitude (km) 8 5 Peak Transmit Power (kw).5 2 Walker ID 5/5/ 9/3/2 27/3/ 66/6/5 Radar Bandwidth (MHz) 5 2 Antenna Area (m^2) 4 Comm. Architecture Direct Downlink Only Relay Backbone antenna type 3 9 flexible sensing operations Shield Thickness (mm) evolution radar bandwidth (GHz) 9 3 retraction of s/c appendages reconfigurable containment s/c fault monitoring and response autonomous control 3 replacement rapid reconstitution constellation SEAri Annual spares Research Summit 3 9 repair on-orbit-servicing s/c 29 servicing Massachusetts interface Institute 9 of Technology survivability variables Constellation Spares 2 6

17 Phase 5: Model Baseline System Performance p y p ( ) Satellite Radar Tradespace by Constellation Spares (n=2268) design utility (dimensionless) number of spares lifecycle cost ($B) 29 Massachusetts Institute of Technology 7

18 Phase 5: Model Baseline System Performance p y p ( ) Satellite Radar Tradespace by Constellation Spares (n=2268) utility (dimensionless) design number of spares 2 y( lifecycle cost ($B) Baseline tradespace only internalizes costs of survivability features 29 Massachusetts Institute of Technology 8

19 Phase 6: Model Impact of Disturbances on Lifecycle Performance Design Vector designs 2 U t, A T Static SR Model cross-sectional area debris flux (>mm) shielding downlink(s) debris impacts 5 Monte Carlo runs per constellation Susceptibility t Vulnerability 3 signal attenuation 4 t Cost Utility spare satellites P k % 5% % kinetic energy Survivability Tradespace - No Filtering utility (dimensionless) time-weighted utility loss (99th percentile) threshold availability (st percentile) threshold availability ( st percentile) 6 utility Resilience attenuation loss replace 5 loss lifecycle cost ($B) Survivability Tear Tradespace U L U U ( t) T dl dt A T TAT T dl t 9

20 Phase 7: Apply Survivability Metrics Tear Tradespace - all designs (n=2268) 9 design utility (dimensionless) time-weighted utility loss (95th percentile) threshold availability (st percentile) threshold availability ( st percentile) lifecycle cost ($B) 29 Massachusetts Institute of Technology 2

21 Phase 7: Apply Survivability Metrics Tear Tradespace - all designs (n=2268) 35 Time-Weighted Average Utility - Design 39 (n=5) 9 design utility (dimensionless) number of runs utility loss time-weighted utility loss (95th percentile) threshold availability (st percentile) threshold availability ( st percentile) lifecycle cost ($B) 29 Massachusetts Institute of Technology 2

22 Phase 8: Explore Tradespace Tear Tradespace - all designs (n=2268) 9 design utility (dimensionless) time-weighted utility loss (95th percentile) threshold availability (st percentile) threshold availability ( st percentile) lifecycle cost ($B) 29 Massachusetts Institute of Technology 22

23 Magnify Tear Tradespace Tear Tradespace (magnified) 9 design utility (dimensionless) threshold availability ( st percentile) lifecycle cost ($B) time-weighted utility loss (95th percentile) threshold availability (st percentile) 29 Massachusetts Institute of Technology 23

24 Magnify Tear Tradespace Tear Tradespace (magnified) 9 design utility (dimensionless) Still too many designs to consider threshold availability ( st percentile) time-weighted utility loss (95th percentile) threshold availability (st percentile) lifecycle cost ($B) 29 Massachusetts Institute of Technology 24

25 Identify Pareto-Efficient Surface of Cost, Utility, and Survivability Pareto Efficient Set for Cost, Utility, Utility Loss, and Threshold Availability (magnified) design utility (dimensionless) time-weighted utility loss (95th percentile) threshold availability (st percentile) threshold availability ( st percentile) lifecycle cost ($B) 29 Massachusetts Institute of Technology 25

26 Identify Pareto-Efficient Surface of Cost, Utility, and Survivability Pareto Efficient Set for Cost, Utility, Utility Loss, and Threshold Availability (magnified) design utility (dimensionless) time-weighted utility loss (95th percentile) threshold availability (st percentile) threshold availability ( st percentile) lifecycle cost ($B) 29 Massachusetts Institute of Technology 26

27 Select Interesting Point Designs Pareto Efficient Set for Cost, Utility, Utility Loss, and Threshold Availability (magnified) design utility (dimensionless) risk averse decision maker time-weighted utility loss (99th percentile) threshold availability (st percentile) threshold availability ( st percentile) lifecycle cost ($B) 29 Massachusetts Institute of Technology 27

28 Select Interesting Point Designs Pareto Efficient Set for Cost, Utility, Utility Loss, and Threshold Availability (magnified) design utility (dimensionless) risk averse decision maker time-weighted utility loss (99th percentile) threshold availability (st percentile) threshold availability ( st percentile) lifecycle cost ($B) 29 Massachusetts Institute of Technology 28

29 utility (dimensionless) design Filtered by Cost, Utility, Utility Loss, and Threshold Availability time-weighted utility loss (99th percentile) threshold availability (st percentile) lifecycle cost ($B) Extract Survivability Insights from Selected Point Designs threshold availability ( st percentile) Design Vector ID orbit altitude (km) 5 5 Walker constellation 9/3/2 9/3/2 27/3/ 66/6/5 66/6/5 transmit frequency (GHz) antenna area (m^2) 4 4 antenna type AESA AESA radar bandwidth (MHz) 2 2 peak transmit power (kw) 2 2 tugable no no comm. architecture direct relay relay direct relay tactical link yes yes shield thickness (mm) satellite spares lifecycle cost ($B) utility utility loss (95th) utility loss (99th) threshold availability (st) Survivability insights from selected point designs Relay backbone critical for achieving continuous threshold availability Investing in spare satellite(s) minimizes utility losses Satellite shielding has limited impact in nominal debris environment Distributed constellation mitigates worst-case risks 29 Massachusetts Institute of Technology 29

30 utility (dimensionless) design Filtered by Cost, Utility, Utility Loss, and Threshold Availability time-weighted utility loss (99th percentile) threshold availability (st percentile) lifecycle cost ($B) Extract Survivability Insights from Selected Point Designs threshold availability ( st percentile) Design Vector ID orbit altitude (km) 5 5 Walker constellation 9/3/2 9/3/2 27/3/ 66/6/5 66/6/5 transmit frequency (GHz) antenna area (m^2) 4 4 antenna type AESA AESA radar bandwidth (MHz) 2 2 peak transmit power (kw) 2 2 tugable no no comm. architecture direct relay relay direct relay tactical link yes yes shield thickness (mm) satellite spares lifecycle cost ($B) utility utility loss (95th) utility loss (99th) threshold availability (st) Survivability insights from selected point designs Relay backbone critical for achieving continuous threshold availability Investing in spare satellite(s) minimizes utility losses Satellite shielding has limited impact in nominal debris environment Distributed constellation mitigates worst-case risks 29 Massachusetts Institute of Technology 3

31 utility (dimensionless) design Filtered by Cost, Utility, Utility Loss, and Threshold Availability time-weighted utility loss (99th percentile) threshold availability (st percentile) lifecycle cost ($B) Extract Survivability Insights from Selected Point Designs threshold availability ( st percentile) Design Vector ID orbit altitude (km) 5 5 Walker constellation 9/3/2 9/3/2 27/3/ 66/6/5 66/6/5 transmit frequency (GHz) antenna area (m^2) 4 4 antenna type AESA AESA radar bandwidth (MHz) 2 2 peak transmit power (kw) 2 2 tugable no no comm. architecture direct relay relay direct relay tactical link yes yes shield thickness (mm) satellite spares lifecycle cost ($B) utility utility loss (95th) utility loss (99th) threshold availability (st) Survivability insights from selected point designs Relay backbone critical for achieving continuous threshold availability Investing in spare satellite(s) minimizes utility losses Satellite shielding has limited impact in nominal debris environment Distributed constellation mitigates worst-case risks 29 Massachusetts Institute of Technology 3

32 Methodological Insights MATE for Survivability incorporates survivability as a decision metric into conceptual design Design principles reveal latent survivability trades and inform selection of survivability design variables Survivability metrics enable discrimination among thousands of design alternatives Implementation considerations Subject percentile reporting levels to sensitivity analysis Balance broad exploration with selected of individual point designs MATE for Survivability improves on existing tradespace approaches Pareto front in traditional MATE study excludes most survivable designs Evaluates survivability implications for selection of baseline architecture 29 Massachusetts Institute of Technology 32

33 Methodological improvements Future Work Parameterize concept-of-operations in design vector Extend scope for systems-of-systems (SoS) engineering Apply MATE for Survivability to additional systems for prescriptive insights power distribution transportation water distribution communications 29 Massachusetts Institute of Technology 33

34 Questions? Matthew Richards, Ph.D.