Using Architecture Models to Understand Policy Impacts Utility 1 0.995 0.99 Policy increases cost B C D 10 of B-TOS architectures have cost increase under restrictive launch policy for a minimum cost decision maker Restrictive launch policy Unrestrictive launch policy 0.985 1 A 0.98 Cost 0 100 200 300 400 500 600 700 800 B-TOS 98% Swarm of B-TOS of small architectures sats. doing have observation increased launch probability Utility for of multiple success under restrictive missions launch policy for a minimum cost decision maker Lifecycle Cost ($M) Utility 0.995 0.99 0.985 0.98 Policy increases launch probability of success 1 2 3 4 5 6 7 8 9 10 Probability of Success From Weigel, 2002 Space Systems, Policy, and Architecture Research Consortium 2002 Massachusetts Institute of Technology 29 Using Architecture Models to Consider Uncertainty TechSat Constellation of satellites doing Performance and Cost move differently for different architectures under uncertainty observation of moving objects on the ground Uncertainties driven by instrument performance/cost [Martin, 2000] From Walton, 2002 Space Systems, Policy, and Architecture Research Consortium 2002 Massachusetts Institute of Technology 30 15
Changes in User Preferences Can be Quickly Understood Architecture trade space reevaluated in less than one hour Original User changed preference weighting for lifespan Revised 0.8 0.8 0.7 y t i l i t U X-TOS 0.7 y t i l i t U 0.6 0.5 0.6 0.5 0.4 0.4 0.3 0.3 0.2 40 42 46 44 48 50 52 Lifecycle Cost ($M) 54 56 58 60 0.2 40 42 44 46 48 50 52 54 56 58 60 Lifecycle Cost ($M) Space Systems, Policy, and Architecture Research Consortium 2002 Massachusetts Institute of Technology 31 Assessing Robustness and Adaptability Pareto front shows trade-off of accuracy and cost Determined by number of satellites in swarm Could add satellites to increase capability 1 E D C Utility Utility 0.995 Most desirable architectures B 0.99 0.985 A 0.98 100 B-TOS Cost 1000 Lifecycle Cost ($M) Space Systems, Policy, and Architecture Research Consortium 2002 Massachusetts Institute of Technology 32 16
Questioning User Desires Best low-cost mission do only one job well More expensive, higher performance missions require more vehicles Higher-cost systems can do multiple missions Is the multiple mission idea a good one? A-TOS Swarm of very simple satellites taking ionospheric measurements Several different missions High Latitude Utility Space Systems, Policy, and Architecture Research Consortium Equatorial Utility 2002 Massachusetts Institute of Technology 33 Cost (M$) 4000.00 3500.00 3000.00 2500.00 2000.00 1500.00 1000.00 500.00 Understanding Limiting Physical or Mission constraints 0.00 0.00 0.20 0.40 0.60 0.80 1.00 Utility (dimensionless) SPACETUG Low Biprop Medium Biprop High Biprop Extreme Biprop Low Cryo Medium Cryo High Cryo Extreme Cryo Low Electric Medium Electric High Electric Extreme Electric Low Nuclear Medium Nuclear High Nuclear Extreme Nuclear General purpose orbit transfer vehicles Different propulsion systems and grappling/obser vation capabilities Lines show increasing fuel mass fraction Hits a wall of either physics (can t change!) or utility (can) Space Systems, Policy, and Architecture Research Consortium 2002 Massachusetts Institute of Technology 34 17
Integrated Concurrent Engineering (ICE) ICE techniques from Caltech and JPL Linked analytical tools with human experts in the loop Very rapid design iterations Result is conceptual design at more detailed level than seen in architecture studies Allows understanding and exploration of design alternatives A reality check on the architecture studies - can the vehicles called for be built, on budget, with available technologies? Space Systems, Policy, and Architecture Research Consortium 2002 Massachusetts Institute of Technology 35 ICE Process (CON with MATE) Chairs consist of computer tool AND human expert Mission Power Thermal Structures Command and Data Handling Electronic communication between tools and server ICE Process Leader MATE Cost ICE-Maker Server Reliability Verbal or online chat between chairs synchronizes actions Key system attributes passed to MATE chair, helps to drive design session Systems Propulsion Communication Configuration Attitude Determination and Control Directed Design Sessions allow very fast production of preliminary designs Traditionally, design to requirements Integration with MATE allows utility of designs to be assessed real time Space Systems, Policy, and Architecture Research Consortium 2002 Massachusetts Institute of Technology 36 18
ICE Result - XTOS Vehicle Early Designs had excessively large fuel tanks and bizarre shapes Showed limits of coarse modeling done in architecture studies Vehicle optimized for best utility - maximum life at the lowest practical altitude Space Systems, Policy, and Architecture Research Consortium 2002 Massachusetts Institute of Technology 37 SPACETUG Biprop One-Way GEO Tug 1312 kg dry mass, 11689 kg wet mass Quite big (and therefore expensive); not very practical (?); Scale for all images: black cylinder is 1 meter long by 1 meter in diameter Space Systems, Policy, and Architecture Research Consortium 2002 Massachusetts Institute of Technology 38 19
SPACETUG Tug Family (designed in a day) Bipropellant Cryogenic Wet Mass: 11689 kg Electric One way Wet Mass: 6238 kg Electric Return Trip Wet Mass: 997 kg Wet Mass: 1112 kg Space Systems, Policy, and Architecture Research Consortium 2002 Massachusetts Institute of Technology 39 Learning from the ICE results: Mass Distribution Comparison C&DH ADACS (dry) Pressurant Propellant 37% Link 1% Power 11% Propulsion (dry) 2% Structures & Mechanisms 17% Link C&DH ADACS (dry) Pressurant Power 1% Propulsion (dry) 6% Structures & Mechanisms 2% Thermal Mating System 3% Payload Payload Mating System 27% Thermal 5% Propellant 88% Electric Cruiser Biprop one-way Low ISP fuel requires very large mass fraction to do mission Other mass fractions reasonable, with manipulator system, power system, and structures and mechanisms dominating Space Systems, Policy, and Architecture Research Consortium 2002 Massachusetts Institute of Technology 40 20
More Than Mass Fractions LEO Tender 1 mass summary 1% 16% ADACS (dry) Power System Mass Breakdown Solar array mass 66% C&DH 5% 3% Link Power Propulsion (dry) 52% 2% Structures & Mechanisms Thermal Mating System Payload 21% Propellant Pressurant Cabling mass 6% PMAD mass 9% Battery mass 19% Minimum efficiency 24.5 % Maximum efficiency 28.0 % Nominal temperature 28.0 C Temperature loss 0.5 %/deg C Performance degredation 2.6 % / year Minimum temperature 0.5 C Maximum temperature 85.0 C Energy density 25.0 W / kg Solar array mass 150.6685167 kg Total solar array area 9.965098159 m^2 # of solar arrays 2 # Individual solar array area 4.98254908 m^2 Space Systems, Policy, and Architecture Research Consortium 2002 Massachusetts Institute of Technology 41 Detailed information can be drawn from subsystem sheets, including efficiencies, degradations temperature tolerances, and areas Select solar array material: 6 Triple Junction (InGaP/GaAs/Ge) Trade Space Check The GEO mission is near the wall for conventional propulsion Space Systems, Policy, and Architecture Research Consortium 2002 Massachusetts Institute of Technology 42 21
SPACETUG LEO Tender Family LEO 1-1404 kg wet LEO 4-1782 kg wet LEO 2-1242 kg wet LEO 4A - 4107 kg wet Tenders Orbit transfer vehicles that live in a restricted, highly populated set of orbits Do low Delta-V transfers, service, observation Space Systems, Policy, and Architecture Research Consortium 2002 Massachusetts Institute of Technology 43 Tenders on the tradespace The Tender missions are feasible with conventional propulsion Space Systems, Policy, and Architecture Research Consortium 2002 Massachusetts Institute of Technology 44 22
What you will learn Trade space evaluation allows efficient quantitative assessment of system architectures given user needs State-of-the-art conceptual design processes refine selected architectures to vehicle preliminary designs Goal is the right system, with major issues understood (and major problems ironed out) entering detailed design Emerging capability to get from user needs to robust solutions quickly, while considering full range of options, and maintaining engineering excellence Space Systems, Policy, and Architecture Research Consortium 2002 Massachusetts Institute of Technology 45 23