MISSION ENGINEERING SPACECRAFT DESIGN

Transcription

1 MISSION ENGINEERING & SPACECRAFT DESIGN Alpbach D.J.P. Moura - CNES MISSION ENGINEERING (1) OVERALL MISSION ENGINEERING IS A COMPLEX TASK SINCE AT THE BEGINNING THE PROBLEM IS GENERALLY BADLY EXPRESSED (too much solutions or none) AND THUS REQUIRES HIGH INTERACTION BETWEEN SCIENTISTS AND ENGINEERS THIS ENGINEERING PHASE IS VERY IMPORTANT SINCE ANY MISTAKES ARE PAINFULL TO CORRECT LATER, IN THE DEVELOPMENT OR TEST PHASES THIS WORK REQUIRES SENIOR SCIENTISTS AND ENGINEERS (OR TUTORS)

2 MISSION ENGINEERING (2) FOR EASING THIS PROCESS, THE SCIENTISTS HAVE TO EXPRESS THE MISSION DRIVERS (core/minimal mission objectives & requirements) AND THE «NICE TO HAVE» SPECS (enhanced mission objectives or additional ones) THE ENGINEERS HAVE TO DESIGN THE MISSION ACCORDING THESE DRIVERS. IF A SOLUTION IS FOUND, ACCOMMODATION OF THE «NICE TO HAVE» SPECS IS EVALUATED, WITHIN THE GIVEN RESOURCES. IF NO SOLUTION CAN BE FOUND, THEY PROPOSE BACK-UP STRATEGIES (axis for scientific descoping, pre-development works ) MISSION ENGINEERING (3) AT FIRST, WORK CAN BE CONCENTRATED ON THE FOLLOWING 5 MAIN FIELDS SCIENCE PAYLOAD MISSION DESIGN PROPULSION LAUNCHERS SPACECRAFT DESIGN GROUND SEG. OPS & COMMS

3 MISSION ENGINEERING (4) SCIENCE EXPRESS THE MAIN SCIENTIFIC QUESTIONS ADDRESSED BY THE MISSION, THE ASSOCIATED SCIENTIFIC OBJECTIVES AND THE EXPECTED SCIENTIFIC RETURN/PRODUCTS EXPRESS THE RATIONALE OF THE MISSION (why realize a space mission now to answer these questions and/or fulfill these objectives?) => SCIENTIFIC REQUIREMENTS IN TERMS OF MEASUREMENTS, OBSERVATIONS & DATA : wavelength, angular & spectral resolutions, sensitivity, pointed directions/areas MISSION ENGINEERING (5) PAYLOAD ENGINEERING, DEFINITION AND COSTING OF THE SCIENTIFIC INSTRUMENT(S) : detectors, collectors, electronics, coolers, interface with spacecraft & ground segment, critical points (for R&T) => INSTRUMENT REQUIREMENTS ON THE SPACECRAFT (accommodation, pointing, data management, thermal control, operational modes...) AND THE GROUND SEGMENT (science interaction with the operations, data processing, distribution and storage...)

4 MISSION ENGINEERING (6) MISSION DESIGN, PROPULSION & LAUNCHER ENGINEERING AND DEFINITION OF THE OPERATIONAL ORBIT(S) AND THE TRANSFER STRATEGIES (from the launcher injection to the operational location) TRADE-OFF ON PROPULSION TECHNOLOGIES AND COMPUTATION OF THE PROPELLANT BUDGETS => GEOMETRIC ASPECTS, OBSERVATION & COMMUNICATION STRATEGIES, LAUNCHER(S), PROPULSION S/S REQUIREMENTS MISSION ENGINEERING (7) GROUND SEGMENT, OPERATIONS & COMMUNICATIONS DEFINITION OF THE OPERATION STRATEGY (functional sharing spacecraft/ground) COMPUTATION OF THE TELECOMMAND & TELEMETRY LINK BUDGETS, IDENTIFICATION OF THE POSSIBLE EARTH STATION(S) ENGINEERING, DEFINITION & COSTING OF THE GROUND SEGMENT, INCLUDING DATA PROCESSING, DISTRIBUTION & ARCHIVING PHILOSOPHIES => OPERATIONAL PROFILE, COMMUNICATION S/S REQUIREMENTS

5 MISSION ENGINEERING (8) SPACECRAFT DESIGN DEFINITION OF THE SPACECRAFT MODES (operational or not) INTERFACE OPTIMISATION WITH THE PAYLOAD AND THE GROUND SEGMENT ENGINEERING, DEFINITION AND COSTING OF THE SPACECRAFT : mechanical architecture (under fairing and operational configurations) and electrical one (data and power lines), system budgets (mass, data & power), critical points (for R&T)... DEFINITION OF A PRELIMINARY DEVELOPMENT PLAN OF THE MISSION MISSION ENGINEERING (9) MAIN INTERACTIONS BETWEEN THE 5 FIELDS SCIENCE Scientific measurements requirements PAYLOAD Instrument(s) parameters & requirements Observation strategy Sun geometry Propulsion S/S Propellants mass Selected launcher Observation requirements A. Santovincento Data requirements MISSION DESIGN PROPULSION LAUNCHERS Earth geometry Communication strategy SPACECRAFT DESIGN Communication S/S Operational profile GROUND SEG. OPS & COMMS

6 MISSION ENGINEERING (10) MISSION CLASSES LAUNCHER SELECTION IS DIRECTLY LINKED WITH THE MISSION COST/CLASS LAUNCHER SELECTION IS POLITICALLY SENSIBLE : ESA MISSIONS SHOULD NOW BE LAUNCHED BY EUROPEAN LAUNCHERS (if no cooperation) ARIANE 5 SOYUZ (from Kourou) VEGA PERFO SSO > 10 T ~ 4.5 T ~ 1.5 T PERFO GTO PERFO ESCAP ~ 10 T ~ 4.3 T ~ 3 T ~1.2 T - - FAIRING D 5.4 m 4.1 m 2.6 m FAIRING L 17 m max 11.4 m max 7.9 m max COST ~ 150 M ~ 50 M ~ 20 M The detailed user s manuals can be downloaded from the arianespace web site MISSION ENGINEERING (11) SYNTHESIS WHATEVER IS THE QUALITY OF THE PERFORMED WORK, THE MESSAGE GIVEN TO EXTERNAL PEOPLE IS ESSENTIAL AND THUS EFFORTS HAVE TO BE MADE TO PRODUCE EFFECTIVE SYNTHESIS COVERING AT LEAST : - MISSION OBJECTIVES AND RATIONALE (why) - MEASUREMENTS, ORBIT & MISSION DESIGN (what) - PAYLOAD, SPACECRAFT & GROUND SEGMENT DESIGNS (how) - RISK ASSESSMENT AND ASSOCIATED MITIGATION PLAN (warnings) - PRELIMINARY DEVELOPMENT PLAN & COST ESTIMATION (how long, how much)

7 SPACECRAFT DESIGN ENGINEERING (1) SPACECRAFT PAYLOAD PLATFORM EXPERIMENTS (scientific satellite) THERMAL CONTROL DATA MANAGEMENT RECEIVERS/AMPLIFIERS/ANTENNAS (telecoms satellite) STRUCTURE MECHANISMS ORBIT & ATTITUDE CONTROL COMMUNICATIONS TELESCOPE/DETECTOR/ELECTRONICS (observation satellite) PROPULSION POWER/ENERGY SUPPLY POWER CONDITIONNING & DISTRIBUTION HARNESS Sub-systems SPACECRAFT DESIGN ENGINEERING (2) DESIGN ENGINEERING IS MAINLY DONE DURING PROJECT EARLY PHASES (A & B). THIS WORK STARTS WITH ANALYSIS OF THE BASIC INPUTS SUCH AS : MISSION PROFILE (maneuvers, mission duration, distances, angles ) PAYLOAD REQUESTS (mass, volume, pointing, data handling, thermal needs, power, cleanliness ) LAUNCH REQUIREMENTS (mass, volume, mechanical loads & frequency ) GROUND SEGMENT CONSTRAINTS (frequency, station characteristics & availability ) THE ALLOWED TECHNICAL COMPLEXITY (linked with the available time and money)

8 SPACECRAFT DESIGN ENGINEERING (3) AT TECHNICAL LEVEL, THE MAIN TRADE-OFFS & OPTIMISATIONS IMPACTING THE OVERALL SPACECRAFT CONFIGURATION ARE DONE, SUCH AS : POWER SOURCES (solar array/rtg / batteries size & type) PROPULSION (solid, cold gaz, monopropellant, bipropellant, electrical) STABILISATION CONCEPT (spin or 3 axis stabilization) TELECOMMUNICATIONS ANTENNAS (type, size, pointing) PAYLOAD ACCOMODATION (internal/external, autonomous pointing...) AUTONOMY LEVEL & OPERATIONAL INTERFACE WITH THE GROUND AND TO FINISH YOU WILL GET THIS ADDITIONAL DOCUMENT GIVING THE NEEDED BASES FOR PERFORMING FIRST ORDER COMPUTATIONS

9 ADDITIONAL CHARTS SPACECRAFT ARCHITECTURE DEFINITIONS (1) A SPACECRAFT IS MADE OF A LOT OF VARIOUS UNITS REQUIRING A LARGE SET OF SKILL AND EXPERTISE. IN ADDITION, ITS DESIGN MUST ALLOW PARALLEL WORK THIS IS WHY, A SPACRAFT IS DIVIDED INTO : A PAYLOAD (the part which realizes the service justifying the mission) A PLATFORM (the part giving the needed ressources to the payload) FURTHER MORE, THESE 2 PARTS ARE ALSO SUB-DIVIDED INTO «FUNCTIONAL CHAINS» (sub-systems for the platform)

10 SPACECRAFT ARCHITECTURE DEFINITIONS (2) USUALLY, THREE DIFFERENT TYPES OF ARCHITECTURE CAN BE DEFINED : THERMAL MECHANICAL ELECTRICAL Nota : mechanical & thermal architectures are very close and thus we speak often about mechanical & thermal architecture THIS ALLOWS PARALLEL ENGINEERING, DEVELOPMENT, ASSEMBLY & TESTS, AS WELL AS OPTIMIZED WORK DISTRIBUTION BETWEEN CONTRACTORS MECHANICAL ARCHITECTURE THE MAIN GOAL IS TO DEFINE AN OVERALL TECHNICAL CONFIGURATION FITTING WITH THE FOLLOWING CONSTRAINTS : MECHANICAL : launcher loads, stiffness, dimensional stability GEOMETRICAL : payload mounting area, views angles, radiative area, launcher interface OTHER : electrical & thermal conductivity, radiation protection TYPICALLY, THIS CONCERNS THE SPACECRAFT STRUCTURE, ALL THE BIG ITEMS (tanks, solar array, antennas ) AND THE MECHANISMS

11 THERMAL ARCHITECTURE THE MAIN GOAL IS TO DEFINE A TECHNICAL SOLUTION WHICH ALLOWS TO : KEEP ALL THE UNITS (internal or external) WITHIN THEIR SPECIFIED TEMPERATURE RANGES AND DURING ALL THE MISSION PHASES AND MODES (under the fairing, in sun or shadow, in stand-by or in full operation) TYPICALLY, THIS CONCERNS THE SPACECRAFT THERMAL CONTROL (and its interfaces with the power s/s) AS WELL AS THE THERMAL CONTROL OF SOME SPECIFIC ITEMS ELECTRICAL ARCHITECTURE WE CAN DIVIDE THIS PART ACCORDING 2 ASPECTS : POWER/ENERGY : GENERATION, STORAGE, CONTROL & DISTRIBUTION (type and number of power lines, protection philosophy ) DATA HANDLING (command/control, on board data processing and storage, redundancy management, autonomy, operational interfaces ) ALL S/S HAVING ELECTRICAL INTERFACES ARE CONCERNED (i.e. all except structure)

12 SPACECRAFT DESIGN VERIFICATION (1) DESIGN VERIFICATIONS ARE DONE ACCORDING VARIOUS MEANS MATHEMATICAL MODELS (thermal & mechanical architectures), USED TO PERFORM SIMULATIONS (IN PHASE C) AND TEST PREDICTIONS (IN PHASE D) PHYSICAL MODELS USED IN PHASE D TO PERFORM REAL TESTS : IN ORDER TO EASE THE TECHNICAL WORK, USUALLY 3 PHYSICAL MODELS ARE DEVELOPPED SPACECRAFT DESIGN VERIFICATION (2) MECHANICAL & THERMAL MODEL (STM) USED TO VALIDATE (qualification) THE MECHANICAL & THERMAL ARCHITECTURE AND GENERATE THE FINAL MECHANICAL & THERMAL SPECIFICATIONS OF ALL THE UNITS

13 SPACECRAFT DESIGN VERIFICATION (3) ELECTRICAL MODEL (EM) USED TO VALIDATE (qualification) THE ELECTRICAL ARCHITECTURE AND PERFORM SOME SPECIFIC TESTS (such as EMC ones) SPACECRAFT DESIGN VERIFICATION (4) FLIGHT MODEL (FM) WHERE TESTS ARE LIMITED TO VERIFICATION & CONTROL (acceptance) SINCE ITS DESIGN IS AS CLOSE AS POSSIBLE FROM STM AND EM ONES. Nota 1 : spare models are also developped to be used in case of problem Nota 2 : in the case of spacecraft family, a Proto Fligth Model approach can be followed (i.e. qualification is done on the FM).