ExoMars 2016 CDR Presentation David Bartolo Shazib Elahi Aaron Tun Junyi Zhang
Brief Recap - ExoMars 2016: ESA + Roscosmos - Joint operation aiming to investigate the Martian atmosphere and surface, and to gain more experience in preparation for future missions - Trace Gas Orbiter (TGO) - Schiaparelli Entry, Descent, and Landing Demonstrator Module (EDM) - TGO: science operations in orbit, EDM: demonstrate ESA’s ability to land on surface of Mars, some scientific objectives as well - Analyses focusing on EDM
Subsystems Breakdown: After Sun Sensors Ablative (2x) UHF System Material Gyroscopes Descent Back Front Camera Back Shell Shell Shell (DECA) Thermal Communication Aluminum with Carbon Fiber Protection Inertial System Reinforced Polymer Skin Systems Measurement Accelerometers Unit (IMU) Schiaparelli Guidance, External Avionics Navigation, Structure EDM Systems and Control Software Predetermined Power Sanity Failsafe Systems Check Calculations Mortar Scientific Crushable Landing Landing Deployed Rechargeable EDL Payloads Structure Systems Parachute Battery System Surface Operations Radar Antennas MetWind DREAMS MicroARES Rechargeable Batt. Propulsion Doppler (4x) System Surface Payload Rechargeable Batt. SIS MetBaro MetHumi MarsTem Electronic Solar array 3 Clusters of 3 Units (2x) Hydrazine Pulse Engines
Subsystems Breakdown: After Sun Sensors Ablative (2x) UHF System Material Gyroscopes Descent Back Front Camera Back Shell Shell Shell (DECA) Thermal Communication Aluminum with Carbon Fiber Protection Inertial System Reinforced Polymer Skin Systems Measurement Accelerometers Unit (IMU) Schiaparelli Guidance, External Avionics Navigation, Structure EDM Systems and Control Software Predetermined Power Sanity Failsafe Systems Check Calculations Mortar Scientific Crushable Landing Landing Deployed Rechargeable EDL Payloads Structure Systems Parachute Battery System Surface Operations Radar Antennas MetWind DREAMS MicroARES Rechargeable Battery Propulsion Doppler (4x) System Surface Payload Rechargeable Battery SIS MetBaro MetHumi MarsTem Electronic Solar Array 3 Clusters of 3 Units (2x) Hydrazine Pulse Engines
Software Sanity Checks ● Implement a Software Sanity Check that monitors the communication between the Inertial Measurement Unit (IMU) and the Radar Doppler Altimeter (RDA). ● The Sanity Check will focus on the attitude, altitude’s magnitude and change over time, and the vertical acceleration (comparing with the Martian gravity). ● The Sanity Check will remain on standby in parallel, analyzing the receiving data, for if the readings of the IMU or the RDA become unreliable. ● Exomars’ main flaw resided in the communication of the received information, and the internal systems inability to respond to the inaccurate readings; however, despite the inertial measurement requiring a higher saturation limit, modeling the exact effects of the IMU reading when entering the Martian atmosphere and deploying the parachute is not feasible nor does the Avionics Test Bench simulator stimulate the IMU navigation function.
Specific Quantitative Requirements Targeted for Analyses Analysis Quantitative Requirements Power Analysis - 25% Power Margin Solar Array Design Analysis - Natural frequencies in the 5.90 - 7.24 Hz range (for modes 1-5) Mass, Volume, Stability Analysis - Mass & Volume: less than 10% increase - Stability: longitudinal variation less than 12.5 degree
Power Analyses Goal of analysis ● Determine the size of the solar array ● Determine required battery capacity ● Choose power regulation techniques and regulator ● Analyze the dissipated heat from new power source
Power Generation and Sources Assumptions, Principles, & Methods ● Assume required power consumption to be 77 Watts for both day and night cycles. ● A 25 % power margin. ● Method to determine the required solar array power output:
Power Generation and Sources Assumptions, Principles, & Methods
Power Generation and Sources Assumptions, Principles, & Methods ● Determine the power that the solar array can produce ● Determine the orbital solar irradiance:
Power Generation and Sources Assumptions, Principles, & Methods
Power Generation and Sources Assumptions, Principles, & Methods ● Determine the Mars surface solar irradiance:
Power Generation and Sources Assumptions, Principles, & Methods
Power Generation and Sources Assumptions, Principles, & Methods ● Determine the beginning-of-life (BOL) power production
Power Generation and Sources Assumptions, Principles, & Methods ● Determine the Lifetime degradation due to dust accumulation and radiation: D = % dust accumulation + % radiation ● Assumed degradation of 0.028 % per sol for % dust accumulation. ●
Power Generation and Sources Assumptions, Principles, & Methods ● Calculate EOL power production: ● Calculate the Solar Array Area:
Power Generation and Sources Results: Solar cell comparison :
Power Energy Storage Assumptions, Principles, & Methods
Power Energy Storage Assumptions, Principles, & Methods ● Concluded with selecting Li-ion cell. ● Size a secondary battery capacity, identify the parameters ● Assumed a DOD of 50% because of small life cycles (~687 cycles)
Power Energy Storage Results
Power Regulation and Control Assumptions, Principles, & Methods ● We will use DET ● Disadvantages of PPT: ○ Additional weight ○ More complex system ○ Less efficient ○ Cost more
Power Regulators Assumptions, Principles, & Methods ● We will use the Switch-Mode Regulators ● Disadvantages of Linear Regulators: ○ Poor efficiencies
Power Distribution And Heat Dissipation P = i * V = i^2 * R, ● Peak current: I p = 2.5 [A] ● Standard of Allowable Internal Resistance: R = 0.276 [Ohms] ● Power Dissipated from heat: (2.5 [A])^2 * 0.276 [Ohms] = 1.725 [Watt] ● Power Capacity of total battery: 2569.32 [W* h] ● From power dissipated, this results in an increases of 4.18 o C. ● Required power consumption of the EDM: P = 77 [W*h] ● Therefore, the actual power at the system’s disposal: 2569.23 - 1.725 = 2567.51 [W* h]; in comparison the EDM requires approximately 77* 12.3 = 924 [W* h] for a Martian night (12.3 h).
Power Discussion: Confidence, Weaknesses, Importance of Results ● The estimated solar array size is reasonable, as well as the battery capacity. ● The weakness of our analysis is that we based the solar array size on the average solar irradiance throughout the year, which means it did not account for global and local dust storms. ● The importance of the results suggest that we can move forward in the process of adding the solar array, which can provide the required power extending the life of the EDM.
Test Plan: Power ● Electromagnetic Interference ● Electromagnetic Compatibility ● Thermal Cycling for the Battery ● High-/-Low-Voltage Limits ● Thermal Limits (Battery) ● Performance
Solar Array Design Analysis Minor Analysis I
Goal of Analysis - Ensure best possible solar array design is selected to meet power requirements of Schiaparelli lander - Identify natural frequencies and mode shapes of deployed & stowed array - First step before assumptions, principles, and methods can be determined: Trade Study
Assumptions, Principles, and Methods - Simplifying assumptions: - Structural analysis done separately: for stowed and deployed positions - Considerably simplifies modeling process in Solidworks - Mass of solar cells is negligible and will be ignored - Array assembly components and materials will be modeled as follows: - Substrate (gores): vectran (20% void) - Supporting structure (spars): aluminum (6601-T6) - Assumptions are based on those made in a research paper for finite element analysis on a larger variant of the UltraFlex design
Assumptions, Principles, and Methods - Principles and Methods - Trade study to select best design concept - UltraFlex - CAD modeling - Solidworks - Finite element analysis - Modal analysis - Solidworks - Resonant and natural frequencies
Ultraflex Solar Array
Math and Models - Ultraflex shape is decagonal - Area of decagon - Calculate side length a based on area from power analysis - Then determine spar length and length of centerline - Centerline = r outer + r inner
Math and Models - To calculate r inner and r outer : - Referenced values from Semke et al. - Outer radius = 101.6 - Inner Radius = 3.81
Math and Models - Deployed Array Aluminum spar Vectran gore Perspective view Top-down view Models created in Solidworks
Math and Models - Stowed Array Models created in Solidworks
Math and Models - Finite Element Models Models created in Solidworks
Results: Deployed Array Analysis - Modes Shapes Mode Shape 2 Mode Shape 1 Mode Shape 3 Mode Shape 4 Mode Shape 5 Frequency/Mode Rad/sec Hertz Seconds Number 1 26.197 4.1694 0.23984 2 29.48 4.6919 0.21314 3 32.173 5.1205 0.1953 4 35.456 5.643 0.17721 5 40.508 6.4471 0.15511
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