Electrical Power System March 13, 2004

Introduction The DINO power system is a direct energy transfer system It will contain a main battery composed of 4 lithium-ion polymer cells with a nominal voltage of 15V +/- 3V It will contain a 28V battery dedicated to the deployment experiments Power generation shall be provided by the Flexible Integrated Thin-films solar array (FITS) A secondary solar array shall be mounted on the panels of the structure The EPS shall provide voltages of 5, +/- 12 and 28V Colorado Space Grant Consortium

Electrical Power System Description Direct energy transfer system Single Solar-Array technologies Conventional body-mount crystalline cells Thin-Film (FITS) Flexible Array System will switch solar array strings and spacecraft loads, and will require 4 switches for the FITS Will require 16 (TBR) switches for the backup SA 4 power distribution switches capable of transferring less than 3 Amps 12 power distribution switches capable of transferring less than 1 Amp System will use 4 A-hr Lithium Polymer cells at 3.7 Volts for power storage 4 Cells will be in series, for a 15V +/- 2V, 4 Ahr battery assembly Battery charging will be accomplished using several charging modes: Nominal sub-capacity charging; entire stack is charged to 95% capacity This will be the default mode Full-charge; entire stack charged to 100% capacity Cell conditioning over-charge; as stack ages, it will lose capacity, which can be restored by judicious over-charging Temperature and voltage monitoring will be the primary means of controlling battery Colorado Space Grant Consortium

Dino EPS Block Diagram Colorado Space Grant Consortium

Changes Since PDR The EPS board will be designed by CSGC and have industries review the design instead of procuring an off the shelf card The 28V supply will deploy 2 frangibolts, 1 set of memory hinges, lightband, the HOPS and the boom Power supply outputs shall have inhibits The EPS card will communicate with C&DH through a RS-422 serial line A PIC and an A/D converter will replace the FPGA Monitors will be placed on the essential components (voltage busses, battery and solar arrays) instead of all switches Power shall have a watchdog to reset C&DH Colorado Space Grant Consortium

Functional Requirements Compliance The EPS shall confirm the status of the inhibits at all times The EGSE and umbilical cord shall confirm the inhibits status. Continuity loops will establish current status and C&DH will indicate inhibits state. The main battery shall last the duration of the mission life of a required 6 months and mission goal of 12 months The battery shall be oversize by 20% using maximum values of all devices. The battery shall be charged every 3 cycles and overcharged periodically to recover capacity lost. 28V supply shall deploy all mechanisms The battery shall be sized to 120% of the needed power and shall be tested with all deploy mechanisms. Colorado Space Grant Consortium

Functional Requirements Compliance The 5V power supply shall power all devices using 5V The supply shall be rated to double of the needed watts based on the power profile. The 12V power supply shall provide the needed power to the systems require 12V. The supply must also have positive and negative voltages The supply shall be rated to double of the needed watts base on the power profile. The supply chosen will be capable of using negative voltages and positive voltages The charge controller shall be capable of charging the main battery to specified ranges. The charge controller shall use a comparator to ensure the battery will remain charging until it is within a desired range The EPS card shall contain a watchdog to reset C&DH If contact with C&DH can not be established for a period of 10 minutes power to the C&DH will be turn on then off. Time will be kept using a PIC. Colorado Space Grant Consortium

Functional Requirements Compliance EPS shall send health and status to C&DH Once the monitors return values it will be processed by the A/D converter and the micro controller will send it onto C&DH. EPS shall receive commands from C&DH to turn on devices and systems Commands will be sent through a serial line to a micro controller. The micro controller will send the appropriate analog command to turn on and off switches. Power Generation The EPS system shall receive power from the primary FITS solar array. Power will also be generated by body mounted solar cells. Storage of power Power shall be stored in the main battery. Charging of the main battery shall occur once every 3 cycles. Distribute Power Power shall be distributed through power lines of 5, +/- 12 and 28V. C&DH shall instruct the EPS system to close switches to give power to subsystems. Colorado Space Grant Consortium

CURRENT BEST ESTIMATE = 10 A DINO EPS Compliance with Requirements PMAD card fits within 10”x10” square on other side of Zenith Plate System masses less than 2.25kg PMAD – .75kg Cells – ~.1kg/each; .4kg FCC – ~.1kg Monitors – ~.1kg Potting/misc – TBD EPS system shall not heat spacecraft unduely Cells use a battery radiator PMAD TBD Colorado Space Grant Consortium

EPS Battery Safety Requirements Compliance and How Addressed Requirement Met? How Addressed Un-powered bus in ICU Main Battery – NO 28V Battery – NO Solar Arrays – YES Inhibits/Battery Design Inhibits 3-fault tolerant battery inhibits YES Latching Relays Protection vs Electrolyte leak Potting/absorbent materials, 28V vent orientation Blocking Diodes on all cells in series Charge Control design/test 28V Battery – testing Blocking Diodes on parallel cell strings 28V Battery – TBD TBD Overcharge/discharge protection Voltage monitoring of battery Cell temp shall not exceed 40°C Thermal design/test Internal Short protection Main Battery – YES 28V Battery – YES Potting physically isolates cells Fuses on each string Cells shall not be damaged by launch Potting/Case design Colorado Space Grant Consortium

EPS Battery Safety Requirements Compliance and How Addressed Requirement Met? How Addressed Cells shall not be damaged by thermal cycling YES Thermal design/test Cells shall be either UL-certified or undergo a flight qualification Main Battery – TBD 28V Battery – Yes TBD UL-certified Cells shall not heat excessively during operation Testing Cell/PMAD Monitors change indicate monitor failure PMAD – TBD 28V Battery – TBD Power feeds using separate lines with a common start and end point shall contain a protective device on each feed Main Battery – NO Flat Conductor Cable – NO Colorado Space Grant Consortium

EPS Circuit Protection Safety Reqs – Compliance and How Addressed Safety Requirement Requirement Met? How Addressed Small, sub-mini, & cartridge fuses shall be derated 50% Yes Design/part selection Shall use a minimum of 1MΩ resistance between DINO and orbiter ground plane YES Design Connector Shells shall have <2.5mΩ resistance to DINO ground Design/test Connector pin-to-pin resistance shall not exceed 50mΩ Connector selection/testing EGSE shall have a minimum of 1MΩ resistance to DINO TBD Parallel power feeds require individual circuit protection Colorado Space Grant Consortium

EPS Monitors/Verification Requirements Compliance and How Addressed Safety Requirement Requirement Met? How Addressed No hazardous events shall occur until DINO is clear of the Shuttle YES ICU sep switches activate a C&DH timer Processes controlling hazards shall be monitored Deployment – YES Radios – NO/TBD Inhibits Un-powered initially Monitoring at launch site shall be provided if needed EGSE Design Colorado Space Grant Consortium

Manufacturing/Test Facility Requirements Manufacturing Facilities: Machining of zenith plate – ITLL machine shop Main Battery assembly & potting – BATC facilities/assistance 28V Battery assembly & potting – CSGC shop PCBs – manufactured with Broad Reach assistance/facilities Covers/mounting hardware – provided by DINO structures team Test Facilities: Thermal-vacuum chamber for system testing – BATC Test battery performance in a vacuum DINO testing with realistic thermal conditions Shaker table for 20g sine-burst testing – BATC Breakout boxes for EGSE – CSGC/BATC 18 pins for Main Battery TBD pins for subsystem switch monitors TBD pins for C&DH Colorado Space Grant Consortium

Power Card Schematic Colorado Space Grant Consortium

Power Card Power Distribution 24 power distribution switches Power Processing Three power supplies (5V, 12V and 3.3V) Communication with flight computer RS-485 Power Management Uses PWM current control technique to transfer the power from the solar array to rest of the spacecraft Safety Provides safety inhibits according to NASA Safety Requirements discussed above Colorado Space Grant Consortium

DINO Battery Schematic Colorado Space Grant Consortium

Battery Description The battery chemistry is Lithium-Ion polymer The cells are in a prismatic configuration The main battery shall contain 4 lithium-ion polymer cells connected in series The cells have a nominal voltage of 3.7V and a capacity of 4 Ahr The battery shall last for 2000 charge/discharge cycles Cell dimension are 4” X 4” Colorado Space Grant Consortium

Battery Size Analysis Colorado Space Grant Consortium

Primary 28V Deployment Battery Description 28V battery system shall consist of cell strings of 3 9V cells, connected in parallel System shall use either 3 strings of Alkaline 9V or TBD strings of Lithium 9V cells System shall provide power to – What devices? Battery shall be contained within an anodized aluminum case Cell strings kept physically isolated Cell contacts and interconnects shall be potted over to form 1 part Absorbent material shall be used in the case to soak up leaked electrolyte Case vents shall be oriented upward during launch (location in DINO TBD) Fuses shall be provided on the individual strings, as well as the battery ground System has been tested and proven w/ Alkaline 9V cells Lithium cells have not been tested yet Positive Battery Assembly 3 Cell String Negative Colorado Space Grant Consortium

Deployment Battery Case 1/8” anodized Aluminum 3-cell string Cell string well String interconnects on outside of case Case interfaces with DINO isogrid Colorado Space Grant Consortium

Analysis and Prototyping Reports 28V power system: Load testing shows that 9 Alkaline 9V cells provide sufficient power Alternate design using 6 Lithium 9V cells is under development A battery short test using a stack of 9 Alkaline cells produced the following: - Cell bottoms swelled, and in some cases, ruptured - Electrolyte material ejected from cell cans - Battery internal temperatures reached 85°C Colorado Space Grant Consortium

Solar Array Analysis Colorado Space Grant Consortium

Solar Array Electrical Properties Beginning of Life End of Life 25° Celsius 78° Celsius – Radiation Degradation Area 1.10 Voltage – String 24 Volts 19 Volts Current – String 1.4 Amps 1.27 Amps Power – Total Watts 110 Watts 90 Watts Array Efficiency 8% 4.60% Colorado Space Grant Consortium

Plans for Support Equipment To emulate the C&DH commands to the EPS system, Flight software shall be used to control switches and charge commands Flight software shall be connected through an RS-422 serial line Outputs shall be verified using multi-meters, oscilloscopes and break out boxes Thermistors, voltage and current sensors shall have a testing harness to record the data and inspected Power supplies shall mimic the input power from the solar arrays Minimized custom Colorado Space Grant Consortium

Document Tree Colorado Space Grant Consortium

Status and Plan of Action Documentation Document Status and Plan of Action Technical Manual 60% complete, once the system design is completed and components are chosen a description of how the components work will be written up System Description Completed Performance Test Outline completed Functional Test Outline completed, CSGC will determine acceptable parameters of operation Environmental Test 20% complete, initial outline for environmental testing has been written. 28V Test 80% complete, CSGC needs to test another set of batteries and make a final decision on the cells that will be used in flight Colorado Space Grant Consortium

Status and Plan of Action Documentation Documents Status and Plan of Action Electromagnetic Interference Test 20% complete, an initial outline has been written up. To complete this document we must choose all of our components and determine the amount of exposure the system will encounter. Mechanical Schematics 80% complete, the mechanical design requires a definite size of the battery cells and refinement on interfaces Electrical Schematics 50% complete, CSGC needs to obtain software to compile an entire system schematic Colorado Space Grant Consortium

Issues and Concerns Starting up the spacecraft when leaving the shuttle (initial power-up) Monitoring inhibits and sensors via GSE with no internal power provided Watchdog timing circuit and an inhibit between Power and C&DH Colorado Space Grant Consortium

Current EPS Status Electrical Design 70% complete Mechanical Design 90% complete Safety designs 70% complete EPS card on track for summer prototyping and testing Colorado Space Grant Consortium