Neptune Power Overview- 1 All rights reserved © 2003, Neptune NEPTUNE power subsystem Progress and Plans April 2003 Harold Kirkham

Neptune Power Overview- 2 All rights reserved © 2003, Neptune Presentation outline Progress review –Converter –Mission Assurance –Delivery system –Documentation Plans

Neptune Power Overview- 3 All rights reserved © 2003, Neptune

Neptune Power Overview- 4 All rights reserved © 2003, Neptune

Neptune Power Overview- 5 All rights reserved © 2003, Neptune Progress: Converter All operating principles demonstrated –Efficiency and Voltage Regulation are excellent –Current is evenly shared by parallel stages –Voltage is evenly divided by series stages DC-DC Converter DC-DC Converter DC-DC Converter DC-DC Converter LOAD

Neptune Power Overview- 6 All rights reserved © 2003, Neptune Progress: Converter Efficiency

Neptune Power Overview- 7 All rights reserved © 2003, Neptune Progress: Converter Regulation

Neptune Power Overview- 8 All rights reserved © 2003, Neptune Mission Assurance Four aspects: –Converter –Node Distribution System –Delivery System –Communications

Neptune Power Overview- 9 All rights reserved © 2003, Neptune Mission Assurance: Converter Converter stack MTBF estimated: 40 years –Assume worst-case: failure takes out stack –Assume cold-standby redundancy –Assume 30 year NEPTUNE lifetime –Observatory may need a few replacements Assume substring failure is not fatal –Converter power de-rated by 17% –Observatory may never need a replacement The Message is: Don’t worry – BE HAPPY!

Neptune Power Overview- 10 All rights reserved © 2003, Neptune Mission Assurance: Node Distribution Distribution system power at 400 and 48 V –Assume 400-V source is solidly available –Assume 48-V COTS converters –Assume COTS switches –This is so simple, we have deferred the design BOTE cost estimates done by JPL & UW –JPL cost: $2,000,000 –UW cost: $250,000

Neptune Power Overview- 11 All rights reserved © 2003, Neptune Mission Assurance: Node Distribution JPL assumes –Hardware handled by certified people only –Complete paper trail for all activities –Extensive testing, with tests traceable back –Environment complies with ESD and contamination rules –All handling requires multiple personnel UW assumes –Hardware handled as needed –Marginal paper trail –Some testing

Neptune Power Overview- 12 All rights reserved © 2003, Neptune Mission Assurance: Node Distribution The difference between these numbers is one of culture The two cost estimates are equally valid Neither is “right” or “wrong” The product of the work is different, however You pay for what you get Is there a middle ground?

Neptune Power Overview- 13 All rights reserved © 2003, Neptune Mission Assurance: Delivery System Triggered by concern over converter reliability, we have devised a “Version 2” The original motivation may not be valid, but the new design brings major benefits The biggest benefit of Version 2 is that node failures (power supply or comm failure) do not affect the backbone This segregation of function leads to better observatory availability

Neptune Power Overview- 14 All rights reserved © 2003, Neptune How does Version 2 work?

Neptune Power Overview- 15 All rights reserved © 2003, Neptune Component availability Zeners, qualified to 2A, preliminary study done for 10A upgrade Capacitors, qualified Latching relay, similar to qualified, limited re-qualification needed Resistors, similar to part in qualification Bridge, qualified Controller, space qualified part may be suitable, limited development, or control by analog electronics (qualified)

Neptune Power Overview- 16 All rights reserved © 2003, Neptune Version 2 power sub-system Pros and Cons High reliability – Parts are qualified or low development cost –Low component count –Low power consumption –Switching only at low power Segregated functionality – Better observatory availability Can use single conductor cable, BU to Node – Cost savings BU requires a ground Controllability reduced –Switches cannot be remotely operated

Neptune Power Overview- 17 All rights reserved © 2003, Neptune Progress: Documentation Configuration Management Plan Configuration Management Plan Project Documentation Plan Requirements Document Deployment Vessel ICD Operations Concept Doc System Description Documents Verification Plan ICD Test Plan Reports and Minutes Power Project History PMACS Protection Converter NEPTUNE levelPower Subsystem level

Neptune Power Overview- 18 All rights reserved © 2003, Neptune Progress: Documentation All key documents started and on web site –Concept of Operations (Rev 5) –Test Plan (Initial) –Converter (3 files) –PMACS (17 files) –Assorted trade-offs –CoDR docs (37 files) Total number of files ~400