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Neptune Power Overview- 1 All rights reserved © 2003, Neptune NEPTUNE power subsystem Progress and Plans April 2003 Harold Kirkham
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-DCConverter
DC-DCConverter
DC-DCConverter
DC-DCConverter
LOAD
Neptune Power Overview- 6 All rights reserved © 2003, Neptune
Progress: Converter Efficiency
0.82
0.84
0.86
0.88
0.9
0.92
0.94
0 100 200 300 400 500 600 700 800 900
Output Power (W)
450 V
500 V
600 V
700 V
800 V
Neptune Power Overview- 7 All rights reserved © 2003, Neptune
Progress: Converter Regulation
-0.050%
-0.040%
-0.030%
-0.020%
-0.010%
0.000%
0.010%
0.020%
0.030%
0 100 200 300 400 500 600 700 800 900-0.050%
-0.040%
-0.030%
-0.020%
-0.010%
0.000%
0.010%
0.020%
0.030%
0 100 200 300 400 500 600 700 800 900
Output Power (W)
450 V
500 V
600 V
700 V
800 V
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
ConfigurationManagement
Plan
ConfigurationManagement
Plan
ProjectDocumentation Plan
RequirementsDocument
DeploymentVessel ICD
OperationsConcept Doc
SystemDescriptionDocuments
VerificationPlan ICD
Test Plan
Reportsand
Minutes
Power ProjectHistory
PMACS
Protection
Converter
NEPTUNE level Power 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
