Transcript 18a-Power.ppt

Power
Philip Luers
NASA/GSFC Code 561
August 16-17, 2005
NASA’s Goddard Space Flight Center
18a - 1
Lunar Reconnaissance Orbiter (LRO)
EPS Level System Requirements
Traceability
Level 1- LRO Requirements
ESMD-RLEP-0010
Level 2- LRO Mission Requirements Document
LRO Technical Resource Allocations
LRO Electrical Systems Specification
LRO Mechanical Systems Specification
LRO Thermal Systems Specification
431-RQMT-000004
431-RQMT-000112
431-SPEC-000008
431-SPEC-000012
431-SPEC-000091
Level 3- LRO Electrical Power Subsystem Spec.
431-SPEC-000013
Level 4- LRO Power Subsystem Electronics (PSE) Spec.
LRO Solar Array Spec.
LRO Battery Specification
431-SPEC-000016
431-SPEC-000037
431-SPEC-000032
NASA’s Goddard Space Flight Center
18a - 2
Lunar Reconnaissance Orbiter (LRO)
EPS System Level 2 Flow Down Key
Requirements
Level 2 Req.
Level 3: Requirements
Paragraph
Concept/Compliance
Requirement
MRD-12
3.3.1.1
The SA shall support a primary circular polar mapping orbit with a
nominal mean altitude of 50 +/- 20 km. Altitude is measured to mean
lunar surface.
SA analysis done for this
orbit/Complies
MRD-13
3.3.1.2
The polar orbit shall be 90 degrees +/- 1 degrees longitude.
SA tracks to meet this
requirement/Complies
MRD-19
MRD-099
MRD-102
3.3.3.1.5
The nominal DOD during a typical lunar orbit shall be limited to 30%
with 1 cell failure.
Analysis done for worst case
eclipse/Complies
MRD-029
3.2.2.1
In addition the battery shall be capable of supporting a DOD of 60% for
launch phase and 80% for lunar eclipse periods and other mission
modes for a total of not to exceed 10 cycles.
NASA’s Goddard Space Flight Center
The EPS mass shall not exceed the allocation as specified LRO
Technical Resource Allocations Specification (431-SPEC-000112).
Complies
18a - 3
Lunar Reconnaissance Orbiter (LRO)
EPS System Level 2 Flow Down Key
Requirements
Level 2 Req.
Level 3: Requirements
Paragraph
Concept/Compliance
Requirement
MRD-098
3.2.3
The LRO power system shall be a Direct Energy Transfer (DET) design
distributing main bus power only to all instruments and subsystems.
Complies
MRD-50
3.1.22.1
The EPS shall support all observatory operational modes and mission
phases as defined in the Lunar Reconnaissance Orbiter Mission
Assurance Requirements (431-RQMT-000004) and summarized here:
Complies
Pre-launch/Launch Readiness
Launch and Lunar Transfer
Orbiter Activation/Commissioning
Measurement Operations
Extended Mission operations
End-of-Mission/Disposal
NASA’s Goddard Space Flight Center
18a - 4
Lunar Reconnaissance Orbiter (LRO)
EPS System Level 2 Flow Down Key
Requirements
Level 2 Req.
Level 3: Requirements
Paragraph
Concept/Compliance
Requirement
MRD-32
1.1
The bus voltage is maintained between 21-35 VDC nominal measured at
the loads during all mission phases through use of the LRO Power
Subsystem Electronics (PSE).
Complies
MRD-103
3.1.2.2.2
The LRO EPS shall support the total power allocation of the LRO
spacecraft bus and instrument suite with margins as specified in LRO
Technical Resource Allocations 431-RQMT-000112.
Max. capability is 823W orbit
average
MRD-21
3.1.1.1
The Orbiter shall be designed for a one-year mission life (after reaching
lunar orbit and post commissioning activities which are expected to be 2
mos.).
EPS shall support a reduced load
extended mission/Complies
The primary mission shall be followed by an extended mission with a total
mission life of up to 60 months as resources allow. The extended
mission is not to drive design requirements or resources.
NASA’s Goddard Space Flight Center
18a - 5
Lunar Reconnaissance Orbiter (LRO)
EPS System Level 2 Flow Down Key
Requirements
Level 2 Req.
Level 3: Requirements
Paragraph
Concept/Compliance
Requirement
MRD-31
3.1.2.2.6
The EPS power consumption shall not exceed the allocation as specified
LRO Technical Resource Allocations Specification (431-SPEC-000112).
Complies
MRD-20
MRD-106
MRD-107
3.3.2.1.11
Hardware over current protection of the main power bus is done for a
maximum of 48 switched services. This is accomplished with the use of
Solid State Power Controllers (SSPC) with re-settable circuit breaker
capability.
Complies
MRD-105
3.1.2.2.3
The LRO EPS shall provide an unregulated 22-35Volts (V) bus as
measured at the PSE to support a peak load of 1500W for a period of 5
minutes.
Complies
MRD-104
3.1.2.2.9
To insure compliance with voltage specifications the spacecraft will
present a minimum load to the power bus of 180W whenever the system
is powered up.
System complies
NASA’s Goddard Space Flight Center
18a - 6
Lunar Reconnaissance Orbiter (LRO)
28v Bus Backplane
EPS Block Diagram
Solar Array Module
2
Solar Array
Segments
1
x14
Loads
Output Module
x12 switched
x3 unswitched
Loads
Output Module
x12 switched
x3 unswitched
11
w / OVbckp
Loads
Output Module
x12 switched
Test Con.
x3 unswitched
Loads
Output Module
Ibatt
x12 switched
x3 unswitched
PSE Monitor Card
Test Con.
5v &
+/-15v
DPC/GSE input
Batt tlm
Rly Drv
1553
Uart / Rs422
Special Commands I/F
NASA’s Goddard Space Flight Center
Secondary Bus
SA temp
*All double sided cards with
heatsinks
18a - 7
•Analysis
Lunar Reconnaissance Orbiter (LRO)
EPS Verification Summary
•System energy balance, Solar array sizing
•Control loop simulation
•Failure Modes and Effects (FMEA), Reliability, Worst-case
•Component Tests
•PSE ETU
•Functional
•Limited environmental
•PSE Flight
•Functional
•Full environmental
•Battery
•Life cycle
•Qual and acceptance testing
•Solar Array
•Qual and acceptance testing
•Spacecraft Level
•Full functional
•Orbiter-level Environmental
•Mission cycle
NASA’s Goddard Space Flight Center
18a - 8
Summary
•The power group has been working closely with systems
to understand and define the EPS requirements.
•Requirements have been defined sufficiently enough to
allow the EPS ETU development to proceed with
confidence.
•Power handling and switching margins have been
incorporated to insure accommodation of any increases,
the system is robust
•Presently proceeding with ETU board layouts and
fabrication
•The EPS is ready to continue with detailed design
NASA’s Goddard Space Flight Center
18a - 9