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Simulating Ground Support Capability Simulating Ground Support Capability for NASA’s Reusable Launch Vehicle for NASA’s Reusable Launch Vehicle
ProgramProgram
Kathryn E. Caggiano Kathryn E. Caggiano
Peter L. Jackson Peter L. Jackson
John A. MuckstadtJohn A. Muckstadt
Cornell UniversityCornell UniversityOperations Research and Industrial Engineering
Cornell UniversityOperations Research and Industrial Engineering
Cornell UniversityOperations Research and Industrial Engineering
NASA Goals
Cornell UniversityOperations Research and Industrial Engineering
Reusable Launch Vehicle Program
Today: Space Shuttle1st Generation RLV Orbital Scientific Platform Satellite Retrieval and Repair Satellite Deployment
2010: 2nd Generation RLV Space Transportation Rendezvous, Docking, Crew Transfer Other on-orbit operations ISS Orbital Scientific Platform 10x Cheaper 100x Safer
2025: 3rd Generation RLV New Markets Enabled Multiple Platforms / Destinations 100x Cheaper 10,000x Safer
2040: 4th Generation RLVRoutine Passenger Space Travel1,000x Cheaper20,000x Safer
Cornell UniversityOperations Research and Industrial Engineering
Systems Approach: Safety, Reliability, and
Cost
DesignCycleDevelopment
OperatingMargin
ReducedVariability
RobustDesignIVHMRedundancy
InherentReliability
IntactAbort
Design forManufacturing
SimplifyDesign
MinimizePart Count
FleetProduction
CrewEscape
Safety
Cost Toxic Fluid
Interfaces
Accessibility
RangeOperations
Operations
100x Cheaper
10,000x Safer
MoveOperating
Range/De-rate
Add MaterialCapability/Weight
Requires Increased Margin
Requires Increased Testing
ReduceVariability
Weight Margin
Cornell UniversityOperations Research and Industrial Engineering
Marshall Space Flight Center: NASA Flight Projects Directorate
• Project Management• Systems Engineering & Integration• Payload Operations Engineering &
Integration• Mission Preparation & Execution• Mission Training Requirements &
Processes• Ground System Design, Development, and
Test• Facility Operations
Cornell UniversityOperations Research and Industrial Engineering
Cornell Project Goals
Develop analysis tools for determining and evaluating spare parts stocking policies for avionics components of Reusable Launch Vehicles
Cornell UniversityOperations Research and Industrial Engineering
Project Objectives
Construct a methodology that:• Evaluates the effectiveness of a
proposed logistics support strategy
• Determines stock levels for recoverable items needed to operate the system effectively
Cornell UniversityOperations Research and Industrial Engineering
• RLV Ground Maintenance Process
• Line Replaceable Unit (LRU) Repair Process
• Shop Replaceable Unit (SRU) Repair Process
System Framework
Cornell UniversityOperations Research and Industrial Engineering
RLV Mission Cycle
In-Flight Time
Vehicle Launches
Vehicle Returns
Planned Maintenance
Cycle
Pre-Launch Activities
Commence
Cornell UniversityOperations Research and Industrial Engineering
0 2 3 3 + Time
Maintenance cycle starts for successive vehicles
Scheduled maintenance cycle completions
RLV Maintenance Cycles
Cornell UniversityOperations Research and Industrial Engineering
One Maintenance Cycle
Maintenance Cycle Begins
Maintenance Cycle
Scheduled to End
LRUs tested for
soundness
Failed LRUs must be replaced by the scheduled end date in order to
avoid a delay.
Cornell UniversityOperations Research and Industrial Engineering
RLV Ground Maintenance
Test LRUsRLV
Begins Service
RLV Ends Service
Removeand Replace Failed LRUs
LRUInventory
Cornell UniversityOperations Research and Industrial Engineering
LRU Repair Process
Removeand ReplaceFailed SRUs
DiagnoseLRU
Failure
RepairLRU
LRUInventory
Test LRUsRLV
Begins Service
RLV Ends Service
Removeand Replace Failed LRUs
SRUInventory
Cornell UniversityOperations Research and Industrial Engineering
SRU Repair Process
RepairSRU
SRUInventory
Test LRUs
RepairLRU
Removeand ReplaceFailed SRUs
LRUInventory
RLV Begins Service
RLV Ends Service
Removeand Replace Failed LRUs
DiagnoseLRU
Failure
Cornell UniversityOperations Research and Industrial Engineering
System Framework
RepairSRU
SRUInventory
Test LRU
RepairLRU
Removeand ReplaceFailed SRUs
LRUInventory
RLV Begins Service
RLV Ends Service
Removeand Replace Failed LRU
DiagnoseLRU
Failure
Cornell UniversityOperations Research and Industrial Engineering
Failed LRU removed from
RLV
LRU available for use
Failed SRU removed from
LRU
LRU Repair Cycle TimeRepair Facility
Location Transport Method
Product Design Repair
TechnologyRepair
Capacity
Priority Rules
SRU Repair Cycle Time
SRU Spare Inventory
Levels Transport
Queue Diagnosis
Wait for SRU
Repair
Transport
Cornell UniversityOperations Research and Industrial Engineering
Simulation Model Features
• Captures many aspects of integrated system– Outsourcing and condemnation– Limited capacity for in-house diagnosis
and repair– Probabilistic transport and service times– Limited inventories of LRUs and SRUs– Dynamic priorities
• Implemented in MS Excel with VBA
Cornell UniversityOperations Research and Industrial Engineering
A Model of RLV Repairs
• Identify Events• Model Delays Between Events• Manage Priorities• Track Inventories• Select Inputs• Capture Outputs
Cornell UniversityOperations Research and Industrial Engineering
RLVArrives
LRUArrives for
Repair
LRUW orkcenterCompletesDiagnosis
LRUW orkcenterCompletes
Repair
LRUArrives in
Stock
LRUInstalled
OutsourcedSRU
Arrives
RepairedSRU
Arrives
ReplacedSRU
Arrives
ReplacedLRU
Arrives
SRUW orkcenterCompletesDiagnosis
SRUW orkcenterCompletes
Repair
SRUArrives for
Repair
OutsourcedLRU
Arrives
Identify Events
Cornell UniversityOperations Research and Industrial Engineering
RLVArrives
LRUArrives for
Repair
RemoveLRUs
LRUW orkcenterCompletesDiagnosis
Condemnand
ReplaceLRU
LRUW orkcenterCompletes
Repair
LRUArrives in
Stock
Install LRULRU
InstalledRelease
RLV
Repair LRUDiagnose
LRU
RemoveSRUs
OutsourceSRU
OutsourcedSRU
Arrives
RepairedSRU
Arrives
ReplacedSRU
Arrives
ReplacedLRU
Arrives
Condemnand
ReplaceSRU
SRUW orkcenterCompletesDiagnosis
SRUW orkcenterCompletes
Repair
SRUArrives for
Repair
if in-house
ifrepairable
ifoutsourced
if ir-repairable
ifirrepairable
if no AW Ps
if LRU in stockif no AW Ps
ifin-house
OutsourceLRU
OutsourcedLRU
Arrivesif outsourced
DiagnoseSRU
Repair SRU
Model Delay Between Events
RLVArrives
LRUArrives for
Repair
RemoveLRUs
LRUW orkcenterCompletesDiagnosis
Condemnand
ReplaceLRU
LRUW orkcenterCompletes
Repair
LRUArrives in
Stock
Install LRULRU
InstalledRelease
RLV
Repair LRUDiagnoseLRU
RemoveSRUs
OutsourceSRU
OutsourcedSRU
Arrives
RepairedSRU
Arrives
ReplacedSRU
Arrives
ReplacedLRU
Arrives
Condemnand
ReplaceSRU
SRUW orkcenterCompletesDiagnosis
SRUW orkcenterCompletes
Repair
SRUArrives for
Repair
If in-house
if idle
ifrepairable
if idle
ifoutsourced
ifrepairable
if ir-repairable
ifirrepairable
if no AW Ps
if LRU in stock
if no AW Ps
if idle&
SRUs in stock
ifin-house
ScheduleLRU
W orkcenter
ScheduleSRU
W orkcenter
OutsourceLRU
OutsourcedLRU
Arrivesif outsourced
DiagnoseSRU
Repair SRU
Manage Priorities
RLVArrives
LRUArrives for
Repair
LRUs inTransit
Undiag-nosedLRUs
AW Ps
RemoveLRUs
LRUW orkcenterCompletesDiagnosis
Condemnand
ReplaceLRU
LRUs toRepair
LRUW orkcenterCompletes
RepairLRUs to
Stock
LRUs inStock
LRUArrives in
Stock
Install LRULRU
InstalledRelease
RLV
GroundedRLVs
SRUs inStock
Repair LRUDiagnoseLRU
RemoveSRUs
OutsourceSRU
Out-sourced
SRUs
OutsourcedSRU
Arrives
SRUs toStock
RepairedSRU
Arrives
ReplacedSRU
Arrives
SRUs onOrder
ReplacedLRU
Arrives
LRUs onOrder
Condemnand
ReplaceSRU
SRUW orkcenterCompletesDiagnosis
SRUW orkcenterCompletes
RepairSRUs inRepair
SRUs inTransit
SRUArrives for
Repair
LRUs inDiagnosis
LRUs inRepair
SRUs inDiagnosis
Undiag-nosedSRUs
If in-house
if idleif
repairable
if idle
ifoutsourced
ifrepairable
if ir-repairable
ifirrepairable
if no AW Ps
if LRU in stock
if no AW Ps
if idle&
SRUs in stock
ifin-house
+
+
+
++ +
+
+
+
+
+
+
+
++
+
++
+
+
+
-
-
-
-
-
-
-
-
-
-
- -
-
-
-
---
ScheduleLRU
W orkcenter
ScheduleSRU
W orkcenter
OutsourceLRU Out-
sourcedLRUs
OutsourcedLRU
Arrives
+
-if outsourced
+
DiagnoseSRU
Repair SRU
Track Inventories
Cornell UniversityOperations Research and Industrial Engineering
Simulation Run ControlsRandom Number
Seed
Run Length (days)
12345 100
RLV Characteristics
Days Between Arrivals
Time to Install LRU
(hours)
Days Until Launch
10 0 26
LRU Workcenters
LRU WC * NameNumber of Stations
Hours Per Day Per Station
Change-over Time
(min.)1 LRUWC01 1 24 0
>Insert additional rows as needed above this row.
SRU Workcenters
SRU WC * NameNumber of Stations
Hours Per Day Per Station
Change-over Time
(min.)1 SRUWC01 1 24 0
>Insert additional rows as needed above this row.
LRU Characteristics
LRU Index NameInitial
Inventory in Stock
Removal Delay Days
Removal Probability
(%)
LRU WC Required
*
Transport Time to Repair (hours)
Transport Time
Coeff. Of Variation
Time to Diagnose
(min.)
Diagnosis Time Coeff. Of Variation
Condem-nation
Probability (%)
Time to Repair (min.)
Repair Time
Coeff. Of Variation
Transport Time to Stock
(hours)
Stock Time Coeff. Of Variation
Replace Time to Stock
(hours)
1 LRU01 5 5 50.00% 0 552 0.5 2880 0.5 0.10% 4320 0.5 552 0.5 962 LRU02 3 10 20.00% 0 552 0.5 2880 0.5 0.10% 4320 0.5 552 0.5 963 LRU03 3 15 10.00% 0 552 0.5 2880 0.5 0.10% 4320 0.5 552 0.5 964 LRU04 3 20 10.00% 0 552 0.5 2880 0.5 0.10% 4320 0.5 552 0.5 965 LRU05 0 10 40.00% 1 72 0.5 2880 0.5 0.10% 4320 0.5 72 0.5 966 LRU06 0 15 50.00% 1 72 0.5 2880 0.5 0.10% 4320 0.5 72 0.5 967 LRU07 1 25 50.00% 1 72 0.5 2880 0.5 0.10% 4320 0.5 72 0.5 96
>Insert additional rows as needed above this row.
*(0 = outsourced repair))
SRU Characteristics
SRU Index NameInitial
Inventory in Stock
(Skip this Field)
Removal Probability
(%)
SRU WC Required
*
Transport Time to Repair (hours)
Transport Time
Coeff. Of Variation
Time to Diagnose
(min.)
Diagnosis Time Coeff. Of Variation
Condem-nation
Probability (%)
Time to Repair (min.)
Repair Time
Coeff. Of Variation
Transport Time to Stock
(hours)
Stock Time Coeff. Of Variation
Replace Time to Stock
(hours)
1 SRU01 1 0 25.00% 1 48 0.5 2880 0.5 0.10% 1440 0.5 48 0.5 962 SRU02 1 0 50.00% 1 48 0.5 1440 0.5 0.10% 1440 0.5 48 0.5 963 SRU03 1 0 25.00% 1 48 0.5 2880 0.5 0.10% 1440 0.5 48 0.5 964 SRU04 1 0 40.00% 1 48 0.5 1440 0.5 0.10% 1440 0.5 48 0.5 96
>Insert additional rows as needed above this row.
*(0 = outsourced repair))
LRU-SRU Usage MatrixSRU Index: 1 2 3 4 5LRU Index Name SRU01 SRU02 SRU03 SRU04 0
1 LRU01 0 0 0 02 LRU02 0 0 0 03 LRU03 0 0 0 04 LRU04 0 0 0 05 LRU05 1 1 1 06 LRU06 0 0 0 17 LRU07 0 0 0 0
>Insert additional rows as needed above this row.
Select Inputs
Cornell UniversityOperations Research and Industrial Engineering
Histogram of RLV Delay Days
0
5
10
15
20
25
30
351 3 5 7 9
11
13
15
17
19
21
23
25
Delay Days
Nu
mb
er
of
RL
V's
De
lay
ed
Histogram of RLV's Delayed by LRU
0
20
40
60
80
100
120
140
1 2 3 4 5 6 7
LRU Index
Nu
mb
er
of
RL
V's
De
lay
ed
Capture Outputs
Cornell UniversityOperations Research and Industrial Engineering
Sample Cases
Case 1: Ample Capacity Case 2: Sufficient InventoriesCase 3: Effective Service Priorities
Three Cases using Simulator
RLV arrivals every 50 daysRLV ground time 20 daysLRU work stations 5SRU work stations 5Service times 75 - 100 daysRepair priority rule simple
Baseline:
Cornell UniversityOperations Research and Industrial Engineering
Case 1: Ample Capacity Baseline Case Results
• Percent of RLV’s Delayed: 60 46• Average Delay Time: 41 26
Case 2: Sufficient LRU Inventories• Percent of RLV’s Delayed: 60 27• Average Delay Time: 41 39
Case 3: Effective Repair Priorities• Percent of RLV’s Delayed: 60 39• Average Delay Time: 41 25
Sample Cases
Simulation Results
Cornell UniversityOperations Research and Industrial Engineering
Sample Cases
1. Sufficient service capacity significantly improves on-time performance.
2. Appropriate LRU and SRU inventory levels improve performance considerably.
3. Effective repair priorities increase utilization, reduce costs, and improve on-time performance.
4. System utilization rates, inventory levels, and on-time service targets cannot be selected independently.
Four General Lessons