Simulating Ground Support Capability for NASAs Reusable Launch Vehicle Program

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• Simulating Ground Support Capability for NASAs
  Reusable Launch Vehicle Program
• Kathryn E. Caggiano
• Peter L. Jackson
• John A. Muckstadt
• Cornell University
• Operations Research and Industrial Engineering

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NASA Goals
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Reusable Launch Vehicle Program

• Today Space Shuttle
• 1st 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 RLV
• Routine Passenger Space Travel
• 1,000x Cheaper
• 20,000x Safer

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Systems Approach Safety, Reliability, and Cost
Weight Margin
Inherent Reliability
Operating Margin
Robust Design
IVHM
Redundancy
10,000x Safer
Toxic Fluid
Operations
Move Operating Range/De-rate
Add Material Capability/Weight
100x Cheaper
Interfaces
Accessibility
Range Operations
Requires Increased Margin
Reduce Variability
Requires Increased Testing
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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

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Cornell Project Goals

• Develop analysis tools for determining and
  evaluating spare parts stocking policies for
  avionics components of Reusable Launch Vehicles

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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

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System Framework

• RLV Ground Maintenance Process
• Line Replaceable Unit (LRU) Repair Process
• Shop Replaceable Unit (SRU) Repair Process

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RLV Mission Cycle
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RLV Maintenance Cycles
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One Maintenance Cycle
Failed LRUs must be replaced by the scheduled end
date in order to avoid a delay.
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RLV Ground Maintenance
Test LRUs
Remove and Replace Failed LRUs
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LRU Repair Process
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SRU Repair Process
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System Framework
SRU Inventory
Test LRU
Remove and Replace Failed LRU
Diagnose LRU Failure
Remove and Replace Failed SRUs
Repair SRU
LRU Inventory
Repair LRU
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LRU Repair Cycle Time
Failed LRU removed from RLV
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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

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A Model of RLV Repairs

• Identify Events
• Model Delays Between Events
• Manage Priorities
• Track Inventories
• Select Inputs
• Capture Outputs

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Identify Events
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Model Delay Between Events
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Manage Priorities
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Track Inventories
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Select Inputs
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Capture Outputs
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Sample Cases
Three Cases using Simulator

• Case 1 Ample Capacity
• Case 2 Sufficient Inventories
• Case 3 Effective Service Priorities

Baseline
RLV arrivals every 50 days RLV ground time 20
days LRU work stations 5 SRU work
stations 5 Service times 75 - 100 days Repair
priority rule simple
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Sample Cases
Simulation Results

• Case 1 Ample Capacity Baseline
  Case Results
• Percent of RLVs Delayed 60
  46
• Average Delay Time 41 26
• Case 2 Sufficient LRU Inventories
• Percent of RLVs Delayed 60
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• Average Delay Time 41
  39
• Case 3 Effective Repair Priorities
• Percent of RLVs Delayed 60
  39
• Average Delay Time 41
  25

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Sample Cases
Four General Lessons

• 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.

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