Simulating Ground Support Capability for NASA’s Reusable Launch Vehicle Program

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


NASA Goals


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


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


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 Project Goals

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


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


• RLV Ground Maintenance Process

• Line Replaceable Unit (LRU) Repair Process

• Shop Replaceable Unit (SRU) Repair Process

System Framework


RLV Mission Cycle

In-Flight Time

Vehicle Launches

Vehicle Returns

Planned Maintenance

Cycle

Pre-Launch Activities

Commence


0 2 3 3 + Time

Maintenance cycle starts for successive vehicles

Scheduled maintenance cycle completions

RLV Maintenance Cycles


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.


RLV Ground Maintenance

Test LRUsRLV

Begins Service

RLV Ends Service

Removeand Replace Failed LRUs

LRUInventory


LRU Repair Process

Removeand ReplaceFailed SRUs

DiagnoseLRU

Failure

RepairLRU

LRUInventory

Test LRUsRLV

Begins Service

RLV Ends Service


SRUInventory


SRU Repair Process

RepairSRU

SRUInventory

Test LRUs

RepairLRU


LRUInventory

RLV Begins Service

RLV Ends Service


DiagnoseLRU

Failure


System Framework

RepairSRU

SRUInventory

Test LRU

RepairLRU


LRUInventory

RLV Begins Service

RLV Ends Service

Removeand Replace Failed LRU

DiagnoseLRU

Failure


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


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


A Model of RLV Repairs

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


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


RLVArrives

LRUArrives for

Repair

RemoveLRUs


Condemnand

ReplaceLRU


Repair

LRUArrives in

Stock

Install LRULRU

InstalledRelease

RLV

Repair LRUDiagnose

LRU

RemoveSRUs

OutsourceSRU

OutsourcedSRU

Arrives

RepairedSRU

Arrives

ReplacedSRU

Arrives

ReplacedLRU

Arrives

Condemnand

ReplaceSRU



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


Condemnand

ReplaceLRU


Repair

LRUArrives in

Stock

Install LRULRU

InstalledRelease

RLV

Repair LRUDiagnoseLRU

RemoveSRUs

OutsourceSRU

OutsourcedSRU

Arrives

RepairedSRU

Arrives

ReplacedSRU

Arrives

ReplacedLRU

Arrives

Condemnand

ReplaceSRU



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


Condemnand

ReplaceLRU

LRUs toRepair


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



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


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


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


*(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


*(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


Select Inputs


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


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:


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


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

Simulating Ground Support Capability for NASA’s Reusable Launch Vehicle Program

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