Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October...

Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003

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Orbital Debris MitigationSafe Disposal Planning Begins at

Concept Design

Scott Hull

Josephine San

GSFC Code 591


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Agenda

• Overview of NPD 8710.3 and NSS 1740.14, Scott Hull And Reentry Analysis Basics

• GSFC Safe Disposal Planning Josephine San

• Design for Demise Examples Scott Hull

• Current Status Scott Hull


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Overview of DocumentationAnd Reentry Analysis Basics

Scott Hull / 591

NASA/GSFC


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NASA Policy

• Debris assessment shall be done for all missions at mission PDR and CDR

• Design for safe disposal at the end of the mission

• Notify other government agencies when NASA related hardware reenters

• Promote international cooperation on debris related issues


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Applicable Documents• NPD 8710.3A

– Recently revised– Requires an ODA to be written– Invokes NSS 1740.14

• NSS 1740.14 (to be replaced by NS 8719.14)– Guidelines for debris mitigation– Evaluation instructions

• GSFC ISO Documents– Debris Mitigation– Controlled Reentry– Reentry Survivability


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NPD 8710.3A ResponsibilitiesProgram/Project Manager

• Ensuring implementation of NSS1740.14

• Ensuring that an ODA has been performed

• Coordinating the ODA results with NASA HQ

• Ensuring that environmental assessment is performed

• Designing for end of mission disposal and submitting an end of mission plan to Code S/Y/U

• Communicating with DOD before significant orbit changes


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NPD 8710.3A ResponsibilitiesNASA Headquarters

• Code S/Y/U– Approving ODA reports– Reviewing the cost analysis if applicable– Approving the end of mission plan

• Code Q– Establishing policies– Providing guidelines and standards– Reviewing ODA reports and end of mission plans– Providing software tools for evaluating orbital debris– Coordinating NASA reentry information within the agency

• Code I– Coordinating international agreements– Developing procedures for coordinating information on significant reentries with other

US government agencies– Coordinating pre-reentry press releases with the National Security Council and the

White House Office of Science and Technology Policy

• Code P– Coordinating pre-reentry press releases


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NPD 8710.3A ResponsibilitiesJSC Orbital Debris Program Office

• Maintaining the orbital debris environment models• Providing technical guidance on ODA issues• Providing technical review of ODA reports• Reviewing end of mission plans• Providing technical and policy guidance to all NASA

HQ offices and centers• Maintaining a list of reentry predictions

– Updated every six months– Sent to Code Q

• Promoting the use of international guidelines


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Orbital Debris Assessment (ODA)Report Review Process

• Program/Project Manager sends report to Code S/Y/U

• Code S/Y/U forwards it to Code Q• Code Q forwards it to JSC-ODPO• JSC-ODPO review comments sent back

through Code Q to Code S/Y/U• Code S/Y/U Associate Administrator

makes the final decision whether to accept the ODA and disposal plans


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What is in an ODA?• Executive Summary• Section 1: Introduction• Section 2: Spacecraft/Mission Description • Section 3: Operational Debris• Section 4: Accidental Explosions and

Intentional Breakups• Section 5: On-orbit Collision Risk• Section 6: Postmission Disposal• Section 7: Reentry Survivability • Conclusion


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ODA Conclusions

• Assessment was performed per NPD 8710.3A

• Overall findings– All applicable guidelines were met– All but X, Y, and Z were met

• Table of findings is recommended– Include all guidelines– Indicate whether each is Met, Not Met, or Not

Applicable, and any necessary comments

• Always include the DCA and casualty odds


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NSS 1740.14 Guidelines

• Basically follows the report structure

• Report doesn’t necessarily call out all of the guidelines, though

• 14 guidelines, 7 sections

• Table of findings helps to prevent holes

• Most heavily scrutinized are 4-2, 5-1, 5-2, 6-1, 6-4, and 7-1


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NSS 1740.14 Guideline 4-2

Accidental Explosions Postmission– Risk to other spacecraft– “All on-board sources of stored energy will

be depleted when they are no longer required for mission operations or postmission disposal.”

Proposed change: Recommendation to perform propellant depletion burns to reduce orbit lifetime.


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NSS 1740.14 Guideline 6-1Disposal from orbits passing through LEO

(choose one)

6-1 a. Atmospheric reentry• Orbit decay < 25 years after end of mission• Uncontrolled reentry• Controlled reentry

6-1 b. Maneuver to a storage orbitPerigee > 2500 km, Apogee < 35,288 km

6-1 c. Direct retrieval

Proposed changes:– Orbital lifetime < 30 years– Specific language on controlled reentry– Perigee > 2000 km, Apogee < 35,588 km


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Reliability of Postmission Disposal– Applies to both spacecraft and upper

stages– Identify all credible failure modes– Probability of success > 0.99

Proposed change: Reliability of > 0.90 acceptable if not performing controlled reentry.


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• Risk from Surviving Debris– Only applies to atmospheric reentry– Function of spacecraft construction and materials

chosen

– Debris Casualty Area < 8 m2

– Complex simulation

• Proposed changes: Reentry risk < 1 in 10,000

considering inclination and year of reentry; casualty

threshold (> 15J) added officially


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Debris Casualty Area (DCA)The DCA is the portion of the Earth surface on which a person is likely to be injured by a piece of falling debris.When an object survives, a 0.3m “man-border” is essentially added to the circumference of the object


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Reentry Process

• Atmosphere entry: 122 km altitude

• Appendages breakoff

• Catastrophic breakup: Typically ~78 km– Some recent evidence for lower breakup

on larger spacecraft

• Object burnup: Generally ~80 to 55 km

• Cooling / survival: Below ~50 km


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Reentry TermsControlled

ReentryTargeted Time & Place

Uncontrolled ReentryWhen? Where?

Breakup

Burnup

Land? Water? Ocean


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Effort Spent on Reentry Simulation

40%

20%

10%

10% 10%

10%

Gather Data

Envision Breakup

Organize Data

Simulate Reentry

Review Output

Write Report


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Component Modeling

• Spacecraft components need to be modeled as one of four shapes:Sphere Cylinder Box Flat Plate

• Choice is based on preserving surface area and cross-sectional area

• Many real components are difficult to model


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Component ModelingExample - Washer

• Circular top view resembles cylinder• Side view resembles a box• If tumbling, sweeps out a sphere• If cut and straightened, flat plate results• JSC recommends using a flat plate model


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Ablation

• An object is said to have ablated (demised) when it has fully melted

• Heat of Ablation

HAblat = Mass x [Cp x (Tmelt – T init) + HFusion]

• Heat Balance Equationqnet = qconv + qrad + qox – qrr

qconv = average aerodynamic heating

qrad = gas cap radiation heating

qox = oxidation heating

qrr = reradiative cooling


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DAS Software Overview

• Debris Assessment Software• Written by JSC ODPO• Very useful for evaluating Guidelines 5, 6, and 7• Current version is 1.5.3

– Stand-alone software• Downloadable from JSC ODPO web site

– Web-based interface• Available to to GSFC domains only at this time

– Version 2.0 to be released soon


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DAS SoftwareGuideline 7 (slide 1 of 2)

• Program Variables– Breakup Altitude– Object Inputs (saved in a text file)

• Name, Shape, Dimensions, Mass, Material– Materials Inputs

• Only uses Specific Heat, Heat of Fusion, and Melt Temp• Synthetic Materials

– Allows an assembly to be modeled with two masses• Aero mass – total mass of the assembly• Thermal mass – mass of the container/ structure

Web-interface version accepts inputs from Excel


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DAS SoftwareGuideline 7 (slide 2 of 2)

• Evaluation Results– Simulation Output

• Repeats input information• Demise Altitude• Debris Casualty Area• DCA Total

– Output can be saved or printed– Easy to make small changes and re-run


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ORSAT SoftwareInputs

• All contained in one input file per run– Start / Stop altitudes– Parent object shape, dimensions, mass,

material, trajectory– Fragment object shapes, dimensions,

masses, materials

• Separate file for each new material– If three objects with that material, three files


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ORSAT SoftwareInputs

• Additional capabilities over DAS– Directly entered thermal masses (sort of)– More detailed analysis

• Up to 15 nodes per object• Multiple material layers per object• Oxidation heating, Radiative cooling

– Ability to scale heating factors– Parametric studies– Specified trajectory


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ORSAT SoftwareSimulation Routine

• Same basic routine as DAS /MORSAT• Five simultaneous modules

– Trajectory: velocity and path of the object– Atmosphere: environment around the object– Aerodynamics: drag experienced by the object– Aerothermodynamics: heating of the object– Thermodynamics: response of the object to heat

• Continuous calculations at small time intervals• Concludes when object either completely

melts or reaches the stop altitude• Software goes on to next object


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ORSAT SoftwareOutputs

As many as nine detailed output files:Detailed Output Basic Output Trajectory Detailed Heating Basic Heating AerodynamicsDetailed Temperature Temperature Atmosphere

– Any or all can be disabled

• Basic Output file information– Time, Altitude, Heating Rate, Demise Factor– If object demises: Demise Altitude– If object survives: Impact Velocity, DCA, Impact

Energy, Maximum Demise Factor


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Safe Disposal Planning GSFC Practical Guidelines

Josephine San/591

NASA/GSFC


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Practical Guidelines - Content

• Objectives • Background• Concept Design Phase – Safe Disposal Planning

begins at Concept Design• Preliminary and Critical Design Phases – Design

Considerations and Planning to Successfully Achieve Safe Disposal

• Operation and End-of-Mission Phases – Implementation of End-of-Mission Plan


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Objectives and Bases

• Objectives– To Provide Practical Guidance in Compliance With NPD

8710.3 and NSS 1740.14 (to Be NASA Standard 8719.14)– To Assist Projects and Engineers in the Planning of Safe

Disposal– To Prevent Reinventing the Wheel

• Bases– NPD 8710.3 and NSS 1740.14– Experiences From CGRO, TRMM, ERBS, LandSat– Experiences From GLAST, GPM


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Background - Procedures and Guidelines

• Orbital Debris Mitigation PG– Provide Practical Guidelines on Orbital Debris Analysis– Discuss Design Process Flow to Decide on A Safe Disposal Method– Address Design Considerations, Necessary Analysis and Planning to

Achieve Safe Disposal Through Concept, to Preliminary and Critical Design Phases

– Status: In the Process of AETD Review, and Will Be Ready for Projects and Code 300 Review by the End of the Month

• End-of-Mission Planning PG– Discuss Necessary Planning for Safe Disposal at the End of the

Mission – Provide Guidance on the Development and Implementation of the

End-of-mission Plan– Serve As a Template for End-of-mission Plan– Status: Ready for Peer Review by the End of the Month


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Background - Procedures and Guidelines (cont.)

• Guidance, Navigation and Control Safe Disposal PG– Provide Guidance to Assist GN&C Flight Dynamic Engineers in the

Mission Planning and End-of-Mission Operation Planning for Safe Disposal

– Status: In the Process of Developing

• Reentry Survivability Analysis Work Instruction– Provide Detailed Instructions on Reentry Survivability Analysis

Using Debris Analysis Software (DAS) and Object Reentry Survivability Analysis Tool (ORSAT)

– Clarify Details of NSS 1740.14

– Establish a Standard Approach for All GSFC Reentry Analysis

– Status: Ready to Submit to ISO


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Safe Disposal Methods

• Controlled Reentry Method– Maneuver the Spacecraft at the End of Mission to a Disposal Orbit With a Perigee Altitude

Low Enough to Control the Location of the Reentry and Ground Impact Point

– Is Applicable to a Spacecraft which Reenters Earth Atmosphere (Usually Spacecraft at or Passing Through Low Earth Orbit Altitude), and Does Not Meet the 1 in 10,000 Casualty Risk Guideline

• Orbit Raising or Lowering Method– Maneuver the Spacecraft to a Storage Orbit by Raising or Lowering Its Final Orbit at the

End of Mission; Is Applicable to Spacecraft With Perigee Above 2000 Km

– At the End of Mission, Lower the Final Perigee So That It Will Meet the Orbit Life Time Guideline; Is Applicable to Spacecraft With Perigee Below 2000 Km (Uncontrolled Reentry)

• Passivation– Put Spacecraft in Passive State With No Energy Source

– Is Applicable to a Spacecraft which Meets the NSS Safe Disposal Guidelines

• Direct Retrieval– By Shuttle or Other Means


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Concept Design Process FlowFor Selection of Safe Disposal Method

No

Need Orbit ManeuverTo Meet 25 Year Orbit Life

Or to Remove Spacecraft From Crowded Area?

ConceptDesign

Re-entrySurvivability Analysis using

DAS

Redesign to Reduce

Debris Casualty

Risk?

ControlledRe-entry Method

Casualty risk < 1 in 10,000

YesCasualty risk > 1 in 10,000

Re-entrySurvivability

Analysis Using ORSAT

Casualty risk > 1 in 10,000

Orbit Lowering/Raising Method

SpacecraftPassivation Method

Yes

No

Spacecraft With Perigee < 2000 km, and reenter Earth starts here

Spacecraft With Perigee > 2000 km, starts here


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Methods to Reduce Debris Casualty Risk

• Design for Demise (D4D)– Alternative Design for Components Made of High Melting

Point, Specific Heat or Heat of Fusion, Such As Titanium, Beryllium, Stainless Steel

• Composite Tank Design Utilizing Easily Demisable Material• Hybrid Design Using Low Melting Point, High Density Materials

for Reaction Wheel Flywheels

– Design a Spacecraft Such That It Will Achieve Orbit Safely but Will Burn up Upon Reentry

• Possible Alternative for Adhesives or Fasteners

– Reduce Area to Mass Ratio

• Reduce Impact Energy Below Required Level by Breaking up Large but Thin Components to Smaller Segment


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Controlled Reentry - Cost

• Material, Design and Development Costs– Full Cost for Hardware to Meet High Probability of Success

• Propulsion System• Structure to Support Propulsion System• ACS Components to Support Controlled Re-entry

– Incremental Cost for Hardware to Meet High Probability of Success Including Power, Communication, Thermal, and C&DH Systems

– Full Cost for Attitude Controller Design and Development Including Delta V Control Mode for Long Duration Burn, Delta H Mode to Achieve Low Perigee Control, and Mode Transitions

– Full Cost for Reentry Software, Including Fault Management for Controlled Re-entry System, Flight Software for ACS Reentry Controlled Algorithm, and Ground Software for Testing, Simulation, and Re-entry Operation Support

– Full Cost for Improved End-of-life Fuel Depletion Computation Method


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Controlled Reentry – Cost (cont.)

– All Full Costs Will Become Incremental Cost for Missions which Require a Propulsion System for Orbit Maintenance

• More Propellant, Larger Tank, and Higher Force Level Thrusters

• ACS Components Sized to Support Controlled Reentry

• I & T Cost for Safe Disposal Segment– Incremental Cost for Missions Required Propulsion System

for Orbit Maintenance Already

• Operational cost– Managing and Planning– Implementation, Training, and Simulation

– Carrying Out Final Reentry


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Concept Design Phase - Design Considerations

• Controlled Reentry– Perform Trades on the Minimum Apogee and Perigee to Ensure the Success of Final

Burns and the Debris Footprint Confidence• Propellant • ACS Actuation Authority • Thermal Control at Lowest Perigee

– Be Sure Low Battery State of Charge Will Not Be the Trigger Point for Reentry

• Passivation– Design a Mission With Orbit Lifetime Less Than 25 Years

– Design All Subsystems Such That They Can Be Passivated at the End of Mission• Put Battery in Permanently Discharge State – Disconnect Solar Array• Purge All Fuel, Power Down Wheels, Gyros, and Communication System

• Orbit Raising/lowering– Maneuver to Storage Orbit: Incremental Cost to Meet the High Probability of Success

– Lower Perigee to Reduce Orbit Life: Trade on Lowest Perigee

– Design All Subsystems Such That They Can Be Passivated at the End of Mission


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Preliminary/Critical Design Phase – Design Considerations, Necessary Analysis and Planning

• Redo Orbital Debris Analysis and Reconsider Safe Disposal Method If Necessary

• Refine Design and Perform Analysis to Verify Design for Safe Disposal

• As a Good Practice, Outline a End-of-Mission Plan by PDR and Produce a Draft by CDR

• Controlled Reentry – Refine Propellant Budget and End-of-life Fuel Mass Estimation

Method– Design Delta V and Delta H Mode, and Lay Out Mode Transition

Sequence– Develop Failure Detection and Correction (FDC) Logic– Develop Failure Modes and Perform Failure Effect Analysis


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Operation and End-of-Mission Phase –Implementation of Safe Disposal Plan

• Perform Orbital Debris Analysis if not Done Already• Evaluate Spacecraft Hardware and Software• Propose or Re-Evaluate Viable Safe Disposal Options • Perform Risk Analysis• Evaluate Ground and Network System Readiness • Complete End-of-mission Plan Including Nominal and

Contingence Plans and Procedures• Prepare for Reviews if Necessary• Implement Safe Disposal Plan at the End of Mission


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End-of-Mission Planning• Management

– Manpower Estimation, Assign Roles and Responsibilities, Prepare for Anomaly Investigation

– External Interfaces Including Space Command, NIMA (Coast Guard, Airline), Public Affairs, HQ, ISS/JSC and State Department

– Disposition of Ground Hardware and Software

– Plan to Continue Reentry Prediction If Needed

– The First Two Items Are Especially Critical for Controlled Reentry

• Trigger Points– Nominal Trigger Point Around Which Safe Disposal Plan Is

Designed, E.G. Fuel Level

– Off Nominal Trigger Points With Different Criticality Level

– Constituent and Actions Associated With Each Trigger Point


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End-of-Mission Planning (cont.)

• System Evaluation and Risk Analysis– Ground Based System Evaluation Including Ground

System and Network Support– Spacecraft State of Health Including Instrument, Bus

Hardware and Software– Assign Trigger Level to Each Critical Component– Perform Risk Analysis for Each Failure

• Documentation Management– Configuration Management for Procedures, Timelines – Final Engineering Report


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Implementation of End-of-Mission Plan

• Nominal Plans, Procedures, and Timeline Script– Orbit Raising/lowering Option

• Maneuver Plan, Maneuver Plan Implementation Procedure, Procedure for Final Jettison of Propellant

• Plan to Coordinate Ground, Network and FDF Support• Plan and Procedure for Lowering the Orbit by Other Means• Sequence Plan to Shutdown Hardware, To Put Battery in Permanent

Discharge State• Timeline Scripts for on Consol Operation

– Passivation Option• Plan to Coordinate Ground, Network and FDF Support• Procedure for Final Jettison of Propellant If Needed• Sequence Plan to Shutdown Hardware, To Put Battery in Permanent

Discharge State• Timeline Scripts for on Console Operation


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Implementation of End-of-Mission Plan (cont.)

• Nominal Plans, Procedures, and Timeline Script (Cont.)– Controlled Reentry Option

• Plan to Coordinate Ground, Network and FDF Support• Mission Design for Controlled Reentry Shall Be Simple

and Robust, It Shall Use the Spacecraft As Close to Its Original Design As Possible

• Some of the End Products From Mission Design Are Maneuver Plan, Operation Sequence Plan, Mode Transition Plan, Plan to Characterization Burns

• Implementation Procedures for All These Plans• Develop Burn Commit and Abort Criteria


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End-of-Mission Planning (cont.)Implementation of End-of-Mission Plan

• Contingence Plans– Event Fault Tree and Probability of Success– Debris Field Error Analysis and Effective Delta V Reserve

Allocation– Contingency Handling Flow– Contingency Plans for Most Likely and Combination of Most

Likely Failures

• Training and Simulation Planning– Plans to Train Support Personnel– Plans to Verify Scripts, Procedures and Contingency Plans– Plans to Simulate Interaction Between Teams


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Design for Demise (D4D) Examples

Scott Hull / 591

NASA/GSFC


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Design for Demise (D4D)

• An effort to create alternate designs with the intent of ensuring complete demise during reentry– Generic designs for perennial survivors– Mission-specific designs for surviving components

• Methods– Different material– Multiple materials– Different shape– New technology


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Design for Demise (D4D)Examples

Reaction Wheel Flywheels (GPM, New Missions)– Often made with Stainless Steel or Titanium

• High torque wheels• Almost always survive reentry

– Alternate Designs• Large diameter Aluminum flywheels• Composite flywheel

– Aluminum with demiseable counterweights on rim


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Propellant / Pressure Tanks (GPM, New Missions)– Most traditional tanks are made from Titanium or

Stainless Steel– As you can see, Titanium and Stainless Steel tanks

often survive!


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Propellant / Pressure Tanks - Alternate Designs• Aluminum Tanks• Composite Tanks

– Al, SS, or even Ti liner for hermeticity– Graphite composite overwrap for strength

• External Heat Sources– Passively initiated pyrotechnics– Burn to provide intense heat, not explode


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Batteries (GPM, New Missions)– Typical NiMH cells are pressure vessels

• Inconel, Nickel, or Stainless Steel• Result: Cells barely demise or survive

– Due to high quantity, DCA can be very large (~10 m2)

– Lithium Ion Batteries• Low pressure operation• Aluminum case• Result: Cells demise


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Instrument Attach Flexures (GLAST)– Original design

• 4 Titanium “boomerang” with flat plates as legs• Result: Flexures survived reentry

– DCA: 0.63 m2 each, 2.61 m2 total

– Modified design• Legs converted to square cross-section• Result: ORSAT simulation showed flexures

demise– DCA=0


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• Tungsten Converter Foils (GLAST)– Original design

• 1024 Thin flat plates ~4” square• Result: Foils survive with impact energy of 24 J• DCA: 0.47 m2 each, 484 m2 total

– Modified design• 2048 Thin flat plates ~4” x 2”• Result: Foils survive with impact energy of 12 J• Below the casualty threshold, DCA =0


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Optical Bench Struts (GLAST)– Original design

• 8 Titanium tubes• Good thermal isolation and CTE• Result: Survived reentry

– DCA: 0.47 m2 each, 3.75 m2 total

– Modified design• Material changed to graphite composite• Maintained thermal properties• Result: ORSAT simulation showed struts demise


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Current Status (slide 1 of 2)

• Orbital Debris Colloquia – Most recent was 3/20/2002 at GSFC– Next colloquium is 11/4-5/2003 at JSC

• NPD 8710.3A– Updated and reissued 1/27/2003

• NSS 1740.14– Updates proposed by JSC– To be discussed 11/5/2003– Will be reissued as NS 8719.14


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Current Status (slide 2 of 2)

• DAS Software– Current version is 1.5.3– Web interface is to be available soon to GSFC domains– Version 2.0 to be discussed 11/5/2003

• ORSAT Software– Current version is 5.8 (only at JSC)– GSFC has version 5.5

• Projects being supportedGLAST, TRMM, GPM, HST, SDO, SNOE, Swift, NPP, EXIST

• ReEntry Breakup Recorder (REBR)– Cooperative effort with Aerospace Corp– Will record temperature, accelometer, integrity data during actual

reentries


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Mir Reentry

Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October...

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