Orbital Debris Mitigation Safe Disposal Planning Begins at

Orbital Debris Mitigation Safe Disposal Planning Begins at Concept Design Scott Hull Josephine San GSFC Code 591 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 1

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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 2

Overview of Documentation And Reentry Analysis Basics Scott Hull / 591 NASA/GSFC Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 3

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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 4

Applicable Documents • NPD 8710. 3 A – 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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 5

NPD 8710. 3 A Responsibilities Program/Project Manager • • Ensuring implementation of NSS 1740. 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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 6

NPD 8710. 3 A Responsibilities NASA 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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 7

NPD 8710. 3 A Responsibilities JSC 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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 8

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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 9

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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 10

ODA Conclusions • Assessment was performed per NPD 8710. 3 A • 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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 11

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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 12

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. Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 13

NSS 1740. 14 Guideline 6 -1 Disposal 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 orbit Perigee > 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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 14

NSS 1740. 14 Guideline 6 -4 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. Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 15

NSS 1740. 14 Guideline 7 -1 • Risk from Surviving Debris – Only applies to atmospheric reentry – Function of spacecraft construction and materials chosen – Debris Casualty Area < 8 m 2 – Complex simulation • Proposed changes: Reentry risk < 1 in 10, 000 considering inclination and year of reentry; casualty threshold (> 15 J) added officially Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 16

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. 3 m “man-border” is essentially added to the circumference of the object Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 17

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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 18

Reentry Terms Uncontrolled Reentry When? Where? Controlled Reentry Targeted Time & Place Breakup Burnup Land? Water? Ocean Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 19

Effort Spent on Reentry Simulation Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 20

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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 21

Component Modeling Example - 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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 22

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 Equation qnet = qconv + qrad + qox – qrr qconv = average aerodynamic heating qrad = gas cap radiation heating qox = oxidation heating qrr = reradiative cooling Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 23

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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 24

DAS Software Guideline 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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 25

DAS Software Guideline 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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 26

ORSAT Software Inputs • 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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 27

ORSAT Software Inputs • 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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 28

ORSAT Software Simulation 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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 29

ORSAT Software Outputs As many as nine detailed output files: Detailed Output Basic Output Trajectory Detailed Heating Basic Heating Aerodynamics Detailed 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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 30

Safe Disposal Planning GSFC Practical Guidelines Josephine San/591 NASA/GSFC Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 31

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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 32

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, Land. Sat – Experiences From GLAST, GPM Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 33

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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 34

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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 35

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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 36

Concept Design Process Flow For Selection of Safe Disposal Method Casualty risk > 1 in 10, 000 Spacecraft With Perigee < 2000 km, and reenter Earth starts here Concept Design Re-entry Survivability Analysis using DAS Casualty risk > 1 in 10, 000 Re-entry Survivability Analysis Using ORSAT Yes Redesign to Reduce Debris Casualty Risk? Controlled Re-entry Method No Casualty risk < 1 in 10, 000 Spacecraft With Perigee > 2000 km, starts here Need Orbit Maneuver To Meet 25 Year Orbit Life Or to Remove Spacecraft From Crowded Area? Yes Orbit Lowering/ Raising Method No Spacecraft Passivation Method Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 37

Methods to Reduce Debris Casualty Risk • Design for Demise (D 4 D) – 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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 38

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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 39

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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 40

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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 41

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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 42

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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 43

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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 44

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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 45

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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 46

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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 47

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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 48

Design for Demise (D 4 D) Examples Scott Hull / 591 NASA/GSFC Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 49

Design for Demise (D 4 D) • 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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 50

Design for Demise (D 4 D) 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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 51

Design for Demise (D 4 D) Examples 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! Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 52

Design for Demise (D 4 D) Examples 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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 53

Design for Demise (D 4 D) Examples Batteries (GPM, New Missions) – Typical Ni. MH 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 m 2) – Lithium Ion Batteries • Low pressure operation • Aluminum case • Result: Cells demise Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 54

Design for Demise (D 4 D) Examples Instrument Attach Flexures (GLAST) – Original design • 4 Titanium “boomerang” with flat plates as legs • Result: Flexures survived reentry – DCA: 0. 63 m 2 each, 2. 61 m 2 total – Modified design • Legs converted to square cross-section • Result: ORSAT simulation showed flexures demise – DCA=0 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 55

Design for Demise (D 4 D) Examples • Tungsten Converter Foils (GLAST) – Original design • 1024 Thin flat plates ~4” square • Result: Foils survive with impact energy of 24 J • DCA: 0. 47 m 2 each, 484 m 2 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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 56

Design for Demise (D 4 D) Examples Optical Bench Struts (GLAST) – Original design • 8 Titanium tubes • Good thermal isolation and CTE • Result: Survived reentry – DCA: 0. 47 m 2 each, 3. 75 m 2 total – Modified design • Material changed to graphite composite • Maintained thermal properties • Result: ORSAT simulation showed struts demise Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 57

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. 3 A – 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 Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 58

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 supported GLAST, TRMM, GPM, HST, SDO, SNOE, Swift, NPP, EXIST • Re. Entry Breakup Recorder (REBR) – Cooperative effort with Aerospace Corp – Will record temperature, accelometer, integrity data during actual reentries Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 59

Mir Reentry Systems Engineering Seminar – Orbital Debris Mitigation Scott Hull and Josephine San, 591 October 7, 2003 60