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Orbital Debris Prevention and Protection for GSFC projects

Orbital Debris Prevention and Protection for GSFC projects. February 2, 2010 GSFC Code 592 Contacts: Scott.Hull@NASA.gov Ivonne.M.Rodriguez@nasa.gov. Outline. Problem Description Protection from Existing Debris Prevention of Future Debris Removal of Existing Debris NASA Requirements

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Orbital Debris Prevention and Protection for GSFC projects

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  1. Orbital Debris Prevention and Protection for GSFC projects February 2, 2010 GSFC Code 592 Contacts: Scott.Hull@NASA.gov Ivonne.M.Rodriguez@nasa.gov Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  2. Outline • Problem Description • Protection from Existing Debris • Prevention of Future Debris • Removal of Existing Debris • NASA Requirements • Conclusions Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  3. Problem Description Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  4. Why is Orbital Debris a Concern? • On-orbit Environment • Currently ~ 19,000 objects >10 cm in size ~ 300,000 objects >1 cm in size Millions of objects <1 mm in size • Growing rapidly • Already self-propagating • Tracking limitations • Spacecraft damage potential Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  5. Debris Sources • Launch • Operations • Lack of proper disposal • Collisions • Small collisions as well as large • Explosions • Batteries • Pressure tanks (usually propulsion system) • Meteoroids • Natural random environment • Meteor showers Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  6. Explosions • Batteries • Overcharge generates gas pressure • NiH most susceptible, Li-ion less so • Most Li-ion cells have cutoff switches • Li-ion must never be recharged after full drain • Pressure tanks • Fuel and oxidizer mix from leaky valve • Overpressure from regulator failure • Small debris object impact Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  7. Long-term Growth of LEO Debris Population Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  8. Collision Predictions with and without disposal efforts Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  9. Debris Flux in the A-Train Orbit Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  10. GSFC Missions(a wealth of diversity) • Quantity • Typically about 20 Space Science and 10 Earth Science missions actively operational • Usually ~70 total missions, including development • Orbits • Typically LEO (300 to 700km) • A few GEO • A few high eccentricity orbits and Lagrange points • Propulsion • About 60% have propulsion systems • Construction • Many high Z materials in detectors • Substantial use of Titanium • Glass mirrors and lenses Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  11. Orbital Debris Protection Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  12. Methods of Protection • Mission Design • Hardware Design • Shielding • Prevention Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  13. Mission Design Considerations • Orbit selection • Debris peaks at ~750, 900, and 1400 km • Usually driven by science needs, though • Operations • Orbit change maneuvers to avoid predicted close approaches • Reorient the spacecraft during meteor showers or close approaches • Have plans in place to help diagnose and/or respond to debris hits Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  14. Debris density vs. Altitude Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  15. Hardware Design Considerations • Component location • Nadir and zenith are lowest exposure • Ram and sides are highest exposure • Take advantage of shadowing • Wall thickness • Add shielding • Redundancy Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  16. Shielding Considerations • Mass • Complexity • Multi-wall much better than thicker wall • Depends on spacing • Material selection is important • Direction of threat • Use geometry to shield instruments Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  17. Multi-wall Shield Mechanisms • ‘Bumper’ layer • Breaks up and melts projectile • High temperature material (Nextel does well) • Inner layer • Traps the slower moving secondary debris • High toughness material (Kevlar does well) • Back wall • Usually the box wall • Provides the last line of defense • Can generate spalling from inside surface, even if not penetrated Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  18. Shield Testing • High velocity impact guns on actual samples • >$10,000 per shot • 3 to ~11 km/sec range (slow for meteoroids) • Tested across a range of velocities, sizes, impact angles, and densities • Produces ballistic limit curves Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  19. Light Gas Gun Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  20. Typical Whipple Shield Ballistic Limit Curve Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  21. Geometrical Shielding of Instrument Sensors Debris Baffle Sensor Debris Particle Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  22. Orbital Debris Prevention Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  23. Prevention Methods • Design for Safety • End of Mission Disposal • Reentry (active or passive) • Storage orbits • End of Mission Passivation • Disconnect battery • Vent pressure sources • Essentially minimize residual stored energy Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  24. Design for Safetyduring and after the mission • Pressure tank design • Burst strength >2X MEOP recommended • Composite tanks may be more robust • Battery selection • Usually driven by power demands • NiH is an explosion risk if overcharged • Li-ion less susceptible, but has strict charging considerations • Component location • Locate tanks and batteries near center of spacecraft • Make use of multi-wall shielding in reverse • Responsible Disposal Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  25. Battery Passivation • Disconnect the battery from the charging circuit • Relays, instead of logic (redundant in parallel) • Reducing charging rate is not enough • Leave small loads attached to the bus • Disable failure detection and correction modes at EOM • Never recharge Li-ion after a deep discharge Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  26. Pressure Tank Passivation • Design for venting • Redundant valves in series on vent lines • Consider effects of cold gas thrust • Add vent lines for pressurant tanks or diaphragms • Vent pressure as much as practical • Latching valves left open if possible • Very small amount often remains Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  27. Passivation Scenarios to retain high reliability + Charge Load - Tank L L Vent Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  28. Recent Major Debris Events * Cataloged objects (> 10 cm) Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  29. Chemical Energy Passivation • Hypergolic Fluids • Can react outside spacecraft • Vent separately, use opposing thrusters, or use propellant for disposal • Monopropellant • Be sure catalyst bed heaters are off • Corrosive Fluids Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  30. Postmission Disposal Methods • Reentry • Controlled or uncontrolled • With or without orbit lowering • Depends on demisability, orbit, propulsion capacity, guidance reliability • Storage • 2000 km to GEO-200 km • Above GEO+200 km • Retrieval Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  31. Orbital Debris Removal Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  32. Challenges to Debris Removal • Cost • Value of removing a rocket body ~$3.7M • Cost of removing a rocket body ~10X value • Ignores the less tangible value of access to the orbit • Legal Aspects • Salvage rights • Removal responsibility • No international jurisdiction or agreements • Target Selection • Technology Selection Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  33. Target Selectionfor debris removal • Orbit selection • LEO: worst density, mostly science missions (government funding) • GEO: low density, mostly commercial missions (industry funding) • Debris size selection • 1 mm to 1 cm: high quantity, low damage • 1 cm to 10 cm: moderate quantity, moderate damage, not trackable • >10 cm: low quantity, catastrophic damage, trackable Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  34. Technology Selectionfor debris removal • Each is suited to a set of orbit and size conditions • Cost varies widely • Most have yet to be demonstrated • Tethers have been used for electric generation, but not necessarily drag or propulsion • Some spacecraft retrieval and on-orbit servicing experience • No single solution will work for all applications and orbits Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  35. Examples of Removal Techniques Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  36. Lasers Mechanism: Laser beam strikes one side of a piece of debris, causing a thin layer of material to evaporate – effectively like a rocket exhaust Debris Size Range: 1 – 10 cm (bullets) Orbits: All of LEO Benefits: Ground based, cheaper, existing hardware Challenges: Undetectable debris size range; unknown object material; tumbling objects Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  37. Collection Devices (AKA Sweepers) Mechanism: Place a relatively large (1 m to 1000 m diameter) rigidized balloon or foam ball in orbit to drift around, collecting small debris impacts until its eventual reentry (some are ballistic launch, not orbital) Debris Size Range: < 10 cm (bullets) Orbits: LEO Benefits: Totally passive (launch and forget), inexpensive, lightweight Challenges: Collision risk with large debris; many needed to make a difference in small debris population Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  38. Drag Augmentation Mechanism: Attach a relatively large (10 to 1000 x object area) thin balloon or sail to object, and reduce its orbit by drag Debris Size Range: 10 cm – 5 m (hubcaps to cars) Orbits: LEO up to about 700 km Benefits: Light weight, passive, fast decay, sweeps small debris Challenges: Collision risk; rendezvous and capture difficulties Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  39. Active Direct Removal(Space Tug) Mechanism: Grapple object, and either attach a propulsion device or directly perform a controlled reentry Debris Size Range: 1 – 5 m (cars) Orbits: LEO through GEO Benefits: Positive control of debris destination; main vehicle may be reusable Challenges: Highest launch cost; rendezvous and capture of tumbling objects Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  40. Autonomous Rendezvous and Capture • Required for most large debris removal • ‘Uncooperative’ targets • Rocket bodies • Derelict spacecraft • Malfunctioning spacecraft • Assumed to be tumbling • Approach and grapple, without collision • Combination of sensors • Visible • Infrared • Radar/ LIDAR Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  41. Sample of Capture Ideas • Soft Capture Mechanism (equip all future missions with one) • Robot Arms • Tethered Net • Free-flying Net • Tethered Free-flyer with Grapple Fixture • Lasso • Harpoon • Many others Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  42. NASA Orbital DebrisRequirements Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  43. Technical Support Headquarters/OSMA ODPO (at JSC) Resources Policy NASA Orbital Debris Structure ODARs andEOMPs Policy GSFC JPL KSC ARC WSFC Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  44. Orbital Debris Structure at GSFC • Combination of efforts from Codes 300, 400, and 500 • Code 32X Chief Safety Officer • Responsible to enforce the requirements • Code 4XX Project Manager • Responsible for generating and submitting the documentation • Code 592 Orbital Debris Engineer • Assist with technical aspects • Code 5XX AETD Discipline Engineers • Provide the technical inputs and designs to help meet the requirements Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  45. NPR 8715.6 ResponsibilitiesProgram/Project Manager Pre-launch • Establish a project orbital debris mitigation activity • Provide copies of ODARs and EOMPs to OSMA for review • Ensure implementation of NASA-STD 8719.14 Post-launch • Monitor spacecraft for debris or disposal threats • Follow NPD 8010.3A at EOM • Notify JSpOC of significant maneuvers • Conjunction assessments • Review and update EOMP annually Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  46. NASA-STD 8719.14 Technical Requirements • 15 Main requirements, in 6 sections • There are requirements in the text, though • Self-assessment helps to prevent holes, but doesn’t catch everything • Most heavily scrutinized are 4-1, 4-2, 5-2, 6-1, and 7-1 • Disposal and passivation are considered to be separate activities • Report basically follows the same structure Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  47. NASA-STD-8719.14 Requirements Section 4.3 (2) Operational Debris Section 4.4 (4) Explosions, Passivation, Intentional Break-up Section 4.5 (2) Collisions Section 4.6 (5) Postmission Disposal Section 4.7 (1) Reentry Risk Section 4.8 (1) Tethers Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  48. Requirement Group 4.4Accidental Explosions Req. 4.4-1: Risk of Accidental Explosions During the Mission • Need to assess and report a quantitative estimate for explosion risk • < 0.001 probability for all credible failure modes Req. 4.4-2: Risk of Accidental Postmission Explosions • Also referred to as passivation • Disconnect battery from charging circuit • Vent pressure • The concern is the risk to other spacecraft, and to the long-term orbital environment Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  49. NASA-STD 8719.14 Requirement 4.5-2 Collision with Small Debris (S/C only) • Size based on ability to prevent postmission disposal • Function of vulnerable component area, inherent shielding, nominal mission lifetime, and object flux • Each disposal-critical component must be examined from ALL directions • <0.01 probability requirement • DAS 2.0.1 must be used for this calculation Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

  50. Large Objects vs. Small Objects Small Objects Prevents disposal Based on design (typically <1 cm) Critical component area < 0.01 (1 in 100) Shielding can be effective Large Objects Catastrophic impact > 10 cm Spacecraft average area < 0.001 (1 in 1000) Shielding ineffective Orbital Debris Prevention and Protection Scott Hull, February 2, 2010

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