Advances in Thermal Protection System Instrumentation for Atmospheric Entry Missions

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Advances in Thermal Protection System
Instrumentation for Atmospheric Entry Missions

• Johnny Fu
• Sierra Lobo, Inc.
• NASA Ames Research Center
• Presentation for the University of Idaho
• April 24, 2008

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Outline

• What is thermal protection system (TPS)
  instrumentation?
• TPS instrumentation past, present, and future
• What are the day-to-day activities for TPS
  instrumentation?
• Summary
• Questions

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What is TPS Instrumentation?

• Thermal protection system
• The material used to protect a spacecraft from
  the heat encountered when entering an atmosphere
• Most well-known example are Space Shuttle tiles
• Any spacecraft entering an atmosphere requires
  TPS to survive
• Temperatures can get up to 2300 F for the Space
  Shuttle

Mars Exploration Rover during entry into Mars
atmosphere
TPS tiles on the space shuttle wing
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Role of Instrumentation

• The use of instrumentation helps answer some
  fundamental questions about TPS and atmospheric
  entry
• How did the material perform in flight?
• How hot did the vehicle get?
• What was the pressure on the spacecraft?
• Answering these questions helps improve the
  design of spacecraft for future missions
• Without knowing the answers, a future mission
  carries risks for flight risks that can be
  reduced with data returned from instrumentation

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History of TPS Instrumentation - 60s

• Fire II mission - launched in 1964
• Calorimeters to measure heating rate
• Radiometers to measure shock layer radiation

Fire II capsule 0.67m dia
Cross-section showing radiometer location
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History of TPS Instrumentation - 60s

• Apollo IV and VI - launched in 1967 and 1968
• Unmanned test flights for Apollo program
• Used ablative TPS material (Avcoat)
• Radiometers to measure shock layer radiation
• Pressure ports to measure local pressures on the
  vehicle

Diagrams of Apollo TPS instruments (NASA TN
D-6843)
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The Galileo Probe

• Galileo probe launched in 1989 and descended into
  Jupiter in 1995
• Entered into the atmosphere at gt 47 km/s
  experiencing heating rates on the order of 35
  kW/cm2 - 70 times that of Apollo!
• TPS contained Analog Resistance Ablation
  Detectors (ARAD) to measure TPS performance

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Space Shuttle

• The Space Shuttle is unique compared to other
  vehicles described because it uses non-ablative
  TPS material and has a different shape
• Instrumentation of early test flights had many
  thermocouples to measure temperature response

• Aerodynamic performance of the vehicle determined
  through arrangement of pressure ports known as a
  flush air data system
• Key challenge was to design a way to penetrate
  the shuttle nosecap without compromising the
  vehicle
• Penetration provided pathway to measure surface
  pressure

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Mars Science Laboratory

• Mars Science Laboratory (MSL) is the
  next-generation Mars rover scheduled to launch in
  2009
• Instrumentation package known as MSL Entry,
  Descent, and Landing Instrumentation (MEDLI)
• Data gathered will help to support design of
  future missions
• Increase knowledge of atmospheric data,
  aerothermal heating models, and TPS performance
  through use of thermocouples, TPS recession
  sensors, and pressure sensors

Recession sensor AIAA-2008-1219
Pressure sensor NASA 20080013510
MEDLI components NASA 20080013510
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Future Missions

• Most prominent mission for TPS instrumentation in
  the near-future is the Crew Exploration Vehicle
  Orion
• Flight tests for Orion will need to demonstrate
  that TPS is certified for use by astronauts
  returning from the moon
• Missions to outer planets and moons will require
  TPS and are also candidates for instrumentation

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Future Sensor Designs

• Wireless sensors
• Micro-meteor impact detection
• Ultrasonic recession sensors
• Fiber-optic based spectral measurements

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Challenges for TPS Instrumentation

• Instruments need to survive harsh space
  environments
• Electronics can undergo extreme exposure to
  radiation (possibility to induce latch-up on
  active components)
• Temperature limits for TPS instruments are
  extreme indeed
• Cruising through space at -150 C
• Entering atmosphere at gt 1000 C
• Mechanical and structural loads during launch and
  entry are severe as well (3000g of shock)
• Planetary protection concerns

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Case Study Recession Sensor

• Hollow aErothermal Ablation Temperature (HEAT)
  sensor
• Measures recession through change in resistance
• Patent-pending design hollow polyimide tube
  filled with TPS core of choice
• Requires external constant current source
  excitation
• Initial electrical connection formed with
  resistance weld operation
• Lead wires are welded polyimide tube slid over
  the top for insulation

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How is this Work Carried Out at NASA?
Moscow
Aerial photo of NASA Ames Research Center
NASA Ames
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Disciplines Involved

• Mechanical and electrical design
• Manufacturing
• Testing
• Modeling
• Project management
• Many others

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Design

• Engineers and scientist develop requirements for
  instruments and translate these into a detailed
  design interative process
• Common tools include SolidWorks for mechanical
  models, MS Office for communication and
  documentation

Example of SolidWorks design for TPS sensor
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Manufacturing

• People involved in assembly perform hands-on work
  to build sensors
• Use variety of materials including epoxy, bonding
  agents, wiring, and TPS
• Work with microscopes, welders, and precision
  hand tools

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Testing

• Arc Jet facilities simulate the severe heating
  environments of atmospheric entry
• Variety of disciplines required to support
  testing including test engineers, mechanical
  technicians, instrumentation specialists,
  electricians, and photographers

Photos of the Ames Arc Jet facility and testing
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Modeling

• Computational modeling of entry environment
  conditions performed by personnel working in
  computational fluid dynamics, supercomputers, and
  software development

NASA Ames Columbia supercomputer facility
CFD plot for MEDLI
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Managing it All

• Project managers develop the project plans,
  schedules, budgets, and provide the organization
  to successfully complete the mission
• Must communicate with all the different variety
  of disciplines described earlier and more

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Summary

• TPS protects a space vehicle from the harsh
  environments of atmospheric entry
• TPS instruments measure the environments and
  performance of the material
• Integrating TPS instruments onto a space vehicle
  poses unique challenges not found on the ground
• Successful use of instruments requires the
  contribution of all kinds of personnel at NASA

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Acknowledgements

• In-Space Propulsion program (ISP)
• CEV TPS Advanced Development Project
• Mars Science Laboratory Entry, Descent, and
  Landing Instrumentation
• Lunar re-Entry Experiment

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Questions

• Questions?
• Johnny Fu, Electrical Engineer,
  johnny.fu_at_nasa.gov
• NASA Ames Research Center -www.arc.nasa.gov