Transcript Advances in Thermal Protection System Instrumentation for

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
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
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
TPS tiles on the space shuttle wing
Mars Exploration Rover during
entry into Mars’ atmosphere
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
History of TPS Instrumentation - 60’s
• 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
History of TPS Instrumentation - 60’s
• 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)
The Galileo Probe
• Galileo probe launched in 1989 and descended into Jupiter in
1995
• Entered into the atmosphere at > 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
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
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
Future Missions
• Most prominent mission for TPS instrumentation in the nearfuture 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
Future Sensor Designs
• Wireless sensors
• Micro-meteor impact detection
• Ultrasonic recession sensors
• Fiber-optic based spectral measurements
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 > 1000 °C
• Mechanical and structural loads during launch and entry are severe as well
(3000g of shock)
• Planetary protection concerns
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
Ablation
direction
1~2 mm OD
Polyimide
insulation barrier
Resistive wound 1
Resistive wound 2
TPS core
Lead 1
Lead 2
V
Voltage
Measurement
Current
source
How is this Work Carried Out at NASA?
Moscow
Aerial photo of NASA
Ames Research Center
NASA
Ames
Disciplines Involved
• Mechanical and electrical design
• Manufacturing
• Testing
• Modeling
• Project management
• Many others…
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
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
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
Modeling
• Computational modeling of entry environment
conditions performed by personnel working in
computational fluid dynamics, supercomputers, and
software development
CFD plot for MEDLI
NASA Ames Columbia supercomputer facility
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
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
Acknowledgements
• In-Space Propulsion program (ISP)
• CEV TPS Advanced Development Project
• Mars Science Laboratory Entry, Descent, and Landing
Instrumentation
• Lunar re-Entry Experiment
Questions
• Questions?
• Johnny Fu, Electrical Engineer,
[email protected]
• NASA Ames Research Center www.arc.nasa.gov