Fuel Cell Flowmeter

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SPACE SHUTTLE FUEL CELL LIFE EXTENSION PROGRAM  
Kerri McCurdy NASA Kenneth Poast NASA Michael
Burghardt The Boeing Company (formerly of
United Space Alliance) Lloyd Mustin The Boeing
Company Henry DeRonck UTC Fuel Cells
PRE1051
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Fuel Cells in the Space Shuttle  

• 3 fuel cells
• Exposed to space vacuum
• All on-board power
• Potable water

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Space Shuttle Fuel Cell  

• Alkaline technology
• 12 kW, 28 vdc
• 113 flights
• 90,264 hours
• Outstanding reliability
• 2600-hour qualified life

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Life Limited by Cell Frame Materials

• KOH electrolyte corrodes
• fiberglass-epoxy cell frame
• 3000 hours to through-
• corrosion
• 2600 hour qualified life
• provides margin
• Life extension program to
• reduce higher-than-desired
• logistics cost

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Life Extension Ground Rules

• 5000-hour life goal
• No new materials
• Same cell planform
• Utilize existing separator plates
• Same cell thickness
• No impact on vehicle installation
• Full-rigor flight certification testing

Vehicle Installation
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Corrosion Mechanism Defined

• Corrosion requires
• presence of O2
• Initiates at cathode-
• frame bond line
• Accelerated by cathode
• potential
• Progresses through
• to anode

Corrosion Path
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Extended Life Design
Original Corrosion Path
Extended Corrosion Path
Extended Foil Substrate
Screen Substrate
Cathode
Extended Matrix
Matrix
Anode
ERP
Frame

• Catalyst boundaries redefined
• Anode durability improved

No Material Changes No External Changes
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10-Cell Stack Verification Testing
Accelerated Corrosion Testing
5000- hour Endurance Testing

• Elevated temperature
• 250 ºF vs 180 ºF
• Evaluated design options

• Simulated mission loads
• Verified extended-life design

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Verification Test Results
5000- Hour Cell Cross-Section
Durability Doubled
Average Cell Voltage
0.98
0.97
Long-Life Cell
0.96
0.95
Original Cell
0.94
0.93
5000 Hours
2600 Hours
No evidence of through corrosion
Performance data confirms extended durability
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Flight Certification Program
Long-Life Features Included
Reduced corrosion cells
More durable separator seals
Flight-quality Powerplant
More rugged insulators
Non-corroding regulator
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Full-Rigor Certification Testing
5000-Hour Endurance
Acceleration
Thermal Vacuum
Vibration
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Extended Life Capability Achieved

• All certification tests successful
• Environmental
• 5000-hour endurance
• Teardown analysis is complete
• Visual exam shows substantial
• corrosion margin
• Fleet implementation being initiated
• Predicted to fly in 2006

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Long Life Alkaline Team

• The NASA Johnson Space Center The Space
  Shuttle Program Office and the Engineering
  Directorates Energy Systems Division
• The United Space Alliance, both at Johnson Space
  Center and Kennedy Space Center, which is
  responsible for Space Shuttle launch and flight
  operations.
• The Boeing Companys NASA Systems Division, at
  Huntington Beach California, and both Johnson and
  Kennedy Space Centers, responsible for Orbiter
  vehicle design and engineering
• UTC Fuel Cells, the developer and manufacturer of
  the Space Shuttle fuel cell