Is Your Shuttle Running

1
Is Your Shuttle Running?

• Fuel Cells on the Space Shuttle as interpreted by
  Austin Jackson

2
What do they power?

• Solid Rocket Boosters
• Orbiter
• External Tank
• Most Payloads

3
General Make-up of a Fuel Cell

• 2 main components
• Fuel Cell Stack- where the reactions take place
• Fuel Cell Accessory Section- monitors the
  performance/status of the stack

4
A Brief History of Fuel Cells

• First conceived by Welsh physicist Sir William
  Robert Grove in 1839
• Francis T. Bacon switched from platinum and
  sulfuric acid cells to safer and cheaper alkaline
  and nickel combination in 1959
• A few years later General Electric created the
  fuel cell power system that NASA used on the
  Gemini and Apollo missions

Grove
5
Other Common Uses for Fuel Cells

• Electric Cars
• Current research into fuel cells which could
  replace standard dry cell batteries and possibly
  provide power for residences
• Used in some areas of industry as a more
  efficient alternative to standard power grids

6
The Technology Involved

• General Information
• 3 onboard the Space Shuttle
• Over 70 efficient
• Use H2 and O2 for reactants and Flourocarbon 40
  for coolant
• Each weighs 260 lbs
• Dimensions are
• 14 x 15 x 45

Location of the Fuel Cells All under payload bay
liner towards front of payload bay
7
Slightly Less General Information

• The Fuel Cell Stack
• Composed of 96 electrochemical shells all
  sandwiched together
• The electrochemical shells each produce about 1
  volt a piece, so there are 32 in each substack to
  ensure that the Shuttle is constantly receiving
  the necessary 28 volts
• Manifolds run the length of the stack to deliver
  the reactants and coolant

8
Slightly Less General Information

• The Fuel Cell Accessory Section
• Reactant Valves
• Reactant Preheaters
• Dual-Gas Regulator
• Condenser
• Water Separator
• Purge Valve
• Coolant Pump
• Startup Heater
• Sustaining Heater
• Accumulator
• Cell Performance Monitor
• Electrical Control Unit

9
The Chemical Reaction

• The hydrogen and oxygen enter the electrochemical
  shell from opposite sides
• They then react with an electrolyte from the
  potassium hydroxide
• The reaction between the hydrogen and an
  hydroxide ion creates water and electrons

10
More Chemical Reaction

• The overall chemical reaction is
• 2H2 O2 ? 2H2O 4e-
• Separate Reactions
• Cathode
• O2 4e- 2H20 ? 4OH-
• Anode
• 2H2 4OH- ? 4H2O 4e-
• When the electrons return through the other side
  of the shell, they react with the oxygen and
  water to form the necessary hydroxide ions

An electrochemical shell
11
The Flow of Things

• Reactant Flow
• PRSD Tanks ? Reactant Preheaters ? Contaminant
  Filters ? Check Valves (no reverse flow) ?
  Dual-Gas Regulator ? O2 sent to stack H2 sent to
  replenish lost H2 and remove water vapor

12
More Flow of Things

• Water Flow
• Removed from stack ? Condenser to form droplets ?
  Water separator/hydrogen pump ? ELCSS Supply
  Tanks
• Coolant Flow
• Coolant Pump ? Control Valve ? Fuel Cell Heat
  Exchanger ? Pre-mixing Valves ? Condenser ? Stack
  Inlet Control Valve ? Startup Heaters ?
  Sustaining Heaters ? Accumulator ? Stack

13
Crew Controls

• Power up the Electrical Control Unit
• Control the reactant flow valves
• Control the heaters
• Start and Stop the Electrical Control Unit
• Purge the system

Panel R1
14
These things are sturdy

• 113 missions flown
• 90,264 operating hours
• Over 99 availability
• Only two missions cut short by fuel cell
  failure-- STS-2 and STS-83

15
Fin Questions?