Oxygen Production on the ISS

1
Oxygen Production on the ISS

• Electrolysis, Sabatier Reactions, and Biological
  Replacement

2
The Need for Oxygen

• Each day, a person produces 1 kg of carbon
  dioxide and needs .83 kg of Oxygen
• Without 21.4 kPa of oxygen, humans begin to
  experience physiological effects such as
  decreased night vision, impaired memory and
  coordination, unconsciousness, convulsions, and
  death of nerve tissue.

3
Hypoxia and Hyperoxia
4
ISS Environment

• Based on a crew of six
• Additional load of test animals 1 Human
• Also off gassing from 75,000 kg of hardware
• Currently use Compressed Oxygen for all needs

5
OGA Oxygen Generation Assembly

• Scheduled to go up on Node 3, July 2005
• Sits in standard Rack
• 73x42 inches
• 386 kg
• Supplies Oxygen through Electrolysis

6
Static Feed Water Electrolysis

• Splits water into Hydrogen and Oxygen Gas
• 2 H20 -gt 2 H2 02
• OGA is split into 24 stacks
• Each stack has a Hydrogen and Oxygen compartment
  which are separated by a Potassium Hydroxide and
  electrode assembly
• Electrolysis produces a water deficiency in the
  electrolyte
• Causes water to diffuse through the hydrogen
  chamber into the electrolyte

7
Static Feed Water Electrolysis
8
The Mechanical Future Sabatier

• While continuously running, the OGA produces
  12lbs of Oxygen gas a day.
• Currently works together with the Carbon Dioxide
  Reduction Assembly(CReA) and leftover Hydrogen is
  vented into space.
• Alternative is to use a Sabatier Reactor
• 4 H2 CO2 -gt CH4 2 H20
• Recycles CO2 and provides Methane for possible
  propulsion applications.

9
The Biological Future BOGS

• Biological Oxygen Generation Systems
• Uses plant photosynthesis to recycle CO2 into 02
• CO2 2 H20 -gt (CH20) 02

10
What type of plant? Algae vs. Higher Plants

• Green Algae chrorella
• Produces enough O2 for 1 person w/ 450g
• Dont purify water or produce food
• Require less crew time attention
• Can regrow entire culture from 1 Cell

• Higher Plants ex. Wheat or Potatoes
• Requires 20 square meters of plantation space to
  produce same amount of O2
• Transpire water
• Ample Food source
• Produce Etheleyne which stunts growth
• Roots absorb less water in Microgravity

11
Closing the Loop?
12
System Management

• Adaptability a must
• Separate Chambers allows for local and global
  control
• Astronauts able to monitor rate of growth and
  photosynthesis
• Able to then adjust temperature, humidity, and
  air flow accordingly

13
Pros and Cons Mechanical OGA

• Pros
• Reliable
• Well Tested
• Mechanical-Mechanical systems integration much
  easier than Biological-Mechanical
• Cons
• Repair can require parts to be sent up from Earth
• Large Energy Consumption

14
Pros and Cons Biological BOGS

• Pros
• Low Dry Weight
• High O2 Production efficiency
• Self Repairing (Can grow new culture from 1 cell)
• Step towards truly closed loop systems
• Cons
• Untested on a large scale in flight
• Requires more crew attention

15
BAM! DONE!Err, I mean, FIN