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reverse-brayton coolers
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Air Separation
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Air Separation/Liquefaction Systems for Aircraft and Portable Applications

Creare has developed a number of advanced technologies to meet the needs of aircraft and portable gas separation applications including Onboard Oxygen Generating Systems (OBOGS) and Onboard Inert Gas (i.e., nitrogen) Generating Systems (OBIGGS) for military and commercial aircraft. On aircraft, nitrogen is used for fuel tank inerting, and oxygen for emergency breathing, aeromedical use, and special operations missions requiring oxygen prebreathing. Small, lightweight oxygen- and nitrogen-generating systems are also needed for mobile hospitals, home oxygen therapy (HOT), and remote equipment servicing uses. These applications often have unique constraints and requirements.

Our technological approaches span a broad spectrum and include cryogenic separation, molecular sieves, semipermeable membranes, ceramic membranes, and proton exchange membranes. Several of these technologies are described below.

Cryogenic Separation Systems
Creare’s cryogenic separation systems extract high-purity oxygen (99+%) and nitrogen (99+%) from aircraft engine bleed air using advanced, compact cryogenic distillation technology. Cryogenic cooling is provided by a reverse-Brayton cryocooler. The systems produce liquid oxygen and liquid nitrogen for storage and gaseous nitrogen for distribution directly to the aircraft fuel tanks. We have developed large-scale systems for military aircraft application and miniaturized systems for HOT that are based on the production and use of low-pressure liquid, rather than high-pressure gaseous oxygen.

Semipermeable Membrane Separation Systems
Creare’s semipermeable membrane-based OBIGGS combines advanced technology with novel turbomachinery and heat exchangers to provide a lightweight, low-power aircraft fuel tank inerting system.

Molecular Sieve Separation Systems
Creare has developed molecular sieve based oxygen generating systems that combine the advantages of a molecular sieve with the advantages of liquid oxygen storage. In applications that have high peak and low off-peak flow requirements, this hybrid approach allows for a very significant reduction in the size of the system. The molecular sieve and its resource requirements can be much smaller than would be required to meet the peak flow requirements. The peak demand requirements can then be met by the stored liquid oxygen.


  • TALON. For large military aircraft, Creare developed the Total Air Liquefaction System for Oxygen and Nitrogen (TALON). TALON allows military transport, cargo, and tanker aircraft to perform a wider range of missions with reduced ground support requirements. This work was supported by the U.S. Air Force.
  • SAFTI. For large commercial aircraft, a System for Aircraft Fuel Tank Inerting (SAFTI) offers several key advantages relative to other OBIGGS (i.e., molecular sieve and semipermeable membrane approaches). SAFTI requires significantly less bleed air and electrical power than other technologies, both key issues for commercial aircraft. This work was supported by NASA.

  • SAMI. For small commercial aircraft, Creare and several key development partners developed technology for the System for Aircraft Membrane Inerting (SAMI). This work was supported by NASA.
  • AHOS. For mobile hospital and medevac applications, Creare developed the cryogenic refrigerator for the Advanced Hybrid Oxygen System (AHOS). This work was supported by the U.S. Air Force.


  • MMOS. For small military transport aircraft (e.g., C-130) Creare developed the cryogenic refrigerator for the Multi-Mission Oxygen System (MMOS). This work was supported by the U.S. Air Force.