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John F. Kennedy Space CenterBIOMEDICAL ENGINEERING
Cryogenic Life Support SystemDonald F. DoerrLABTECH Inc.
(formerly)NASA - Biomedical Engineering
Kennedy Space Center, FL 32899
Doerr-BO-Mining-02222012
John F. Kennedy Space CenterBIOMEDICAL ENGINEERING How did we get to cryo life support?
• Rocket engines need fuel + oxidizer (atmospheric air is not available in upper atmosphere and space)
• For shuttle – supply 1,359,142 lb of oxygen to 3 shuttle engines for 8.5 minutes.
• Gaseous, compressed oxygen tank would be too heavy• Solution go to cryogenic form of oxygen• Liquid O2 – 53 lb/ft3, - 297°F, store at 22 psi. • Total tank weight (empty – 66000 lb) 154’ long, 27.6’ dia.
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Oxygen tank at top
John F. Kennedy Space CenterBIOMEDICAL ENGINEERING Why cryos for life support?
• Similar challenges with gas supplies faced ground crews:– Whole body protective suit for toxic propellant handling –
lengthy operations (e.g. hypergol load = 10 workers x 30 hrs)– Pad rescue of 7 crewman from outside blast danger– No commercially available alternatives
• By same process, determined that cryogenic air (or oxygen) could power long duration life support equipment– At least twice the duration of compressed air– Store at 22 psi, operate at 150 psi (max)– Storage vessels (dewars) much lighter– Avoid hazards of high pressure gas (air or oxygen)– Body cooling a by-product
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John F. Kennedy Space CenterBIOMEDICAL ENGINEERING Mollier Chart for AIR
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John F. Kennedy Space CenterBIOMEDICAL ENGINEERING Advantages of cryogenics
• Advantages of liquid air– More useable air per volume
• (53 lb/ft3 liquid vs. 22 lb/ft3 4500psi compressed air)– Much lower, safer, storage pressure (22 psi vs 4500 psi)– Body cooling is secondary product
• Advantages of storing oxygen in liquid form– Large respirable “air” supply created by adding only O2 to system
and scrubbing CO2 such as rebreather– Considerable duration for minimal supply volumes
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John F. Kennedy Space CenterBIOMEDICAL ENGINEERING
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Physical Properties
CompressedAir
Liquid Air SupercriticalAir (gas)
Liquid Oxygen
Temperature ambient -321°F -321°F -297°F
Temperature ambient 77°K 77°K 90°K
Density 22 lb/ft3@ 4500psi
53 lb/ft3 53 lb/ft3 75 lb/ft3
Density ~0.35 gm/cm3 0.85 gm/cm3 0.85 gm/cm3 1.14 gm/cm3
Pressure 60 min. cyl.4500 psi
> 14.7 psi< 575 psi
> 575 psi< 950 psi
> 14.7 psi< 737 psi
ExpansionRate
728 x 728 x 861 x
John F. Kennedy Space CenterBIOMEDICAL ENGINEERING Disadvantages of cryogenic air/O2
• Disadvantages• Typical standby time is 24 hr, so use for planned ops• Stored liquid air can become oxygen rich over time
• Nitrogen (colder) boils off first leaving oxygen• Dewars can be attitude sensitive• Quantity indicators are more difficult
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John F. Kennedy Space CenterBIOMEDICAL ENGINEERING How do you make liquid air?
• Two basic ways to make liquid air• Cool gaseous, dry air to condensation point (- 320°F)• Mix liquid oxygen and liquid nitrogen
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Can adjust oxygen/nitrogen ratio as desired-Oxygen rich – e.g. NOAA II (36% O2)- Applications in diving- Applications for rebreathers
John F. Kennedy Space CenterBIOMEDICAL ENGINEERING
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Liquid Air Storage
Liquid Air Pack fill Station (in shop)
Liquid Air Trailer – 150 gallon (also available in 158 gal and 600 gal.)
John F. Kennedy Space CenterBIOMEDICAL ENGINEERING How does liquid air pack work?
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Dewar holds 6 lb liquid air(vacuum jacketed vessel)
Buildup loop (pressurizes system)
Heat exchanger for buildup loop
Heat exchanger for supply loopAccumulator
Pressure demand SCBA mask
John F. Kennedy Space CenterBIOMEDICAL ENGINEERING Long term cryogenic gas storage
• Zero loss cryogenic storage vessel (dewar)– Store cryogenic air, oxygen, or nitrogen for extended time periods– Use electric power to operate cryo-cooler– Combination of commercially available components
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300 liter storage vessel
Commercially availablecryo-cooler. Recuperatormounted in storage vessel
John F. Kennedy Space CenterBIOMEDICAL ENGINEERING Zero loss liquid air storage data 1
12-350.00
-300.00
-250.00
-200.00
-150.00
-100.00
-50.00
0.00
50.00
0 1440 2880 4320 5760 7200 8640 10080 11520 12960 14400 15840 17280 18720
Temp Low F
Temp Mid Low F
Temp Mid High F
Temp High F
Tank Press PSIG
CryoCooler Current A
Lost Data
<---Pump Run Tim<---Dwell Time
Average powerconsumption = 396 W
1.55 Pump cycles
~2L Sample taken from liquid side.
T-0 @ 0937 8/15/2011
Time in minutes
End of TestStart Vent
Liquid Evaporated
Data by Dave Bush
John F. Kennedy Space CenterBIOMEDICAL ENGINEERING Zero-loss Liquid Air Dewar Test 2
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Summary• Test conducted for 90 days• Digital pressure control for cryocooler activation• Entire 300 liter dewar and liquid air on digital platform scale • Sampled once per month for oxygen concentration which used about ~10 lb air each time• Conclusion
• Lost less than 1 lb liquid air over 90 days (except samples)• Oxygen sample within 0.1 % start to finish
John F. Kennedy Space CenterBIOMEDICAL ENGINEERING
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Cryogenic Air Systems in use
Portable Liquid Air Ventilator– used by astronauts to cool flight
suit prior to launch
Liquid Air Pack-1 hr positive pressure demand SCBA- Used by pad rescue and SAR teams- 38 units in use each shuttle launch/landing
Propellant Handlers Ensemble-2 hr totally encapsulated suit- body cooling- 5000 uses per year
John F. Kennedy Space CenterBIOMEDICAL ENGINEERING Prototype cryogenic systems
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Supercritical Air Pack-1 hr pos. pres. SCBA- Liquid Cooled garment- For use by pad rescue team- 2 hr unit in development
Supercritical SCUBA-equiv. to 90 ft3 tank-Buoyancy compensator- full face dive mask
John F. Kennedy Space CenterBIOMEDICAL ENGINEERING
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