Doerr-BO-Mining-02222012
John F. Kennedy Space Center
BIOMEDICAL ENGINEERING
Cryogenic Life Support System
Donald F. Doerr
LABTECH Inc.
dsquare@cfl.rr.com
321-258-7052
(formerly)
NASA - Biomedical Engineering
Kennedy Space Center, FL 32899
John F. Kennedy Space Center
BIOMEDICAL ENGINEERING
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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.
Oxygen tank at top
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John F. Kennedy Space Center
Why cryos for life support?
BIOMEDICAL ENGINEERING
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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 Center
Mollier Chart for AIR
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John F. Kennedy Space Center
BIOMEDICAL ENGINEERING
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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 Center
Physical Properties
BIOMEDICAL ENGINEERING
Compressed
Air
Liquid Air
Supercritical
Air (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
728 x
728 x
861 x
Expansion
Rate
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John F. Kennedy Space Center
BIOMEDICAL 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 Center
How do you make liquid air?
BIOMEDICAL ENGINEERING
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Two basic ways to make liquid air
• Cool gaseous, dry air to condensation point (- 320°F)
• Mix liquid oxygen and liquid nitrogen
Can adjust oxygen/nitrogen ratio as desired
-Oxygen rich – e.g. NOAA II (36% O2)
- Applications in diving
- Applications for rebreathers
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John F. Kennedy Space Center
Liquid Air Storage
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Liquid Air Trailer – 150 gallon (also available in 158 gal and 600 gal.)
Liquid Air Pack fill Station (in shop)
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John F. Kennedy Space Center
BIOMEDICAL ENGINEERING
How does liquid air pack work?
Pressure demand SCBA mask
Buildup loop (pressurizes system)
Dewar holds 6 lb liquid air
(vacuum jacketed vessel)
Heat exchanger for buildup loop
Accumulator
Heat exchanger for supply loop
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John F. Kennedy Space Center
BIOMEDICAL ENGINEERING
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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
300 liter storage vessel
Commercially available
cryo-cooler. Recuperator
mounted in storage vessel
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John F. Kennedy Space Center
BIOMEDICAL ENGINEERING
Zero loss liquid air storage data 1
50.00
Liquid Evaporated
<---Dwell Time
<---Pump Run Tim
0.00
Average power
consumption = 396 W
-50.00
End of Test
Start Vent
1.55 Pump cycles
-100.00
Lost Data
~2L Sample
taken from
liquid side.
-150.00
-200.00
Temp Low F
-250.00
Temp Mid Low F
Temp Mid High F
Temp High F
-300.00
T-0 @ 0937 8/15/2011
Data by
Dave Bush
Tank Press PSIG
Time in minutes
CryoCooler Current A
-350.00
0
1440
2880
4320
5760
7200
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8640 10080
11520 12960 14400 15840 17280 18720
John F. Kennedy Space Center
BIOMEDICAL ENGINEERING
Zero-loss Liquid Air Dewar Test 2
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
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John F. Kennedy Space Center
BIOMEDICAL ENGINEERING
Cryogenic Air Systems in use
Propellant Handlers Ensemble
-2 hr totally encapsulated suit
- body cooling
- 5000 uses per year
Liquid Air Pack
-1 hr positive pressure demand SCBA
- Used by pad rescue and SAR teams
- 38 units in use each shuttle launch/landing
Portable Liquid Air Ventilator
– used by astronauts to cool flight
suit prior to launch
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John F. Kennedy Space Center
BIOMEDICAL ENGINEERING
Prototype cryogenic systems
Supercritical Air Pack
-1 hr pos. pres. SCBA
- Liquid Cooled garment
- For use by pad rescue team
- 2 hr unit in development
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Supercritical SCUBA
-equiv. to 90 ft3 tank
-Buoyancy compensator
- full face dive mask
John F. Kennedy Space Center
BIOMEDICAL ENGINEERING
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