ENVIRONMENTAL
CONTROL
AND
LIFE
SUPPORT
SYSTEMS
Life Support Functions and Relationships (Doll and Case, 1990)
The arrows represent how material flows between the four major life support
functions and across the system boundary (outer box).
ECLSS Requirements
• Safety
o Every failure is possible
o Design should take into consideration two simultaneous failures
• Reliability
o ECLSS should be designed to work flawlessly throughout their
operational lifetime to ensure crew survivability
• Workability in microgravity
o Phase separation (solid, liquid, gas), heat transfer and heat
rejection are of particular concern
o Air circulation must have distinct defined patterns
Cautions
• Spacecraft are isolated chambers
• Free gases, fluids and particulate mater are difficult to handle and
can pose hazards
• Human factors and human interfaces are critical in an environment
designed for extended, long term habitation, and are not necessarily the
same interface requirements as in 1 G
Main Functions of the ECLSS
Main Functions of the ECLSS
INPUT
OUTPUT
Oxygen
Carbon Dioxide
Solid Waste
Food
Urine
Water
Waste Water
Engineering Block Diagram
Human Inputs and Outputs
ECLSS MODES OF OPERATION
OPEN vs. CLOSED LOOP ECLSS
Resupply Reductions for ECLSS
Human Input/Output
(mean values, kg/person/day
MSFC Environmental Control and Life Support Group
Human Needs and Effluents Mass Balance
(per person per day)
Note: these values are based on an average metabolic rate of 136.7 W/person (11,200 BTU/person/day) and a respiration
quotient of 0.87. The values will be higher when activity levels are greater and for larger than average people. The respiration
quotient is the molar ratio of CO2 generated to O2 consumed.
Main Functions of ECLSS
• Typical Balanced Diet:
-1600 – 2000 calories of carbohydrates
- 630 – 1000 calories of fat
- 400 – 600 calories of protein
- Vitamins
- Minerals
International Space Station
Galley Water Dispenser
Russian Segment Service Module
Main Functions of the ECLSS
Shuttle Waste Management System
Shuttle Waste Management System
 The waste management system (WMS) is an integrated multifunctional
system primarily utilized to collect and process bio-wastes from all
crewmembers in a zero gravity environment. The WMS is located in the
middeck of the orbiter compartment in a 29-inch-wide area.
Shuttle Waste Management System
Functions
1.
2.
3.
4.
5.
The WMS collects, stores, and dries solid wastes.
The WMS processes urine, and transfers it to wastewater tank
The WMS processes Extravehicular Mobility Unit (EMU) condensate
waster from the airlock, and transfers it to the wastewater tank if an
Extravehicular Activity (EVA) is required on a mission.
The WMS provides an interface for venting trash container gases
overboard.
The WMS provides an interface for dumping atmospheric revitalization
wastewater overboard in a contingency situation.
Shuttle Waste Management System
WMS Major Components
1.
Commode
2.
Urinal
3.
Fan Separators
4.
Odor and Bacteria Filter
5.
Vacuum Vent Quick Disconnect
6.
WMS control
Shuttle Waste Management System
WMS Major Components
Commode
 The commode contains a single multi-layer hydrophobic porous bag liner
for collecting and storing solid waste. When it use, the commode is
pressurized and transport air flow is provided by the fan separator. When
not in use, the commode is exposed to vacuum for solid waste drying and
deactivation.
Shuttle Waste Management System
WMS Major Components
Urinal
 The urinal assembly is a flexible hose with attachable funnels that can
accommodate both men and women. And it provides the capability to
collect and transport liquid waste to the wastewater tank. The flexible
urinal hose allows use while standing, sitting or floating in any attitude.
Shuttle Waste Management System
WMS Major Components
Fan Separators
 The fan separators provide transport air flow through the commode and
urinal and separate the waste liquid from the air flow. The liquid is drawn
off to the wastewater tank, the air returns to the crew cabin through the
odor and bacteria filter. All waste management system gases are ducted
from the fan separator into the odor and bacterial filter and then mixed
with cabin air.
Shuttle Waste Management System
WMS Major Components
Odor and Bacteria Filter
Vacuum Vent Quick Disconnect,
WMS Controls
 The Odor and Bacteria Filter removes odors and bacteria from the air that
returns to the cabin.
 The vacuum vent quick disconnect is used to vent liquid directly
overboard from equipment connected to the quick disconnect through the
vacuum line.

The waste management system controls have several valves and switches
which are used to configure the commode for the different operational
modes.
Shuttle Waste Management System
WMS Restraint and Adjustment Features
 The first foot restraint (toe bar) - used for restraint for standup urination
and this restraint consists of two flexible cylindrical pads on a shaft that
can be adjusted to various heights by releasing two locking levers that
turned 90 degrees counterclockwise.
 The second foot restraint - allows the crewmember’s feet to be
restrained while sitting. This foot restraint consists of an adjustable
platform with detachable Velcro straps for securing the crewmember’s
feet.
 Body restraint (thigh bar) - sitting position is secured by lifting up each
thigh bar out of its detent position, rotating over the thigh, and releasing.
Space Shuttle Urine Dump
Pee Over Hungary,
By the Ruins of Essegvar
Tamas Ladanyi
Last Wednesday, several skygazers
scratched their heads when they
saw this mysterious glow in the sky.
International Space Station
Waste Management System
Overview
 Component Description
 Operation
New Rack-based compartment for placement in US modules
Solid Waste Container
 Composed of welded frame and
swiveling panel attached by hinges
 A lid and seal, hinged seat, and the
collector opening are attached to
the panel
 The porous inserts are attached to
the collector opening and held in
place by an elastic material
 When not being used the lid is
closed and secured by a lock
 The ISS system is essentially the
same as that used previously on the
Mir Orbital Station
Porous Inserts
 Porous to allow airflow through the bag
 A rubber ring at the top of the insert holds the
bag in place
 A red tab on the rubber ring is pulled after usage
to release and seal the insert in one step
 Each insert is used only once
Solid Waste Receptacle
 Collects and stores inserts containing waste
 Conical tank with a double wall
 Inner wall – perforated bottom
 Outer wall – airtight
 Attached to the solid waste container collector by a
flange
 Full after a 20 person day, or 7 days for a crew of 3
 The top of the container is made of charcoal to
control odors
Fan
 Creates a stream of air to provide a suction and move waste




into the solid waste receptacle
Continuous operating time of 15 minutes
Flowrate into the toilet is 700 L/min
Flowrate back into the cabin is 600 L/min
The service life is 250 days of continuous operation
Toilet Receptacle
 Consists of a funnel and a manual stopcock
 When the stopcock is open the fan, the air-water separator,
and the pre-treat/water dispenser is turned on
 The stopcock prevents any reverse flow
 Clean by wiping down the funnel with a wash cloth
Pre-Treat and Water Dispenser
 Here the flush water and the pre-treat enter their
respective chambers and then are moved to the
mixing chamber
 The pre-treat/flush water mixture is then sent to
the air-water separator
Air-Water Separator
 Separates any liquid in the air downstream of the
commode/urinal and upstream of the charcoal filter
 Comprised of:


Pump/Separator – dynamic electric drive gas-liquid separator
Blocking Device – operates automatically to control operation
 Automatically started when a crew member places the




stopcock in the open position
The pump/separator uses centrifugal force to enlarge the
liquid outer ring
The gas is pushed out through a central pipe
The liquid drains and is moved into the urine container
Service life of 180 days
Operation
Operation
 The Urine Collection Assembly transports urine,
due to airflow, to the air-water separator after a




filter removes the brine.
The gas is then filtered to remove any moisture
and is then returned to the cabin
The liquid is mixed with pre-treat and water
The mixture is then stored in the urine container
When the urine container is full it is stored in the
Progress so it can burn up in the atmosphere
during re-entry
Operation
 The Commode Assembly uses the porous insert to




allow for the air to flow though the bag
The bag is held in place by an elastic band that fits
around the hole in the commode tank
After each use, the entire bag is removed by pulling a
red tab on the elastic band
The bag is then released and sealed in one motion
The atmospheric flow then pulls the bag into the Solid
Waste Receptacle for storage and later disposal in the
Progress
Main Functions of the ECLSS
Heat Index (Apparent Temperature)
Cabin temperature should range from ~ 18 – 27 o C
Heat Index (Apparent Temperature)
Cabin temperature should range from ~ 18 – 27 o C
High Humidity can promote the growth of microbes and fungi.
Low Humidity can cause drying of the eyes and skin and the mucous membranes of
The nose and throat, decreasng protection against respiratory infections.
Main Functions of the ECLSS
Environmental Components
Lack of Oxygen (Hypoxia)
Inside an altitude (depressurization) chamber
Assumed Physiological Bounds
• Normoxic equivalent
corresponds to sea-level
alveolar pAO2
of 13.9 kPa (104 mm
Hg).
• Hypoxic boundary
corresponds to
alveolar pAO2 of
10.3 kPa (77 mm Hg)
for which
“acclimation can be
nearly complete”
according to
Waligora (1993).
• Assumes more
conservaKve
“textbook”
conditions.
Elektron Oxygen Generator in the Zvezda, Service Module,International Space Station
The Elektron
Elektron
Overview
 The System
 System Breakdown
 Safety Devices
 Problems
ELEKTRON
 Main source of oxygen production aboard ISS
 Russian system
 Built by Niichimmash
 Scientific-Experimental Institute of ChemicalMachine-Building
 Utilizes electrolysis process
 Generates O2 at the rate of 25-160 L/hr
 1 L H2O => 25 L O2
 One crewmember requires 25 L/hr of O2 on average
 O2 generation rate
 Increased by increasing the electrical current consumption rate of
the unit
Location on the International Space Station
 In the Service Module (SM)
 Panel 429
 Panel 430
Technical Specs
 Volume
 8.4 ft3
 Mass
 324 lb
 Designed for a
lifespan of 7
years
The Schematic
The Liquid Unit
 Divided into two sections
 Pressurized capsule
 Unpressurized chamber
 Two different processes occur
 Electrolysis
 H2 and O2 phase separation
The Liquid Unit
Unpressurized Chamber
 Buffer tank
 Receives water from external container
 Replenishes water in the liquid electrolyte loop
 Pressure relays monitor pressure in loop
 Primary Micropump
 Provides continuous circulation of electrolyte
The Liquid Unit
Pressurized Chamber
 Electrolysis Unit
 Electrolytic decomposition of water
 Hydrogen and electrolyte
 Oxygen and electrolyte
 Heat Exchanger
 Removes heat from gas-liquid mixture
 No higher than 3 degrees Celsius from ambient
 Phase Separators
 Separate the gas-liquid mixture
 Gaseous O2 and H2
 Liquid electrolyte
The Liquid Unit
Pressurized Chamber
 Liquid Sensor Units
 Sense and remove any residual electrolyte
 Send a message to crew if excess moisture remains
 Pressure Equalizer
 Equalizes H2 and O2 line pressures
O2 Delivery and H2 Removal Lines
 Gas Analyzers
 H2 in O2
 2 percent by volume
 O2 in H2
 15 mmHg O2 partial pressure
 Secondary Purification Unit
 Platinum catalyst and filter
 Removes H2 from O2
 H2 dumped to vacuum
 O2 vented to cabin
Nitrogen Purge Assembly
 Pressurizes liquid unit
 Purges gas lines and
analyzers
 Part of shutdown sequence
Safety Devices
 11 emergency conditions
that warrant a shut
down:




Empty water container
Electrolyte in oxygen line
Electrolyte in hydrogen line
Nitrogen pressure in the
pressurized capsule < 0.9
kg/cm2
 O2 in H2 line exceeding 15
mmHg
 H2 in O2 line exceeding 2
percent by volume
Problems
 Constantly broken
 Electrolyte in gas
lines
 Air bubbles in
electrolyte mix
Main Functions of the ECLSS
Spacecraft Closed Environment
Spacecraft Closed Environment
Changing out LiOH
modules on the
Space Shuttle
Spacecraft Closed Environment
Main Functions of the ECLSS
Historical Contaminants in Spacecraft
Contaminants
ISS Trace Contaminant Control
Systems
What are Trace Contaminants?
 There are 216 different Trace
Contaminants.
 They are grouped into
categories based on how they
affect the human body.
 Carbon Monoxide affects the
central nervous system and is
commonly attributed to
machine off-gassing
 Chemicals like ammonia are
irritants and usually come from
cleaning supplies
Why are Trace Contaminants BAD?
 On earth these contaminants are found in such
small amounts that they are not a problem.
 But on the ISS there is a finite amount of air that is
constantly reused and the chemicals will accumulate
if the air is not cleansed.
Spacecraft Maximum AllowableConcentrations
(SMAC)
 US SMAC Table
 Russian SMAC Table
How are such harmful contaminants removed?
 The US Elements use the
Trace Contaminant Control
System (TCCS)
 The Russian Elements use
the Micro Purification Unit
(BMP)
How the TCCS works
 Has 3 contaminant removal components
 Charcoal Bed Assembly
 Catalytic Oxidizer Assembly
 Sorbent Bed Assembly
 There is a fan that pulls the air into the TCCS,
a flow meter that controls the amount of air
that goes into the catalytic oxidizer, and an
electrical interface that controls and monitors
the whole system.
What does the Charcoal Bed does
 It Removes Compounds with High Molecular
Weights including compounds containing:
 Sulfur
 Nitrogen
 Halogens
 All of these compounds would impede the
Catalytic Oxidizer.
What does the Catalytic Oxidizer do?
 It gets 1/3 of the total flow. The rest is sent
directly back to the cabin.
 It oxidizes compounds at high temperatures
(roughly 400 C).
 Organic compounds form C02 and H20 which is taken care of
by different ECLSS systems.
 Inorganic compounds form acidic gasses that are removed by
the Sorbent Bed
What does the Sorbent Bed does
 It removes acid by-products of the Catalytic
Oxidizer such as:
 Hydrogen Chloride
 Sulfur Dioxide
Schematic of the TCCS
How the BMP works
 The BMP has two different types of charcoal beds.
 An Expendable Bed which removes high boiling point and high
Mol. Wt. compounds.
 A Regenerative Bed which removes low boiling point and low
Mol. Wt. compounds.
 It also has a Catalyst Bed
 It is made of Palladium or a suitable substitute
 CO and H2 are Catalytically Oxidized at ambient temperatures.
 A fan blows 20 m3/hr of air through the BMP
Schematic of the BMP
What happens if one fails?
 Each system can run the entire station by
itself.
 Neither system monitor the other.
Microbiological Assessment
Mir Orbital Station
Residents in the Condensate
Dust Mites
Ciliated Protozoa
Spirochetes
Water Microbiology Kit
The crew examines the culture and then
calls down the number to mission control
International
Space Station
Atmospheric
Revitalization
System (ARS)
CO2 (LiOH) and Trace Contaminant (activated charcoal) control
for Shuttle EMU spacesuit. 1 module is good for ~ 12 hours of EVA.
Summary of US spacecraft air purification technologies
ECLSS Trade-Offs
When comparing different ECLSS technologies, just comparing
the mass is insufficient, because different systems have different
power consumptions and thermal loading.
Main Functions of the ECLSS
Oxygen
Hydrogen
Potable Water
International Space Station Closed Cycle Life Support
System Racks
Space Shuttle Active Thermal
Control System (ATCS)
Functions of the ATCS System
• Protection
• Maintain comfortable temperatures for crew
• Maintain operating temperatures of avionics on board
• To cool and heat orbiter subsystems
• Reject excess heat
Components of the ATCS
• Flash Evaporator
• Radiators (fixed and deployable)
• Ammonia Boiler System
• Freon‐21 Coolant Loop
• Water Coolant Loop
(Each system utilizes
heat exchangers, interfaces,
cold plates)
Flash Evaporator System
• Uses:
- ascent (above 140,000 ft)
- orbit
- de‐orbit and reentry (to 100,000 ft)
• Removes 1,000 Btu/hr. per lb. water used
• Total Heat Rejection: 148,000 Btu/hr.
• Operates at 39°F (controls will deactivate
the system if the temperature goes below
37°F or above 41°F)
Radiator System
• Acts as a heat sink during
orbit
• Three or Four panels
• Location: payload bay
doors inside
• 1,195 sq ft area of heat
rejection
• Total heat rejection:
61,000 Btu/hr.
• Operate at temperature of
38°F to 57°F
• Two types: fixed and
deployable
Fixed
• Material: aluminum
honeycomb face sheet
bonded with silver Teflon
tape
• 126 in. wide, 320 in. long
• Fixed with 12 ball joints
• One sided heat rejection
• 0.5 in. thickness
• One sided coaKng
vs.
Deployable
• Material: aluminum
honeycomb face sheet bonded
with silver Teflon tape
• 126 in. wide, 320 in. long
• Attached by 6 motor operated
latches during ascent and
reentry
• Torque lever to extend 35°
from bay doors
• Two sided heat rejection
• Two sided coating
• 0.9 in. thick
Ammonia Boiler System
• Components:
– NH3 storage tank
(49 lbs.) pressurized
with helium gas
– Feed line
– Control System
– Two Control Valves
– Isolation Valve
Ammonia Boiler System
• Uses: landing (activated at altitude of 100,000 ft.)
• Two identical, parallel subsystems (A and B)
• Total Heat Rejection: 113,200 Btu/hr.
• Operates at a temperature range of 33°F to 37°F
• Three temperature sensors and overboard relief valve
for safety
Freon‐21 Coolant Loop
•
•
•
•
Uses: active during entirety of mission
Two parallel loop systems
5,336 to 5,972 lb. Freon‐21 per hour
Absorbs heat from: Fuel cell heat exchangers (HX), cold plates attached to
avionics, and internal water coolant loop
• Eject heat through: Hydraulic system HX, flash evaporator, radiators, and
ammonia boilers
• Components:
– Two pumps: powered by 115 volt ac motors
– Accumulator: pressurized with nitrogen gas
– Ball check valve
Water Coolant Loops
Water Coolant Loop
•
•
•
•
•
Uses: entire mission duration
Two Coolant Loop systems: one has two pumps, the other only one
Absorbs heat from: avionics bay cold plates
Ejects heat to: Freon‐21 loop at interchanger
Cools: garment HX in airlock, potable water storage tanks, cabin HX,
Internal Measurement HX
• Maintains cabin temperature of 65°F to 80°F
• Components
– Pump: powered by 115 volt ac motor
– Accumulator: pressurized with nitrogen gas
– Ball check valve
ECLSS Technologies for Future Space Systems
• Fundamentals of water reclamation
• Water reclamation
– Potable
– Hygiene
– Urine
• Solids disposal
ISS Consumables Budget
Consumable
Oxygen
Water (drinking)
Water (in food)
Water (clothes and dishes)
Water (sanitary)
Water (food prep)
Food solids
Design Load
(kg/person-day)
0.85
1.6
1.15
17.9
7.3
0.75
0.62
Resupply with Open Loop Life Support
from Ewert, “Life Support System Technologies for NASA Exploration Systems” ARO
Workshop on Base Camp Sustainability, Sept. 2007
Effect of Regenerative Life Support
• Open loop life support
+ Waste water recycling
+ CO2 absorbent recycling
+ O2 regenerate from CO2
+ Food from wastes
+ Eliminate leakage
100% resupply
45%
30%
20%
10%
5%
Types of Water
• Potable water
– Drinking and food preparation
– Organic solids < 500μg/liter
• Hygiene water
– Washing
– Organic solids <10,000 μg/liter
• Grey water (used hygiene water)
• Condensate water (from air system)
• Urine
Potable Water Reclamation Technologies
• Multifiltration
• Reverse Osmosis
• Electrochemical Deionization
Potable Water Multifiltration Schematic
Potable Water Reverse Osmosis Schematic
Close-up of Reverse Osmosis Concept
Electrochemical Deionization Schematic
Hygiene Water Reclamation Technologies
• Multifiltration
• Reverse Osmosis
Hygiene Water Reverse Osmosis Schematic
Multifiltration for Hygiene Water
Urine Reclamation Technologies
• TIMES - Thermoelectric Integrated Membrane Evaporation System
• VCD - Vacuum Compression Distillation
• VPCAR - Vapor Phase Catalytic Ammonia Removal
• AIRE - Air Evaporation
TIMES
Thermoelectric Integrated Membrane Evaporation System
Schematic
VCD
Vacuum Compression Distillation Schematic
VCD Vacuum Compression Distillation
Drum Distillation Schematic
VPCAR
Vapor Phase Catalytic Ammonia Removal
Schematic
VPCAR
Vapor Phase Catalytic Ammonia Removal
Simplified Schematic
AES - Air Evaporation for Urine Treatment
Water Distillation
• Vapor Compression Distillation (VCD)
– 300 kg; 1.5 m3; 350 W (for 100 kg H2O processed per day)
• VAPCAR
– 550 kg; 2.0 m3; 800 W (for 100 kg H2O processed per day)
• TIMES
– 350 kg; 1.2 m3; 850 W (for 100 kg H2O processed per day)
Selected Design Parameters
from Jones, “Breakeven Mission Durations for Physicochemical Recycling to Replace Direct Supply Life
Support” ICES 2007-01-3221, International Conference on Environmental Systems, July 2007
Water System Design Parameters
from Jones, “Mars Transfer Vehicle (MTV) Water Processor Analysis” ICES 2008-01-2193,
International Conference on Environmental Systems, July 2008
Solid Waste Disposal Technologies
• Freeze Drying
• Thermal Drying
• Combustion Oxidation
• Wet Oxidation
• Supercritical Water Oxidation
Freeze Drying Schematic
Thermal Drying Schematic
Combustion Oxidation Schematic
Wet Oxidation Schematic
Supercritical Water Oxidation Schematic
References
• Peter Eckart, Spaceflight Life Support and Biospherics, Kluwer Academic, 1996
• Ewert, “Life Support System Technologies for NASA Exploration Systems” ARO
Workshop on Base Camp Sustainability, Sept. 2007
• Jones, “Breakeven Mission Durations for Physicochemical Recycling to Replace
Direct Supply Life Support” ICES 2007-01-3221, International Conference
on Environmental Systems, July 2007
• Jones, “Mars Transfer Vehicle (MTV) Water Processor Analysis” ICES 2008-012193,
International Conference on Environmental Systems, July 2008
• Wiley Larson and Linda Pranke, Human Spaceflight: Mission Analysis and Design,
McGraw-Hill
• A. E. Nicogossian, et. al., eds., Space Biology and Medicine - Volume II: Life
Support and Habitability, American Institute of Aeronautics and
Astronautics, 1994
• Susanne Churchill, ed., Fundamentals of Space Life Sciences, Krieger Publishing,
1997