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6.0.0 ECLSS Subsystem
6.1.0 Overview
6.1.1 Objective
Within the Mars habitat design, it is necessary to develop a new Environmental Control
and Life Support System (ECLSS). Some of these issues include the inability to quickly
return home, living in a range of gravity conditions, and the psychological factors that
will arise from a long duration, high-risk mission. In order to meet the system and
mission requirements, available life support technologies will be analyzed and integrated.
The Mars Design Reference Mission (DRM) document will be used as the baseline
mission and an approach will be developed to provide a comprehensive life support
system that will optimally satisfy the needs of the Mars DRM.
6.1.2 Class Specific Scope
The scope of this project is to research relevant technologies and determine an integrated
system that will successfully accomplish the above-mentioned objective. This section of
the project was completed over the course of the Fall 2002 semester for 3 credit hours.
There were two reports from two different teams that were used to find the optimal
design for the ECLSS subsystem.
6.1.3 System Design Philosophy
The ECLSS subsystem is separated into four subsystems: Atmosphere, Water, Waste, and
Food. The four subsystems are then integrated into one functional system. Figure 6.1.1
shows the subsystem interactions with the human in the loop. All subsystems interact
with one another on different levels. All subsystem interactions are taken into account
and an iterative system design is implemented to maximize efficiency. The final ECLSS
subsystem is based off the optimum individual subsystems that interact best with the
other subsystems while maintaining a high overall system performance. Individual
subsystem requirements and assumptions will be analyzed while taking into account the
overall system requirements and assumptions previously laid out. An iterative design of
the overall system and its subsystems is completed to determine the optimal way of
meeting all requirements.
Because of time limits on this project, it was decided that the most important product
should be a workable system. Trade studies were not considered a priority and as a result
the system that was chosen was a combination of two papers that were final reports in a
previous class, ASEN 5116. These were Shidemantle, Ritch. et al, 2002, and
Kungsakawin, Nancy. et al, 2002. The base design components for the food, waste, and
atmosphere subsystem came directly from Shidemantle’s report while the water
subsystem came from Kungsakawin’s report. The full references for these papers are
included at the end of this report.
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FOOD
WAST
E
WATE
R
AIR
Figure 6.1.3.1: Subsystem Interactions
6.2.0 Requirements
As mentioned earlier, The Environmental Control and Life Support subsystem (ECLSS)
is responsible for providing a physiologically and psychologically acceptable
environment for humans to survive and maintain health in the Mars habitat. This includes
providing and managing food, water, waste, and atmospheric conditions, as well as
supplying crew accommodations and medical services. To determine how to provide
what is necessary requirements must be determined. Top-level requirements, which are
also known as level 1 requirements, are requirements that are stated in the DRM. From
those, assumptions and level 2 requirements can be derived. Top Level requirements and
level 2 requirements for the ECLSS subsystem are given below.
Top Level Requirements
 Provide life support functions for a crew of 6
 180 worst-case transit time between Earth and Mars
 600 day worst-case surface stay on Mars
 Perform the entire mission assuming no resupply from Earth
 Take advantage of ISRU when possible
 Operate during launch, transit, descent, and surface g-loads
 Provide 2 levels of backup (life critical)
 Do not rely on biological systems for life support functions
 Provide as much loop closure as possible
 Reliability, maintainability, and safety
Derived Requirements and Assumptions
 Shall provide adequate atmosphere, gas composition, and pressure control.
 Must have necessary Gas Storage for mission duration.
 Must have adequate Ventilation.
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 Must provide Trace Contaminant Control.
 Shall provide Temperature and Humidity Control.
 Must have Fire Detection and Suppression.
 Must supply entire crew with adequate sources and amounts of food and potable
water for a 4-6 month transit to Mars, and 600-day stay on the surface of
Mars.
 Shall be able to collect and store liquid, solid, and concentrated wastes for
immediate and/or delayed resource recovery.
 Must provide adequate supply of hygiene water.
 Shall provide psychological support by taking into account crew environment
and other human factors.
 Shall monitor and report radiation levels in habitat to other subsystems.
 Mass must not exceed 4661 kg.
 Target life support system power usage of 12.1 kW
 Must allow for crew input to habitat temperature and humidity levels.
6.3.0 Atmosphere Subsystem
The purpose of an atmosphere management subsystem is to maintain an acceptable
atmosphere for human life. For a Mission to Mars, analysis of the system level
requirements revealed that the subsystem would operate in 1/3g gravity. This exercise
will push the current limits in knowledge about long-term reliability and functionality.
The following evaluation accounts for these system level concerns in the design approach
and in the discussion of subsystem level integration results.
6.3.1 Responsibility and Assumptions
An acceptable atmosphere for human life on a Mars mission consists of providing a safe
environment that meets the physiological and psychological needs of the crew. This
general requirement translates into subsystem process tasks. These tasks are oxygen
provision, pressure regulation, thermal control, trace contaminant control, carbon dioxide
control, and fire detection and suppression. For most of these tasks, the selected
technologies must provide the basic functionality while maintaining the key parameter(s)
within a specific range of values.
The ecosystem of the Earth incorporates most of the tasks in the regulation of the
atmosphere as a whole and in specific areas. On a large scale, the atmosphere provides
oxygen (~3.1 psia ppO2) to humans, removes metabolic byproducts (trace contaminants
and carbon dioxide), and maintains a buffer that regulates temperature, pressure and
relative humidity with physical/chemical and biological processes. However, with
changes in latitude, longitude, and altitude there are can be distinct changes in
temperature, total and partial pressures, and relative humidity.
In an enclosed environment, these same tasks operate with a smaller buffer size;
however, the same basic requirements still need to be met. For the first task, oxygen
needs to meet the base metabolic oxygen demand of 1 kg O2/person/day along with losses
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due to oxidative technology demands. The ECLSS subsystem is also responsible for
supplying the EVA subsystem with all the life support needs. Considering all the
leakages and EVA needs, the cabin still has to maintain a 3.1 psia ppO2, with an
acceptable range of 2.83 to 3.35 psia ppO2. The total pressure is regulated to 10.2 psia
due to the frequency of EVA scheduled to the crew. The combination of oxygen and
nitrogen results in variations of the total pressure is possible. The thermal control system
maintains relative humidity between 25%-70% and temperature between 18.3oC –
26.7oC. Carbon dioxide removal needs to offset the metabolic production rate of 0.85 kg
CO2/person/day in addition to technology products that interact with the crew cabin
atmosphere. Humans, material off-gassing, and technologies generate a variety of organic
and inorganic compounds (ammonia, nitric oxide, methane, ethylene, and benzene) in
volatile state or adsorbed to particulates that need to be controlled below the long term
Spacecraft Maximum Allowable Concentrations (SMAC), which are 7 mg/m3, 0.9
mg/m3, 3800 mg/m3, 340 mg/m3, and 0.2 mg/m3, respectively. Finally, on Earth fires are
eventually self-limiting, but in an enclosed environment, the final task of fire detection
and suppression needs to operate quickly and reliably to avoid both direct (life and limb)
and indirect (oxygen consumption) hazards (Eckart 1996).
6.3.2 Design Approach
The evaluation of the atmosphere subsystem entailed a multi-tiered approach. This
approach iteratively examined requirements, key mass drivers, and the functionality and
integration of different technologies. The air subsystem requirements were driven by the
top-level requirements and derived from known and assumed technology specific data.
The key mass drivers were identified in the baseline mission scenario, which consisted of
only existing (and allowable) non-regenerable technologies. These mass drivers were
then initially examined to minimize consumables. After gathering information and
ranking current technologies, a functional subsystem was created and then iteratively
changed to maximize the reuse or recycle of materials to reduce mass losses while still
conforming with the top level and subsystem level requirements.
6.3.3 Technologies and Trade Study
To understand the key mass drivers and interactions, a baseline system with existing nonregenerable technologies used on Space Shuttle, ISS, and MIR was created. The basic
system details and interactions are shown in Table 6.3.3.1 and Figure 6.3.3.1.
The key mass drivers for the baseline system were the carbon dioxide removal (46%),
oxygen provision (38%), and total pressure regulation (13%) systems. These identified
systems are all high in consumable mass. As a first cut for mass savings, the oxygen,
nitrogen and carbon dioxide system variables are reviewed to determine options for the
minimization of consumables. The consumable mass for the carbon dioxide removal
system is due to the LiOH canisters, which translates into mass savings dependent
completely upon the selected carbon dioxide removal or reduction technology. The mass
of the oxygen system was sized for humans (91.5%), venting (7.9%), leakage (0.6%), and
technology (0%) usage; similarly the total pressure regulation system was sized only for
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leakage and EVA venting. At this level, the potential areas for mass savings are
reductions in the leakage and venting of oxygen and nitrogen.
Table 6.3.3.1: Baseline Non-regenerable Physical/Chemical Air Life Support System
Subsystem
O2 Provision
Total
Pressure
Regulation
CO2 removal
Temperature &
Humidity Control
Trace
Contaminant
Control (TCC)
Fire Detection &
Suppression
Selection
Chemical oxygen
Mass
7466
Power
0.0
Volume
0.02
Heat
Produced
0.02
Crew
Time
29.5
ESM
7496
N2 pressure tanks
LiOH canisters
Rotating
Heat
Exchanger
2562
8988
0.0
0.0
0
7
0
0
0
281
2562
9333
175
1.31
3.9
0.82
20.5
233
Space Shuttle TCCS
N2
extinguishers
&
photoelectric detectors
Total
178
0.15
11
0.15
78
361
65
19,434
0.003
1.5
0.047
21.8
0
1.0
6
415
71
20,056
Given the 1.45 kg/day predicted leakage rate of the Habitat, under normoxic conditions,
1.009 kg of N2 and .441 kg O2 will be lost to the Martian environment each day. For the
600-day mission, therefore, the minimum required buffer tank sizes are 605.6 kg and
264.4 kg for N2 and O2, respectively. However, this system trade has several potential
disadvantages: an increase in the percentage of oxygen (and thus flammability), reduced
heat rejection capacity of the air, and the unknown long term effects of living at reduced
atmospheric pressure with normoxic oxygen levels.
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cabin
leakage
N2 storage
tanks
N2
FDS
O2
crew cabin
chemical
LiO2
TCCS
T&H
control
LiOH
To: trash
compactor
N2 , O2 , H2O
To: hygiene
water tank
To: trash
To: trash
compactor
H2O
Figure 6.3.3.1: Baseline non-regenerable Physical/Chemical Air ECLSS Schematic
This schematic illustrates the basic subsystem level intra-and interactions for the air
management system.
The remaining mass savings in this system are based on the selection of individual
candidate technologies and maximization of recyclables for compatible subsystem and
system level interactions. Initially, information on a variety of technologies for meeting
the different tasks was compiled into spec sheets. These technologies were then sized in
a similar fashion to the baseline system calculations to meet the associated task. In the
case of missing information for a specific technology, some assumptions were made.
After the technologies were reasonably detailed, the technologies were ranked based
upon their equivalent system mass in Table 6.3.3.2.
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Table 6.3.3.2: Air Management Life Support Technology Rankings
Technologies
TRL
Oxygen
SPWE (w/ EDC)
9
SPWE (w/ Sabatier)
9
SPWE (w/o Sabatier)
9
Tank- cryogenic
9
O2 chemical (TRK)
9
Tank- pres vessel
9
Total Press Reg (Nitrogen)
Tank- cryogenic
9
Tank- pres vessel
9
Carbon Dioxide Removal or Reduction
EDC
6
SAWD
6
4BMS (CDRA)
8
Sabatier (CDReA w/ H2 tanks)
9
Bosch
6
LiOH
9
Thermal and Humidity Control
CHX-rotating
6
TCC
Detection
GC/MS
9
Treatment
TCCA
9
TCCS
9
Activated Charcoal
9
Catalytic Oxidation
9
Particulate Filters
9
FDS
Detection
ISS Photoelectric
9
STS Ionization
9
Suppression
Nitrogen Agent
9
Halon 1301 Agent
9
CO2
9
Depressurization
9
ESM
RANK
2119
4394
5515
6573
7496
7681
1
2
3
4
5
6
2224
2562
1
2
162
190
418
450
885
9333
1
2
3
4
5
6
267
1
150
1
135
1
201
2
In TCCS & TCCA
In TCCS & TCCA
In TCCS & TCCA
21
21
1
2
68
68
85
694
1
2
3
4
Note: ESM = mass + 0.0115 kg/kW (power) + 9 kg/m3 (volume) + 0.0069 kg/kW (heat
rejection) + 1 kg/crew-hour (crew time) + 5% kg total surcharge/TRL less than 9.
The highest ranked systems were subsequently analyzed and deemed compatible.
However, further analysis was required to determine the potential recyclables between
the selected oxygen generation system (solid polymer water electrolysis [SPWE]) and the
carbon dioxide reduction/removal systems (Sabatier, Bosch, and electrochemical
depolarized concentrator). For the primary option A (Figure 6.3.3.2), there is a high
degree of water return from the EDC to the SPWE, which reduces the additional water
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supply required to produce oxygen from 5250 kg H2O to 1,854 kg H2O, see Table
6.3.3.3. Option B (Figure 6.3.3.3) has a lower degree of water return from the Sabatier
reactor which only reduces the additional water supply required to produce oxygen from
5,250 kg H2O to 4,129 kg H2O, see Table 6.3.3.4. Based on these tradeoffs along with the
fixed mass differences, the option A saves 2,500 kg of mass over option B and 14,000 kg
of mass over the baseline scenario.
Table 6.3.3.3: Physical/Chemical Air Life Support System for Mars Mission–Option A
Subsystem
O2 Provision
Total
Pressure
Regulation
CO2 removal
Temperature
&
Humidity Control
Trace
Contaminant
Control (TCC)
Fire Detection &
Suppression
Selection
SPWE
N2
pressure
tanks
EDC
Rotating
Heat
Exchanger
Mass
2096
Power
1.84
Volume
2.24
Heat
Produced
1.84
Crew
Time
2
TRL
9
ESM
2119
2562
133
0
0.30
0
0.2
0.00
0.67
0
5.4
9
6
2562
162
175
1.31
3.9
0.82
20.5
6
267
GC/MS,TCCA
N2 extinguishers
& photoelectric
detectors
Total
273
0.08
0.9
0.18
4
9
286
80
5319
0.003
3.53
0.3
7.5
0.00
3.51
6
37.9
9
88
5485
Notes:
1) Acronyms: SPWE: solid polymer water electrolysis, EDC: electrochemical
depolarized concentrator, GC/MS: gas chromatography/mass spectrometer,
TCCA: trace contaminant control system (catalytic oxidation, activated carbon, &
particulate filters)
2) SPWE mass includes the consumable water supply
Table 6.3.3.4: Physical/Chemical Air Life Support System for Mars Mission–Option B
Subsystem
O2 Provision
Total
Pressure
Regulation
CO2
removal/reduction
Temperature
&
Humidity Control
Trace
Contaminant
Control (TCC)
Fire Detection &
Suppression
Selection
SPWE
N2
pressure
tanks
Sabatier w/ H2
Tanks
Rotating
Heat
Exchanger
Mass
4371
Power
1.84
Volume
2.24
Heat
Produced
1.84
Crew
Time
2
TRL
9
ESM
4394
2562
0
0
0.00
0
9
2562
389
0.0006
0.3
0.0029
35
9
450
175
1.31
3.9
0.82
20.5
6
267
GC/MS,TCCA
N2 extinguishers
& photoelectric
detectors
Total
273
0.08
0.9
0.18
4
9
286
80
7850
0.003
3.2
0.3
10.1
0.00
2.8
6
67
9
88
8048
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cabin
leakage
N2 storage
tanks
N2 , O2 , H2O
N2
FDS
O2
crew cabin
SPWE
TCCA
H2 , O2
H2O
To: vent
H2
From: H2O tank
H2O
T&H
control
EDC*2
To: vent
To: hygiene
water tank
To: trash
compactor
CO2
Figure 6.3.3.2: Physical/Chemical Air Life Support System Schematic – Option A
This schematic illustrates the subsystem level intra-and interactions for the air
management system; option A.
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cabin
leakage
N2 & H2
storage
tanks
N2 , O2, H2O
N2
FDS
O2
crew cabin
SPWE
TCCA
H2
H2 O
SB *10
T&H
control
H2
From: H2O tank
H2O
To: vent
To: hygiene
water tank
To: trash
compactor
CH4
H2O
Figure 6.3.3.3: Physical/Chemical Air Life Support System Schematic – Option B
This schematic illustrates the subsystem level intra-and interactions for the air
management system; option B.
6.3.4 Design
The subsystem generally operates autonomously to control process functions and
air/water flow rates with optional crew control of the temperature set point. Since Option
A was selected, the processes and its functionality are detailed in Figure 6.3.3.2 and
Table 6.3.3.3 and represent the unsupplemented operational state of the subsystem on
Mars.
On Mars, a tertiary option may be exercised in case of a partial or full failure of the fuel
generation system (ISRU) due to filter clogging. This option would entail the direction of
the excess H2 and CO2 from atmospheric subsystem to the ISRU unit by a sealed source.
Specifically, there are nine nitrogen tanks for the mission, and one tank will be empty
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upon landing with a second tank available in 30 days after arrival. These tanks could be
retrofitted to capture the H2 and CO2 and secure them for use by the ISRU system.
The analysis of the atmosphere subsystem intra- and interactions proved integral
information to the determination of the optimal system. In the baseline system design, the
key mass drivers were the carbon dioxide removal, oxygen provision, and total pressure
regulation systems. With the addition of alternative physical/chemical technologies, the
key mass drivers shifted to oxygen and nitrogen provision system due to leakage and
EVA losses.
The values for heat, power, and volume for the completed atmosphere system are located
below in table 6.3.4.1.
Table 6.3.4.1: Heat, Power, and Volume for ECLSS atmosphere technologies
Atmosphere System
Heat
Generated
(kW)
Power
(kW)
Volume
(m^3)
Mass (kg)
Solid Polymer Water Electrolysis (SPWE)
Electrochemical Depolarized Concentrator (EDC)
1.8400
0.6700
1.840
0.300
2.240
0.200
2096.00
133.00
Rotating Heat Exchanger
0.8200
1.310
3.900
175.00
Gas Chromatography/Mass Spectrometer (GC/MS)
Trace Contaminant Control System (TCC)
Fire Detection System
0.1800
0.0030
0.080
0.003
0.900
0.300
273.00
80.00
N2 Pressure tanks
0.0000
0.000
0.000
2562.00
Component
Plumbing (10% of total)
n/a
n/a
7.540
275.70
Spares
0.3513
0.35
1.51
303.27
Total
3.8643
3.8863
16.5880
5897.97
6.4.0 Water Subsystem
The baseline water management requirements are to provide potable and hygiene water to
the crew for the duration of the mission. As outlined in the human mass balance section,
3.905 kg/6 person crew/day of potable water and 23.65 kg/6 person crew/day of hygiene
water must be provided and meet the water quality requirements.
6.4.1 Responsibility and Assumptions
The requirements for water management are defined in
Table 6.4.1.1 All the water that the crews will receive has to meet the following
requirement for the purpose of maintaining the health of the crews. Water will be tested
using the monitoring technologies that will be discussed later in Water subsystem. If the
water does not meet the standards, it will be sent back for future processing.
Table 6.4.1.1: Water Quality Requirement: Maximum Contaminant Levels
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Quality Parameters
Potable
Hygiene
Total Solids (mg/l)
100
500
Color, True (Pt/Co units)
15
15
Taste (TTN)
3
N/A
Odor (TON)
3
3
Particulates (max size - microns)
40
40
pH
6.0-8.5
5.0-8.5
Turbidity (NTU)
1
1
Dissolved Gas (free @ 37 C
No Detectable Gas
N/A
Free Gas (@ STP)
No Detectable Gas
No Detectable Gas
Ammonia
0.5
0.5
Arsenic
0.01
0.01
Barium
1.0
1.0
Cadmium
0.005
0.005
Calcium
30
30
Chlorine (total - include chloride)
200
200
Chromium
0.05
0.05
Copper
1.0
1.0
Iodine (total - include organic
iodine)
15
15
Iron
0.3
0.3
Lead
0.05
0.05
Magnesium
50
50
Manganese
0.05
0.05
Mercury
0.002
0.002
Nickel
0.05
0.05
Nitrate (NO3-N)
10
10
Potassium
340
340
Selenium
0.01
0.01
Silver
0.05
0.05
Sulfate
250
250
Sulfide
0.05
0.05
Zinc
5.0
5.0
Physical Parameter
Inorganic Constituents (mg/l)
Bactericide (mg/l)
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Quality Parameters
Potable
Hygiene
Residual Iodine (minimum)
0.5
0.5
Residual Iodine (maximum)
4.0
6.0
Cations
30
N/A
Anions
30
N/A
CO2
15
N/A
Total Count
1
1
Anaerobes
1
1
Coliform
1
1
Virus (PFU/100 ml)
1
1
Yeast & Mold (CFU/ 100ml)
1
1
Total Acids
500
500
Cyanide
200
200
Halogenated Hydrocarbons
10
10
Total Phenols
1
1
Total Alcohols
500
500
Total Organic Carbon (TOC)
500
10,000
Uncharacterized TOC (UTOC)
100
1,000
Aesthetics (mg/l)
Micobial
Bacteria (CFU/100ml)
Organic Parameters (ug/l)
6.4.2 Design Approach
The first step in the design process involves calculating a baseline system. The baseline
system is simple. All the water will be lifted and carried for the entire mission duration.
However, this accounts for a mass of nearly 99,198 kg of water. Closing the water loop
by recycling urine, hygiene water, and atmospheric condensate will make very significant
mass savings. Candidate technologies were then identified to close the loop and were
ranked taking into account TRL, mass, power, volume, efficiency, and hazard level.
Winning technologies were then integrated into the water subsystem.
6.4.3 Technologies and Trade Study
The baseline architecture is simple. The water comes from the storage and all the water
was taken with the crew.
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To Waste Management
2.5
Laundry
9.4
Hygiene
18.216
Potable
Water
Storage
0 .214
Food at Crew
Accommodation
Figure 6.4.3.1: Open Loop Diagram w/ Flow Rates in kg/day for 6 Crewmembers
Table 6.4.3.1: Water Management Parameters
600 Days
Mass (kg)
Power (kW)
Volume (m3)
99198.0
0.02
99.24
Figure 6.4.3.1 shows the baseline system block diagram for the water management
subsystem. The only components needed to operate the system include storage and
delivery. The storage mass was assumed to be 20% of the stored mass.
Water processing technologies were broken down into two main categories, Potable and
Hygiene processing and urine processing since urine needs more treatment than hygiene
water. Table 6.4.3.2 shows the candidate technologies considered for the potable and
hygiene water processing.
Table 6.4.3.2 Hygiene & Potable Water Treatment Candidate Technologies
WM Function
Candidate Technologies
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WM Function
Hygiene & Potable Water 
Treatment












Candidate Technologies
MIR Technology (Condensate)10
Reverse Osmosis (RO)1,13
Multifiltration (MF)1,13
Electrodialysis1
Oil and Water Seperation2
 Rock/Plant/Microbial Filtering System3,4
 Thermoelectric
Integrated
Membrane
Evaporation (TIMES)1
Granular Activated Carbon (GAC)5
Aqueous Phase Catalytic Oxidation Subsystem
(APCOS)
Ultrafiltrtion10
MilliQ Absorbtion Beds
Pasteurization
Ionic Silver1
Regenerable Microbial Check Valve (Iodine)12,15
UV-visible Spectrophotometer (laser)11
Due to the significant list of candidate technologies, a series of selection criteria needed
to be used to rule out undeveloped technologies. TRL levels less than 6 and complete
lack of information were the primary criteria used to reduce the number of candidate
technologies. Further elimination of technologies was performed during the formation of
the spec sheets due to key information (such as mass or power) missing.
The potable and hygiene water processing consisted of numerous technologies, each
consisting of unique pre and post treatment processes. This required the development of
systems of different technologies to be traded between. Hygiene and potable water will
be processed with the same system. Consumable data is primarily described for complete
processing to potable quality water, therefore the data is not available for a unique
hygiene water processing trade. The following systems were traded:
-UltraFiltration/Reverse Osmosis + APCOS
-UltraFiltration/Reverse Osmosis + MilliQ Absorbtion Beds
-Multifiltration
The UF/RO and MilliQ Absorption Beds won the trade. Multifiltrations downside was
its large consumable mass while the APCOS was significantly penalized due to the
unknown oxygen consumption for the oxidation process.
Microbial control was separated from this trade study due to its need in any system
chosen. Due to lack of information, the Iodine Microbial Check Valve was chosen. Iodine
removal beds are also required before potable use to eliminate long-term effects of Iodine
consumption.
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Urine processing is separated from hygiene water processing due to its complexity. Table
6.4.3.3 shows the candidate technologies for urine processing.
Table 6.4.3.3: Urine Treatment Candidate Technologies.
Water Management Function
Urine Treatment













Candidate Technologies
MIR Technology (evaporation, steam condensation, sorption,
electrolysis)10
Vapor Compression Distillation (VCD)1,13
Vapor Phase Catalytic Ammonia Removal (VAPCAR)1
Air Evaporation (AES)1
Aqueous Phase Catalytic Oxidation Post-Treatment System
(APCOS)10,13
Super Critical Water or Wet Oxidation (SCWO)1
Incineration (oxidation)11
Pyrolysis11
Aerobic Slurry11
Aerobic Solid Processing (composting)11
Anerobic Solid Processing11
Aquaculture (fish)11
Electrochemical Oxidation11
Again this large list of technologies was reduced through a few selection criteria. The
primary selection factor in urine treatment was the elimination of biological systems
following the DRM requirements. TRL levels below 6 and lack of information rules out
many of the other candidates.
Due to the severe elimination of technologies by initial selection criteria, only two were
left. The urine distillation trade was performed between the following technologies:
-Air Evaporation System (AES)
-Vapor Compression Distillation (VCD)
Vapor Compression Distillation won the trade study with the Air Evaporation System in
second. The primary reason the AES places second was due to the high power
consumption of 1 kW. This is approximately 10% of the allotted power for the spacecraft
dedicated to one system. A simple trade between carrying makeup water in the VCD only
system versus using an AES to process the brine water on a low duty cycle resulted in a
significant mass savings of approximately 175 kg as well as providing a very simple
redundant system in the case of a VCD failure.
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Figure 6.4.3.2: Closed Loop Water Management Flow Diagram
Figure 6.4.3.2 shows the integration of the water management subsystem components.
The urine treated by the VCD must be pretreated with Ozone (a commercial oxidizer) and
sulfuric acid to prevent the release of ammonia during the distillation process. Brine
water from the reverse osmosis filter is also passed through the VCD to reclaim more
water. The water flow through the VCD can be arranged in numerous forms and is not
completely shown on this diagram. Brine water from the VCD can be passed back
through itself to maximize the solid concentration of the brine. The remaining brine water
is stored and periodically processed by the AES. Current AES testing shows a slightly
reduced quality of water from the AES, so this water is reprocessed through the VCD to
ensure complete processing of the urine. Product water from the VCD is combined with
the remaining wastewater from the craft including that from hygiene. The water stream
then flows through an Ultra filtration unit, which consists of mechanical filtration media.
This increases the lifetime and efficiency of the following reverse osmosis filter. As
stated earlier, the brine water produced in processed through the VCD. The product water
then flows through the Milli-Q absorption bed, which consists of activated carbon and a
proprietary organic carbon scavenger media to reduce the TOC to acceptable potable
water quality standards. At this time, Iodine is then added to the water stream for
microbial control. Monitoring then checks the PH, conductivity, TOC and Iodine levels
before the water is stored. Hygiene water is used directly from this source. Potable water
must first be passed through the iodine removal bed to reduce the iodine level to
acceptable amounts. Online iodine monitoring then ensures this level.
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Water Monitoring is a major subsystem within the water management. Therefore, any
technology that has the Technology Readiness Level (TRL) of less than 7 is assumed to
be unacceptable for life critical component and not studied in this section. The TRL of 7
indicates that the system prototype has been demonstrated in a space environment.
However, if the technology is not gravity dependent, the acceptable TRL is said to be 5.
At this TRL level, the component and/or the breadboard have been validated in relevant
environment and shows promising evidences that it would also work in space. With this
in mind, the first tread study would be to do the simple pass/fail elimination due to the
TRL level.
Table 6.4.3.4: List of Technologies & Associated TRLs
Technologies
Fiber Optic Sensor for Water11 (for turbidity, color, pH, iodine, metals, ions, NOC, VOC, semivolatiles and hardness level)
Electronic Nose11 (for taste, metals, NOC and odor)
Ion Mobility Spectrometry (IMS)11 (monitor iodine level)
Ion Specific Electrodes (ISE)11 (for conductivity level)
Capillary Electrophoresis (CE)11 (for metals level)
Liquid Chromatography (LC)11 (for metals, ions level)
Ion Coupled Plasma (ICP)11 (for metals, ions and silver)
Solid Phase Extraction-Mass Spectrometry (SPE-MS)11 (for NOC, VOC and semi-volatiles)
Supercritical Fluid Chromatography (SFC)11 (for NOC, VOC and semi-volatiles)
Liquid Chromatography-Mass Spectrometry (LC-MS)11 (for NOC, VOC and semi-volatiles)
Fourier Transform Infrared (FTIR)11 (for NOC, VOC and semi-volatiles)
Total Organic Carbon-Infrared (TOC-IR)11 (for TOC/COD)
Total Organic Carbon (TOC) - conductivity11
Total Organic Carbon (TOC) - reagentless11
Total Organic Carbon Analyzer14
Gas Chromatography (GC)11 (for NOC and semi-colatiles)
Voltametry11 (for metals and silver)
UV-visible Spectrophotometer (laser)11 (for turbidity, color, pH, iodine, metals, ions, NOC,
VOC, semi-volatiles and hardness level)
Surface Acoustic Wave (SAW) Detector11
Test Kits11 (for pH, chem-strips for specific compounds)
Conductivity11
Test Kits11 (for pH, chem-strips for specific compounds)
Therefore, the technologies that will be studied are the following:
1. Electronic Nose11 (for taste, metals, NOC and odor)
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[TRL 6]11
TRL
4
6
2-4
2-8
3-4
2-3
3
2-4
1-2
3
4
4
6
2
3
4
3
2
4
9
8-9
5-9
MARS OR BUST, LLC
Figure 6.4.3.3 Electronic Nose Equipment
2. Ion Specific Electrodes (ISE)11 (for conductivity level)
[TRL 2-8]11
Figure 6.4.3.4 Ion Specific Electrode
3. Total Organic Carbon (TOC) - conductivity11
Figure 6.4.3.5 Total Organic Carbon - Conductivity Diagram
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[TRL 6]11
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Figure 6.4.3.6 Actual Total Organic Carbon device
4. Conductivity11
[TRL 8-9]11
Figure 6.4.3.7 Sample of Conductivity device
5. Test Kits11 (for pH, chem-strips for specific compounds)
[TRL 5-9]11
Figure 6.4.3.8 Sample Test Kits
devices
Table 6.4.3.5 Water Sample Requirement for Off-Line Monitoring (initial On-Orbit
Operations)
Location
ECLSS Storage Tank
Random (Tank or Use Port)
Avg. Total Volume
Avg. No. Sample
Sample Volume
500 ml/day
500 ml/day
5,250 ml/week
10.5 times/week
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Frequency
Every day
Every 2 days
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Table 6.4.3.6 Water Sample Requirement for Off-Line Monitoring (Mature
Operations)
Location
ECLSS Storage Tank
Random (Tank or Use Port)
Avg. Total Volume
Avg. No. Sample
Sample Volume
110 ml/day
500 ml/day
110 ml/day
500 ml/days
1,990 ml/week
11.0 times/week
Frequency
6 days/week
1 days/week
3 days/week
1 days/week
Since each technology can detect different contaminates in water, the trade study cannot
be conducted to compare them to one another. The combination of all the technologies is
considered to be the best arrangement. The repetition of the monitoring provides for the
redundancy of the subsystem.
ISE Conductivity
pH, Iodine, TOC/COD,
hardness
TOC
TOC/COD
Conductivity
Gross quality indicator
Electronic Nose
Odor, taste
Test Kits
Conductivity, pH, Iodine,
TOC/COD, Hardness
Figure 6.4.3.10: The Order of Monitoring Devices
6.4.4 Design
Current technology provides a substantial choice of operational subsystems within water
management. Detailed testing has been performed on several occasions and provides
excellent information on physical/chemical and biological systems. Many promising
technologies in development or in use have been developed in the private sector and
almost all information is proprietary. While these technologies could provide the
optimum solution to our design requirements, they had to be eliminated or severely
penalized within the trade study due to the lack of detailed information. The water buffer
capacity of this system is 324.28 kg. In an event of total water system failure, this allows
for 14 days under normal potable water use without any hygiene use. This should be
enough time to address the issue. This is a very critical design feature that will
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significantly affect the mass and safety of the system. Further research or testing is
needed on this subject.
The values for heat, power, and volume for the completed water system are located below
in table 6.4.4.1.
Table 6.4.4.1: Heat, Power, and Volume for ECLSS water technologies
Water System
Heat
Generated
(kW)
Power
(kW)
Volume
(m^3)
Mass (kg)
Air Evaporation System
Iodine Microbial Check Valve
1.000
0.012
1.000
0.010
0.300
0.600
75.00
43.80
MilliQ Absorption Bed
Reverse Osmosis and Ultrafiltration
0.060
0.350
0.000
0.600
0.060
0.350
107.68
214.00
Vapor Compression Distillation
Iodine Removal
0.115
0.000
0.120
0.000
0.490
0.060
144.80
20.00
Quality Monitoring
0.080
0.080
0.080
90.00
Urine/RO Brine Storage Tank
0.000
0.000
0.060
3.60
VCD Brine Storage Tank
0.000
0.000
0.080
5.00
Water Storage
0.200
0.200
0.610
32.43
Plumbing (10% of total*)
0.000
0.000
0.269
73.63
Spares
0.182
0.201
0.296
80.994
Total
1.999
2.211
3.255
890.935
Component
6.5.0 Waste Subsystem
The waste subsystem is designed to maintain simplicity while minimizing the
consumables and maximizing the things that can be recycled.
6.5.1 Responsibility and Assumptions
The Waste Management Subsystem for the mission to Mars requires that all waste be
processed in an efficient manner. Waste management is a mission critical issue, and must
be handled appropriately. Failure of the spacecraft’s life support system to handle
mission generated waste materials will ultimately cause the loss of the spacecraft habitat
balance, and effectively reduce the overall function of the crew to a minimum at best.
The waste subsystem shall collect and store liquid, solid, and concentrated wastes for
immediate and/or delayed resource recovery. Long-term storage shall be provided for
non-recovered wastes and unprocessed items.
The waste subsystem should be capable of handling approximately 11.092 kg/day of
human, biomass, and technological waste products from a 6-person crew (Eckart 1996).
Table 6.5.1.1 shows the breakdown for each of these products.
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Table 6.5.1.1: Waste product breakdown for a 6-person crew (Eckart 1996).
Waste Product
Urine
Feces
Technology & Biomass
Flow Rate [kg/day]
9.36
0.72
1.012
6.5.2 Design Approach
As stated above, several different technologies were considered as viable options for the
Waste Management Subsystem. Specification sheets were generated for each of the
technologies and judged according to TRL, Design Simplicity, Crew Safety, and
Reliability. Trade studies were then conducted with regard to each of the technologies,
and rated according to each of the priorities stated above. Simply stated, the approach in
designing a waste subsystem should be to deliver a system that is both reliable and
comprised of proven technologies.
6.5.3 Technologies and Trade Study
The waste subsystem selected for the mission to Mars consists of 1 urine/feces collection
mechanism (toilet/urinal), and 2 ‘ISS’ trash compactors. The system designed for the
Mars mission meets the simplicity, reliability, safety, and TRL requirements for the waste
subsystem. Several other technologies were considered for the subsystem. One
technology, which was rather enticing, was the Super-Critical Water Oxidation method of
processing waste. Using this strategy, 99.99% of the waste is broken down into some
usable component. The SCWO would have been an ideal candidate for the waste
subsystem, but because of its low TRL (~3), high operating pressure and temperature,
and the fact that it has yet to be flown in a space environment; it had to be dropped from
the available pool of technologies. Using the SCWO would have sufficiently closed the
loop for the Waste Management Subsystem. Pyrolysis was another technology that
operates at high temperature and high pressure resulting in high power consumption. This
technology would also close the loop of the waste subsystem. All the gas generated
would return to the atmosphere subsystem, water will be return to the water management
subsystem and the trivial amount of carbon will be stored. Other technologies
considered, but not used were electrochemical incineration, photo-catalytic oxidation, and
other combustion methods. However, all of these methods either required too much
consumable mass, too much power, or were not considered safe enough to use. Also, it
was determined that there would be enough water on board the spacecraft so that water
loss from not processing the fecal water, would be tolerable. This trade allowed for the
consideration of a flight proven method of handling waste products, instead of one with a
lower TRL.
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Urinal
Commode
fecal
storage
feces
compactor
urine
compactor
To: waste
water tank
H2O
From: TCCA
food trash
microfiltration
VCD
solid
waste
storage
trash
Figure 6.5.3.1: Schematic of the Waste Management Subsystem.
There are two inputs for the system: (1) human, and (2) biomass and technological
wastes, such as spent cartridges from the TCCA and VCD filters. The Water
Management Subsystem will process the urine.
The flow of waste through the waste subsystem follows the schematic in Figure 6.5.3.1.
Human waste is deposited in either the commode or the urinal. Fecal matter and
associated toiletries are deposited by the crewmember into a fecal bag. The fecal bags
are then placed into one of two trash compactors. The compactor for fecal matter will
use small UV degradable bags before placing into larger trash bags. Trash from TCCA
(cartridges & filters), food packaging, and micro-filtration devices, are placed into a
compactor. Both the fecal waste and other solid waste are then placed into hermetically
sealed bags for long term storage. The fecal matter will breakdown and become fertilizer
for future mission. During the surface stay (600 days), the crew will place all the trash in
the designated storage area outside of the habitat during the frequent EVA scheduled or
be stored inside the habitat due to the concern about the Mars environment
contaminations. Whether the storage of trash will be outside or inside will have to be
determined after performing a study to determine amount of contamination is performed.
This is because MOB is very sensitive to the issues surrounding the contamination of the
surface of Mars.
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6.5.4 Design
Although many different waste processing methods are readily available here on earth,
very few of these technologies have been tested in similar environments to that of space,
and even fewer have been flight tested in micro-gravity. The Waste Management
Subsystem selected for this mission, meets the requirements of simplicity, reliability, and
safety. The waste system used has a fixed mass of 279 kg, a consumable mass of 2.3
kg/day, and has a total power consumption of 0.22 kW. The toilet/urinal used for the
mission has been flight proven on both the Space Shuttle, and the International Space
Station. This system requires minimal power and its reliability is proven. The crew will
have a provision of fecal bags and compactor bags for the duration of the mission plus
10%. Having such a large provision ensures that the crew will have enough resources for
the entire mission, plus any contingency. Finally, the waste subsystem selected for the
mission is capable of handling more than the required 11.012 kg/day of waste. This
flexibility was an important element in the final selection of this specific system.
One of the potential drawbacks to this system is that it does require crew interaction for
the collection of the fecal matter. While this may have a negative psychological impact
on the crew, overall failure of a more complex waste system was deemed to have a much
larger impact. Future considerations should give preference to the Super-Critical Wet
Oxidation method and Pyrolysis for processing waste because of its efficiency and
capability of handling both human and technological waste products.
The values for heat, power, and volume for the completed waste system are located
below in table 6.5.4.1.
Table 6.5.4.1: Heat, Power, and Volume for ECLSS waste technologies
Waste System
Heat
Generated
(kW)
Power
(kW)
Volume
(m^3)
Mass (kg)
0.220
0.110
0.220
0.110
0.720
0.360
25.94
25.94
Pop-up net, stowed config (fecal waste)
n/a
n/a
0.125
9.00
Pop-up dumpster, stowed config (solid waste)
n/a
n/a
0.500
205.00
Plumbing (10% of total)
n/a
n/a
0.171
6.088
Spares
0.033
0.033
0.188
5.797
Total
0.363
0.363
2.063
277.765
Component
Fecal Compactor
Solid Waste Compactor
6.6.0 Food Subsystem
The objective of this stage of the Mars mission project is to provide an analysis of the
food subsystem requirements and available technologies necessary for food supply. The
functional requirement is to meet the nutritional needs of the astronauts in a safe and
healthy manner while taking into account the conditions of 1/3g gravity (Eckart 1996).
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6.6.1 Responsibility and Assumptions
The Mars Design Reference Mission (DRM) document was reviewed to develop an
approach to provide a comprehensive life support subsystem and a food supply for the
crew. The DRM shows that six crewmembers must be supplied with enough food for
600 days stay on the surface of Mars (Drake 1998). In order to determine mass and
volume of food to supply crewmembers, an average of 2,200 kCal was assumed for this
system. This is based off the fact that a minimum of 2,000 kCal is needed per person per
day to keep the astronauts healthy (Miller 1994). Many trade factors needed
consideration in the design of the food subsystem.
6.6.2 Design Approach
One of the predominant trade factors is physiological nutritional need versus
psychological palatability and desires. The requirement for this system is to meet the
nutritional needs of the astronauts in a safe and healthy manner (Klaus 2002). The intake
of food for energy purposes needs to be sufficient to maintain weight and composition of
the body and allow levels of activity anticipated for operations in space (Lane 2000). The
basic nutritional needs dictate the amount of food that is necessary to bring. A minimum
of 2,000 kCal is needed per person per day to keep the astronauts healthy and an average
of 2,200 was chosen for this system (Miller 1994). Nutritional needs are important but
factors related to changes in body composition and energy expenditure at different levels
of gravity must also be taken into account. The relationship between diet and exercise
must be considered because that can affect the levels of kilocalorie intake.
6.6.3 Technologies and Trade Study
In choosing types of food for the mission, considerations include minimal in-flight
preparation, minimal waste (inedible biomass and packaging), ambient stowage, minimal
mass, shelf life and good taste. For a long duration mission, stability, variety, and
production during the mission need to be considered.
Food stabilization defines packaging requirements and necessary mass allocations. Food
supply stabilization has evolved from food fed through a tube for the Mercury missions to
dehydrated sources for the Gemini missions to adding thermo stabilized and irradiated
items during the Apollo missions. Current day brings us to the Shuttle (STS) and the
International Space Station (ISS), both of which have all of the aforementioned items, as
well as intermediate moisture and natural form foods. ISS and STS also have condiments
to add flavor since food tastes bland in space (Klaus 2002).
Physical-Chemical (PC) systems cannot produce food. However, this system has been
chosen to be a PC system and in so doing, all food must be brought. If food production is
considered, then those considerations include plants, animals, aquaculture, and other
technologies. Animals are impractical as that brings up inefficiency factors, therefore
they will not be considered. Aquaculture is more practical because of rapid growth and
steady state production. Aquaculture requires a large mass of water, which can also be
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used as an emergency buffer for water supply. This is something to consider for future
research and design.
All of the aforementioned factors and technologies must be combined to create a system
that meets nutritional needs, palatable desires, and minimization of waste and mass
When designing the food subsystem, the first step taken in the design approach was to
consider the requirements, and to identify candidate technologies. These candidate
technologies were then researched and put into a trade matrix. Once all candidate
technologies were part of the matrix, any unknown values were researched.
Unfortunately due to limited available detailed information, often times because the
information is proprietary to a company, not all necessary values were found for the
candidate technologies. This posed a problem in calculating ESM and choosing a
technology because any decision to be made would have to be made with a certain lack of
information.
The food subsystem is different than the other subsystems because variety is a
requirement and in order to achieve this more than one candidate technology must be
chosen. For example, a variety of different foods are being brought and will be stabilized
using different stabilization methods. After the matrix was ranked it was sent to the
System Engineer to pick the top technologies that best integrate with the rest of the life
support subsystems and in some cases the top 4 were chosen. After a final system was
chosen, mass calculations were finalized.
To develop a food supply subsystem various parameters had to be explored: food supply,
food production, food storage, and food processing.
For this mission, all food will be brought. Bringing all of the food required for surface
stay is necessary for safety precautions, mainly because all of the food supply bioregenerative technologies have fairly low TRLs. If the astronauts had to rely on bioregenerative technologies for their food supply then they risk the possibility that those
technologies would fail, leaving the astronauts without enough food for the trip. When
bringing food a variety of stabilization methods were examined. There is always the
possibility of bacteria contaminating one type of food or food stabilized using a certain
method. This is part of why variety is so important. Because variety was considered a
requirement, dehydrated, thermo stabilized, natural form, irradiated, and intermediate
moisture were chosen for use in this system. Pre-cooked and frozen were eliminated due
to lack of a refrigerator. A refrigerator provided will not be used for storing frozen food
but will be used for refrigerating drinks and minor food preparations. The total mass for
stabilized food is approximately 2,787 kg, which is a minimum value. An extra 10% of
this value was taken and brought as a buffer. To calculate this mass number, the value of
0.62 kg/day per person was taken and multiplied by the number of crewmembers and the
length of the trip (Miller, 1994).
Food storage methods are defined by the way the food required to be stocked. Storage
methods utilized at room temperature are mainly based on different ways of packaging
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the food. These include, cellulose used for biodegradable rigid packaging, bioplastics
used for biodegradable rigid packaging, edible rice wafer used for biodegradable rigid
packaging, aluminum or bimetallic tins for thermo stabilized foods, retort pouches for
thermo stabilized foods, flexible pouches for natural form foods and intermediate
moisture foods, foil laminate bags for beverages, and dropper bottles for condiments. All
of these packaging methods are going to be used because of the need for variety.
Different types of food have to be packaged differently. The other type of food storage is
refrigeration. The candidate technologies include, a Coolant Loop, Vapor-compression
Refrigeration, Stirling Cycle Heat Pump, Thermoelectric Heat Pumps, Thermo acoustic
Refrigeration, and Phase-change Materials. Due to power constraints, storing food by
refrigeration was not chosen for this system.
Food processing defines how the astronauts prepare the food for consumption. Various
technologies that were considered include a microwave (roasting and baking), water rehydration, fluid immersion, and direct contact and/or radiant heating. Two technologies
were chosen, a microwave that can also be used as a convection oven and grill, and a
sink/tap that can be used to re-hydrate and heat food as well as be used for drinking
purposes. The specs for these technologies are in table 6.6.3.1.
Table 6.6.3.1: Food Technology Specs
Food
Quantity Mass
Power
Technology
(each) (each)
Volume
(each)
Heat
Produced
Crew Time
TRL
Microwaves
(Convection
Oven/ Grill)
Sink/tap
2
33 kg
(1 kW)
~0.3 m3
(1 kW)
(62 hrs)
6
1
5 kg
1 kW
(~0.4 m3)
(1 kW)
0
9
Refrigerator
1
200 kg
1 kW
1 m3
1 kW
0
9
NOTE: Parentheses indicate an educated estimate.
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food preparation
water
microwave
Food waste &
packaging
refrigerator
food &
drink
food
storage
Potable water
To: trash
compactor
H2O
trash
Figure 6.6.1: Food System Schematic
6.6.4 Design
Operation of the food subsystem is fairly straightforward. The operation of the system is
laid out in the food schematic in Figure 6.1. When it comes time to eat, one or all of the
astronauts will retrieve packaged and stabilized food from storage. The food can then be
prepared in the microwave or by using water from the sink/tap. The excess food and
packaging is then thrown away.
The final resulting food system is a preliminary system. Many parameters are still
unknown, but the basics values and the structure of the food system have been decided.
This primary system is the best system possible while taking into account its integration
into the entire life support system. This primary food system has a mass of 4,247 kg and
is made up of stabilized food, a microwave which can also be used as a convection oven
and grill, a sink/tap with hot and cold water to re-hydrate food and for drinking purposes.
The values for heat, power, and volume for the completed food system are located below
in table 6.6.4.1.
Table 6.6.4.1: Heat, Power, and Volume for ECLSS food technologies
Food System
Component
Heat
Generated
(kW)
Page 29 of 40
Power
(kW)
Volume
(m^3)
Mass (kg)
MARS OR BUST, LLC
Microwave Oven/Convection Oven/Grill (2)
1.800
1.800
0.600
66.00
Sink
Refrigerator
1.000
1.000
1.000
1.000
0.400
1.000
5.00
200.00
Plumbing (10% of total)
n/a
n/a
0.200
27.100
Food (dehydrated)
n/a
n/a
2.600
2455.20
Spares (10% of total)
0.380
0.380
0.480
275.330
Total
4.180
4.180
5.280
3028.630
6.7.0 Integrated System
6.7.1 Integration Process
The four systems discussed in the previous sections, Atmosphere, Water, Waste, and
Food, combine to form an integrated system that addresses the mission needs regarding
environment and life support within the habitat. Beyond the ECLSS Subsystem, the
ECLSS components operate in conjunction with other subsystems to meet mission goals.
During the integration process ECLSS collected requests from the other subsystems of
needs for ECLSS support and also presented requests to other subsystems for support.
Trade studies were performed on each of the ECLSS technologies considering their
overall integration within the MOB Habitat with a focus on minimizing mass,
maximizing efficiency, and minimizing mission and program risk. Through this process,
solutions were found that meet the needs of both ECLSS and the other MOB subsystems,
and the following design emerged.
6.7.2 Integrated Design
The integrated ECLSS design is shown in Figure 6.7.2.1. The integrated system provides
greater efficiency than would be possible with four independent ECLS systems. The
interactions of the four main ECLSS functions are evident in the diagram.
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Crew Accommodations
(shower, washer, etc.)
Water
System
Food
System
Ultra Filtration
Hygiene Water
Food
Preparation
Food
Trash
RO
Iodine Removal
Bed
Monitoring
ISE Monitoring
MCV
Iodine
AES
TCCA
VC
D
Pretreated Urine
Milli Q
Pretreatment
Oxone, Sulfuricacid
Potable Water
Atmosphere
System
Brine water
Fecal
SPWE
Waste
System
Urine
H2
Atmospheric
Condenser
EDC
Vent
to
Mars
Atm.
Compactor
Compactor
Solid Waste
Storage
Processed water
Liquid Waste
Solid Waste
Gases
Figure 6.7.2.1: MOB ECLSS Integrated Design
Starting with the Food System and proceeding clockwise around the diagram, the Food
System receives potable water from the Water System. This water is used both to rehydrate food and for drinking with or without powdered drink mixes. The Water System
also provides water to the Atmosphere System. This water does not need to undergo the
additional treatment to qualify as potable water, so it exits the Water System as hygiene
quality water, increasing the efficiency of the overall ECLS Subsystem. The Waste
System is also integrated with the Water System. When crewmembers eliminate urine it
is then passed to the water system for rigorous treatment allowing the ECLS Subsystem
to reclaim the valuable water for future use. Finally, the ECLSS design integrates
collection of waste, by passing waste from the Food System and Trace Contaminants
Control System to the Waste System. The waste from the Food System will include a
combination of packaging plastics and food waste generated during meal preparation and
clean up.
6.7.3 Integration with other subsystems
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The previous discussion and diagram focus on the integration within the ELCSS
Subsystem. The interfaces between ECLSS and the other subsystems are presented in
Figure 6.7.3.1.
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ISRU Plant
Mars Environment
Robotics/Automation
Legend
Oxygen
Nitrogen
Carbon Dioxide
Cabin Air
Trace Contam.
Food
Potable H20
Non-Potable H20
Solid Waste
Liquid Waste
Command
Telemetry
Data Bus
Video
Audio
Packetized Data
TCP/IP
Electrical Power
Heat
Structures
ISRU
Thermal
ECLSS
C3
EVAs
Power
Nuclear Reactor
Crew Accommodations
Mars Com
Satellites
Habitat Boundary
Figure 6.7.3.1: MOB interfaces between ECLSS and all other subsystems
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The interfaces between ELCSS and the other subsystems will be described starting with
the interface between the Power Subsystem and ECLSS, and proceeding clockwise on
figure 6.7.3.1
6.7.3.1 Power Interface with ELCSS
The Power Subsystem provides power to all the ECLSS components requiring power.
This includes conditioning of the standard Habitat 28 VDC power to meet the needs of
various components. The average ECLSS power demand is estimated to be 9.6 kW. A
breakdown of the ECLSS equipment power needs is presented in Table 6.7.2.1.
Table 6.7.2.1: ECLSS total mass, power, and volume estimates.
ECLSS Technologies Totals for each Subsystem
System
Water
Waste
Food
Atmosphere
Heat Generated (kW)
1.999
0.363
4.18
3.8643
ECLSS system Total 10.406
Power (kW)
2.211
0.363
4.18
3.8863
Volume (m^3)
3.255
2.063
5.28
16.588
Mass (kg)
890.935
277.765
3028.63
5897.3
10.64
27.186
10095.3
6.7.3.2 CCC Interface with ECLSS
The CCC Subsystem is responsible for the control and command of the ECLSS
components. Telemetry is sent from the various ECLSS equipment to the CCC
computers. The computers then use this information to control the ECLSS equipment
appropriately. The telemetry is also distributed by CCC to Earth Mission Control and the
Master MOB database for future use in troubleshooting and trend analysis. See Section
9.0 for more information on the design and operations of the CCC Subsystem.
6.7.3.3 Thermal Interface with ECLSS
ECLSS interfaces with the Thermal Subsystem by rejecting heat to and receiving heat
from the Thermal subsystem as needed to maintain the proper temperatures of the ECLSS
equipment. More information on the design and operations of the Thermal subsystem are
presented in Section 7.0.
6.7.3.4 Structures Interface with ECLSS
The Structures Subsystem and ECLSS interact via the habitat’s atmosphere. ECLSS
vents the atmosphere through the Habitat outer structure. Also, ECLSS will gradually
lose a fraction of the Habitat atmosphere as a result of leakage through the exterior walls.
The Habitat is being designed to contain leakage to less than 1.45 kg/day. In addition,
Structures supports ECLSS by providing the structure and volume in which the ECLSS
equipment is housed. The total estimated mass and volume of the ECLSS Subsystem is
10095.3 kg and 27.2 m3, respectively, as shown in table 6.7.2.1. These totals include
consumables at start of mission. The details of the current best estimates are presented in
Table 6.7.2.1 and Sections 6.3 through 6.6.
6.7.3.5 ISRU Interface with ECLSS
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Although ECLSS is not dependent on the products of the ISRU, it will make use of these
products if they are available. The ISRU is designed to produce non-potable water,
Oxygen, and food for use by ECLSS. The utilization and testing of the integrated
ISRU/ECLSS system will provide valuable information for future crewed Mars missions.
Also, through production of spare consumables, the integrated ISRU/ECLSS system
decreases the overall mission risk. Section 3.0 provides more information on the design
and operations of the ISRU plant.
6.7.3.6 EVA Interface with ECLSS
There are several interfaces between the EVA Subsystem and ECLSS. Food, potable
water, and Oxygen are provided by ECLSS to the EVA suits for use when a suit is
donned. Through natural human processes occurring inside the EVA suit, trace
contaminants and Carbon Dioxide are produced that must be removed from the
atmosphere inside the suit. These elements are returned to the ECLS Subsystem for
processing. Due to the length of extravehicular activities, it is necessary to provide
crewmembers the ability to eliminate urine and feces. These liquid and solid wastes are
collected within the EVA suit by specially designed diapers. These diapers are then
returned to ECLSS for processing. Also, ECLSS supplies EVAS with Nitrogen and
Oxygen for use in pressurizing and depressurizing the EVA airlock. See Section 11.0 for
more information on EVA suit design and operations.
6.7.3.7 Crew Interface with ECLSS
ECLSS supplies four elements essential to life to the crewmembers: food, water, Oxygen,
and Nitrogen. Through the food storage and food preparation components of the ECLS
Subsystem, the crew receives the nourishment needed to stay healthy. The crewmembers
receive the proper air make-up and pressure needed by their bodies through the Oxygen
and Nitrogen supplied by the controlled atmosphere. Again, through natural human
processes, CO2, trace contaminants, Oxygen, and Nitrogen are returned from the
crewmembers to ECLSS for processing. Also, urine and feces produced by the
crewmembers are returned to ECLSS for processing and storage, respectively.
6.7.3.8 Crew Accommodations Interface with ECLSS
The final set of interfaces between MOB subsystems and ECLSS is the set of interfaces
between ECLSS and Crew Accommodations. ECLSS provides both potable and nonpotable water to the Crew Accommodations Subsystem. The potable water is used by
Crew Accommodations in operation of the dishwasher, kitchen sink, and crew
mouthwash and face wash faucet. Crew Accommodations requires non-potable water for
operation of the clothes washing machine and crew shower. Dirty water is produced
through use of these various Crew Accommodations components and is then sent back to
ECLSS for processing to reclaim the water. Heat from the Crew Accommodations
equipment, in particular the clothes dryer and dishwasher, is released into the Habitat
interior atmosphere. ECLSS manages this additional heat through operation of the heat
exchanger. More information on the design and operations of the Crew Accommodations
can be found in Section 12.0.
6.7.4 ECLSS consumables
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A large portion of the mission mass comes from the consumables. Food, water, oxygen,
and nitrogen all need to be carefully calculated. Table 6.7.4.1 shows an overview of the
major consumables.
Table 6.7.4.1: Total Mass and Volume values for Consumables
Mass and Volume values for Consumables
Consumables
Mass (kg)
Volume (m^3)
Food (including packaging)
11088
31.68
Water
6482
6.48
Nitrogen
1057.2
1.27
Water to produce Oxygen
4314.6
4.31
It was assumed that the crew would not obtain any food from the Martian environment
therefore all necessary food for the mission must be brought to Mars. A day’s ration of
food that is completely dehydrated weighs 1.3 kg (3.5 kg completely hydrated). In
general, the higher the water content, the better the food tastes, therefore, for a longduration mission such as this it was decided that 2.3 kg/person/day would provide a
comfortable diet. The water needed to hydrate this food is 1.2 kg/person/day. Packaging
is about 0.5 kg/person/day. A ten percent margin was then added in order to provide an
extra element of safety.
Table 6.7.4.2 shows how much water is designated for common tasks. The subtotal
values for one were calculated for six crewmembers.
Table 6.7.4.2: Water Requirements
Water Requirements
Mass per Person (kg)
1 Day Subtotal (kg)
Food
Drinking
Hygiene
Toilet Flush (5/p/d)
Laundry
Dishes
EVA Cooling System
1.2
1.3
7
0.5
12.5
5.4
0.14
7.2
7.8
42
15
75
32.4
0.28
Cooking
0.75
4.5
The water needed to re-hydrate the food was discussed earlier. Each crewmember needs
to take in 3.5 kg of water a day in order to stay healthy and active. It was found that the
total water in the hydrated food is 2.2 kg so each astronaut needs to drink 1.3 kg in order
to intake that water they need. The amount of water for hygiene, laundry, dishes, and
cooking was based on previous missions. When calculating how much water was needed
to flush the toilet each day, it was assumed that each crew member would urinate around
5 times a day. The EVA cooling water number was calculated based on the assumption
that there will be two EVAs a week, each having two crewmembers. It is also important
to note that this calculation is based on a re-generable, non-venting heat sink. The value
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of 0.14 kg is the average amount of water that will need to be replaced before each EVA
(on top of this value, 5.5 kg will need to be added for the very first EVA for each suit).
Finally the amount of oxygen and nitrogen needed to be decided upon. The amount of
oxygen and nitrogen for the habitat, airlock, and rover were calculated based on the
volume (615.75 m3, 35 m3, and 23 m3), pressure (10.2 psi), and temperature (23 C).
This number includes the amount of each gas that will be needed to make up for the loss
due to leakage and cycling the airlock (10% of the total airlock air). The nitrogen will be
brought to Mars in tanks, but the oxygen will be produced from water via SPWE.
6.7.5 Verification of Requirements
Below in table 6.7.5.1 there is a description of the requirements for the ECLSS subsystem
and to the right of that show whether the requirement was met or not and how it was met
with the design. The table shows that all requirements for ECLSS were met except for
the requirement that mass must not exceed 4661 kg. The mass is only exceeded by
approximately 200 kg and with more iteration of the current design the mass can most
likely be reduced.
Table 6.7.5.1: Table of Requirements and how they are met by the current design
Design
Requirement Description
Provide adequate atmosphere
Gas Storage
Provide Trace Contaminant Control.
Provide Temperature and Humidity Control.
Fire Detection and Suppression.
Provide potable water for 600 days on Mars.
Provide food for 600 days on Mars.
Collect wastes
Provide hygiene water.
Mass must not exceed 4661 kg.
YES, with SPWE & EDC
N2 tank, O2 tank
TCCA
Thermal Heat Exchanger
FDS N2 extinguisher
YES
YES, based on 2200 kCal/p/d
YES, with waste compactors
YES
NO, exceed the mass by approximately 200 kg
6.7.6 Failure Mode Effect Analysis
The failure mode effect analysis (FMEA) of ECLSS has to be studied in order to
formulate the best possible arrangement in case failure occurs in the system. Each
subsystem of ECLSS has its own specific concerns that are apparently unrelated to other
subsystems; therefore the FMEA of each subsystem is addressed separately. The effort to
fix the problem depends entirely on the cause. Tracking down the component or
components that fail is the key to solving the problem. In this section of the report, the
potential cause of each crisis is determined. The technique of repair is not covered in this
section.
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6.7.6.1 Atmosphere Subsystem
Within the atmosphere subsystem, there are potentially 6 problems that can occur, total
pressure is too low, total pressure is too high, ppO2 is too low, ppO2 is too high, tracecontaminant is too high and fire in the cabin. If one of the above crises occurs, the
appropriate action should be executed.
If the total pressure of the cabin is too low, the crews will no longer have shirtsleeve
environment and this will violate one of our top-level requirement in the ECLSS
subsystem. The cause of this problem can be due to malfunction of the sensor which
detect the problem, low level of N2 alone, low level of O2 alone and leakage which
potentially lead to low level of air in the habitat. Malfunction sensor is always one of the
possibilities, to confirm that the sensor is working; a back up sensor should be used to
verify the first sensor. In case of N2 or O2 level being too low, there are 4 possibilities,
supply line is broken, supply line is clog or restricted, broken valve or valves and the
storage tank is empty which lead to low pressure in the storage tank and the pressure
gradient which is the mean of delivering the gas is no longer exists. Repairing, replacing
and resupply have to be considered. In the last case of leakage, there must be a failure in
the structure of the habitat since the leak rate was predicted, but any failure in the
habitat’s structure would lead to more leakage than previously predicted. Proper cause
and action is addressed in the Structure FMEA section of this report.
Another problem that can take place is the total pressure becoming too high. As
mentioned before, malfunction sensor can be the case of this fault alarm but too much N2
and O2 can also be the reason of this increase in pressure. Too much of the two gases can
be due to broken valve or valves or leakage in the supply line inside the habitat structure.
If, however, the ppO2 is too low, normoxic condition is no longer present. The cause of
low ppO2 can be due to too much N2. This is the only possibility since the multiple
failures will not be addressed, i.e. if there’s a normal level of N2 and ppO2 level is
dropped, then the total pressure of the habitat is too low, in which case, the problem is
already being addressed in the previous paragraph. The reason of high level of N2 is the
same as previously mentioned. There can be broken valves and leakage in the supply ling
inside the habitat structure. Another problem is of cause the malfunction sensor.
If the ppO2 is too high, the air can affect the flammability property of the air and fire is
more likely to occur. The cause of this problem can be due to low level of N2. in this
case, the same cause (from low total pressure section) from previous paragraph can be
applied.
Trace-contaminant is another problem in the habitat. The level of the trace-contaminant is
monitored at all time. The TCCA system (see Atmosphere Subsystem Section) should
take care of the trace-contaminant to keep an acceptable range. However, if the tracecontaminate is too high, the only cause other than malfunction sensor is the TCCA
system. The crew should then fix or replace the technology.
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Fire is another major problem that the atmosphere subsystem is responsible for. When the
fire occurs, the N2 extinguisher should suppress the fire instantaneously. If this system
fails to go off, the fire will have to be manually suppressed by the crews. The cause of the
fire is faulty wiring and other over heating and malfunction of other technologies.
6.7.6.2 Water Subsystem
Within the water subsystem, there are 4 different failures that can arise, potable water
doesn’t meet the standard, hygiene water doesn’t meet the standard, there is no potable
water delivery, and no hygiene water delivery. Each of these problems would be
discovered at the faucet where the water is to be used. If this occurs, then there is no
sensor to detect the failure other than the visual observation of the crews. Therefore, there
should not be any malfunction of sensor. If the water doesn’t meet the standard inside the
water treatment, the water would of cause be retreated. Therefore, the malfunction sensor,
in this case, would be the sensor inside the water processing system. Damaged or any
failure in any of the technologies could also contribute to the cause of this problem for
both hygiene and potable water.
In the case of no water delivery, the cause would have to be due to the failure in the
delivering process. Broken pipe, restricted pipe, broken valves and broken pump
anywhere in the system could be the cause.
6.7.6.3 Waste Subsystem
Since the waste subsystem is very simple, the only technology that can fail is the
compactors. Overflow of the toilet is caused by a malfunction of the fecal genie
compactor. If the fecal genie is not working, the first logical thing to check would be if
the UV biodegradable bag is out. Secondly, the compactor itself can also be broken. In
this case, the crews have to fix or replace the compactor. For other waste such as food
packaging, the compactor can also be malfunction. The cause is the same as the fecal
genie technology.
6.7.6.4 Food Subsystem
Food subsystem has even less components than the waste subsystem. The only critical
technology that is in the system is the microwave oven. If the microwave ovens are not
working, then there might be a power outage or the ovens simply are broken. Repairing
and replacing of the ovens have to be considered.
6.8.0 Conclusion
It is concluded that successful completion of a Phase-A equivalent study has been
accomplished for the design of a full-up Life Support System to facilitate a human
mission to Mars. All subsystems have been effectively integrated into one functional
system. The functional Life Support System design successfully satisfies all the design
requirements and assumptions that have been laid out.
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6.8.1 Limitations
This project had two major limitations, lack of adequate time and information. The
project was given three months to complete a Phase-A equivalent study while most
NASA Phase-A studies typically last on the order of six months. Because time played
such a large factor, it was more difficult to research all areas of the candidate
technologies. The lack of information is mostly due to organizations not sharing detailed
technical information either because of proprietary reasons or International Trade and
Arms Regulations (ITAR).
6.8.2 Recommendations
First thing that is needed to improve upon the system is to develop partnerships with
organizations to obtain and share detailed information on selected technologies. To take
it from there, the system should be analyzed for weaknesses and redesigned to improve
efficiency. Special attention should be paid to the lower TRL technologies (i.e. 6’s and
7’s) to take them up to 8 and 9. Take a look at more supplemental technologies (i.e.
Aquaculture and ISRU) and see if they can be incorporated into the system to improve
efficiency. It would also be beneficial to research some of the newer technologies (i.e.
those with low TRLs) and determine if they have the potential to be verified technologies
and incorporated into the system before the launch dates.
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