6.0.0 ECLSS Subsystem

MARS OR BUST, LLC

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 WASTE

WATER 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. Page 2 of 40 MARS OR BUST, LLC

 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

of 40 MARS OR BUST, LLC 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 non- regenerable 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

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 Heat Crew Subsystem Selection Mass Power Volume Produced Time ESM

O2 Provision Chemical oxygen 7466 0.0 0.02 0.02 29.5 7496 Total Pressure Regulation N2 pressure tanks 2562 0.0 0 0 0 2562

CO2 removal LiOH canisters 8988 0.0 7 0 281 9333 Temperature & Rotating Heat Humidity Control Exchanger 175 1.31 3.9 0.82 20.5 233 Trace Contaminant Control (TCC) Space Shuttle TCCS 178 0.15 11 0.15 78 361

Fire Detection & N2 extinguishers & Suppression photoelectric detectors 65 0.003 0.047 0 6 71 Total 19,434 1.5 21.8 1.0 415 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.

cabin N , O , H O leakage 2 2 2

N storage 2 N tanks 2

O FDS 2

chemical crew cabin TCCS LiO 2

LiOH T&H control

To: trash To: trash To: hygiene To: trash compactor water tank compactor H O 2

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.

Table 6.3.3.2: Air Management Life Support Technology Rankings Technologies TRL ESM RANK Oxygen SPWE (w/ EDC) 9 2119 1 SPWE (w/ Sabatier) 9 4394 2 SPWE (w/o Sabatier) 9 5515 3 Tank- cryogenic 9 6573 4 O2 chemical (TRK) 9 7496 5 Tank- pres vessel 9 7681 6 Total Press Reg (Nitrogen) Tank- cryogenic 9 2224 1 Tank- pres vessel 9 2562 2 Carbon Dioxide Removal or Reduction EDC 6 162 1 SAWD 6 190 2 4BMS (CDRA) 8 418 3 Sabatier (CDReA w/ H2 tanks) 9 450 4 Bosch 6 885 5 LiOH 9 9333 6 Thermal and Humidity Control CHX-rotating 6 267 1 TCC Detection GC/MS 9 150 1 Treatment TCCA 9 135 1 TCCS 9 201 2 Activated Charcoal 9 In TCCS & TCCA Catalytic Oxidation 9 In TCCS & TCCA Particulate Filters 9 In TCCS & TCCA FDS Detection ISS Photoelectric 9 21 1 STS Ionization 9 21 2 Suppression Nitrogen Agent 9 68 1 Halon 1301 Agent 9 68 2 CO2 9 85 3 Depressurization 9 694 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

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 Heat Crew Subsystem Selection Mass Power Volume Produced Time TRL ESM

O2 Provision SPWE 2096 1.84 2.24 1.84 2 9 2119 Total Pressure N2 pressure Regulation tanks 2562 0 0 0.00 0 9 2562

CO2 removal EDC 133 0.30 0.2 0.67 5.4 6 162 Temperature & Rotating Heat Humidity Control Exchanger 175 1.31 3.9 0.82 20.5 6 267 Trace Contaminant Control (TCC) GC/MS,TCCA 273 0.08 0.9 0.18 4 9 286 N2 extinguishers Fire Detection & & photoelectric Suppression detectors 80 0.003 0.3 0.00 6 9 88 Total 5319 3.53 7.5 3.51 37.9 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 Heat Crew Subsystem Selection Mass Power Volume Produced Time TRL ESM

O2 Provision SPWE 4371 1.84 2.24 1.84 2 9 4394 Total Pressure N2 pressure Regulation tanks 2562 0 0 0.00 0 9 2562 CO2 Sabatier w/ H2 removal/reduction Tanks 389 0.0006 0.3 0.0029 35 9 450 Temperature & Rotating Heat Humidity Control Exchanger 175 1.31 3.9 0.82 20.5 6 267 Trace Contaminant Control (TCC) GC/MS,TCCA 273 0.08 0.9 0.18 4 9 286 N2 extinguishers Fire Detection & & photoelectric Suppression detectors 80 0.003 0.3 0.00 6 9 88 Total 7850 3.2 10.1 2.8 67 8048

N storage 2 N 2 tanks

FDS O 2

SPW crew cabin E TCCA H , O 2 2

T&H H O control 2 EDC* 2

To: vent From: H O tank To: vent To: hygiene To: trash 2 water tank compactor H H O CO 2 2 2

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.

N & H 2 2 N storage 2 tanks FDS O 2

SPW crew cabin TCCA E

H 2 H O 2 SB *10 T&H control H 2

From: H O tank To: hygiene To: trash 2 To: vent water tank compactor H O CH 2 4 H O 2

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

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 Power Volume Component (kW) (kW) (m^3) Mass (kg) Solid Polymer Water Electrolysis (SPWE) 1.8400 1.840 2.240 2096.00 Electrochemical Depolarized Concentrator (EDC) 0.6700 0.300 0.200 133.00 Rotating Heat Exchanger 0.8200 1.310 3.900 175.00 Gas Chromatography/Mass Spectrometer (GC/MS) Trace Contaminant Control System (TCC) 0.1800 0.080 0.900 273.00 Fire Detection System 0.0030 0.003 0.300 80.00 N2 Pressure tanks 0.0000 0.000 0.000 2562.00 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.

The requirements for water management are defined in .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 Quality Parameters Potable Hygiene Physical Parameter

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 Inorganic Constituents (mg/l) 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 15 15 iodine) 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 Bactericide (mg/l) Residual Iodine (minimum) 0.5 0.5

Quality Parameters Potable Hygiene Residual Iodine (maximum) 4.0 6.0 Aesthetics (mg/l) Cations 30 N/A Anions 30 N/A

CO2 15 N/A Micobial Bacteria (CFU/100ml) Total Count 1 1 Anaerobes 1 1 Coliform 1 1 Virus (PFU/100 ml) 1 1 Yeast & Mold (CFU/ 100ml) 1 1 Organic Parameters (ug/l) 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

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.

The baseline architecture is simple. The water comes from the storage and all the water was taken with the crew.

To Waste Management

2.5 Laundry

Water 9.4 Hygiene Storage

18.216 Potable

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 Mass (kg) Power (kW) Volume (m3) 600 Days 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

Hygiene & Potable Water  MIR Technology (Condensate)10

Treatment  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

WM Function Candidate Technologies

 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.

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 Candidate Technologies

Urine Treatment  MIR Technology (evaporation, steam condensation, sorption,

electrolysis)10

 Vapor Compression Distillation (VCD)1,13

 Vapor Phase Catalytic Ammonia Removal (VAPCAR)1 Page 15 of 40 MARS OR BUST, LLC

Water Management Function Candidate Technologies

 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.

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.

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 TRL

Fiber Optic Sensor for Water11 (for turbidity, color, pH, iodine, metals, ions, NOC, VOC, semi- 4 volatiles and hardness level)

Electronic Nose11 (for taste, metals, NOC and odor) 6

Ion Mobility Spectrometry (IMS)11 (monitor iodine level) 2-4

Ion Specific Electrodes (ISE)11 (for conductivity level) 2-8

Capillary Electrophoresis (CE)11 (for metals level) 3-4

Liquid Chromatography (LC)11 (for metals, ions level) 2-3

Ion Coupled Plasma (ICP)11 (for metals, ions and silver) 3

Solid Phase Extraction-Mass Spectrometry (SPE-MS)11 (for NOC, VOC and semi-volatiles) 2-4

Supercritical Fluid Chromatography (SFC)11 (for NOC, VOC and semi-volatiles) 1-2

Liquid Chromatography-Mass Spectrometry (LC-MS)11 (for NOC, VOC and semi-volatiles) 3

Fourier Transform Infrared (FTIR)11 (for NOC, VOC and semi-volatiles) 4

Total Organic Carbon-Infrared (TOC-IR)11 (for TOC/COD) 4

Total Organic Carbon (TOC) - conductivity11 6

Total Organic Carbon (TOC) - reagentless11 2

Total Organic Carbon Analyzer14 3

Gas Chromatography (GC)11 (for NOC and semi-colatiles) 4

Voltametry11 (for metals and silver) 3

UV-visible Spectrophotometer (laser)11 (for turbidity, color, pH, iodine, metals, ions, NOC, 2 VOC, semi-volatiles and hardness level)

Surface Acoustic Wave (SAW) Detector11 4

Test Kits11 (for pH, chem-strips for specific compounds) 9

Conductivity11 8-9

Test Kits11 (for pH, chem-strips for specific compounds) 5-9

Therefore, the technologies that will be studied are the following:

1. Electronic Nose11 (for taste, metals, NOC and odor) [TRL 6]11

Figure 6.4.3.3 Electronic Nose Equipment

2. Ion Specific Electrodes (ISE)11 (for conductivity level) [TRL 2-8]11

Total Organic Carbon (TOC) - conductivity [TRL 6] 3. Figure 6.4.3.4 Ion Specific11 Electrode 11

Figure 6.4.3.5 Total Organic Carbon - Conductivity Diagram

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 Sample Volume Frequency ECLSS Storage Tank 500 ml/day Every day Random (Tank or Use Port) 500 ml/day Every 2 days Avg. Total Volume 5,250 ml/week Avg. No. Sample 10.5 times/week

Table 6.4.3.6 Water Sample Requirement for Off-Line Monitoring (Mature Operations) Location Sample Volume Frequency ECLSS Storage Tank 110 ml/day 6 days/week 500 ml/day 1 days/week Random (Tank or Use Port) 110 ml/day 3 days/week 500 ml/days 1 days/week

Avg. Total Volume 1,990 ml/week Avg. No. Sample 11.0 times/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 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 Power Volume Component (kW) (kW) (m^3) Mass (kg) Air Evaporation System 1.000 1.000 0.300 75.00 Iodine Microbial Check Valve 0.012 0.010 0.600 43.80 MilliQ Absorption Bed 0.060 0.000 0.060 107.68 Reverse Osmosis and Ultrafiltration 0.350 0.600 0.350 214.00 Vapor Compression Distillation 0.115 0.120 0.490 144.80 Iodine Removal 0.000 0.000 0.060 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

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.

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.

Table 6.5.1.1: Waste product breakdown for a 6-person crew (Eckart 1996). Waste Product Flow Rate [kg/day] Urine 9.36 Feces 0.72 Technology & Biomass 1.012

As stated above, several different technologies were considered as viable options for the Waste Management Subsystem. Specification sheets were generated for each of the Page 22 of 40 MARS OR BUST, LLC 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.

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.

Urinal Commode

fecal storage feces compactor

urine solid waste storage compactor

From: TCCA trash To: waste food trash water tank H O microfiltration 2 VCD

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.

6.5.4 Design Page 24 of 40 MARS OR BUST, LLC

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 Power Volume Component (kW) (kW) (m^3) Mass (kg) Fecal Compactor 0.220 0.220 0.720 25.94 Solid Waste Compactor 0.110 0.110 0.360 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

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).

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.

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.

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

of 40 MARS OR BUST, LLC 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 bio- regenerative technologies have fairly low TRLs. If the astronauts had to rely on bio- regenerative 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

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 re- hydration, 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 Volume Heat Crew Time TRL Technology (each) (each) (each) Produced Microwaves 2 33 kg (1 kW) ~0.3 m3 (1 kW) (62 hrs) 6 (Convection Oven/ Grill) Sink/tap 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.

food preparation

refrigerator microwave water

food & drink Food waste & packaging food storage

Potable water H O To: trash compactor 2 trash 6.6.4 Design Figure 6.6.1: Food System Schematic

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 Heat Generated Power Volume Component (kW) (kW) (m^3) Mass (kg) Microwave Oven/Convection Oven/Grill (2) 1.800 1.800 0.600 66.00 Sink 1.000 1.000 0.400 5.00

Refrigerator 1.000 1.000 1.000 200.00 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

1.1.1 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.

1.1.2 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.

Crew Accommodations (shower, washer, etc.)

Food Water Ultra Filtration System System Hygiene Water RO AES Brine water

Food VCD Iodine Removal Monitoring Milli Q Preparation Bed MCV Pretreated Urine Food ISE Monitoring Iodine Trash Pretreatment Oxone, Potable Water Sulfuricacid

Atmosphere Fecal Waste TCCA SPWE System System Urine H 2 Vent to Compactor Atmospheric Mars Solid Waste Condenser Atm. EDC Compactor 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 re- hydrate 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

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.

ISRU Plant

Mars Environment Robotics/Automation Structures

Legend Oxygen Nitrogen Carbon Dioxide Cabin Air Trace Contam. ISRU Food Thermal Potable H20 Non-Potable H20 Solid Waste Liquid Waste Command ECLSS Telemetry Data Bus Video C3 Audio Packetized Data TCP/IP EVAs Electrical Power Power Heat

Nuclear Reactor

Crew Accommodations Crew

Mars Com Satellites

Habitat Boundary

Figure 6.7.3.1: MOB interfaces between ECLSS and all other subsystems

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 Heat Generated (kW) Power (kW) Volume (m^3) Mass (kg) Water 1.999 2.211 3.255 890.935 Waste 0.363 0.363 2.063 277.765 Food 4.18 4.18 5.28 3028.63 Atmosphere 3.8643 3.8863 16.588 5897.3 ECLSS system Total 10.406 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

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 non- potable 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

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 long- duration 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 1.2 7.2 Drinking 1.3 7.8 Hygiene 7 42 Toilet Flush (5/p/d) 0.5 15 Laundry 12.5 75 Dishes 5.4 32.4 EVA Cooling System 0.14 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

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

Requirement Description Design Provide adequate atmosphere YES, with SPWE & EDC Gas Storage N2 tank, O2 tank Provide Trace Contaminant Control. TCCA Provide Temperature and Humidity Control. Thermal Heat Exchanger Fire Detection and Suppression. FDS N2 extinguisher Provide potable water for 600 days on Mars. YES Provide food for 600 days on Mars. YES, based on 2200 kCal/p/d Collect wastes YES, with waste compactors Provide hygiene water. YES Mass must not exceed 4661 kg. 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.

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, trace- contaminant 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 trace- contaminate is too high, the only cause other than malfunction sensor is the TCCA system. The crew should then fix or replace the technology.

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.

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.