The ECLSS system design encompasses the life support system on board the Crew
Transit/Surface Habitat. As specified by the DRM, the life support system onboard the
Earth Return Vehicle will be a duplicate of the Crew Transit/Surface Habitat that arrives in orbit around Mars prior to the departure of the Crew Transit/Surface Habitat with the crew onboard.
The ECLSS is broken down into four subsystems:
" Atmosphere Management (AM),
" Food Supply (FS),
" Waste Processing (WP), and
" Water Management (WM).
These four subsystems work together in an integrated system that provides all of the necessary functions of the ECLSS.
The main system-level driving requirements are:
" 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,
" Target life support system mass of 4661 kg + consumable weight,
" Target life support system power usage of 12.1 kW,
" 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.
These driving requirements were primary considerations in the overall design.
Requirements:
Atmosphere Management (AM) Requirements:

CO2 Removal and Reduction o ppCO2: 0.4 kPa or below, while not exceeding 1 kPa o Remove/reduce approximately 1 kg/man/day

Total Pressure: 99.9 – 102.7 kPa

O2 Provision, ppO2: 19.5 – 23.1 kPa

N2 Provision, ppN2: 79 kPa

Atmosphere Monitoring and Control

Gas Storage

Ventilation

Trace Contaminant Control o Protect crew for airborne biological and chemical contaminants and particles in the closed environment of a space habitat

o Detect hazardous trace gases and particle density in the atmosphere o Control contaminants below Space Maximum Allowable Concentrations
(SMAC) for humans o For the purposes of this trade study, the following contaminants are examined based on one or more of the following factors: high generation rates, human and plant toxicity, known carcinogen, and high/low water solubility:

Ammonia (NH
3
)

Nitric Oxides (NO
7 mg/m
3
(SMAC)
X
) 0.9 mg/m
3
(SMAC)

Ethylene (C
2

Benzene (C
6

Methane (CH
H
4
)
H
6
)
4
)

Particulates (PM 10)
340 mg/m
0.2 mg/m 3
3
(SMAC)
3800 mg/m
(SMAC)
3
(SMAC) o Deal with Sources of trace contaminants

Humans

Structural and aesthetic materials

Payload chemicals

Propellants (e.g., hydrazine)

Coolants

Thermodegradation of materials heated (Pyrolytic Toxicology)

Plants

Temperature and Humidity Control

Fire Detection and Suppression o Detect fire regardless of location or type. o Robust system providing 100% fire detection with minimal false alarms. o Suppression systems must effectively eliminate the fire, while minimizing toxic effects on the crew.

3.1 psia ppO2, with an acceptable range of 2.83 to 3.35

Provide approximately 0.9 kg/man/day + leaks + EVA loss, normal range of 0.636 to
1 kg/man/day

Temperature: 18.3 – 26.7 degrees C

Humidity: 25 – 70%
Food Requirements:

Must supply crew with adequate sources of food (number of calories)

Must supply crew with means for food processing
*The DRM shows that six crewmembers must be supplied with enough food for a 4-6 month transit to Mars, and an 18-20 month stay on the surface of Mars (Drake 1998).
Waste Processing (WP) Requirements:

Must deal with Sources of waste o Dry human waste (feces, urine, shower/hand wash and sweat) o Inedible Plant Biomass o Filters o General waste

Packaging Material


Paper

Tape

Miscellaneous
The Waste Management Subsystem (WMS) 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 (LSS) 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 WMS 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 WMS 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
6.1 shows the breakdown for each of these products.
Water Management (WM) Requirements:
The next step in the design requires the quantification of the amount of water the crew will need. The USRDA recommends drinking eight glasses a day. That gives a baseline.
However several resources estimate the amount of drinking water for micro-gravity will be 3 Liters/person/day. (Eckart 1994, Larson 1999). Larson further breaks this water down into that required for cooking needs, 1.86 L/person/day and to drink, 1.14
L/person/day. Others may estimate lower potable water needs for the crew (Nicogossian
1994), however, this subsystem was sized to provide the higher recommendation.
Hygiene water will also be required on the surface stay for person hygiene purposes, laundry, housekeeping, and toilet flush. There are several estimates in the literature ranging from 4.5 L/person/day (Eckart 1994) to 50 L/person/day (Nicogossian, 1994).
Again however, only Larson broke this down into the amount of water required for each purpose. A total of 18.5 L/person/day will be required for Laundry 12.5 L/person/day, toilet flush 0.5 L/person/day, and personal hygiene 5.5 L/person/day. This total reasonably estimates the amount of hygiene water required for each crewmember and jives with the hygiene water requirements from the Lunar Mars Life Support Test
Program (LMLSTP), (Edeen, 2000). During the test program the crew required 110.6
L/day. However, they also used water for dishes. Dirty dishes will be handled by the waste system.
A water buffer is required because the crew water needs may vary from day to day. The buffer size will allow the crew an average amount of water for each day. Also, in case of a failure in a key component of the water system the crew will have time to fix or replace it. The buffer size for the water system will be based on the LMLSTP. They had three days of potable water and 10 days of hygiene water. However, as laundry is the main constituent of the hygiene water and is not an urgent need for the crew only a 1 day buffer will be provided for laundry.

One final requirement set on the water subsystem involves keeping the water standards for potable and hygiene at acceptable levels. Common parameters monitored by a water quality monitoring system include acidity, ammonia, total organic carbon, electrical conductivity, and microbial content. Furthermore, pathogens will need to be rapidly detected and destroyed. Further monitoring of the water will include color, odor, heavy metal content, turbidity, foam, and taste.
Crew Accommodations Requirements:
General

All workstation designs must consider human reach profiles and encourage comfortable body posture.

The habitat must provide adequate lighting for the crew members and storage space for spare lighting hardware.
Sleep Quarters and Personal Space:

The sleep quarters must provide a quiet, dark, comfortable sleep environment to ensure the crew remains productive and alert during working hours.

Each crew member must have their own private quarters for sleeping and personal time.

The sleep quarters must provide controls for light, airflow, sound, and odor.

Historical data suggests that the sleep quarters should provide 1.5m
3
volume for sleeping, 0.63 m
3
volume for stowing personal equipment, and additional space if a desk or grooming space is included.

Personal recreational equipment and belongings must be stored within the habitat.
Galley

The galley must provide the tools and equipment needed to prepare and consume food, to store and inventory food supplies, and to clean up after meals. This may include an oven, water heater, water chiller, refrigerator, freezer, trash receptacle/compactor, and dishwasher.

Equipment and tools for galley maintenance must be provided, such as spare filters and appliance light bulbs.

Provisions must be provided for disposal and/or recycling of galley paper/plastic goods and food waste.

Power must be provided to the galley appliances.
Food

Food must be selected in accordance with established nutritional requirements, crew tastes and preferences, and anticipated caloric requirements.

Emergency/Contingency food and drink rations must be provided.

Approximately 2.3 kg of food should be provided to each crew member each day.
This will require an approximate volume of 0.008 m 3 /person/day for food storage.
Hygiene

Personal hygiene supplies must be provided and stored within the habitat.


Power may need to be provided to certain hygiene appliances.

Towels used in body cleansing must be non-linting and shall be washed in a clothes washer.
Clothing

Crew clothing must be provided and stored within the habitat.

Crew clothing must be cleaned using a clothes washer.

The clothes washer will require power and thermal dissipation.
Medical

Medical supplies must be provided both for routine medical needs and emergency situations. Estimated minimum medical mass and volume: equipment (1000kg), consumables (500kg), total volume (6.5 m
3
)

Crew members must be trained with the medical skills needed to handle routine and emergency medical needs.

Detailed instructions for emergency medical procedures must be available electronically, since the communication delay with Earth makes it not possible to get real-time instructions from Mission Control.

Some medical equipment will require power.

The crew must have adequate protection from harmful radiation through habitat design and/or safe-haven capability.
Wardroom

The Wardroom should serve be a multi-purpose space for dining, group recreation, team meetings, etc…

The wardroom should provide adequate space for all crew members to eat meals together.

It is desirable for the wardroom to contain a window to the outside, storage for recreational items, and equipment for two-way communication with the crew and with Mission Control.
Exercise

Exercise equipment is required to help maintain cardiovascular health, bone and muscle strength, and as a recreational tool.

A variety of exercise equipment types shall be provided in the habitat.

Exercise equipment must be designed with necessary isolation and damping mechanisms to meet vibration requirements of the habitat.

Spare parts for the exercise equipment must be stored within the habitat.

Some exercise equipment may require power.
Housekeeping

The habitat will require regular housekeeping.

Housekeeping supplies must be stored within the habitat.

Housekeeping trash must be disposed of and/or recycled.

Emergency Provisions

In the event of a fire, environmental contamination, depressurization, or toxic spill, the equipment necessary to combat these situations must be easily available in the habitat.
Photographic Equipment

Photographic equipment for public affairs, friends and family communication, and science requirements must be provided and stored within the habitat.

Power will be required to operate the photographic equipment.
Psychological Support Requirements
Pressurized Volume Physical Environment

An appropriate habitable volume must be set depending on the crew size
(6 crewmembers) and the amount of time they’ll be operating in that volume
(600 days).

The habitat must be divided into 3 environments: living quarters, workstations and recreation facilities.

All living quarters must provide crewmembers private space for sleeping and personal time.

All environments must have windows, appropriate lighting conditions, noise levels and thermal conditions.
Mission Duration and Schedule

All crewmembers must be aware of the mission duration (600 days worst-case scenario) so they can prepare themselves psychologically.

The set mission duration window must not be lengthened or shortened as to compromise the crewmembers’ psychological health and well being.

Good work/rest schedule(8 hrs/day of work and 2 days off/week).

Crewmembers must be allowed leisure time.

Regular team meeting must be held.

Celebration events must be held (e.g. holidays).
Crew Characteristics

All crewmembers must have been pre-screened for habitability (On Earth).

All crewmembers must have habitability training (On Earth).

The crew assembly must seek a balance of skills and leadership style.
Onboard Resources

A sufficient amount of water and food must be supplied to all crewmembers.

Domestic vs. foreign food?

Self-monitoring.

Music

Psychological training and awareness.
Communication


Good communication with ground control.

Indefinite communication with family members and friends back on Earth (Via email, web cams, etc).

Communication among crewmembers (Language).
Radiation Requirements and Concerns:
Although radiation concerns are not addressed in the design of the LSS, they are a major issue that cannot be ignored. Only the sources of radiation and basic exposure limits will be discussed here. Means of protecting the crew is outside the scope of this project and will have to be developed at a later time.
Solar Flares are energized alpha and beta particles that can be blocked with a few centimeters of shielding. A ‘storm shelter’, or elevator sized safe haven padded with food and water stores is sufficient to block this radiation.
Galactic Cosmic Rays cause more of a concern than solar flares. Cosmic rays come from every direction and are constantly present. The heavy, slow-moving atomic nuclei cause much more damage than the alpha and beta particles and are very difficult to block. The penetrating radiation is especially damaging to fast regenerating cells such as DNA, cells and tissues. Several meters of shielding are required to block this radiation.
Ultraviolet radiation is most prevalent at the Martian surface. Nucleic acids (i.e. DNA) absorb uv-radiation and activate chemical formations that prohibit replication and transcription of DNA. Only heavy shielding can lower the risk of damage from uvradiation.
Table 2.3 gives ionizing radiation exposure limits for intervals of travel. In any case, all crew does rates need to be kept “As Low As Reasonably Achievable” (ALARA).
Table 2.3: Ionizing Radiation Exposure Limits (Eckart 1996)
Duration of exposure
BFO [Sv]
5.0 cm depth
Eye [Sv]
0.3 cm depth
Daily
30 days
90 days
Annual
Career
0.002
0.25
0.35
0.5
1-4*
0.003
1
0.52
2
4
* values vary for males and females
Skin [Sv]
0.01 cm depth
6
1.5
1.05
3
6
Testes [Sv]
3 cm depth
0.001
0.13
0.18
0.38
1.5