17 ECLSS

ECLSS (Ch. 17): 

ECLSS (Ch. 17) Objectives Define requirements for an ECLSS Describe categories of technologies / subsystems used to meet the requirements Distinguish between open/closed loop systems and regenerable/non-regenable technologies Discuss system-level trade factors

ECLSS Requirements: 

ECLSS Requirements Satisfy physiological needs of the crew Metabolic (oxygen, water and food) Environmental (pressure, thermal control) Provide resources for hygiene, medical and science needs and other systems (e.g. EVA) Crew = resource consumers / waste producers Human I/O = ECLSS O/I

Technology Categories: 

Technology Categories Physico-Chemical Reliable, mature, current use Can recycle O2 and water, but not food Bioregenerative Multifunctional, complex infrastructure Can produce food Hybrid Open/closed (w.r.t.) Does any mass or energy cross the cabin boundary? Regenerable/non-regenerable (w.r.t.) Can technology and/or consumable be refurbished on orbit? ISRU

ECLSS Design Process: 

ECLSS Design Process Establish baseline system for comparison Open loop, non-regenerable is simplest Compare impact of more complex functions Typically = f (M, P, V, crew time, reliability, etc.) Mission duration is the key trade factor Determine M, P, V and thermal load Infrastructure, consumables and leakage Evaluate candidate options Equivalent Mass (or Equivalent System Mass)

Life Support Areas: 

Life Support Areas Atmosphere Control pressure, temperature, humidity Remove CO2 and TC’s Provide ventilation and make up gases Monitor composition Fire detection / suppression Water Provide potable (and hygiene) water Store, distribute and monitor quality Collect waste condensate from atmosphere Waste Collect, process, store/jettison n on-recoverable waste Food Provide, store, prepare

Atmospheric Functions: 

Atmospheric Functions Control pressure and composition Typically O2/N2 mix Sea level conditions or reduced pressure? Physiology Leak rate, structural load Flammability EVA transition Off-gassing Convective heat transfer efficiency (by volume)

Atmospheric Functions: 

Atmospheric Functions Temperature and humidity Comfort range Condensation concerns (electronics, microbial growth) Ventilation Particularly important in microgravity Removal of CO2, thermal gradients, particulates, contaminants (dictated by SMAC) Critical for some sensor functions (e.g., fire)

Atmospheric Functions: 

Atmospheric Functions Monitoring Temperature, humidity, ppO2, ppCO2, P total, TC’s, microbial contamination Provide make up gases O2 consumption, leakage, venting FDSS

Pressure Monitoring and regulation: 

Pressure Monitoring and regulation Absolute pressure monitors Delta-pressure monitors Air flow monitors Regulators Positive and negative pressure relief valves

Fire Detection and Suppression: 

Fire Detection and Suppression Smoke detectors Fire extinguishers CO2 Halon Water

Emergency Breathing Apparatus: 

Emergency Breathing Apparatus For contaminated atmosphere/smoke

Oxygen: 

Oxygen Human usage ~ 600 liters (gas @ 1 atm)/person/day ~ 0.85 kg/person/day ~ 0.02 kg/day leakage – ISS, has been less Apollo was more (~1 kg / day) Production by electrolysis ~1 liter water → 25 liters (1 atm) of O2

Oxygen Supply Systems: 

Oxygen Supply Systems Technology options to provide O2 Physico-chemical Storage Electrolysis Chemical release Bioregenerative Plants Algae

Shuttle O2 Storage: 

Shuttle O2 Storage Stores liquid oxygen Used for breathing and electrical power production Cryogenic Thermally insulated, double walled vacuum annulus tanks -176 °C High pressure - 5 MPa Heaters maintain pressure Up to 5 spherical tanks (+4 more for EDO- OV105) Tank volume = 320 liters Tank mass = 98 kg O2 mass = 354 kg / tank Inconel 718 inner and 2219 Aluminum outer shells Regulates at PPO2 = 20.3 to 23.8 kPa

Electrolysis: 

Electrolysis Uses electrical power to split H2O Electrical power 2 H2O → 2 H2 + O2 Used on MIR In use on ISS - Russian “Elektron” 1 liter H2O → 25 liters O2 (1 crew member for 1 hr) 10 to 64 amps yield 25 to 160 liters/hr O2 +

Chemical Release: 

Chemical Release ISS Solid oxygen generator Back up O2 production Burn Potassium Perchlorate candle Heat KClO4 → KCL + 2 O2 Exothermic chemical reaction at 400-500 °C Packaged in a cassette (~30 cm x 8 cm dia) Produces 600 liters O2 (~1 person / 24 hrs)

Carbon Dioxide: 

Carbon Dioxide CO2 levels: Earth ~ 0.03% (0.03 kPa) Space Shuttle ~ 0.2 – 0.3 % ISS ~ 0.6 – 1.0 % Safety limit: 1% Too much: no O2, fainting Too little: hyperventilation, fainting Must remove ~ 1kg /person/day Eliminate with: Absorbers (LiOH canisters, Molecular Sieves) Regenerators to retrieve O2 (Sabatier, Bosch)

Vozdukh: 

Vozdukh Operation principal : Use of regenerable chemical adsorbers to separate and remove carbon dioxide from the atmosphere of the ISS

Sabatier CO2 Regeneration: 

Sabatier CO2 Regeneration Uses CO2 taken from CO2 removal system Combines with hydrogen Methane byproduct can be used or vented overboard Water can be stored and used by the crew or electrolysized to generate O2 and H2 H2 can then be used again in the Sabatier process

Sabatier Reactor : 

Sabatier Reactor CO2 regeneration system Reaction discovered in 19th century by French chemist and Nobel Prize winner Paul Sabatier CO2 + 4H2 => CH4 + 2H2O Exothermic reaction that occurs spontaneously at temperatures above 150°C while a catalyst is present

Sabatier Functional flow diagram: 

Sabatier Functional flow diagram

Temperature and Humidity: 

Temperature and Humidity Cabin 18-28 C set point RH 25-70% set point Touch Temp 4-45 C (49 C max) Heat Load plan for 230-300 W/person payloads and vehicle avionics external gain/loss

Water Functions: 

Water Functions Potable water has highest standards Iodine or silver biocide Monitoring pH, ammonia, TOC, electrical conductivity and microbial concentrations (CFU’s) Color, odor, turbidity, foaming and heavy metal accumulation Hygiene water standards less stringent, but total mass may be greater

Water Functions: 

Water Functions Store and distribute water Challenges in microgravity include transport forcing function, leak detection, two-phase fluid handling (water / air separation), biofilm fouling Collecting and processing condensate, hygiene and potentially urine

Water: 

Water Planning (kg/person/day) Potable water - 2.8 Personal hygiene – 1.1 (7.0 if shower) Clothes wash – 12.5 (if desired) Dish wash – 5.4 (if desired) Can recover water Condensate and ‘grey’ water Urine (harder) Fecal water (hardest) Medical / Experimental waste (not likely)

Slide26: 

ISS Water Reclamation ISS Water Reclamation System is an improved version of the system used onboard the Russian space station Mir. Recycles water from ISS Service Module Air Conditioning System condenser. Has 9 components: - Filters - Condensate Separation and Pumping Units - Purification Column Unit - Water Conditioning Unit - Distribution and Heating Unit - Potable Water Container - Non-Potable Water Containers - Sensor Unit - Control Panel

Waste Functions: 

Waste Functions Collect, transport, store, stabilize, treat or dispose Feces, non-edible biomass, non-recoverable liquids/solids, wet/dry trash Becomes increasingly difficult to define waste as system closure level increases

Waste Management: 

Waste Management Humans generate waste Urine Feces Trash Medical / Experimental Store (return), remove (jettison) or re-use (recycle) Tanks, cans, bags Overboard dump Burn up in atmosphere Return to Earth Regeneration

ISS Waste Management System Components: 

ISS Waste Management System Components Receptacles Solid Waste Receptacle Plastic Baggy Solid Waste Container Receptacle for Urine Vacuum Hose Preservative flush water H2SO4 CrO3 Fluid Transportation Fan 700 liters per min.

Separation And Filtration: 

Separation And Filtration Miniature Pump Separator Filters waste water from air transport using centrifuge forces Centrifugal Collector Air Filter

Food Functions: 

Food Functions Provision and preparation Not always considered part of ECLSS Processing ranges from ready-to-eat or rehydration to grow, harvest, modify and cook

Slide32: 

Life Support Systems Water Supply Food Supply Fire Detection And Suppression Waste / Hygiene Atmosphere Control Pressure Monitoring CO2 / TC Removal Pressure Regulation Gas Analysis Oxygen Supply Temperature And Humidity Control Review

System-level Trade Factors: 

System-level Trade Factors Total Launch Mass (System and Consumables) Open / Closed loop & Regenerable / Non-regenerable Resupply availability & ISRU influence Break-even plots ESM Power Volume Fixed equipment Consumable stowage Crew time / training (complexity) Safety & Reliability Cost Development (TRL) Operation (Flight & Ground)

TRL & ESM: 

TRL & ESM

Slide36: 

Consider the relationship between TRL and the Design Phases A, B and C/D – at what TRL can you confidently include a technology at various stages in the design process?

Equivalent System Mass (ESM): 

Equivalent System Mass (ESM) ESM is the sum of the masses of life support equipment and supplied commodities, plus the mass penalties for infrastructure support, notably power and cooling (heat rejection), corrected for crew time required to operate and maintain the system (Drysdale, et al., NASA CTSD ALS Research and Technology Development Metric – FY 2001, NASA CTSD-ADV-482, 17 January 2002) Used for comparison of unlike parameters normalized to mass by assigning coefficients/penalties for power, heat rejection and crew time requirements  

Slide38: 

ESM = System Mass (dry mass, consumables, expendables, spares) + (Power x Conversion Factor) + (Heat Rejection x Conversion Factor) + (Volume x Conversion Factor) + (Crew Time x Conversion Factor)