PDR – Crew Systems Jesse Cummings Sukhjohn Kang Chris O’Hare Brendan Smyth

Overview – Initial Considerations Mission Schedule EVA 4 lunar EVA’s Total cabin decompression Mission StageDays – type Transit – Depart3 – nominal Lunar Sortie4 – active Transit – Return3 – nominal Contingency3 – active Total6 – nominal, 7 – active

Overview – Initial Considerations Crew 3 95% males of med-heavy build Body dimensions: 1.9 x 0.44 x 0.28 m Body mass: 82.6 kg Using NASA Mk3 space suits with primary life support backpacks Total mass per unit: 74 kg

Overview – Initial Considerations Crew Capsule Conical shape 3.47m base diameter Cone half-angle degrees 10 cm wall thickness

Crew Consumption/Production

Total for crew of 3, 95 th percentile males 13 day trip, 6 nominal and 7 active days

Cabin Atmosphere Total Pressure Want to minimize to prevent loss (leakage, EVA decompression) N 2 percentage Want to minimize for no/little decompression time for EVA prep Ideally, ppN2 < 51.6 kPa (Equivocates to R=1.5 vs EVA suits) O 2 percentage 30% O2 Minimized to prevent fire risk Maximized to lower total pressure

Cabin Atmosphere Resulting ppN2 at various ppO2 in cabin at 30% O2. Acceptable ppO2 levels are below R threshold.

Cabin Atmosphere Cabin pressures of 64.3 to 73.7 kPa prevents necessary EVA decompression time Designed Cabin Pressure: 71 kPa – ppO2 at normoxity level for better crew acclimation

Cabin Atmosphere From Scheuring et.al., “Risk Assessment of Physiological Effects of Atmospheric Compositino and Pressure in Constellation Vehicles” 16 th Annula Humans in Space, Beijing, china, May 2007 Proposed Atmosphere Proposed atmosphere is within acceptable safe numbers

Cabin Gas Loss Analysis Given: – 30% O 2, 70% N 2 at a pressure of 71kPa – 298 Kelvin cabin temperature (room temperature) – Cabin volume of 10 m 3 – Total EVA days: 4; Total days: 13 – Gas lost due to leakage/purges: 2% per day – 100% depressurization during EVAs – Assuming 0.7 kg tank/kg gas (for liquid storage)

Cabin Gas Loss Analysis Partial Pressure (kPa) Mass Required to Fill Cabin (kg) Total Mass Lost Due to Leaks (kg) Total Mass Lost During 4 EVAs (kg) Total Mass Lost (kg) Oxygen Nitrogen

CO 2 Scrubbing Systems The optimal criteria for CO 2 scrubbing systems are as follows: – Lowest system mass – Safety considerations (i.e. possibility of fire) – External power requirements – External substances required (i.e. H 2 and O 2 for EDC) Considering the last two factors, a “Net Effective Mass” can be generated for each system, which takes into account the mass of required power systems and substances that the system requires to function.

The study below compares the raw masses of each system (excluding any external factors)

Net Effective Masses Factors that influence the Net Effective Mass – Raw mass of the system (based on data given in slides) – Products produced by the system (O 2, H 2 O, etc.) – Power required to operate system Assuming fuel cells as power sources with a power density of 500 W-h/kg – Additional substances required to operate system (O 2, H 2, H 2 O, etc.) The Net Effective Mass reflects the overall impact of each system on the global mass of the system. The system with the lowest Net Effective Mass is therefore the most mass-effective system. EDC’s and Potassium Superoxide systems have many external factors associated with them, and are broken down individually in the next two slides to illustrate what factors are driving the value of Net Effective Mass

Net Effective Mass Breakdown of Potassium Superoxide (non-regenerable) 2KO 2 + CO 2 → K2CO 3 + 3/2 O 2

Net Effective Mass Breakdown of Electrochemical Depolarization Concentration (Regenerable) CO 2 + 1/2O 2 + H 2 --> CO 2 + H 2 O + electricity + heat (electricity is solely used by system)

Net Effective Masses of all CO 2 Scrubbing Systems Considered

Narrowing the Selection The two most favorable systems based on the Net Effective Mass comparison are the EDC and the KO 2 systems. Advantages of EDC – Generates water via a built-in fuel cell reaction – Fuel cell reaction eliminates the need for external power supply Disadvantages of EDC – Creates an unsafe, combustible mixture at the anode – Increases tank size requirements for O 2 and adds an entire new tank for H 2, which takes up more physical space in the vehicle Advantages of KO 2 – Generates O 2, entirely eliminating the need for large O 2 tanks, creating more usable space – No need for an external power supply – Systems have been developed that interact directly with CO 2 to produce O 2, eliminating the need for water Disadvantages of KO 2 – Very dangerous substance when reacting with water vapor in air, but research has been done that proves the reactivity can be greatly reduced by diluting the KO 2 with silicone polymers that prevent it from reacting with water vapor – Non-regenerable

Comparison of Net Effective Masses: KO 2 and EDC KO2 Net Effective Mass for 13 days: 61 kgKO2 Raw Mass: 159 kg EDC Net Effective Mass for 13 days: 61 kgEDC Raw Mass: 44.2 kg

CO 2 Scrubber Selection Both systems are roughly equivalent in terms of Net Effective Mass cost, however the Potassium Superoxide system offers more attractive advantages than the EDC – The Potassium Superoxide system consumes less physical space inside of the vehicle by utilizing fewer tanks than the EDC and greatly reducing the size of O 2 tank needed* – Because it requires no power source, the Potassium Superoxide system is more dependable, eliminating the possibility of astronauts losing their O 2 supply if there is a power issue – By diluting the KO 2 with silicone polymers, the safety issues associated with Potassium Superoxide are mitigated, making it a safer system to consider than the EDC which produces combustible gas mixtures *Very small tank still needed for atmosphere replenishment after venting during EVAs and emergencies

Water Storage and Distillation kg of water required for mission (Including contingency) – kg drinking water – kg food water – kg hygiene water Plus 0.1 kg of tank mass / kg of water Without any filtration this would result in kg of payload for water and storage Using water distillation will decrease the amount of water needed for the trip VCD distillation method selected because it is most mass and power efficient option

Mass Totals for Water Storage/Distillation

Water Storage and Distillation VCD unit distills kg of water per day – Filters hygiene water and urine – Assuming 70% filter efficiency Our total water storage mass: kg – Stored water: kg – Mass of water tank: kg – VCD unit: kg

Air Filtration HEPA unit selected for air filtration – HEPA removes 99.97% of all particles > 3um kg; 0.13 m 3 ; 39 W unit Filters the 10 m 3 module 4 times per hour

Waste Disposal Due to limited space, we want to minimize storage Waste will be stored during transit, deposited on lunar surface during EVA stage

Radiation Must consider shielding from various radiation sources Background radiation Event radiation (ex: solar flare) We want to keep crew exposure to acceptable safe levels ISS crew receives mSv per 6-month visit Background Radiation - Shielding material Dedicated - Aluminum walls Multiple use - drinking/waste water Need twice as much thickness to be as effective as Al

Radiation – Solar Flare Event August 1972 GCE Theoretical exposure of up to 1000 rad skin exposure with 1 g/cm2 shielding Shielding considerations Not feasible to protect entire ship Create radiation shelter for crew in case of solar flare event Radiation shelter Requires over 10 g/cm2 Al to prevent significant radiation exposure Smallest shelter would be 5.6 m2 Would need 540 kg Al at least Radiation shielding mass not being considered for this design

Crew Chairs Chairs dimensions and angles adjustable for varying astronaut size Values shown are for 95 th percentile male, and spacesuit, in Neutral Buoyancy Position Each chair takes up m 3 of space when extended to NBP for 95 th % male Chairs are attached to the wall and can be stowed when not in use Aluminum construction – 50 kg each

Final System Specifications Mass margin: 22.9% SystemSystem Mass (kg)Volume (m^3)Power (Watts) Oxygen Nitrogen CO2 Scrubber negligible Air Filtration Water Food negligible People (3) n/a Suits negligible Chair (3) Personal Effects CTB (3) Total

Window SightLines Want crew to be able to see at least 0.5 m in from of capsule base Window must accommodate crew of various heights Window designed to be 0.42 m long

Capsule Drawing (Control Panel positioned 1m above crew beds and control interface at an ergonomic 1.3m height for landing)

Interior Top Down – No control Panel

Interior Top Down – With Control Panel

Water Storage, VCD

Crew Chair

O2 tank

N2 Tank

KO2 CO2 Scrubber

CTB

References Kim, Jin, Yoonkook Park, and Soon Jeong. "CO2 conversion to O2 by chemical lung in the presence of potassium superoxide in the silicone polymer matrix." Korean Journal of Chemical Engineering 27.1 (2010): Print. Man-Systems Integration Standards. Overview of Solar Energetic Particle Event Hazards to Human Crews. Townsend, Lawrence. University of Tennessee. (Powerpoint Presentation) Understanding Space Radiation. Johnson Space Center. FS JSC