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AERO 4740

Space Mission Design Lecture 8

For information and photos on ISS ECLSS systems for your research papers and presentations:

ISS Environmental Control Overview 2004.ppt

What's happening in space:

Physiology of Spaceflight

Human system needs make it harder:
– Air (O2, CO2, pressure, temperature, humidity, cleanliness)
– Water
– Food
– Protection (radiation, noise, vibration, acceleration)

Environmental Parameters
• Atmosphere
• Temperature
• Radiation exposure
• Noise
• Vibration
• Lighting
• Acceleration

Oxygen
• Planning:
~ 600 liters/person/day (~ 0.85 kg/person/day)
~ 0.02 kg/day leakage ISS has been less
Electrolysis (ISS): 0.11 liters water ? 600 liters of O2

Nitrogen
• Periodically replenish for leakage, EVA loss
• Can substitute other gases

Carbon dioxide
• CO2 levels:
– Auburn ~ 0.03% (0.03 kPa)
– Space Shuttle ~ 0.2 – 0.3 %
– ISS ~ 0.6 – 1.0 %
– Nominal 180 day mission limit is 0.87 kPa
– Safety limit: 1%
• Too much: no O2, fainting
• Too little: hyperventilation, fainting
• Must remove ~ 20 liters/person/day

Other Atmospherics
• Ventilation
– CO2 pockets
– 0.05-0.2 m/s
– Exercise - .42 m/s
• Contaminants
– Dust, skin, hair, lint, food, offgassed products
– Filtering required
– < 0.05 mg/m3 desired
– Table 5.6 SMACs

Temperature design considerations
• Cabin: 18-28 ºC
• Comfort affected by relative humidity
– 25-70% desired
• Touch: 4-45 ºC (momentary to 49 ºC)
• Plan for 230–300 W/person heat production

Human Needs - Water   Most massive consumable for human spacecraft
• Planning (kg/person/day)
– Potable water - 2.8
– Personal hygiene – 1.1 (7.0 if shower)
– Flush – 0.5
– Clothes wash – 12.5 (if desired)
– Dish wash – 5.4 (if desired)
• On ISS with condensate recovery:
– 2 kg/person/day

Food
• 2300-3200 kcal/person/day
• Nutritional balance and variety are important

Radiation exposure
• Exposure limits based on mission duration and age
• Recall Rem = Rad x Q
Data shows Q = 2.5 for LEO
• National Council on Radiation Protection recommended to NASA an administrative 1-year Dose Limit of 20 Rem to the blood forming organs to limit career risks
• Auburn ~ 20 mrem / year
• Rocky mountains ~ 90 mrem / year
• Then add:
~ 40 – 160 mrem / year for cosmic rays
~20 – 50 mrem / year for food and water
~0.5 mrem / hour on a commercial jet
• Your average yearly radiation dose is: ~ 0.1 rem/year
Astronaut LEO dose
• 180 day mission will exceed 20 rem/yr limit at solar minimum
• ISS TEPC data (solar maximum – best case)
– Dose rate is 0.079 rem/day = 14.2 rem in 180 days

Radiation comparisons

Radiation Design Considerations
• Orbit Inclination
• Altitude selection
• Age and Sex of crews
• Mission duration
• Shielding and use topology advantage - H2 is best shielding
Need to shield

Radiation shielding with water
• Multi use material
– Radiation shield
– Drink it
– Wash with it
– Cool with it
– Make O2 with it

High Density PolyEthylene (HDPE)
• Good shielding at ~ 14% H2, but heavy and highly flammable
• NASA study of 2” of HDPE in crew quarters– meets 20 rem/yr limit for 250 days at solar minimum
• Weight of HDPE ~ 800 lb per crew quarters

Noise
• Affects human performance
50-60 dB must raise voice to communicate
65 dB hearing threshold shift, may be permanent
75 dB performance degradation
110 dB irritability and chronic fatigue
120 dB pain, nausea
• NASA long duration spec: 51 dB
• Flight rule: Maximum 24 hour average: 65 dB
• Actual ISS values
• Lab: 55 dB
• SM: 65 dB
• Documented ISS crew hearing loss

Noise design considerations
• Reduce sound producing sources
– Fans, pumps, valves
• Dampen / Insulate
– Blankets or foam to deaden
– BiscoTM or similar to block
– Isolate sound producers
• Hearing protection
– Active – Bose headsets
– Passive – earplugs, helmets, headsets

Acceleration
• Linear: most tolerant of gx
• Shuttle ascent ~ 3 gx max
• Shuttle entry ~1.5 gz max
• Soyuz ~ 9 gx emergency escape
• Rotational: ~ 6 RPM but training increases tolerance
• Impact: 15-20 g at 500-1000 g/s

Acceleration design considerations
• Crew positioning and orientation
• Engine throttling
• Solid rocket combustion chamber design

Vibration
Stress, fatigue, nausea
• Amplitude and frequency dependant
• 0.1 – 0.63 Hz cause motion sickness
• Vibration design considerations
– Active damping (launch pad water suppression)
– Passive damping – isolators on SM A/C compressors

Lighting
• Affects ability to do work
• Psychologically important
• Design considerations:
– More is better
– Planning – use industry standards Table 5-15
– Fixed, portable and indirect
– Filter/shade external light

Other Physiological Factors
• Contamination
– Microbe and fungal growth
– Keep colony forming units in air to < 1000CFU/m3
• Design considerations
– Cleaning supplies, disinfectants, fungicides
– Filters
– Sampling

Effects on humans - short term
• Space Adaptation Sickness
– 2/3 who fly in space have some form
• Nausea, vomiting, headache, backache, vestibular upset, malaise
– Persists hours to few days
– Due to changes in
• Vestibular system
• Muscular-skeletal system
• Fluid shift/loss
• Re-adaptation
– Vestibular disturbances most common
– Orthostatic intolerance (fainting)
– Some nausea

Long term effects
• Cardiovascular deconditioning
• Muscular atrophy
• Bone mass loss
• Cell damage/cancer

Other effects
• Vision changes
• Memory changes
• Separation and isolation

Countermeasures
• Low resistance, high frequency exercise of large muscle groups for cardiovascular and muscle
– Treadmill
– Bicycle-ergometer
– Bungees
• High resistance, low frequency exercise for loading muscles and skeletal system
– Resistive exercise device
– Bungees

Exercise Countermeasures
• Pharmaceuticals for SAS, bone loss (?)
• Fluid loading before entry
• Lower Body Negative Pressure – Chebis suit

More Countermeasures
• Artificial gravity systems
– Low RPM and large radius better
– Consider < 1g
– Sleeper?
– Running/bicycling track?
– Not much data on effects and trades

Example……..

Artificial Gravity by Rotation
• a=ω²r
• Generally < 6 rpm better
• For 1 g at 6 rpm rotation:
r = (9.7 m/s2)(57.3 deg/rad)2 / (36deg/sec)2
= 24.5 m
• Lower g example:
• 0.5 g at 4.7 rpm = 20m
• Coriolis forces a problem if moving not parallel to axis of rotation Fc=?v

Psychological
• Numerous examples of impact to missions
• Health, well-being and performance
• Design considerations for psych support
– Family/friend contact
– Environment – personal space, colors, human factors
– Care packages/Surprises
– Reminders of home
– Psychologist, other consultation
– Teambuilding
– Self monitoring/analysis Training