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Advanced Topics in Space Studies: Commercial Barriers and Solutions. Human Factors/Space Medicine Dr. John M. Jurist Biophysicist CRM, Inc. What Happens to People Living and Working in Space?. The dream:. What Happens to People Living and Working in Space?. Reality:. Human Factors. - PowerPoint PPT Presentation
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Advanced Topics in Space Studies: Commercial Barriers and Solutions
Human Factors/Space Medicine
Dr. John M. JuristBiophysicist
CRM, Inc.
What Happens to People Living and Working in Space?
The dream:
What Happens to People Living and Working in Space?
Reality:
Human Factors
Space is a very, very hostile and unforgiving place:
1. None of the comforts of home unless brought along2. It is largely empty (both blessing and curse)3. Transport from Earth is very expensive4. We don’t really know much about living there5. Repairs and help are far away6. Truism: Space can always hurt you more
Human Factors
• 862 gms O2
• 2,200 gms H2O
• 523 gms food
• 982 gms CO2
• 2,542 gms H2O
• 61 gms solid waste (min)
Consumables for a 70 kg Man (level flying) at 2,830 kcal/day on specific diet:
(after Hans G. Clamann, Problems of Metabolism in Sealed Cabins)
Human Factors
1. Air
2. Water/urine
3. Food/solid wastes
4. Toxic accumulations of whatever
Consumables requirements make recycling more attractive for longer missions and larger crews:
Human Factors
Considered in the context of mission parameters:
1. Suborbital2. Orbital3. Lunar4. Solar System
Human Factors
Considered in the context of mission parameters:
1. Duration2. Life Support3. Consumables4. Acceleration5. Microgravity6. Radiation7. Other Considerations
Human Factors
Suborbital:
1. Duration – minutes
2. Life support – hypoxia – pressure suits
3. Consumables – minimal – no waste handling
4. Acceleration – multidirectional? – cardiac arrhythmias
5. Microgravity – nausea (in a pressure suit?)
6. Radiation – negligible
Human Factors
Orbital:
1. Duration – hours to weeks2. Life support – + contaminants, noise3. Consumables – +transported and stored4. Acceleration – + tolerance after microgravity5. Microgravity – +fluid shift, bone & muscle atrophy6. Radiation – not negligible7. Other – medical emergencies – can’t call 911
Human Factors
Lunar:
1. Duration – hours to weeks2. Life support – + contaminants, noise3. Consumables – +transported and stored4. Acceleration – + tolerance after microgravity5. Microgravity – +fluid shift, bone & muscle atrophy6. Radiation – roughly 2x orbital, flares fatal7. Other – dust, medical emergencies, procreation?
Pulmonary Physiology
Abating effects of altitude:
1. Pressurize the cabin – 8,000 feet airline standard
2. Supplemental oxygen
Pulmonary Physiology
Pressurizing cabin to 8,000 feet results in inadequate oxygen saturation and need for additional oxygen for otherwise healthy people:
1. 44% of 65 year old
2. 27% of 55 year old
3. 14% of 45 year old
Pulmonary Physiology
Breathing pure oxygen at altitude equivalent to:
1. Sea level air at 33,000 feet
2. 10,000 feet air at 39,000 feet
3. 20,000 feet air at 45,000 feet
Pulmonary Physiology
Pressure suits:
1. Full pressure suit more than $1 Million
2. EVA capable suit more than $3 Million
3. Partial pressure suits uncomfortable -- Get me down alive !!
4. Poor heat dissipation especially with exercise
5. Heat stroke running from downed spacecraft?
Acceleration Effects
Acceleration duration:
1. Prolonged if more than 0.2 seconds
2. Fluid shifts important and dominate effects
3. Impact if less than 0.2 seconds
4. Viscoelastic nature of tissues
5. Delta-V or acceleration onset best indicator
Acceleration Effects
Acceleration definitions:
1. Eyeballs down plus Gz
2. Eyeballs up minus Gz
3. Eyeballs in plus Gx
4. Eyeballs out minus Gx
Acceleration Effects
Prolonged acceleration:
1. Normal blood pressure at heart 120/75 mm Hg
2. Pulmonary artery 20/7 mm Hg
3. Pressure drop to brain 35 mm Hg at 1 G
4. Pressure drop to brain of 105 mm Hg at 3 G
5. Venous blood pooling
Acceleration Effects
Prolonged acceleration:
1. Grey out, loss of vision, loss of consciousness
2. Visual acuity decrease (deformation)
3. Compensatory mechanisms
4. Carotid sinus reflex dominates (5 seconds)
5. Respiratory difficulties
Acceleration Effects
Abating effects of prolonged acceleration:
1. Decrease uphill heart-brain distance
2. Modify flight profile
3. Counter pressure suit to decrease blood pooling
4. Counter pressure by straining
Acceleration Effects
Cardiac effects of prolonged acceleration:
1. Irregular heart beat 47% medical professionals
2. 4.5% potentially dangerous
3. Irregular heart beat 30-50% fighter pilots
4. 4.6% potentially dangerous
5. Aging effects poorly characterized
Consideration of Failure
Fundamental decisions :
1. Vertical or horizontal takeoff and landing2. FAA/AST-2 essentially laissez faire3. Definition of failure modes and probabilities 4. Passenger education and training
Consideration of Failure
Ejection seat utility:
1. Part of atmospheric flight2. HTO vehicle in early flight3. Limited at high speeds4. Limited at high stagnation temperatures
Consideration of Failure
Ejection seat upper envelope:
1. Mach 0.9 at sea level2. Mach 3.7 at 65,000 feet3. High stagnation temperatures above 65,000 feet
Consideration of Suborbital Failure
Cabin depressurization:
1. Unstrap for short time in microgravity?2. Emergency egress for landing mishaps3. Lawyers have 20-20 hindsight4. So do congressional committees
Radiation Exposure
Sources of exposure:
1. On board fluid level sensors2. Cosmic photons (includes gamma bursts)3. Cosmic particulate radiation4. Solar photons5. Solar particulate radiation (includes flares)6. Trapped particulate radiation belts (Van Allen)7. Terrestrial background
Radiation Exposure
Units:
Energy/Mass Bioeffect
100 Rad times Q(RBE) 100 Rem
1 Gray (Gy) times Q 1 Sievert (Sv)
Radiation Exposure
Short term acute whole body exposure (rems):
10-50 Minor blood changes50-100 5-10% nausea (1 day), blood, survivable100-200 1/4-1/2 nausea (1 day), blood, GI, survivable200-350 Most nausea (1 day), blood, GI, 5-50% die350-550 450 LD50 Most nausea, blood, GI, 50-90% die
550-750 Nausea (hours), blood, GI, almost all die750-1,000 Nausea (hours), blood, GI, fatal (2-4 weeks)1,000-2,000 Nausea (hours), fatal (2 weeks)4,500 Incapacitation (hrs), fatal (1 week)
Radiation Exposure
Living and medical:
1. Polar airline flight 0.10-0.23 mSv per day2. 2 view chest X-ray 0.06-0.25 mSv3. Bone scan 0.15 mSv4. Chest CT 0.3-30 mSv (typical 10 mSv)5. Billings MT background 1.2 mSv per year (quiet sun)6. Typical US background 2.4 mSv per year7. Typical US medical 0.6 mSv per year
Radiation Exposure
Dose vs Altitude(nonTerrestrial)
1
10
100
1,000
1 10 100 1,000 10,000
Altitude (thousands of feet)
Do
se
(m
icro
Sie
ve
rts
/da
y)
Radiation Exposure
Based on HTO suborbital:
1. Upper limit 0.0053 mSv per flight2. Polar airline flight 0.10-0.23 mSv per day
Radiation Exposure
Based on orbital and beyond:
1. 0.6-0.9 mGy/day (Skylab)2. 0.2-1.3 mGy/day (Apollo landing flights)3. ~0.06 mGy/day (STS)4. 0.049-1.642 mGy/day (STS-2, STS-31)5. 0.053 mGy/day 0.146 mSv/day galactic cosmic6. 0.042 mGy/day 0.077 mSv/day trapped belt
Radiation Exposure
The problem:
1. 2 view chest X-ray 0.06-0.25 mSv2. Public limit 1 mSv per year3. NASA classifies astronauts as radiation workers4. Worker whole body 50 mSv or 0.05 Sv per year5. Worker organ limit 0.5 Sv per vear6. Worker organ limit 0.25 Sv per month
Radiation Exposure
Career limits for radiation workers (1994):
Blood-Forming Organs
Limit at Lens Skin Male Female
Age 25 4.0 Sv 6.0 Sv 1.5 Sv 1.0 SvAge 35 4.0 Sv 6.0 Sv 2.5 Sv 1.75 SvAge 45 4.0 Sv 6.0 Sv 3.2 Sv 2.5 Sv Age 55 4.0 Sv 6.0 Sv 4.0 Sv 3.0 Sv
Radiation Exposure
Radiation carcinogenesis:
0.5/106/mSv/year Breast
0.4/106/mSv/year Thyroid
0.3/106/mSv/year Lung
7-17/106/mSv/year All cancers
100 mSv/105 800 deaths added to 20,000 w/o radiation (4% increment/10
rads)
10 mSv/year cont. 5% increment/1 rad lifetime increase
Radiation Exposure
Is radiation a show-stopper for a trip to Mars?
1. Minimum energy transfer roughly 9 months each way2. Assume STS-like free space galactic radiation exposure of 0.146
mSv/day 3. 270 days times 0.146 mSv/day = 39.4 mSv for 1 way4. Is it legal? 50 mSv/year whole body worker limit5. Is it legal? Compare to career limits (3 Sv age 55)6. Boost cancer death risk 1.7% for baseline trip to Mars7. Boost cancer death risk 25% for continuous 0.146 mSv/day8. Flares and Mars orbit time, surface time 9. Radiation issues become significant
Radiation Exposure
The conundrums:
Are long term space missions legal?Informed consent vs. legal limitationsConceive and raise children?Remember planets shield by geometryLarge variability in exposure (flares)Large variability in response
Weightlessness
Based on HTO suborbital:
1. Maximum of 3½ minutes of microgravity2. Greatest risk is nausea (other risks in orbit)3. Familiarization aircraft flights4. Minimize head movements5. Medication6. Avoid vomiting into oxygen mask or closed helmet7. Nausea is contagious (smells and sounds)
Discussion
Suborbital Human Factors Status
Alt.space awaremess is dismal:
1. Assumption that it is accomplished and can be ignored
2. Lack of appreciation of risks
3. Aging normative population undefined
4. Suborbital floating free in shirt sleeves?
5. Buy a Russian space suit on EBAY
Orbital (and Beyond) Human Factors Status
Alt.space awaremess is even more dismal:
1. Assumption that it is accomplished and can be ignored
2. Lack of appreciation of risks
3. Aging normative population undefined
4. Minimal gravity level is undefined
5. Radiation issues become significant
6. Working is microgravity is hard
Orbital (and Beyond) Human Factors Status
Why? Culture shock (engineering vs. biomedical):
Engineers look for limiting parametersEngineers design to limiting parametersEngineers minimize variablesHuman responses vary enormouslyHuman responses probabilisticHuman responses – many variablesHuman responses poorly characterizedNever say never in medicine
Orbital (and Beyond) Human Factors Status
Medical issues related to living in space and going to Mars:
1. Outside assistance is impossible or very difficult2. Life support degradation – toxin accumulation3. Acute urinary retention -- renal lithiasis4. Cardiac event5. Cancer (Antarctica example)6. Drug shelf life (accelerated degradation with radiation) 7. Medical/surgical infrastructure -- how much is enough?
Opportunities
What we don’t know can hurt us or provide opportunities for play/research:
1. Microgravity – musculoskeletal, cardiovascular, reproductive, and immune systems; embryogenesis, fetal development; aging; optimization
2. Radiation – shielding (mass, electrostatic, or magnetic), abatement (pharmaceutical, antioxidants, modification of humans – genetic engineering)
3. Long term exposure to different gas mixes vs. standard air4. Other – lunar dust and urban/rural pollution effects
Opportunities
Role for small business niche operations:
1. Training MDs in aerospace medicine
2. Training passenger candidates
3. Screening passenger candidates
4. “Space Camp” for passengers
5. Life support equipment – esp. pressure suits
6. Ever present consulting
Opportunities
Role for academic operations:
1. Training MDs in aerospace medicine2. Training passenger candidates3. Education – public outreach4. Research – specialized – intradepartmental5. Research – interdisciplinary –
multidepartmental or multischool6. Ever present consulting
Solutions
Becoming a spacefaring culture:
1. Drive down cost to LEO and beyond2. Find and exploit commercial opportunities3. Justification for manned presence4. Technology (microgravity, radiation, life
support)5. Technology (shorten trip times)6. Motivation (national security?, lifeboat?)
Solutions
Becoming a spacefaring culture:
1. Time
2. Money
3. Research
4. Technology
5. Management
6. Motivation