Advanced Topics in Space Studies: Commercial Barriers and Solutions Human Factors/Space Medicine Dr....

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


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




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


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 definitions:

1. Eyeballs down plus Gz

2. Eyeballs up minus Gz

3. Eyeballs in plus Gx

4. Eyeballs out minus Gx


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


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


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


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


Ejection seat utility:

1. Part of atmospheric flight2. HTO vehicle in early flight3. Limited at high speeds4. Limited at high stagnation temperatures


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


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


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

Advanced Topics in Space Studies: Commercial Barriers and Solutions Human Factors/Space Medicine Dr....

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