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Space Radiation ENAE 697 - Space Human Factors and Life Support
U N I V E R S I T Y O FMARYLAND
Space Radiation• Sources of radiation• Biological effects• Approaches to shielding• Probabilistic estimation• Spacecraft shielding design• Recent revisions to understanding radiation effects
Space Radiation ENAE 697 - Space Human Factors and Life Support
U N I V E R S I T Y O FMARYLAND
Issues of Human Radiation Exposure• Acute dosage effects• Carcinogenesis • Central nervous system effects• Chronic and degenerative tissue risks
2
Space Radiation ENAE 697 - Space Human Factors and Life Support
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The Origin of a Class X1 Solar Flare
3
Space Radiation ENAE 697 - Space Human Factors and Life Support
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Solar Radiation• Produced continuously (solar wind)• Increases dramatically during solar particle events
(SPEs) – Coronal ejections– Solar flares
• Primarily high-energy electrons and protons (10-500 MeV)
4
Space Radiation ENAE 697 - Space Human Factors and Life Support
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Image of Galaxy in Gamma Rays
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Space Radiation ENAE 697 - Space Human Factors and Life Support
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Galactic Cosmic Rays• Atomic nuclei, stripped of electrons and
accelerated by supernova explosions to nearly the speed of light
• Constituents:– 90% protons– 9% alpha particles– 1% heavier elements
• Ionization potential proportional to square of charge (Fe26+=676 x p+)
6
Space Radiation ENAE 697 - Space Human Factors and Life Support
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Radiation in Free Space
7
Space Radiation ENAE 697 - Space Human Factors and Life Support
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Radiation Damage to DNA
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Space Radiation ENAE 697 - Space Human Factors and Life Support
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Radiation Units• Dose D= absorbed radiation
• Dose equivalent H= effective absorbed radiation
• LET = Linear Energy Transfer <KeV/µ m>
9
1 Gray = 1Joule
kg= 100 rad = 10, 000
ergs
gm
1 Sievert = 1Joule
kg= 100 rem = 10, 000
ergs
gm
H = DQ rem = RBE � rad
Space Radiation ENAE 697 - Space Human Factors and Life Support
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Radiation Quality Factor
10
Radiation QX-rays 1
5 MeV γ-rays 0.51 MeV γ-rays 0.7
200 KeV γ-rays 1Electrons 1Protons 2-10
Neutrons 2-10α-particles 10-20
GCR 20+
Space Radiation ENAE 697 - Space Human Factors and Life Support
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Symptoms of Acute Radiation Exposure• “Radiation sickness”: headache, dizziness, malaise,
nausea, vomiting, diarrhea, lowered RBC and WBC counts, irritability, insomnia
• 50 rem (0.5 Sv)– Mild symptoms, mostly on first day– ~100% survival
• 100-200 rem (1-2 Sv)– Increase in severity and duration– 70% incidence of vomiting at 200 rem– 25%-35% drop in blood cell production– Mild bleeding, fever, and infection in 4-5 weeks
11
Space Radiation ENAE 697 - Space Human Factors and Life Support
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Symptoms of Acute Radiation Exposure• 200-350 rem (2-3.5 Sv)
– Earlier and more severe symptoms– Moderate bleeding, fever, infection, and diarrhea at 4-5
weeks• 350-550 rem (3.5-5.5 Sv)
– Severe symptoms– Severe and prolonged vomiting - electrolyte imbalances– 50-90% mortality from damage to hematopoietic system
if untreated
12
Space Radiation ENAE 697 - Space Human Factors and Life Support
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Symptoms of Acute Radiation Exposure• 550-750 rem (5.5-7.5 Sv)
– Severe vomiting and nausea on first day– Total destruction of blood-forming organs– Untreated survival time 2-3 weeks
• 750-1000 rem (7.5-10 Sv)– Survival time ~2 weeks– Severe nausea and vomiting over first three days– 75% prostrate by end of first week
• 1000-2000 rem (10-20 Sv)– Severe nausea and vomiting in 30 minutes
• 4500 rem (45 Sv)– Survival time as short as 32 hrs - 100% in one week
13
Space Radiation ENAE 697 - Space Human Factors and Life Support
U N I V E R S I T Y O FMARYLAND
Long-Term Effects of Radiation Exposure• Radiation carcinogenesis
– Function of exposure, dosage, LET of radiation
• Radiation mutagenesis– Mutations in offspring– Mouse experiments show doubling in mutation rate at
15-30 rad (acute), 100 rad (chronic) exposures
• Radiation-induced cataracts– Observed correlation at 200 rad (acute), 550 rad (chronic)– Evidence of low onset (25 rad) at high LET
14
Space Radiation ENAE 697 - Space Human Factors and Life Support
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Radiation Carcinogenesis• Manifestations
– Myelocytic leukemia– Cancer of breast, lung, thyroid, and bowel
• Latency in atomic bomb survivors– Leukemia: mean 14 yrs, range 5-20 years– All other cancers: mean 25 years
• Overall marginal cancer risk– 70-165 deaths/million people/rem/year– 100,000 people exposed to 10 rem (acute) -> 800
additional deaths (20,000 natural cancer deaths) - 4%
15
Space Radiation ENAE 697 - Space Human Factors and Life Support
U N I V E R S I T Y O FMARYLAND 16Francis Cucinotta, “What’s New in Space Radiation Research for Exploration?” NASA FISO, May 18, 2011
Space Radiation ENAE 697 - Space Human Factors and Life Support
U N I V E R S I T Y O FMARYLAND 17Francis Cucinotta, “What’s New in Space Radiation Research for Exploration?” NASA FISO, May 18, 2011
Space Radiation ENAE 697 - Space Human Factors and Life Support
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NASA Radiation Dose Limits
18
Space Radiation ENAE 697 - Space Human Factors and Life Support
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SPE and GCR Shielding
19
Shielding Depth, g/cm20 5 10 15 20 25 30 35
Dose
Equ
ivalen
t, rem
/yr
1
10
100
1000
10000GCR L. HydrogenGCR PolyethyleneGCR GraphiteGCR AluminumGCR RegolithSPE GraphiteSPE RegolithSPE L. Hydrogen
August 1972 SPE and GCR Solar Min
Francis Cucinotta, “What’s New in Space Radiation Risk Assessments for Exploration” NASA Future In-Space Operations Telecon, May 18, 2011
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Density of Common Shielding
20
0
2
4
6
8
10
12
Polyethyle
neWate
rGr/E
p
Acrylic
s
AluminumLea
d
Space Radiation ENAE 697 - Space Human Factors and Life Support
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Comparative Thickness of Shields
21
0
1
2
3
Polyethyle
neWate
rGr/E
p
Acrylic
s
AluminumLea
d
Space Radiation ENAE 697 - Space Human Factors and Life Support
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Comparative Mass for Shielding
22
0
1
2
3
4
5
Polyeth
ylene
Water
Gr/Ep
Acrylics
Aluminu
mLe
ad
Space Radiation ENAE 697 - Space Human Factors and Life Support
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Effective Dose Based on Shielding
24
Francis A. Cucinotta, Myung-Hee Y. Kim, and Lei Ren, Managing Lunar and Mars Mission Radiation Risks Part I: Cancer Risks, Uncertainties, and Shielding Effectiveness NASA/TP-2005-213164, July, 2005
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Shielding Materials Effect on GCR
25
–, Human Integration Design Handbook, NASA SP-2010-3407, Jan. 2010
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Lunar Regolith Shielding for SPE
26
–, Human Integration Design Handbook, NASA SP-2010-3407, Jan. 2010
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Mars Regolith Shielding Effectiveness
27
–, Human Integration Design Handbook, NASA SP-2010-3407, Jan. 2010
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Radiation Exposure Induced Deaths
28
Francis A. Cucinotta, Myung-Hee Y. Kim, and Lei Ren, Managing Lunar and Mars Mission Radiation Risks Part I: Cancer Risks, Uncertainties, and Shielding Effectiveness NASA/TP-2005-213164, July, 2005
Space Radiation ENAE 697 - Space Human Factors and Life Support
Annual Fatality Rates from Accidents in Different Occupations noted by NCRP Report 98 (1989)a, NCRP Report 132 (2000)b, and recent values from National Safety Councilc. Percent probabilities for occupational fatality for careers of 45 years are listed in parenthesis.
Risk in Less-Safe Industries have decreased to <1%
54Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Alternative Comparative Risk Basis?• CurrentLossofCrew(LOC)riskforSpaceflightis1in270accordingtoNASA.
• GCR dose and SPE probability are anti-correlated over 11-year solar cycle. • Hsolid is Organ Dose Equivalent for Solid cancer risks • Lines show times for 43 largest of ~400 SPE’s since 1950 (organ doses >10 mGy)
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Comparison of MSL RAD Measurements to NASA Space Cancer Risk Model (NSCR-2012):
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Risk for Exploration (Cucinotta et al. 2013) Cancer and Circulatory Disease
ISS = International Space Station; lower risk because GCR partially shielded By Earth Shadow and Magnetic Field Circulatory disease estimate from human data on Stroke and Ischemic Heart disease
69Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
PC = Probability of Causation at 10 years Post-exposure in these Calculations. If cancer is discovered In astronaut probability Radiation was the cause
70Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Table 6. Parameter estimates for combined data sets for TE and NTE models for the dose response for percentage tumor prevalence. For each statistical test considered, which adjust for the differences in the number of model parameters, the model providing the optimal fit is shown in bold-face.
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Components to Solution of Space Radiation Problem
94
Radiation Shielding Materials, Optimization, and
neutron minimization
▪ The current risk for a Mars mission is nearly 3-fold above acceptable risk levels ▪ Baseline DRM for a 1000 day mission has >3-fold uncertainties, assumes aluminum shielding, and radiation sensitivity of the U.S. average population
Dosimetry and Forecasting Ensure minimal SPE threat
Crew Selection Never-smokers, Screening for
sensitivity to GCR
Biological Mitigator’s New approaches to chronic, high
LET exposure protection
<1-fold (+100%)
15 %
50 %
30 %
Solar max. safety
Science understanding, radiobiology data-base for cancer, CNS, and other risks
Testing and validation
Biomarker developments, science discovery and verification, largely based on uncertainty reduction research
Drug testing and discovery, and validation based on uncertainty reduction research
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
CNS Injury After High and Low Doses
• Higher Doses: • Generally restricted to white matter; • A late effect, appearing after a latent period; • Imaging and clinical changes; • Histology: demyelination, vascular damage, necrosis.
• Low Doses: Neurocognitive effects occur after radiation doses that do not result in overt tissue destruction:
• Progressive, currently untreatable and poorly understood;
• Hippocampal functions of learning, memory and spatial information processing;
• Other poorly understood - Unknown pathogenesis.
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Low priorities - Space Physics and Acute Radiation Syndrome Research
96Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
2013 National Academy of Sciences Review of NSCR-2010 Model
111Wangetal.RadiatRes(2014)Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Argonne National Lab Inverse Dose-Rate Effect- D. Grahn et al, 1993
(24 or 60 week x 5 d/wk gamma or fission neutron)
112Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Lung tumors: Inverse Dose-Rate Effect Found?
113Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Space Radiation ENAE 697 - Space Human Factors and Life Support
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References• Francis Cucinotta, “New Estimates of Radiation Risks”
NASA Future In-Space Operations Working Group, May 18, 2011
• –, Human Integration Design Handbook, NASA SP-2010-3407, Jan. 2010
• Lora Bailey, “Radiation Studies for a Long Duration Deep Space Habitat” NASA Future In-Space Operations Working Group, Oct 31, 2012
• Francis A. Cucinotta, Myung-Hee Y. Kim, and Lei Ren, Managing Lunar and Mars Mission Radiation Risks Part I: Cancer Risks, Uncertainties, and Shielding Effectiveness NASA/TP-2005-213164, July, 2005
114
National Aeronautics and Space Administration
Mars Mission and Space Radiation Risks
Overview
Briefing to
NAC HEOMD/SMD Joint Committee
April 7, 2015
Steve Davison • HEOMD • NASA Headquarters
Space Radiation Presentations
Overview
• Mars Mission and Space Radiation Risks Steve Davison, NASA-HQ, 30 min
Health Standards Decision Framework David Liskowsky, NASA-HQ, 10 min•
Space Radiation Environment
• Introduction Chris St. Cyr, NASA-GSFC, 5 min
Solar Energetic Particles Allan Tylka, NASA-GSFC, 30 min
Comparison and Validation of GCR Models Tony Slaba, NASA-LaRC, 30 min
GCR Radiation Environment Predictions Nathan Schwadron, Univ. of NH, 30 min
Emerging GCR Data from AMS-2 Veronica Bindi, Univ. of Hawaii, 30 min
•
•
•
•
Radiation Health Risk Projections Eddie Semones, NASA-JSC, 45 min
• NCRP Recommendations, Permissible Exposure Limits, Space Radiation Cancer Risk Model,
Operations and In-Flight Solar Particle Event Mitigations
Space Radiation R&T for Risk Mitigation Lisa Simonsen, NASA-LaRC, 45 min
• Radiobiology Research Portfolio (Cancer, CNS, Cardio) and Spacecraft Shielding Design,
Analysis, and Optimization
2
Overview of Mars Mission Crew Health Risks
• Mission And Crew Health Risks Are Associated With Any Human Space Mission
– Briefing is focused on space exploration crew health risks associated with space
radiation
• Exploration Health Risks Have Been Identified, And Medical Standards Are In
Place To Protect Crew Health And Safety
– Further investigation and development is required for some areas, but this work
will likely be completed well before a Mars mission launches
• There Are No Crew Health Risks At This Time That Are Considered “mission-
stoppers” for a Human Mission to Mars
– The Agency will accept some level of crew health risk for a Mars mission, but that
risk will continue to be reduced through research and testing
• The Most Challenging Medical Standard To Meet For A Mars Mission Is That
Associated With The Risk Of Radiation-induced Cancer
– Research and technology development as part of NASA’s integrated radiation
protection portfolio will help to minimize this long-term crew health risk3
Human Spaceflight Risks are Driven by
Spaceflight Hazards
Distance from Earth
Drives the need for additional “autonomous” medical care
capacity – cannot come home for treatment
Hostile/
Closed Environment
Vehicle DesignEnvironmental – CO2 Levels, Toxic Exposures, Water, Food
Isolation & Confinement
Behavioral aspect of isolationSleep disorders
Space Radiation
Acute In-flight effectsLong-term cancer risk
CNS and Cardiovascular
Altered Gravity -Physiological Changes
Balance DisordersFluid Shifts
Visual AlterationsCardiovascular DeconditioningDecreased Immune Function
Health Outcomes Resulting from Sleep Loss, Circadian Desynchronization, & Work Overload
10.Decompression Sickness11.Toxic Exposure12.Hearing Loss Related to Spaceflight13.Injury from Sunlight Exposure14.Electrical shock/plasma
5
Mars Mission Human Health Risks
Based On The On-going Human System Risk Board (HSRB) Assessment, The Following Risks Are The Most Significant For A Mars Mission:
• Adverse affect on health space radiation exposure (long-term cancer risk)
spaceflight-induced vision alterationsrenal stone formation compromised health due to inadequate nutritionbone fracture due to spaceflight induced bone changesacute and chronic elevated carbon dioxide exposure
•
•
Post
Mission
Risks
Inability to provide in mission treatment/care lack of medical capabilitiesineffective medications due to long term storage
Adverse impact on performancedecrements in performance due to adverse behavioral conditions and training deficienciesimpaired performance due to reduced muscle and aerobic capacity, and sensorimotor adaptation
In-
Mission
Risks
6
Current Space Flight Health Standards
• NASA Should Be Able To Meet
All Fitness for Duty (FFD) And
Permissible Outcome Limits
(POL) Standards For A Mars
Mission
– Based on long-duration ISS
flight experience and
mitigation plans
• Meeting The Current Low Earth
Orbit (LEO) Space Radiation
Permissible Exposure Limit
(PEL) Standard Will Be
Challenging For A Mars
Mission
– NASA exposure limit is the
most conservative of all space
agencies
Area Type Standard
Bone POL Maintain bone mass at ≥-2SD
Cardiovascular FFD Maintain ≥75% of baseline VO2 max
Neurosensory FFD Control motion sickness, spatial disorientation, & sensorimotor deficits to allow operational tasks
Behavioral FFD Maintain nominal behaviors, cognitive test scores, adequate sleep
Immunology POL WBC > 5000/ul; CD4 + T > 2000/ul
Nutrition POL 90% of spaceflight-modified/USDA nutrient
requirements
Muscle FFD Maintain 80% of baseline muscle
strength
Radiation PEL ≤ 3% REID (Risk of Exposure Induced
Death, 95% C.I. 7
Space Radiation Challenge
Galactic cosmic rays (GCR) – penetrating protons and heavy nuclei
Solar Particle Events (SPE) – low to medium energy protons
What are the levels of
radiation in deep
space and how does
it change with time?
SMD R&D
Helio- & Astrophysics
Characterization/meas
urement
Modeling/Prediction &
Real-time Monitoring
How much radiation is inside the spacecraft, on Mars surface, and in the human body?
HEOMD R&D
Radiation Transport Code Development
Transport of radiation into body
Tissue/Organ doses
What are the health
risks associated
with radiation
exposure?
Cancer risks
Acute radiation
Non-cancer risks
How do we mitigate
these health risks?
NSRL research
Spacecraft Shielding
Bio-Countermeasures
Medical Standards
8
Space Radiation Health Risks
Health Risk Areas
CarcinogenesisSpace radiation exposure may cause
increased cancer morbidity or mortality risk in
astronauts
Status
Cancer risk model developed for mission risk
assessment
Model is being refined through research at
NASA Space Radiation Laboratory (NSRL)
Health standard established
Acute Radiation Syndromes from SPEsAcute (in-flight) radiation syndromes, which
may be clinically severe, may occur due to
occupational radiation exposure
Acute radiation health model has been
developed and is mature
Health standards established
Risk area is controlled with operational &
shielding mitigations
Degenerative Tissue EffectsRadiation exposure may result in effects to
cardiovascular system, as well as cataracts
Central Nervous System Risks (CNS)Acute and late radiation damage to the
central CNS may lead to changes in
cognition or neurological disorders
Non-cancer risks (Cardiovascular and CNS)
are currently being defined
Research is underway at NSRL and on ISS
to address these areas
Appropriate animal models needed to assess
clinical significance
9
Mars Mission Space Radiation Risks
Mars Missions May Expose Crews To Levels Of Radiation Beyond Those
Permitted By The Current LEO Cancer Risk Limit (≤ 3% REID, 95% C.I.)
• May increase the probability that a crewmember develops a cancer over their
lifetime and may also have undefined health effects to central nervous system
and/or cardiovascular system; these areas are currently under study
Mars Missions Cancer Risk Calculations
• Calculations use 900-Day conjunction class (long-stay) trajectory option for Mars
mission (500 days on Mars surface)
– Exposure levels are about the same for 600-Day opposition-class (short-stay)
trajectory option (30 days on Mars surface)
• Based on 2012 NASA Space Radiation Cancer Risk Model as recommended by
the National Council on Radiation Protection and reviewed by National Academies
– Model calculates risk of exposure induced death (REID) from space
radiation-induced cancer with significant uncertainties
Calculations take into range of solar conditions and shielding configuration
Mars surface calculations include shielding by the planet, atmosphere, &
lander
–
–
10
Post Mission Cancer Risk For A 900-day Mars Mission
Radiobiology research on cancer, CNS, and cardiovascular
12
Reducing Mars Mission Radiation Risks
NASA Is Working Across All Phases Of The Mars Mission To Minimize The Space Radiation Health Risk
Pre - Mission
Radiation FactorsIndividual Sensitivity –
Biomarkers*
Selection – age, gender
Model Projection of Risk
Space Radiation Envir. Model
In - Mission
Radiation FactorsShielding
Mission Duration
Solar Min vs. Max
Operational Planning
Dosimetry
Countermeasures*
- Pharmaceutical &
Nutritional
Post - Mission
Radiation FactorsOccupational Health Care
for Astronauts*
- Personalized Cancer
Screening, Biomarkers
- Cancer Treatment
Reduction in Total Risk Posture
*long-term
development
13
Reducing Radiation Health Risks
Space Radiation Research at NSRL
• Key to reducing the space radiation health effects uncertainties, refinement of cancer risk model, and understanding cardiovascular and CNS risks
•
•
•
•
•
•
LRO-CRaTER
radiation
measurements
Space Radiation Environment Characterization
LRO-CRaTER measurements of radiation environment
SEP real-time monitoring and characterization
MSL-RAD Measurements of radiation environment during transit and on the surface of Mars
Medical Approaches Applied Pre-/Post-Mission
Understanding the individual sensitivities and enhancing post mission care are the key areas that can significantly reduce the space radiation risk
MSL-RAD
radiation
measurements
on Mars
Exploration Space Radiation Storm Shelter Design and Real-time Radiation Alert System
Development of these capabilities for exploration missions can reduce crew exposure risk to SPEs to negligible levels
Mars Mission Design and Deep Space Propulsion
Reducing deep space transit times can reduce space radiation exposure and mitigate human health risks
NSRL simulates space cosmic
and solar radiation environment
14
Summary
Based on current mitigation plans for Crew Health and Performance Risks, NASA can support a Mars Mission
• Mars Mission Health Risks Have Been Identified And Medical Standards Are In Place To Protect Crew Health And Safety
– While there is a fair amount of forward work to do, there are no crew health risks at this time that can be considered “mission-stoppers”
There will be a level of crew health risk that will need to be accepted by the Agency to undertake a Mars mission, but that risk will continue to be reduced through R&D
–
• Based on present understanding of risks and standards
– Exercise countermeasure approaches (hardware & prescriptions) require further refinement/optimization to meet exploration mission, vehicle, and habitat designs
Additional data needed to fully quantify some risks (vision impairment, CO2 exposure)
Renal stone risk needs new intervention/treatment approaches
Some risks (nutrition, inflight medical conditions) require optimization in order to support a Mars Mission
Pharmaceutical & food stability/shelf life needs to be improved for a Mars Mission
Behavioral health and human factors impacts need to be further minimized
–
–
–
–
–
– The radiation standard would not currently be met 15