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Human Space Travel:
Medical Challenges
Present and Future
Diane Byerly, Ph.D.
NASA Johnson Space Center
Houston, TX
Contributors
•
•
•
•
•
•
•
•
•
•
•
Neal Pellis, Ph.D.
Marguerite Sognier, Ph.D.
Diana Risin, MD., Ph.D.
Lalita Sundaresan, Ph.D.
Thomas Goodwin, Ph.D.
Steve Gonda, Ph.D.
Dennis Morrison, Ph.D.
Diane Byerly, Ph.D.
Mark Clarke, Ph.D.
John Charles, Ph.D.
Tacey Baker, M.S.
• J. Milburn Jessup, MD.
• Gordana Vunjak-Novakovoc,
Ph.D.
• Lisa Freed, M.D., Ph.D.
• Robert Akins, Ph.D.
• Timothy Hammond, M.D.
• Lelund Chung, Ph.D.
• Anil Kulkarni, Ph.D.
• Arthur Sytkowski, M.D.
Space exploration
imposes new challenges
on human systems and
terrestrial life in general.
Challenges
• Present
– Orbital Missions
•
•
•
•
Known medical risks
Communications
Access to Earth
Minimum autonomy
• Future
– Moon (Short duration)
• Mostly known medical risks
• Communications
• 2-3 day to access Earth
facilities
• Greater autonomy
necessary
• Future (con’t)
– Moon (Long duration)
• Many known medical risks,
others unknown but
anticipated
• Communication
• 2-3 day to access Earth
facilities
• Greater autonomy
necessary
– Mars
• Many medical risks (known,
unknown, unanticipated)
• Communications difficult
• Probably no access to
Earth facilities
• Autonomous medical care
absolutely required
Human Mars Mission Trajectory
Flight Profile
Mars Departure
Jan. 24, 2022
Transit out: 161 days
Mars surface stay: 573 days
Return: 154 days
3
1
Mars Arrival
June 30, 2020
2
4
Earth Arrival
June 26, 2022
Earth Orbit
Mars Orbit
Piloted Trajectories
Stay on Mars Surface
Earth Departure
Jan. 20, 2020
Physical factors that influence nature
• Life evolved on earth while the force of gravity has been
constant for 4.8 billion years.
• Therefore, there is little or no genetic memory of life
responding to gravitational force changes.
• As we transition terrestrial life to low gravity
environments and study the adaptive processes in cells,
our understanding of the role of gravity in shaping
evolution on Earth will increase.
• The response of higher organisms to this ‘new’
environment may be less ordered than the response to
say, thermal change.
Risks to Humans in Microgravity
•
•
•
•
•
•
•
•
•
•
•
•
•
Exposure to ionizing radiation
Bone density decrease
Muscle Atrophy
Cardiovascular Deconditioning
Psychosocial impacts
Fluid Shifting
Vestibular Dysfunction
Hematological changes
Immune Dysfunction
Delayed wound healing
Gastrointestinal Distress
Orthostatic Intolerance
Renal stones
What happens to humans in space?
•
Early response (<3 weeks)
–
–
–
–
•
Intermediate (3 weeks to 6 months)
–
–
–
–
–
–
•
Cephalad fluid shift
Neurovestibular disturbances
Sleep disturbances
Bone demineralization
Radiation exposure
Bone resorption
Muscle atrophy
Cardiovascular deconditioning
GI disturbances
Hematological changes
Long Duration (6 months to 3 years)
–
–
–
–
–
–
Radiation exposure
Muscle atrophy
Cardiovascular deconditioning
GI disturbances
Hematological changes
Declining immunity
•
Long Duration (6 months to 3 years)
–
–
–
–
–
–
–
Radiation exposure
Muscle atrophy
Cardiovascular deconditioning
GI disturbances
Hematological changes
Declining immunity
Renal stone risk
Impacts of Extended Weightlessness
Physical tolerance of stresses during aerobraking, landing,
and launch phases, and strenuous surface activities
Bone loss
 no
documented end-point
or adapted state
 countermeasures in work
on ground but not yet flight
tested
Cardiovascular alterations
 pharmacological
treatments
for autonomic insufficiency
Neurovestibular adaptations
Muscle atrophy
 resistive
exercise under
evaluation
 vehicle
modifications,
including centrifuge
 may require auto-land
capability
Radiation
• Different from ionizing radiations on Earth
• Two types
– Galactic cosmic radiation (GCR) dominated
by neutrons
– Solar particle events (SPE)- sun storms
dominated by protons
• Earth is protected by the magnetosphere
(van Allen Belt)
Radiation
Issue: Radiation Environment
• Attenuation of GCR and SPE by atmosphere and bulk
of planet
• Possible risk from neutron backscatter from surface
• TBD shielding for vehicle and habitat
• Shielding high energy particles is difficult
Radiation effects (possible synergy with
hypogravity and other environmental factors)
• Early or Acute Effects from Radiation Exposure (esp.
damage to Central Nervous System)
• Carcinogenesis Caused by Radiation
• Immune system compromises
Bone Loss in Weightlessness
Change from pre-flight (%)
5
2 years post-menopause, n=13
(for comparison only)
Space flight
n=22
0
-5
-10
-15
-20
?
-25
(months)
6
12
18
24
30
36
Causes of bone loss
• No load because of low
gravity
• Poor muscle performance
• Metabolic and hormonal
changes
• Fluid dynamic changes in the
bone marrow sinusoids
– Decreased hydrodynamic
shear
– Loss of hydrostatic pressure
gradient
1G
mG
Countermeasures for bone loss
•
•
•
•
Resistive Exercise
Loading
Nutrition
Bisphosphonates
Muscle
• Disuse Atrophy
– Most locomotion achieved with the upper body
– No load
– No position based use and deployment of muscle activity
akin to 1G environment
– Unusual uses of selected muscle groups
• Countermeasures
– Exercise, exercise, exercise
– Before, during, and after the mission
Physical Challenges
Gravity
G-Load
Earth
Launch
up to 3 g
Transit
Mars
Landing
Mars
Surface
Mars
Launch
Transit
Earth
Landing
0g
3-5 g
1/3 g
TBD g
0g
3-5 g
boost phase
4-6
(8min);
months
TMI (min)
Notes
Acceleration
18
aerobraking
months
(min);
parachute
braking
(30s);
powered
descent(30s)
4-6
aerobraking
boost phase
months
(min);
(min);
parachute
TEI (min)
braking (min)
Cumulative
hypo-g
0
4-6 months
22-24 months
26-30 months
G transition
1 g to 0 g
0 g to 1/3 g
1/3 g to 0 g
0 g to 1g
TMI: trans-Mars injection
TEI: trans-Earth injection
Transitions in G levels
Physical tolerance of stresses during aerobraking, landing, and
launch phases, and strenuous surface activities
•
Musculo-skeletal atrophy
– Inability to perform tasks due to loss of skeletal muscle
mass, strength, and/or endurance
– Injury of muscle, bone, and connective tissue
– Fracture and impaired fracture healing
– Renal stone formation
•
Cardiovascular alterations
– Manifestation of serious cardiac dysrhythmias and latent
disease
– Impaired cardiovascular response to orthostatic stress and
to exercise stress
•
Neurovestibular alterations
– Disorientation
– Impaired coordination
– Impaired cognition
Human Behavior and
Performance
Issues:
•Small group size
•Multi-cultural composition
•Extended duration
•Remote location
•High autonomy
•High risk (to health and
mission)
•High visibility (e.g., high
pressure to succeed)
Behavior and
Performance
• Sleep and circadian
rhythm problems
• Poor psychosocial
adaptation
• Neurobehavioral
dysfunction
• Human-robotic interface
• Episodic cognition
problems
Human Behavior and Performance
• Human intrinsic rhythm = 24.1 + 0.15 hr
– synchronization not assured – may require (chronic)
intervention?
• Synchronization successful (best case): Unknown efficacy in
maintaining circadian health
– Daylight EVA ops: safety, efficiency
– Complicated Earth-based support
• Failure to synchronize (worst case):
– Crew awake during Mars night every 41 days (40 sols)
• Well-rested “night-time” ops vs. fatigued daylight ops
• Limited visibility: increased risk of accident, trauma
– Radiation minimized: reduced SPE influence at night (?)
Clinical Problems
Medical care systems for
prevention, diagnosis or
treatment
– Difficulty of rehabilitation
following landing
– Trauma and acute medical
problems
– Illness and ambulatory health
problems
– Altered pharmacodynamics
and adverse drug reaction
• Expected illnesses and problems
– Orthopedic and musculoskeletal
problems (esp. in hypogravity)
– Infectious, hematological, and
immune-related diseases
– Dermatological, ophthalmologic,
and ENT problems
• Acute medical emergencies
– Wounds, lacerations, and burns
– Toxic exposure and acute
anaphylaxis
– Acute radiation illness
–Development and treatment of
decompression sickness
– Dental, ophthalmologic, and
psychiatric
• Chronic diseases
– Radiation-induced problems
– Responses to dust exposure
– Presentation or acute
manifestation of nascent illness
Illness and injury during space flight
Incidence Common
(>50%)











skin rash, irritation
foreign body
eye irritation, corneal
abrasion
headache, backache,
congestion
gastrointestinal
Conceptualization of crew
disturbance
healthcare & exercise
cut, scrape, bruise
facilities
musculoskeletal strain,
sprain
fatigue, sleep disturbance
space motion sickness
post-landing orthostatic
intolerance
post-landing
neurovestibular symptoms
Data from R. Billica, Jan. 8, 1998
Incidence
Uncertain
infectious disease
 cardiac dysrhythmia,
trauma, burn
 toxic exposure
 psychological stress,
illness
 kidney stones
 pneumonitis
 urinary tract infection
 spinal disc disease
 unplanned radiation
exposure

Projected Rates of Illness or Injury
Based on U.S. and Russian space flight data, U.S.
astronaut longitudinal data, and submarine, Antarctic
winter-over, and military aviation experience:
Past

Incidence of significant illness or injury is 0.06 per personExperience
year
as

defined by U.S. standards
requiring emergency room (ER) visit or hospital
admission
Subset requiring intensive care (ICU) support is 0.02 person
0.06
person/year
per year
For DRM of 6 crewmembers on a 2½ year mission, expect:
 0.9 persons per mission, or ~one person per mission,
Mars DRM
to require ER capability
 0.3 persons per mission, or ~once per three missions,
to require ICU capability

0.90
person/mission

~80% require intensive care only 4-5 days
~20% do not.
Note: Decreased productivity, increased risk while crew
reduced by 1-2 (including care-giver)
Data from R. Billica, January 1998, and D. Hamilton, June 1998
Autonomous Clinical Care
Crew Health Care Facility
non-invasive
diagnostic
capabilities for medical/surgical care
“smart”
non-invasive
systems
imaging systems
definitive
surgical therapy
including robotic surgical assist
devices and surgical simulators
blood
replacement therapy
laboratory
support
Telemedicine


preventive health care
diagnostic/therapeutic capabilities from groundbased consultants
Mars Surface Stay Requirements
Autonomous facilities
Crew health care




Radiation Protection
Medical Surgical care
Nutrition - Food Supply
Psychological support
 meaningful work
surface
–
–
science
planetary
biomedical
simulations
of Mars
launch, trans-Earth
injection, and
contingencies
progressive debriefs,
sample processing, etc.
housekeeping
 communications
HRET: human-robotic exploration team
capability
Habitat
Maintenance/housekeeping
– workshop with HRET
capabilities
 Exercise supplemental to
Mars surface activities
 Recreation
 Privacy

Risk Elements & Categories
Space Medicine

in-flight debilitation, long-term
failure to recover, clinical
capabilities, and skill retention
Medical
Care
Advanced Life Support

atmosphere, water, thermal
control, logistics, waste disposal
Environmental Health

atmosphere, water,
contaminants
Planetary Extra-Vehicular
Activity

dust, suit design, serviceability
Environment
&
Technology
Radiation Effects

carcinogenesis, CNS damage,
fertility, sterility, heredity
Human Performance

psychosocial, workload,
sleep
Human
Behavior &
Performanc
e
Human
Health &
P erformance
Risk Elements & Categories
Bone Loss

fractures, renal stones,
osteoporosis, drug reactions
Cardiovascular Alterations

dysrhythmias, orthostatic
intolerance, exercise capacity
Food and Nutrition

malnutrition, food spoilage
Immunology & Hematology

infection, carcinogenesis, wound
healing, allergens, hemodynamics
Muscle Alteration

mass, strength, endurance, and
atrophy
Neurovestibular Adaptations

monitoring and perception errors,
postural instability, gaze deficits,
fatigue, loss of motivation and
concentration
Human
Health/
Physiology
Human
Health &
P erformance
Mars Transit Requirements
Facilities must be mostly autonomous
(one-way Earth-Mars communications time is 3-22 min.)
Health care functions
Nutrition
 Exercise
 Psychological support
 planned activities
entry/landing simulations
housekeeping
refresher training
cruise science (rover
operations/site preparation,
microgravity, astronomy,
and biomedicine)
 communications
reliable contact with
mission control, family, &
friends
 Health Care
 autonomous care
 telemedicine

Habitat facilities
Exercise &
conditioning
for Mars
surface
activities
Recreation &
privacy
Maintenance &
housekeeping
(including
workshop)
artwork from Constance Adams and Kris Kennedy for the JSC TransHab Team
Conclusions
 Mars Design Reference Mission
requires novel technologies that allow
human adaptation to:
 interplanetary space travel
 planetary habitation
 The medical and physiological
challenges associated with
interplanetary space travel will depend
upon
 mission duration
 propulsion system
 The integration of human and robotic
activities will be a critical determinant
of the success of planetary exploration
•
6o
head tilt down
Bed Rest Studies
• Remain in bed continually for various time
intervals; i.e., 60 days
• Mimics many alterations that occur in
microgravity due to fluid shift to head and
lack of weight bearing lower limbs; i.e., bone
loss & muscle atrophy
•Often involved in countermeasure testing
ESA, WISE
NASA Microgravity Analog
Cell Culture System
Manufactured by Synthecon, Inc.
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