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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
Earth OrbitMars OrbitPiloted TrajectoriesStay on Mars Surface
4
1
3
2
Human Mars Mission Trajectory
Earth ArrivalJune 26, 2022
Mars ArrivalJune 30, 2020
Mars DepartureJan. 24, 2022
Earth DepartureJan. 20, 2020
Flight ProfileTransit out: 161 days
Mars surface stay: 573 daysReturn: 154 days
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)
– Cephalad fluid shift– Neurovestibular disturbances– Sleep disturbances– Bone demineralization
• Intermediate (3 weeks to 6 months)– 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
Muscle atrophy resistive exercise under
evaluation
Impacts of Extended Weightlessness
Neurovestibular adaptations vehicle modifications,
including centrifuge may require auto-land
capability
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
Physical tolerance of stresses during aerobraking, landing, and launch phases, and strenuous surface activities
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)
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
Radiation
Bone Loss in Weightlessness
(months)
Ch
ang
e fr
om
pre
-flig
ht
(%)
-256 12 18 24 30
0
5 Space flightn=22
2 years post-menopause, n=13(for comparison only)
-5
-10
-15
-20
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
1 G m G
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
Gravity Acceleration
Mars Launch
TBD g
boost phase (min);
TEI (min)
22-24 months
1/3 g to 0 g
Mars Landing
3-5 g
aerobraking (min);
parachute braking (30s);
powered descent(30s)
Earth Landing
3-5 g
aerobraking (min);
parachute braking (min)
26-30 months
0 g to 1g
Transi
t
0 g
4-6 months
Mars Surfac
e
1/3 g
18 months
Transi
t
0 g
4-6 months
Earth Launch
up to 3 g
boost phase (8min);
TMI (min)
0
1 g to 0 g
G-Load
Notes
Cumulative
hypo-g
G transition
0 g to 1/3 g
4-6 months
Physical Challenges
TMI: trans-Mars injectionTEI: trans-Earth injection
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
Transitions in G levels
Human Behavior and Performance
Behavior and Performance
• Sleep and circadian rhythm problems
• Poor psychosocial adaptation
• Neurobehavioral dysfunction
• Human-robotic interface• Episodic cognition
problems
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)
• 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 (?)
Human Behavior and Performance
Clinical Problems • 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
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
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
Illness and injury during space flightIncidence Common
(>50%) skin rash, irritation foreign body eye irritation, corneal
abrasion headache, backache,
congestion gastrointestinal disturbance cut, scrape, bruise musculoskeletal strain,
sprain fatigue, sleep disturbance space motion sickness post-landing orthostatic
intolerance post-landing
neurovestibular symptoms
Conceptualization of crew healthcare & exercise
facilities
Data from R. Billica, January 1998, and D. Hamilton, June 1998
For DRM of 6 crewmembers on a 2½ year mission, expect: 0.9 persons per mission, or ~one person per mission,
to require ER capability 0.3 persons per mission, or ~once per three missions,
to require ICU capability ~80% require intensive care only 4-5 days ~20% do not.
Based on U.S. and Russian space flight data, U.S. astronaut longitudinal data, and submarine, Antarctic winter-over, and military aviation experience: Incidence of significant illness or injury is 0.06 per
person- 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
per year
Note: Decreased productivity, increased risk while crew reduced by 1-2 (including care-giver)
Mars DRM
PastExperience
0.90 person/mission
0.06 person/year
Projected Rates of Illness or Injury
Autonomous Clinical Care
Telemedicine preventive health care diagnostic/therapeutic capabilities from ground-
based consultants
Crew Health Care Facility non-invasive diagnostic
capabilities for medical/surgical care
“smart” systems non-invasive imaging systems
definitive surgical therapy including robotic surgical assist devices and surgical simulators
blood replacement therapy
laboratory support
Mars Surface Stay Requirements
Crew health care Radiation Protection Medical Surgical care Nutrition - Food Supply Psychological support
meaningful worksurface science
– planetary– biomedical
simulations of Mars launch, trans-Earth injection, and contingencies
progressive debriefs, sample processing, etc.
housekeeping communications capability
Habitat Maintenance/housekeeping
– workshop with HRET capabilities
Exercise supplemental to Mars surface activities
Recreation Privacy
HRET: human-robotic exploration team
Autonomous facilities
Space Medicine in-flight debilitation, long-term
failure to recover, clinical capabilities, and skill retention
Advanced Life Support atmosphere, water, thermal
control, logistics, waste disposalEnvironmental Health
atmosphere, water, contaminantsPlanetary Extra-Vehicular Activity
dust, suit design, serviceability
Radiation Effects carcinogenesis, CNS damage,
fertility, sterility, heredity
Medical Care
Environment &
Technology
Human Behavior
& Performa
nce
Risk Elements & Categories
HHuman
HHealth &
PPerformance
Human Performance psychosocial, workload,
sleep
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
Risk Elements & Categories
HHHH
PP
uman
ealth &erformance
Health care functions Nutrition Exercise Psychological support
planned activitiesentry/landing simulationshousekeepingrefresher trainingcruise science (rover operations/site preparation, microgravity, astronomy, and biomedicine)
communications reliable contact with mission control, family, & friends
Health Care autonomous care telemedicine
Mars Transit RequirementsFacilities must be mostly autonomous
(one-way Earth-Mars communications time is 3-22 min.)
artwork from Constance Adams and Kris Kennedy for the JSC TransHab Team
Recreation & privacy
Maintenance & housekeeping
(including workshop)
Habitat facilities
Exercise & conditioning
for Mars surface
activities
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
Conclusions
ESA, WISE
Bed Rest Studies• 6o head tilt down• 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
Manufactured by Synthecon, Inc.
NASA Microgravity Analog Cell Culture System
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