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