EFFECTS OF MICROGRAVITY
ACCELERATION
• FIRST PROBLEM ASTRONAUTS FACE
• SPEED IS NOT A PROBLEM
• YOU ARE CURRENTLY TRAVELING AT
APPROXIMATELY 67,000 MPH
THROUGH SPACE AS THE EARTH
ORBITS THE SUN AND SPINNING AT
APPROXIMATELY 1,000 MPH AS THE
EARTH TURNS ON ITS AXIS
• ACCELERATION IS MEASURED IN
TERMS OF G-FORCE WHERE 1 G IS
THE PULL OF THE GRAVITY ON THE
SURFACE OF THE EARTH
• GRAVITY = 9.806 N/KG
• 1 NEWTON = FORCE REQUIRED TO
GIVE A MASS OF 1 KG AN
ACCELERATION OF 1 M/SEC/SEC (1
METER PER SECOND SQUARED)
GREATEST G FORCE OCCURS AS:
• THE SPACECRAFT ACCELERATES
AS IT ENTERS ORBIT WHEN IT IS
MUCH LIGHTER (MOST OF THE
FUEL HAS BEEN USED) AND THE
ROCKETS ARE STILL AT FULL
THRUST
• THE SPACECRAFT DECELERATES
DURING RE-ENTRY INTO THE
EARTH’S ATMOSPHERE
EFFECTS OF INCREASED G FORCE
• 2 G - BODY FEELS HEAVIER, FACIAL
TISSUES SAG, AND IT IS DIFFICULT TO
STAND-UP FROM SITTING POSITION
• 3G - IMPOSSIBLE TO STAND AND
COLOR VISION FADES AS A GRAY
CURTAIN SETS IN AS G-FORCE
FURTHER INCREASES
• 4.5 G - VISION IS LOST
• 8 G - IMPOSSIBLE TO RAISE ARMS OR
LIFT HEAD
• 12 G - CONSCIOUSNESS LOST
EFFECTS OF INCREASED G FORCE
• G FORCE PULLS BLOOD INTO
LOWER EXTREMITIES, HEART CAN
NOT COMPENSATE, AND
UNCONSCIOUSNESS OCCURS
• GAS EXCHANGE ALSO DECREASES
AS DIAPHRAGM IS PULLED
DOWNWARD RESULTING IN
BREATHING DIFFICULTY AND
DECREASED ALVEOLAR
VENTILATION
NOTE: AN ADDITIONAL PROBLEM
AT TAKE-OFF IN ADDITION TO THE
INCREASED G FORCE IS THE
SEVERE VIBRATIONS RESULTING
IN IMPAIRED ABILITY TO
PERFORM MANUAL TASKS,
NAUSEA, HYPERVENTILATION,
AND PHYSICAL COLLAPSE
EFFECTS OF WEIGHTLESSNESS
EFFECTS OF WEIGHTLESSNESS
• ASTRONAUTS GROW TALLER
• DECREASED RED BLOOD CELL
PRODUCTION AS (1) THE SHIFT OF
BLOOD TO THE CHEST TRICKS THE
BODY INTO THINKING THAT IT HAS TOO
MUCH BLOOD VOLUME, WHICH LEADS
TO A DECREASE IN ERYTHROPOIETIN
RELEASED FROM THE KIDNEYS AND
HENCE RBC SYNTHESIS BY THE BONE
MARROW AND (2) RBCs WAITING TO BE
RELEASED FROM THE BONE MARROW
ARE DESTROYED
EFFECTS OF WEIGHTLESSNESS
• DECREASED BLOOD VOLUME
NOTE: THE INCRESED BLOOD VOLUME IN THE
THORACIC CAVITY DUE TO FLUID SHIFTS
INCREASES BLOOD PRESSURE, WHICH LEADS
TO DECREASED ANTI-DIURETIC HORMONE
(ADH) AND ALDOSTERONE RELEASE AS WELL
AS DECREASED SNS ACTIVITY RESULTING IN
INCREASED URINE PRODUCTION AND
DECREASED BLOOD VOLUME
EFFECTS OF WEIGHTLESSNESS
• DECREASED OXYGEN CARRYING CAPACITY
OF THE BLOOD
• INCREASED BLOOD VISCOSITY WHICH
INCREASES RESISTANCE TO BLOOD FLOW
• INCREASED RESISTANCE TO BLOOD FLOW
POTENTIALLY DECREASES CARDIAC OUTPUT
AND/OR INCREASES BLOOD PRESSURE
• DECREASED PHYSICAL WORK CAPACITY
EFFECTS OF WEIGHTLESSNESS
• LOSS OF LEAN BODY WEIGHT (BONE, MUSLCE,
AND CONNECTIVE TISSUE) AND CARDIAC
TISSUE WHICH ALSO CONTRIBUTES TO A
DECREASE IN PHYSICAL WORK CAPCITY
• BONE LOSS DUE TO REDUCED BONE STRESS
• MUSCLE LOSS DUE TO REDUCED USE
• CARDIAC ATROPHY DUE TO DECREASED
BLOOD VOLUME AND DECREASED
GRAVITATIONAL PULL
• ASTRONAUTS EXERCISE SEVERAL HOURS PER
DAY IN ORDER TO MINIMIZE LOSS OF LEAN
BODY WEIGHT AND CARDIAC TISSUE
EFFECTS OF WEIGHTLESSNESS
• SLEEP DIFFICULTY DUE TO LITTLE
SENSE OF PRESSURE AND HENCE
SECURITY
• ASTRONAUTS SLEEP IN SLEEPING
BAGS ATTACHED TO WALLS
WITH HEAD AND KNEE STRAPS
TO INCREASE SENSE OF PRESSURE
• NEED TO SLEEP IN VENTILATED
AIR FLOW TO INSURE THAT
EXHALED CO2 IS NOT RE-INHALED
EFFECTS OF WEIGHTLESSNESS
• INCREASED SPREAD OF INFECTIOUS
DISEASES AS BACTERIA FROM SKIN AND
SNEEZES/COUGHS FLOATS IN
CIRCULATING AIR FOR LONGER PERIODS
OF TIME WITHOUT GRAVITY
• SPACE SICKNESS (HEADACHES, NAUSEA,
DIZZINESS, LOSS OF APPETITIE, LACK OF
MOTIVATION, DROWINESS, AND
IRRITABILITY) DUE TO TILTING THE
HEAD FORWARD OR BACKWARD OR A
VISUALLY DISORIENTATING SCENE
COSMIC RADIATION
• ON EARTH THE ATOMOSHERE AND
EARTH’S MAGNETIC FIELD SHIELDS
MOST RADIATION EXCEPT FROM
VISABLE LIGHT AND RADIO WAVES
• THREE SOURCES OF EXTRETERRESTRIAL
RADIATION THAT ASTRONAUTS
EXPERIENCE ARE GALATIC RAYS, SOLAR
RADIATION, TRAPPED BELT RADIATION
(E.G., VAN ALLEN BELT THAT ENCIRCLES
EARTH LIKE A HOLLOW DONUT)
COSMIC RADIATION
• RADIATION LEVELS ARE USUALLY LOW
• LONG TERM EXPOSURE MAY:
• DAMAGE GENETIC MATERIAL (DNA)
THEREBY INCREASING THE RISK OF
CANCER
• DAMAGED GERM CELLS (SPERM AND
EGG CELLS) MAY CAUSE
INFERTILITY OR GENETIC
ABNORMALITIES IN THE CHILDREN
OF ASTRONAUTS
COSMIC RADIATION
• ASTRONAUTS CARRY RADIATION DOSIMETERS
• RADIATION EXPOSURE IS USUALLY WITHIN
ACCEPTABLE LIMITS ALTHOUGH ASTRONAUTS
WHO SPEND A LONG TIME IN SPACE CRAFTS OR
WORK STATIONS MAY HAVE RECEIVED A
SIGNIFICANT DOSE
• SUPERSONIC AIRCRAFTS (E.G., CONCORDE)
CRUISE CLOSE TO THE EDGE OF THE EARTH’S
ATMOSPHERE AND ARE NOT SHIELDED FROM
COSMIC RADIATION, ALTHOUGH IT WOULD
TAKE 14 ROUND TRIP FLIGHTS FROM LONDON
TO NEW YORK TO REACH TOXIC LEVELS
SOLAR FLARES
SOLAR FLARES
SOLAR FLARES
• VERY HIGH INTENSITY RADIATION
• KILLS CELLS OUTRIGHT
• DEATH MAY OCCUR WITHIN HOURS DUE
TO DAMAGE TO THE CENTRAL NERVOUS
SYSTEM OR WITHIN A FEW DAYS DUE TO
DESTRUCTION OF WHITE BLOOD CELLS
OR THE RAPIDLY-DIVIDING CELLS THAT
LINE THE INTESTINAL WALLS
RETURNING TO EARTH
• UNABLE TO STAND WITHOUT FAINTING (I.E.,
FAILURE OF THE ORTHOSTATIC TOLERANCE
TEST) DUE TO:
• FLUID SHIFTS BACK TO LOWER
EXTREMITIES DUE TO GRAVITY
• BLOOD VOLUME IS DECREASED
• MUSCLE PUMPING IS IMPAIRED DUE TO
LOSS OF MUSCLE MASS
• THEREFORE, POOLING OF BLOOD OCCURS IN
THE LOWER EXTREMITIES WHICH DECRESES
END-DIASTOLIC VOLUME, STROKE VOLUME,
AND CARDIAC OUTPUT
RETURNING TO EARTH
• LOSS OF MUSCLE MASS MAKES IT DIFFICULT
TO WALK
• DIFFICULT TO MAINTAIN BALANCE OR REMAIN
UPRIGHT WITH EYES CLOSED
• DIZZINESS AND NAUSEA
• INCREASED RISK OF INJURY
RETURNING TO EARTH
• MOVEMENT OF HEAD RESULTS IN FALSE
ILLUSIONS THAT THE WORLD, RATHER THAN
THE HEAD, IS MOVING, SUGGESTING THAT
SIGNALS FROM RECEPTORS IN THE
SEMICIRCULAR CANALS OF THE EARS (WHICH
RESPOND TO LINEAR ACCLERATION) NEED TO
BE RE-PROGRAMMED BACK FROM A
MICROGRAVITY ENVIRONENT TO A
GRAVITATIONAL ENVIRONMENT
QUESTIONS??
CARDIOVASCULAR SYSTEM IN SPACE
HOW DOES WEIGHTLESSNESS IN SPACE
AFFECT
• BODY FLUID DISTRIBUTION?
• BLOOD VOLUME?
• RED BLOOD CELL LEVEL?
• MUSCLE AND BONE MASS?
• IMMUNE SYSTEM?
• FACIAL EDEMA?
• LEG SHAPE?
CARDIOVASCULAR SYSTEM IN SPACE
HOW DOES WEIGHTLESSNESS IN SPACE AFFECT
• MOTION SICKNESS?
• EXERCISE CAPACITY?
• HEADACHES?
• POST-FLIGHT ORTHOSTATIC TOLERANCE?
KNOW AND UNDERSTAND IN GENERAL HOW
RESEARCH FOR WEIGHTLESSNESS IN SPACE
MAY HELP SOLVE MEDICAL AND HEALTH
PROBLEMS ON EARTH.
MUSCULOSKELETAL SYSTEM IN SPACE
HOW DOES WEIGHTLESSNESS IN SPACE
AFFECT
• WEIGHT-BEARING WEAKNESSES IN
MUSCLE, CARTILAGE, AND BONE?
• HEAVY WORK IN SPACE?
• MUSCLE ATROPHY?
• MUSCLE TONE AND STRENGTH?
• MUSCLE FATIGUE?
• MUSCLE SYNERGISM?
• MOTOR CONTROL?
MUSCULOSKELETAL SYSTEM IN SPACE
HOW DOES WEIGHTLESSNESS IN SPACE
AFFECT
• MOTOR-END PLATE DEGENERATION?
• CONTRACTION VELOCITY?
• BONE MINERALIZATION?
• CONNECTIVE TISSUE?
• BACK PAIN?
KNOW AND UNDERSTAND IN GENERAL HOW
RESEARCH FOR WEIGHTLESSNESS IN SPACE
MAY HELP SOLVE MEDICAL AND HEALTH
PROBLEMS ON EARTH.