Aviation and space physiology

1. Aviation and Space Physiology
Dr. Sara Sadiq
(MBBS, M.Phil)

2. Acceleratory forces on the body in aviation
1. Linear Acceleration
• Rapid change in velocity of motion
• Induces forces during normal flight which are not sufficient to cause major
physiologic change

3. 2. Centrifugal acceleration:
• Rapid change in direction of motion
(airoplane turns, dives or loops)
• Induces forces which cause severe
derangement of bodily functions
• Centrifugal Acceleratory Forces
F= (mv2)/r

4. Measurement of acceleratory force  “G”
1. Positive centrifugal acceleration (Positive G)
• Weight of aviator on his seat due to gravity intensity of this force
is said to be +1 G
2. Negative centrifugal acceleration (Negative G)

5. • Aircraft flying level: 1+G
• Aircraft goes into dives: Negative G
force
• Aircraft pulls/come out of dive:
Positive G force

6. Positive G
• Blood centrifuge to lower extremities
• Venous pooling, decreased cardiac output
• Effects on the Vertebrae- causes fracture
• “Black out”
• Unconsciousness followed by death

8. Negative G
• Causing intense momentary hyperemia of
the head
• Cerebral blood pressure reaches 300 to
400 mm Hg,
• “red-out” due to hyperemia in eye

10. Protection of the body against
centrifugal acceleratory forces
• Tightening abdominal muscles and leans
forward prevents venous pooling
• “Anti- G suits” compress legs & abdomen to
prevents venous pooling

11. Deceleratory forces associated with
parachute jumps
• parachuting aviator leaves the airplane, his velocity of fall is at first
• exactly 0 ft/sec
• 32 ft/sec
• 64 ft/sec
• At 12th sec 110 miles/hr reaching terminal velocity
• “Opening shock load” up to 1200 pounds occur when parachute is opened
• Speed of landing is 20 ft/ sec

12. “Artificial Climate” in the Sealed Spacecraft
• There is no atmosphere in outer space
• an artificial atmosphere and climate must be produced in a spacecraft
• Atmospheric pressure 760mmHg
• Prolong space travel: needs recycle of oxygen

13. Weightlessness in Space
• near-zero G force  microgravity

14. Physiologic problems of weightlessness
(Microgravity)
• Motion sickness during the first few days of travel
• Translocation of fluids within the body  failure
of gravity to cause normal hydrostatic pressures
• Diminished physical activity because no strength
of muscle contraction is required to oppose the
force of gravity

15. • Earth gravity pulls on your
blood causing it to pool in
your legs
• In microgravity the blood
shifts from your legs to
your chest and head
causing your legs to shrink
in size
• This is called a “fluid
shift”
Astronaut Susan Helms on
Earth (left) and in space (right)

16. Effects of prolonged stay in space
• Decrease in blood volume
• Decrease in red blood cell mass
• Decrease in cardiac output
• Decrease in muscle strength and work capacity
• Loss of calcium and phosphate from the bones  loss of bone mass

18. Thank You