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Flashcards in Space Deck (25):

The force wt which the aviator is pressing against the seat

+1 G

Equal to the pull of gravity, equal to his weight


The force the aviator presses against his seat during pull-out from a dive

+5 G


Force if the airplane goes thru an outside loop

- G

If force wt which person is held down by his belt is equal to the wt of his body : -1 G


Effects of Centrifugal Acceleratory Force on the Circulatory system ( +G)

Blood is centrifuged toward the lowermost part of the body

As pressure in the vessels of the lower body increases, these vessels passively dilate
Blood is pooled, less is available for cardiac output

Acceleration greater than 4-6 G causes black-out of vision wtn a few secs, and unconscousness shortly thereafter; increased acceleration - death
Circulatory collapse


Effects of Centrifugal acceleratory force on the vertebrae (+G)

Extremely high acceleratory forces = fracture


The degree of postive acceleration that the person can withstand in the sitting pos before vertebral fraction occurs

20 G


Effects of -G on the body (-4 to -5G)

-4 to -5G : intense momentary hyperemia of the head; occasionally, psychotic disturbances lasting for 15-20 minutes as a result lf brain edema


Effect of greater -G on the body

Great -G (-20G): cerebral blood pressure reaches 300 to 400mmHg, causing small vessels on the surface of the head and in the brain to rupture;
- csf is centrifuged to the head, blood is centrifuged toward the cranial vessels; greatly increased pressure of csf acts as cushioning buffer to prevent intrecerebral vascular rupture
- intense hyperemia - eyes often become temp blinded wt 'red-out'


Prevents some of the pooling of blood in the large vessels of the abdomen delaying onset of black out

Aviator tightens his abdminal muscles to an extreme degree and leans forward to compress the abdomen


Prevents pooling of blood in the lower abdomen and legs

Special anti G suits

Simplest form- applies (+) pressure to the legs & abdomen by inflating compression bags as the G increases


Types of linear acceleration

Blast-off acceleration (+)
Landing acceleration ( -)


What position can withstand great acceleration (9G - 8G) with ease?

Semireclining pos (transverse to the axis of acceleration)

Reclining seats used by astronauts


The speed of sound and of fast airplanes

Mach 1

can be safelet decelerated in about 0.12 mile


a speed possible in interplanetary space travel


10,000 miles for safe deceleration


Deceleration must be accomplished much more slowly from high velocities than is necessary at lower velocites

A human being can w/stand far less deceleration if the period of deceleration lasts for a long time than for a short time

The total amt of energy that must be dispelled during deceleration is proportional to the square of the velocity


As the velocity of fall increases the air resistance tending to slow the fall also increases

The deceleratory force of the air resistance exactly balances the acceleratory force of gravity,
So after falling for abt 12 secs, the person will be falling at a "terminal velocity"


How does a trained parachutist land the earth?

Knees bent but muscles taut to cushion the shock of landing

Unless forewarned, the parachutist will be tricked by his senses into striking the earth with extended legs, resulting in tremendous deceleratory forces along the skeletal axis of the body, resulting in fracture of his pelvis, vertebrae or leg


What effect does presence of nitrogen have in sealed spacecraft?

Greatly diminished likelihood of fire and explosion

Protection against dvelopment of local patches of lung atelectasis (occurs when breathing pure oxygen)


For space travel lasting more than several months recycling techniques for oxygen have been proposed.

- electolysis of water to release oxygen
- biological methods such as algae


A state of near-zero G force, whc is sometimes called microgravity


Gravity from any heavenly body is still active. The gravity acts on the spacecraft and the person at the same time, both are pulled wt exactly the same acceleratory forces and direction. Person is not attracted toward any specific wall of spacecraft


Effects of weightlessness

1. Motion sickness
2. Translocation of body fluids
- failure to cause normal hydrostatic pressures
3. Diminished physical activity


Observd effects of prolonged stay in space

Decrease in
- blood volume
- RBC mas
- muscle strenght and work capacity
- maximum CO
Loss of Ca and phosphate from the bones
Loss of bone mass

*also upon returning to earth:
- tendency to faint upon standing up becauss of diminished arterial pressure ctrl mechs and diminsihed blood volume


"Deconditioning" effects of weightlessness

- 1% of bone mass lost each month
- substantial atrophy of cardiac and skeletal muscles
- CVS deconditioning: decreased work capacity; decreased blood volume; impaired baroreceptor reflexes; reduced orthostatic tolerance
- susceptibility to bone fractures


One countermeasure for weightlessness

Intermittent "artificial gravity"
- short periods of centrifugal acceleration of the astronauts while they sit in specially designed short-arm centrifuges that create up to 2G-3G


Centrifugal acceleratory forces

When an airplane makes a turn

As the velocity increases, the force of centrifugal acceleration increases in proportion to the square of the velocity

The force of acceleration is directly proportional to the sharpness of the turn (the less the radius)