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The film opens with scenes of astronauts moving in the
direction of the long axis of the Skylab.
FILM SECTION 1
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This film section illustrates the most complex motion shown
in the film. In short sequence, the astronaut starts
(initial conditions) with a movement of his center of mass
through space (translation) and a rotation about the center
of mass (rotation). These two degrees of movement are,
in this case, quite independent of one another and may be
considered separately.
As the motion of the astronaut proceeds, the movement of
his center of mass through space (translation) is along a
straight line and his linear momentum is constant, even
though he may be rotation. Likewise, the rotation of
the astronaut may be considered without regard for the
translation as discussed above. The rotation, however,
is more complicated because the angular momentum of a
rotating body is the product of a moment of inertia and an
angular speed. Considering the astronaut to be
rotating at the start, he will have angular momentum and
this angular momentum will remain constant as he moves
through space if he does not encounter forces from
surrounding objects. You will note changes in rotation
rate as the astronaut changes his moment of inertia by
tucking, bending or making other changes in body limb
orientations, but his angular momentum is constant.
This section of the film includes the following scenes:
1. Astronaut Allen Bean somersaults, spins and
twists from the
dome of orbital workshop (OWS) to the grid floor.
2. Astronaut Jack Lousma somersaults from the
dome of the OWS.
3. Astronaut Owen Garriott somersaults towards
the dome of
OWS.
4. Astronaut Garriott pushes off from the right
side and spins
across the OWS. He decreases his spin rate by
extending
his arms and legs.
5. Astronaut Garriott pushes off from the left
and spins
across the OWS. He decreases his spin rate by
extending
his arms and legs.
FILM SECTION 2
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In this film sequence, the astronaut's center of mass is
initially moving and will continue to move along a straight
line throughout the sequence.
The astronaut, however, is not rotating initially and
therefore has no angular momentum. As you observe him
twisting and turning this time, note that each attempt to
twist will leave him with no net rotation. For
example, with no initial rotation, an attempt to twist his
arms one way will result in his lower body twisting in the
opposite direction. The net result will be no
rotation, although some reorientation may occur.
This section of the film shows Astronaut Garriott gently
pushing off from the dome of the OWS with no initial
rotation. Notice how any rotation of one part of his
body is compensated by counter-rotation of another part of
his body.
FILM SECTION 3
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In this final sequence, the astronaut will be perfectly at
rest at the beginning, and his linear momentum and the
angular momentum will remain zero throughout. The
center of mass will remain stationary, and no movement by
the astronaut will result in any net translation of his
center of mass.
This section of the film shows Astronaut Joseph Kerwin being
very carefully placed near the center of the OWS by his
fellow Astronaut, Conrad. You will see the care that
must be used to get Joe Kerwin completely at rest at the
beginning of this sequence. Then Astronaut Krewin
performs a series of body maneuvers. At the end of
these maneuvers he is rescued from his isolated position by
a helping hand from Conrad.
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