1 Before plans can be finalized for a
space station that maintains a low-earth
orbit, scientists must first answer
questions about the durability of
5 materials involved in its construction,
allowing them to determine which
sections of the space station will need
the greatest protection and to ensure
that such a craft is not overprotected
10 and consequently too heavy. In 1984
NASA deployed a satellite called the
Long-Duration Exposure Facility
(LDEF). Each of LDEF's experimental
specimens-materials intended for use
15 in the construction of spacecraft-was
mounted on the LDEF surface. LDEF
was balanced to maintain a constant
near-vertical orientation, leaning slightly
forward, so that the satellite did not spin
20 while it orbited the earth. This feature
allowed scientists to measure damage
caused to "leading" and "trailing" parts of
a spacecraft and to what extent the
damage suffered was affected by the
25 craft's orientation.
Initial reports indicate that LDEF could
yield much invaluable information. LDEF
data have already revealed the damage
atomic oxygen causes and confirmed
30 that its effects are much more
pronounced on leading than on trailing
surfaces. Atomic oxygen, comprising
most of the low-earth orbit atmosphere,
is much less stable than molecular
35 oxygen. It has no thermal velocity, and
as a result, it is effectively motionless.
Scientists now know that a fast-moving
object in space sweeps up oxygen
atoms as it travels (eventually
40 abandoning them in its wake) and they
understand to what degree an object's
orientation affects the damage caused
by atomic oxygen. The data promise to
yield other useful insights.
It can be inferred from the passage that the rotation of an object orbiting the earth
A)can be neutralized in the design process
B)will cause the object to maintain a near vertical orientation
C)is determined by the weight of the object itself
D)is caused by a combination of space-borne elements and atmospheric pressure
E)cannot be maintained indefinitely without the imposition of an outside force such as atmospheric oxygen
space station that maintains a low-earth
orbit, scientists must first answer
questions about the durability of
5 materials involved in its construction,
allowing them to determine which
sections of the space station will need
the greatest protection and to ensure
that such a craft is not overprotected
10 and consequently too heavy. In 1984
NASA deployed a satellite called the
Long-Duration Exposure Facility
(LDEF). Each of LDEF's experimental
specimens-materials intended for use
15 in the construction of spacecraft-was
mounted on the LDEF surface. LDEF
was balanced to maintain a constant
near-vertical orientation, leaning slightly
forward, so that the satellite did not spin
20 while it orbited the earth. This feature
allowed scientists to measure damage
caused to "leading" and "trailing" parts of
a spacecraft and to what extent the
damage suffered was affected by the
25 craft's orientation.
Initial reports indicate that LDEF could
yield much invaluable information. LDEF
data have already revealed the damage
atomic oxygen causes and confirmed
30 that its effects are much more
pronounced on leading than on trailing
surfaces. Atomic oxygen, comprising
most of the low-earth orbit atmosphere,
is much less stable than molecular
35 oxygen. It has no thermal velocity, and
as a result, it is effectively motionless.
Scientists now know that a fast-moving
object in space sweeps up oxygen
atoms as it travels (eventually
40 abandoning them in its wake) and they
understand to what degree an object's
orientation affects the damage caused
by atomic oxygen. The data promise to
yield other useful insights.
It can be inferred from the passage that the rotation of an object orbiting the earth
A)can be neutralized in the design process
B)will cause the object to maintain a near vertical orientation
C)is determined by the weight of the object itself
D)is caused by a combination of space-borne elements and atmospheric pressure
E)cannot be maintained indefinitely without the imposition of an outside force such as atmospheric oxygen
.
