Before plans can be finalized for a space station that maintains a lo

Before plans can be finalized for a space station that maintains a low-earth orbit, scientists must first answer questions about the durability of 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 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 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 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 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 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 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 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.

1. All of the following can be inferred from the passage EXCEPT:

A. Chemical compounds that constitute hazards to a spacecraft already exist in the orbital atmosphere.
B. Some of the experiments carried by LDEF have already yielded useful results.
C. Most communications satellites cannot endure a long tenure in space.
D. Weight constitutes a major design consideration for those planning the construction of a spacecraft.
E. Elements with no thermal velocity can be considered, for all practical purposes, motionless.



2. According to the passage, care was taken in the design of the LDEF so that the spacecraft

A. would maximize the number of chemical reactions between the materials in its experiment trays and those elements naturally occurring in space
B. would maintain a constant position relative to its orbit, enabling scientists to measure the results of a variety of impacts
C. would survive the impact of any space debris, even in the unlikely event that debris was many times its weight
D. could position itself so as to maximize impact with some space hazards, such as atomic oxygen, while entirely avoiding others
E. could maneuver itself into a more advantageous position by adjusting the orientation of its "leading" and "trailing" surfaces



3. Which of the following best expresses the main idea of the passage?

A. It cannot be determined whether LDEF was a success, since most of its experiments have not yet yielded results.
B. Determining the different types of damage done to leading and trailing components of a spacecraft is the key preparatory task involved in designing a successful space station.
C. The development of new technologies resulting from the LDEF project will lead to unexpected advances in space travel.
D. The results of LDEF experiments may provide previously unavailable information that is necessary to design a space station sturdy enough to endure a long term in orbit.
E. It is necessary to construct a space station in order to monitor the atmospheric conditions in one of space's busiest traffic zones.


4. Which of the following is characteristic of much of the oxygen found in low-earth orbit?

A. It is indistinguishable from typical, atmospheric oxygen.
B. It is more reactive than is molecular oxygen.
C. |t poses a significant threat to the stability of the planned space station.
D. It moves at a much higher velocity than does molecular oxygen.
E. It was first discovered by scientists working on the LDEF project.


5. 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


6. It can be inferred from the passage that which of the following is true of the construction of a low-earth orbit space station?

A. A space station must be able to withstand collisions from molecular oxygen if it is to be viable.
B. Scientists must devise a way to stabilize atomic oxygen before they can design a low-earth orbit space station.
C. Design engineers will have to underprotect certain less vulnerable portions of the Spacecraft in order to contain the costs of such a large project.
D. A the station's weight is one of the concerns of the scientists working on the craft.
E. Were scientists to discover that atomic oxygen had thermal velocity, all data collected by LDEF would be rendered useless.


7. The author implies that, were the LDEF to rotate during its orbit of the earth,

A. the data its experiments yielded would not have been pertinent to questions concerning the directional nature of damage to the spacecraft
B. the data from experimental materials mounted within LDEF would have been accurate, but data from the measuring devices mounted on its outside would have been tainted
C. the craft would not have swept up atomic oxygen as it traveled through its orbit
D. the craft would have been damaged by massive exposure to Space-borne radiation
E. scientists would not have been able to determine the thermal velocity of atomic oxygen