Page 89 - Intro to Space Sciences Spacecraft Applications

CHAPTER 4

Spacecraft

Environment

Spacecraft operate in an environment totally different from that experi-
enced by systems on earth. In some cases, this environment is relatively
benign compared to what earth-based systems must withstand (hurricanes,
for example), but in many ways the space environment is harsh on the
equipment (and people) sent out to perform there. The space systems
engineer must understand this environment and design spacecraft to oper-
ate within it. In addition, the spacecraft must be capable of performing its
mission through this environment. The effects of the environment on typ-
ical spacecraft missions will be discussed in subsequent chapters.

THE SUN

The sun is the major environmental influence on the earth and the space
around it. This section presents a brief description of the sun and discuss-
es the radiations it emits into space. Following sections describe the prop-
erties of these radiations in the vicinity of earth and the environment that
results from the interaction of the two. Finally, the effects of this environ-
ment on the operation of systems in space is discussed.

Cosmology

Cosmology is the study of the evolution of the universe and includes the
theory of how our sun came into being. It is believed that 12 to 18 billion
years ago the universe had a violent beginning in an expanding fireball
known as the “Big Bang.” The Milky Way galaxy represents one of the
countless lumps of the products of that explosion, made up mainly of
hydrogen and helium. Our solar system began as a cloud of interstellar gas
(also mostly hydrogen) which probably contained the debris of the destruc-

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