Page 111 - Intro to Space Sciences Spacecraft Applications

Introduction to Space Sciences and Spacecraft Applications
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heat generated by onboard systems. Many of these sources may cycle on
and off, such as the solar inputs when orbiting from dark to light or from
spacecraft systems as they turn on and off. Spacecraft also continuously
emit heat, especially toward the “cold” (absorptive) blackness of space.
For some applications, certain spacecraft parts may always point toward
the sun while others may always point toward space. Within certain
defined limits, the craft must be able to balance the temperatures of all its
components. Several spacecraft have been lost or impaired due to the
freezing of propellant lines or the heating of an electronic component to
the point of failure.

Spacecraft Charging

As we have seen, the space environment is full of charged materials,
trapped solar particles, and ionized atmospheric constituents as the major
examples. Also, as they travel through space, orbiting spacecraft cut
through magnetic field lines of flux which tends to make charges want to
move. Operation within such an electrically rich and magnetically dynam-
ic environment can result in a buildup of charges on the surfaces of the
spacecraft to the point at which a current flow or discharge from one com-
ponent to another may result in damage to the system.

Radiation

Some of the higher-energy particles present in space can penetrate the
skin and components of a spacecraft. These may deposit an electrical
charge inside electrical components or may even change the physical
structure of materials. Sudden depositions of electrical charge in comput-
er logic circuits or memories can corrupt data or even disrupt operation of
the satellite if a “phantom command” is sensed from such an event.
Buildup of radiation damage to semi-conductor materials can cause com-
puter chips to degrade to the point where commands may no longer be
able to be processed. Satellite operators have to be especially vigilant for
signs of these effects during periods of high solar activity.

VacuumKorrosion

As we have seen, the near-earth space environment is not a total vacu-
um. A spacecraft in orbit is constantly being bombarded by atmospheric