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Design and Application of Space-Based MEMS 335

TABLE 15.1
Environmental Factors Checklist (Typical)
Natural Occurring Application Induced

Albedo, planetary IR Acceleration
Electromagnetic radiation Chemicals
Electrostatic discharge Corona
Gravity, low Electromagnetic, laser
Humidity, high Electromagnetic radiation
Ionized gases Electrostatic discharge
Magnetics, geo Explosion
Meteoroids Icing
Particulate levels, high Magnetics
Pollution, air Moisture
Pressure, high Nuclear radiation
Pressure, low, vacuum Particulate levels, high
Radiation, cosmic, soar Shock, pyro, thermal
Temperature, high Space debris
Temperature, low Temperature, high, aero. heating, fire
Temperature, low, aero. cooling
Turbulence
Vapor trails (plumes)
Vibration, mechanical, microphonics
Vibration, acoustic

may be able to ignore some other factors. Other natural environmental concerns are
seen in a long duration balloon or unmanned aerial vehicles (UAV) type applica-
tions but primarily lower atmosphere and terrestrial could include: wind, rain, salt
spray, sand and dust, sleet, snow, hail, lightning, ice, fog, clouds, freezing rain,
frost, and fungus.

15.5.1 COMBINATIONS OF ENVIRONMENTALLY INDUCED STRESSES
Concurrent (combined) environments may be more detrimental to reliability than
the effects of a single environment. In characterizing the design process, design
or test criteria must consider both single and/or combined environments in antici-
pation of providing the hardware capability to withstand the hazards identified
in the system profile. The synergistic effects of typical combined environments
can be illustrated in a matrix relationship, which shows combinations where the
total effect is more damaging than the cumulative effect of each environment
acting independently. For example, an item may be exposed to a combination
such as temperature, humidity, altitude, shock, and vibration while it is being
transported. The acceptance to end-of-life history of an item must be examined
for these effects. Table 15.2 provides reliability considerations for pairs of envir-
onmental factors. 29

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