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Microelectromechanical Systems and Microstructures in Aerospace Applications 3

When we think of MEMS or micromachining, wrist and pocket watches do not
necessarily come to our mind. While these devices often are a watchmaker’s piece
of art, they are a piece of their own, handcrafted in single numbers, none like the
other. Today, one of the major aspects of MEMS and micromachining is batch
processing, producing large numbers of devices with identical properties, at the
same time assembled parallel in automatic processes. The introduction of micro-
electronics into watches has resulted in better watches costing a few dollars instead
of a few thousand dollars, and similarly the introduction of silicon surface micro-
machining on the wafer level has reduced, for example, the price of an accelerom-
eter, the integral part of any car’s airbag, to a few dimes.
Spacecraft application of micromachined systems is different in the sense that
batch production is not a requirement in the first place — many spacecraft and the
applications are unique and only produced in a small number. Also, the price tag is
often not based on the product, but more or less determined by the space qualifi-
cation and integration into the spacecraft. Reliability is the main issue; there is
typically only one spacecraft and it is supposed to work for an extended time
without failure.
In addition, another aspect in technology development has changed over time.
The race into space drove miniaturization, electronics, and other technologies.
Many enabling technologies for space, similar to the development of small chro-
nometers in the 15th and 16th centuries, allowed longitude determination, brought
accurate navigation, and enabled exploration. MEMS (and we will use MEMS to
refer to any micromachining technique) have had their success in the commercial
industries — automotive and entertainment. There, the driver as in space is cost,
and the only solution is mass production. Initially pressure sensors and later
accelerometers for the airbag were the big successes for MEMS in the automotive
industry which reduced cost to only a few dimes. In the entertainment industry,
Texas Instruments’ mirror array has about a 50% market share (the other devices
used are liquid crystal-based electronic devices), and after an intense but short
development has helped to make data projectors available for below $1000 now.
One other MEMS application which revolutionized a field is uncooled IR detectors.
Without sensitivity losses, MEMS technology has also reduced the price of this
equipment by an order of magnitude, and allowed firefighters, police cars, and
luxury cars to be equipped with previously unaffordable night vision. So the
question is, what does micromachining and MEMS bring to space?
Key drivers of miniaturization of microelectronics are the reduced cost and
mass production. These drivers combine with the current significant trend to
integrate more and more components and subsystems into fewer and fewer chips,
enabling increased functionality in ever-smaller packages. MEMS and other sensors
and actuator technologies allow for the possibility of miniaturizing and integrating
entire systems and platforms. This combination of reduced size, weight, and cost
per unit with increased functionality has significant implications for Air Force
missions, from global reach to situational awareness and to corollary civilian
scientific and commercial based missions. Examples include the rapid low-cost
global deployment of sensors, launch-on-demand tactical satellites, distributed

© 2006 by Taylor & Francis Group, LLC