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4 MEMS and Microstructures in Aerospace Applications

sensor networks, and affordable unmanned aerial vehicles (UAVs). Collective
arrays of satellites that function in a synchronized fashion promise significant
new opportunities in capabilities and robustness of satellite systems. For example,
the weight and size reduction in inertial measurement units (IMUs) composed of
MEMS accelerometers and rate gyros, global positioning system (GPS) receivers
for navigation and attitude determination, and MEMS-based microthruster systems
are enablers for small spacecraft, probes, space robotics, nanosatellites, and small
planetary landers.
The benefits include decreased parts count per spacecraft, increased function-
ality per unit spacecraft mass, and the ability to mass produce micro-, nano-, and
picosatellites for launch-on-demand tactical applications (e.g., inspector spacecraft)
and distributed space systems. Microlaunch vehicles enabled by micromachined
subsystems and components such as MEMS liquid rocket engines, valves, gyros,
and accelerometers could deliver 1 or 2 kg to low-Earth orbit. Thus, it will be
possible to place a payload (albeit a small one) as well as fully functional micro-
satellites into orbit for $10,000 to $50,000, rather than the $10 million to $50
million required today. 1
In fact, researchers at the SouthWest Research Institute have performed
extensive tests and determined that the vacuum of space produces an ideal envir-
onment for some applications using MEMS devices. MEMS devices processed in
a vacuum for 10 10 cycles had improved motion with decreased voltage. 2
MEMS devices for space applications will be developed and ultimately flown in
optimized MEMS-based scientific instruments and spacecraft systems on future
space missions.

1.3 MEMS IN SPACE

While many of the MEMS devices developed within the last decade could have
applications for space systems, they were typically developed for the civilian or
military market. Only a few devices such as micropropulsion and scientific instru-
mentation have had space application as a driving force from the beginning. In both
directions, there have been early attempts in the 1990s to apply these devices to the
space program and investigate their applicability. A sample of these demonstrations
are listed herein and acknowledged for their important pathfinding roles.

He who would travel happily must travel light.
Antoine de Saint-Exupe ´ry

1.3.1 DIGITAL MICRO-PROPULSION PROGRAM STS-93
The first flight recorded for a MEMS device was on July 23, 1999, on the
NASA flight STS-93 with the Space Shuttle Columbia. It was launched at 12:31
a.m. with a duration of 4 days and carried a MEMS microthruster array into
space for the first time. DARPA funded the TRW/Aerospace/Caltech MEMS
Digital Micro-Propulsion Program which had two major goals: to demonstrate

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