Major Areas of Opportunity - Implications of Emerging Micro-and Nanotechnologies - page 73

payload, the structure, the launch site (hydrazine on the tarmac) and the payload
itself are candidates for monitoring.

Load Monitoring

Load monitoring has historically been achieved primarily by individual strain
gages (a typical F-18 has seven). However, owing to system weight penalties and
the difficulties of installation and repair, they have been used infrequently in
aircraft and space applications. Recent developments in optical fiber sensors 129
and wireless transponders 130,131 have helped solve some of these difficulties.
However, there has not been much successful commercialization of these tech-
nologies, primarily because of limitations on the availability of power and very
small antenna elements, both of which may have micro- and nanotechnology
solutions, and overall lack of maturity of the embedment process and its associ-
ated egress and embedding issues.

Air Pressure Monitoring

MEMS-based flow monitoring has been pursued for underwater vehicles,
but the most notable effort in monitoring the local environment of an aerostructure
was developed by the Boeing Company and Endevco. Their pressure belt 132
(Figure 3-11) contains silicon-based multichip modules (MCMs), each of which
contains a MEMS pressure sensor, a temperature sensor, and data acquisition and

Silicon-based MCM Modules
with Pressure and Temperature
Sensors

Tape End
Interconnection Wiring Bus

Polymeric Tape Carrier

Width = 70 mm (28 inches)

Length = 315 mm (12.4 inches)

MEMS Sensor ASICs

High-reliability
Coating

3 mm
(0.1 inches)

Inter-segment
Connector Tab

Bus Wiring Traces

Tape Carrier

25 mm (1.0 inches)

FIGURE 3-11 Boeing/Endevco pressure belt. SOURCE: North Atlantic Treaty Organi-
zation Advisory Group for Aerospace Research & Development (NATO/AGARD). 1996.
Smart Structures and Materials: Implications for Military Aircraft of New Generation,
AGARD-LS-205. Ottawa, Canada: Canadian Aeronautics and Space Institute.