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Miniature
Wireless Sensors Size Up to Big Applications
Industrial Productivity and Manufacturing Technology
Originating Technology/NASA Contribution
Like the environment of space, the undersea world is a hostile,
alien place for humans to live. But far beneath the waves
near Key Largo, Florida, an underwater laboratory called
Aquarius provides a safe harbor for scientists to live and
work for weeks at a time.
Aquarius is the only undersea laboratory in the world. It
is owned by the National Oceanic and Atmospheric Administration
(NOAA), administered by NOAA’s National Undersea Research
Program, and operated by the National Undersea Research Center
at the University of North Carolina at Wilmington. Aquarius
was first deployed in underwater operations in 1988 and has
since hosted more than 200 scientists representing more than
90 organizations from around the world.
For NASA, Aquarius provides an environment that is analogous
to the International
Space Station (ISS) and the space
shuttle.
As part of its NASA
Extreme Environment Mission Operations (NEEMO) program, the Agency sends personnel to live in the
underwater laboratory for up to 2 weeks at a time, some of
whom are crew members—or “aquanauts”—who are subjected to
the same tasks and challenges underwater that they would
face in space. In fact, many participants have found the
deep-sea diving experience to be much akin to spacewalking.
To maintain Aquarius, the ISS, and the space shuttle as safe,
healthy living/research habitats for its personnel—while
keeping costs in mind—NASA, in 1997, recruited the help of
Conroe, Texas-based Invocon,
Inc., to develop wireless sensor
technology that monitors and measures various environmental
and structural parameters inside these facilities.
Partnership
This project, funded through a Johnson Space Center Small
Business Innovation Research (SBIR) contract, focused on
developing wireless sensors to help cut back on the integration
costs associated with wired sensors. It included the conceptual
design, fabrication, and demonstration of a battery-powered,
miniature, wireless temperature sensor. NASA and Invocon
agreed to take Invocon’s existing wireless network communication
system and combine it with various microelectromechanical
systems (MEMS) sensors. The innovation consisted of a PC
interface unit, a graphical user interface, and multiple
wireless sensors that are each equivalent in size to a stack
of five quarters.
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Crew
members for the ninth NASA Extreme Environment
Mission Operations (NEEMO) excursion arrive at
their underwater home: the Aquarius Underwater
Laboratory, off the coast of Key Largo, Florida.
Canadian astronaut Dave Williams led the crew of
four, which included NASA astronauts Ronald Garan
and Nicole Stott, and University of Cincinnati
physician Tim Broderick. |
Upon completion of the miniature wireless sensor technology,
Johnson’s Human Exploration and Development of Space program
(now part of the Space
Operations Mission Directorate) sought
to apply it to the space shuttle to acquire temperature data
from several fundamental locations in and around the shuttle
crew compartment and avionics equipment. High above the depths
of Aquarius, the sensor system has flown and operated successfully
on space shuttle missions STS-92, STS-96, STS-97, STS-100,
STS-101, STS-104, STS-106, and STS-108. Further use of the
technology is being investigated for monitoring carbon dioxide
concentrations onboard the ISS, in the crew’s sleeping quarters,
and in regions of reduced airflow.
Product Outcome
After emerging from the sea and shooting high into the heavens,
Invocon’s wireless sensor system has made a terrestrial landing
as a product called MicroWIS-CO2. This commercial offspring
is a wireless, remote, low-power, carbon dioxide data-acquisition
system for near-static sensing and recording applications.
It uses a non-dispersive infrared diffusion method for carbon
dioxide measurement. Carbon dioxide diffuses into the sensor’s
optical chamber, and molecules of the gas absorb infrared
light. This absorption is measured to derive the carbon dioxide
concentration.
MicroWIS-CO2 offers three modes of data transfer once the
carbon dioxide level is determined. The unit can transmit
data in real time to an associated receiver; store information
in a memory bank for later downloading, via radiofrequency,
to either the receiver or a PC; or conveniently combine both
of these modes to stream real-time information while backing
it up in memory.
Invocon has also spun off several “next-generation” MicroWIS
products that are configured for applications other than
carbon dioxide sensing. The latest of these products, the
MicroWIS-XG, can be used for sensing environmental, temperature,
strain, and pressure parameters, for example.
In the area of construction, one of these next-generation
systems was used to monitor external grout pressure during
the building of three tunnels in the Netherlands. When boring
tunnels through the ground, proper grout pressure is critical,
because it controls the amount of grout that is deposited
on the exterior of the tunnel, which ultimately determines
the strength of the water-seal and durability of the tunnel
throughout its useful life. Another important reason to maintain
proper grout pressure is that it influences surface elevation
of the ground directly above the tunnel. When the grout pressure
becomes too low during construction, the surface can sink.
This becomes problematic in areas where much of the land
is at or below sea level.
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| The
miniature wireless sensor developed for NASA is
equivalent in size to a stack of five quarters.
The technology has helped NASA acquire important
data to keep astronauts’ remote living quarters
safe and has been applied to a variety of sensing
applications on Earth. |
Dutch Government regulations required that strict controls
were used during construction in order to ensure that the
tunnels would maintain their integrity for 100 years or longer.
The MicroWIS technology was called upon to monitor grout
pressure at several locations during the building phase to
verify that the project met quality and safety requirements.
The wireless nature of the system greatly simplified the
building process and eliminated any risks that could have
come from wires and power cables that could have been cut
when exposed to the boring machines used to dig through the
ground to assemble
the tunnels.
In 2002, MicroWIS systems were used by the University of
Houston to study stresses during construction and testing
of a local bridge. This application stemmed from concerns
that certain sections of a bridge may actually be compromised
in the construction process due to inadequate support during
handling and installation.
To test this theory, 112 MicroWIS units were mounted at key
locations on the bridge—between main box girders and on temporary
k-frames—to determine stress loads during the 6-month construction
process. Data sampling took place once every 8 minutes or
once every 30 minutes, depending on the stage of construction.
The units measured the strains induced on the bridge beams
by both mechanical loads and diurnal temperature effects.
The measurements taken and the resulting data produced by
the units prevented the builders from adding any unnecessary
loads or strains to the sections of the bridge in question.
Since developing the sensors for NASA, Invocon has gone on
to manufacture monitoring solutions that have flown on 20
space shuttle missions, including the latest STS-114 mission.
By continuing to support NASA with new technologies bound
for space, the company is reaping the benefits of bringing
new ideas down to Earth.
MicroWIS™ is a trademark of Invocon, Inc.
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