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Laser
Mapping for Visual Inspection and Measurement
Industrial Productivity and Manufacturing Technology
Originating Technology/NASA
Contribution
Each space
shuttle orbiter has 38 Primary Reaction Control
System (PRCS) thrusters to help power and position the vehicle
for maneuvers in space, including reentry and establishing
Earth orbit. Minor flaws in the ceramic lining of a thruster,
such as a chip or crack, can cripple the operations of an
orbiter in space and jeopardize a mission. The ability to
locate, measure, and monitor tiny features in difficult-to-inspect
PRCS thrusters improves their overall safety and lifespan.
These thrusters have to be detached and visually inspected
in great detail at one of two NASA facilities—the White
Sands Test Facility or the Kennedy
Space Center—before and after
each mission, which is an expense of both time and money.
Partnership
Laser Techniques Company,
LLC (LTC), of Bellevue, Washington,
builds customized laser-based measurement and inspection
devices to help improve the safety, reliability, and useful
life of high-value, safety-critical equipment and industrial
machinery for the commercial, defense, and aerospace industries.
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James
Doyle, Laser Techniques Company, LLC, president,
kneels to examine the thrusters on Space Shuttle
Atlantis. |
In 2002, James Doyle, president of LTC, successfully demonstrated
that a miniature, high-performance laser could locate and
map hidden flaws in PRCS thrusters that were smaller than
the head of a pin, to an accuracy of 0.0003 inches.
Through the NASA-sponsored Montana
State University TechLink Center, Doyle delivered a presentation
of his work at White Sands, which led to the issuance of
a NASA contract to build a full-scale, portable, in situ
thruster mapping system.
The project was successful, resulting in the development
of an automated laser-based scanning system that included
a miniature, high-performance laser sensor. With the scanning
laser system, the area of a thruster can be quickly inspected
and mapped, providing technicians with accurate 3-D data
for evaluating the ceramic surface condition. The portable
laser scanner system was sent to White Sands, where it is
used in thruster life-testing projects and routine thruster
overhaul and refurbishment programs.
NASA is interested in extending the use of LTC’s portable
scanning system to on-shuttle applications, enabling inspectors
to detect and map flaws in the lining of the thrusters while
they are attached to the shuttle. This would be a significant
improvement over the current visual methods of inspection,
which require removal and shipping of the thrusters.
The successful results of the thruster mapping project resulted
in positive exposure of LTC’s capabilities to other branches
of NASA. Working with the technical staffs of NASA; the United
Space Alliance, of Houston; and Hamilton Sundstrand Corporation,
of Windsor Locks, Connecticut, LTC developed an automated,
laser-based corrosion mapping system for the gas generators
used in the auxiliary power units on both the solid rocket
boosters and the main orbiter. This system, which is being
put into full production this year, will eliminate the laborious
and difficult task of measuring corrosion and pitting on
the external surface of the gas generator units.
A significantly more difficult challenge was then presented
to LTC by the same group of NASA researchers. As Doyle recalls,
“They basically said ‘Okay, you did a great job on the external
surface of the gas generator unit, but can you build a microsensor
that maps the inside surface of the gas generator injector
stem? Oh, by the way,
its inner diameter is only 0.095 inches, and it is only 3
inches deep!’”
The inside surface of the injector stem is the most difficult
area to inspect. Eve
n tiny flaws in the gas generator can
result in the condemnation of these expensive parts, and
since they are considered flight critical, no flaws can be
allowed.
Approximately 4 months after receiving a contract to develop
a proof-of-principle gas generator stem-mapping sensor,
LTC notified NASA that it was ready to demonstrate the device.
Not only was LTC ahead of schedule, the sensor exceeded the
design goals, providing high-resolution, 3-D images of pits
as small as 0.005 inches deep. It will be put into full production
for inspection of all gas generators during the refurbishment
process at the Hamilton Sundstrand facility, in Rockville,
Illinois. This system, which will be capable of mapping both
the gas generator external surface and the injector stem,
will significantly improve the inspection process by automating
the onerous task of manually inspecting these critical parts.
The TechLink center provides assistance for small businesses,
such as LTC, to get exposure to NASA and the U.S. Department
of Defense—a task that is otherwise particularly difficult
for small businesses. For LTC, that is all it needed.
To date, LTC has successfully introduced its technology to
NASA’s Marshall Space Flight Center, Glenn Research Center,
White Sands Test Facility, and Kennedy Space Center.
Product Outcome
The developments accomplished through the projects conducted
for NASA are being directly extended to the commercial industry
and for military defense applications. Conventional visual
inspection and measurement methods can be time-consuming,
laborious, and inaccurate. “Our objective,” stated Doyle,
“is to eliminate the possibility of missing a potentially
crucial flaw due to the effects of operator subjectivity,
visual acuity, or fatigue.”
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A
3-D image of corrosion generated using the laser
sensor developed under the NASA-funded partnership. |
LTC’s laser-based scanning measurement and inspection systems,
advanced under the NASA contracts, are ideal and cost-effective
solutions to these problems. Their small size allows them
to scan otherwise inaccessible areas, and they can map virtually
100 percent of a target surface in a matter of minutes. In
addition, the unique LaserVideo image dataset from the laser-scanning
probe provides valuable qualitative visual information about
surface condition. These laser-generated visual images provide
nearly photographic image quality of surfaces that would
be impossible to photograph using conventional bore scopes,
and expose flaws such as scratches, scuffs, and discoloration.
LTC offers a variety of noncontact measurement and inspection solutions using
laser-based sensors. For inspection of critical components, LTC has developed
a wide range of products based on three core technologies: laser profile mapping,
LaserVideo imaging, and Laser-Scanned Fluorescent Penetrant Inspection (LSPI).
All of the company’s technologies are supported by its Laser MicroMap data acquisition
system and utilize its LaserViewer software for flexible data acquisition, real-time
display of collected data, and data analysis. It has developed a standard product
line to meet the needs of a number of diverse applications, and can, as it proved
with the variety of work it performed for NASA, quickly adapt those products
to new requirements.
Laser profile mapping involves a group of sensors that provide precise, noncontact
measurement and
3-D images of tubes, bores, plates, and complex surfaces. These sensors are high-resolution
“laser calipers” that take a rapid succession of single-point distance measurements
while scanning over the target surface. The result is a 3-D image that provides
a quantitative map of the inspected part. Features such as pits, erosion, and
deformation can be rapidly located and accurately measured. LTC also develops
systems that integrate eddy current sensors, complementary nondestructive testing
technology that can detect subsurface flaws.
With LaserVideo imaging, a highly focused laser spot provides high-resolution,
undistorted images of hard-to-access surfaces such as tubes and bores, revealing
features like cracks, scratches, stains, and variations in surface roughness.
These images are acquired along with the profile data and provide a visual image
that complements the topographical data set.
The patented LSPI technique provides automated fluorescent penetrant inspection
for real-time detection and mapping of surface-breaking cracks and other
defects. Like LaserVideo imaging, this noncontact inspection method is ideal
for detecting surface defects in difficult-to-access components.
Using these three core technologies, LTC offers an in-house laser inspection
service, as well as a fully equipped laboratory, including multi-axis, computer-controlled
scanning fixtures; optical breadboard tables; and a full cadre of test instruments
and sensors. The company can quickly set up and test samples that clients provide
for evaluation. It also offers remote or onsite consulting to customers, to develop
solutions for challenging inspection and measurement applications.
LTC practices its trade in the defense, aerospace, and energy industries. Defense
applications of this laser-sensing technology include detecting and mapping erosion,
deformation, and pitting in weapons ranging from small caliber rifles, to mortars,
to large caliber cannons. Aerospace applications, in addition to detecting chips
in the space shuttle thrusters, include detecting cracks in aircraft engine parts
and measuring thruster erosion. In the energy industry, this technology is useful
for dent measurement, quality measurement, and crack detection in nuclear steam
generator tubes, and underwater mapping of piping.
LaserVideo™, LSPI™, and Laser
MicroMap™ are trademarks of Laser Techniques Company, LLC.
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