NASA’s Radio Frequency Bolt Monitor: A Lifetime
of Spinoffs
Industrial Productivity/Manufacturing Technology
Originating Technology/ NASA Contribution
This story begins in the 1970s, when Dr. Joseph Heyman,
a young scientist at NASA’s Langley Research Center,
was asked to support the investigation of a wind tunnel
accident at a sister center. Although the work was
outside of his physics background, it sparked a research
focus that guided his lengthy NASA career and would
earn him a slew of accolades, including NASA’s highest
award medals for Exceptional Leadership, Exceptional
Achievement, and Exceptional Service; the coveted “Silver
Snoopy” Astronaut Award for Space Shuttle Return to
Flight; and the Arthur Fleming Award for being one
of the Top Ten Federal Scientists in Government Service.
He won 30 additional NASA awards, including the Agency’s
“Invention of the Year” and the Agency’s highest award
for technology transfer, and was the only person to
ever win 4 R&D 100 Awards.
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Deep within a mine
shaft, Dr. Joseph Heyman looks on at early testing
of NASA’s bolt elongation monitor. Heyman is
monitoring mine roof bolt preload during a test
to compare the P2L2 data to that of a pressure
plate. The tests demonstrated that, with the
P2L2, each bolt could become its own precision
load monitor. |
Back in 1973, though, Heyman was a young civil servant
with a background in physics who was asked to sit
on an accident review panel. The panel met at Ames
Research Center, in Moffet Field, California, and
after considerable investigation, concluded that
a high-pressure pebble heater used for heating gas
had failed, due to improperly tightened bolts in
a 1,000-pound gate valve control section. The accident
showered the facility with incendiary ceramic spheres
and nearly a ton of metal, but, luckily, caused no
injuries.
Heyman returned to Langley and began work on a solution.
He developed an ultrasonic device that would measure
bolt elongation, as opposed to torque, the factor typically
measured in testing bolt preload or tension. Torque
measurement can lead to load errors, with miscalculations
as high as 80 percent that can be passed over during
installation. Bolt stretch, however, is nearly always
accurate to 1 percent or better.
Within 1 month, he had an acoustic resonance solution
that accurately determined bolt elongation. He assumed
his work on this project had ended, but it was actually
the start of nearly 15 years of work perfecting, improving,
inventing, and modifying the “bolt monitor”—all the
while, filing numerous patents, presenting papers,
and holding demonstrations as the technology matured.
Industry engineers challenged Heyman’s inventiveness,
and reminded the physicist that most bolts are not
perfect resonators, and that early devices required
that the bolt have reasonably flat and parallel faces.
The U.S. Geological Survey asked NASA for help in determining
the load in mine roof bolts, which are 8- to 10-feet-long
and rough cut. To solve that problem, Heyman modified
the original device to operate at a lower frequency
and to generate propagation modes that could be used
to “lock” the instrument on a particular mode. Further
work in this vein led to the development of the Pulsed
Phase Locked Loop (P2L2) that worked on the mine bolts.
The next set of problems involved high-strength bolts
with head markings. For this solution, Heyman invented
a modified P2L2 that tracked a specific phase point
in the measurement wave. This class of instrumentation,
well suited to measuring small changes in acoustic
velocity, won the NASA “Invention of the Year” award
in 1982.
Other scientists and engineers have continued the evolution
of this technology both inside NASA and outside of
the Agency. Within NASA, the technology has been improved
for medical applications, with a particular focus on
intercranial pressure (ICP) monitoring.
Astronauts exposed to microgravity experience an elevation
in ICP, which contributes to space adaptation syndrome,
or “space sickness,” with symptoms similar to motion
sickness on Earth, consisting of general discomfort,
queasiness, nausea, vomiting, vertigo, headache, malaise,
drowsiness, and lethargy. There is concern for astronauts
developing ICP during long-duration missions, because
experiencing these symptoms will not allow them to
work to full capacity.
A second medical application, unrelated to space travel,
involves muscle pressure that can build to a point
where blood is unable to properly circulate, and leads
to tissue damage and possibly death. This condition
is called compartment syndrome. The compartments are
groups of muscles surrounded by inelastic fascia, and
thus, any swelling of muscles leaves no room for expansion.
Blood supply is progressively cut off. Drs. Tom Yost
and John Cantrell of Langley are working on applications
that relieve the pressure using the P2L2.
Partnership
Heyman retired from the Agency in 2001, and he joined
Nascent Technology Solutions, a small Virginia-based
company in the field of nondestructive evaluation (NDE)
that was recently purchased by Virginia neighbor, Luna
Innovations, Inc. The scientists at Luna use diverse
core technologies, including the P2L2 technology developed
at Langley; so now, Luna is where Heyman continues
his life’s work.
He is chief scientist for Luna and working with a new
team to build a fully digital P2L2-equivalent device
with broad applications ranging from medical to NDE.
Product Outcome
Luna has licensed rights from Langley to continue the
work on studying compartment syndrome and ICP as well
as found myriad uses for the P2L2 technology in the
commercial realm.
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Luna’s current compartment
syndrome prototype is now being tested for noninvasive
diagnosis. A next-generation design will reduce
the size of the unit by a fourth and increase
functionality. Here, its is shown taking internal
pressure reading. The most common method for
performing this test is a
painful biopsy. |
Compartment syndrome is a significant cause for surgery
among soldiers in Iraq. It stems from blunt trauma
causing inflamed muscles, which then creates pressure,
resulting in heart strain, as the organ is not getting
the blood it needs. The result, if left untreated,
may lead to amputation or death. The current treatment
involves slicing into the muscle tissue to relieve
pressure, which, in addition to being quite excruciating,
creates a large wound with risk of infection and a
painful recovery time.
The current measurement to determine if the surgery
is necessary is a bioptic pressure plunger, another
painful procedure involving extraction of tissue from
the aggravated area.
With cooperation from NASA’s team, Luna’s Dr. Ted Lynch
has advanced the commercialization of the P2L2 to alleviate
the need for this procedure and prevent unneeded surgery.
It is already in use in a teaching hospital and should
be more widely disseminated as the studies advance.
In addition to its uses in the aforementioned medical
applications and its original use of measuring bolts,
fasteners, and bond strength—which is still one of
the most widespread uses for the P2L2—Luna has found
many other innovative applications for this technology.
For example, it anticipates widespread application
in the field of radiation dosimetry, the accurate measure
of radiation doses for medical purposes. It has teamed
with the National Institute of Standards and Technology
and demonstrated the ability to measure changes in
water temperature of 13 micro-degrees at room temperature.
This breakthrough resolution translates into the ability
to assess a radiation treatment beam for energy deposited
and beam geometry critical for effective treatment.
In short, it can make radiation dosages more safe,
accurate, and effective.
In the field of groundwater analysis, Luna has been
able to monitor the slightest flow of groundwater in
sand. This work enables a new class of devices capable
of determining water flow underground to assess contaminant
transport, aquifer impact for pumping, and the movement
of oil. This groundbreaking application eliminates
the need for breaking too much ground.
Luna has also found a home for the P2L2 in the field
of materials characterization. The system is being
used by the U.S. Army to measure elastic properties
of materials that are related to stiffness as well
as nonlinear properties linked to strength. It essentially
tells the military how strong things are and how long
they will last. This application has uses spread across
many additional industries for quality assurance, and
life-cycle maintenance.
In the railroad industry, P2L2 is being used as a rail
performance-monitoring system. It can detect defects
in the rails so that they can be corrected before growing
and becoming unsafe.
The P2L2 already has a variety of uses, and the list
of applications keeps growing as Heyman continues the
work that he was called to do over 30 years ago
at Ames.
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