The ultrasonic/sonic anchor (U/S anchor) is an anchoring device that drills a hole for itself in rock, concrete, or other similar material. The U/S anchor is a recent addition to a series of related devices, the first of which were reported in "Ultrasonic/Sonic Drill/Corers With Integrated Sensors

Bar-Cohen, Yoseph

Sherrit, Stewart

NASA Technical Reports Server

22 NASA Tech Briefs, February 2009
verse pressure gradient and moving the
flow separation away from the critical stern
components of the ASDS and harmlessly
onto the host hull downstream of the
ramp, as depicted schematically in the
lower part of Figure 2.
In water-tunnel tests on a scale model,
the installation of the compact ramp was
found to result in reductions of as much
as 50 percent in unsteady hydrodynamic
forces and moments on the stern ap-
pendages of the ASDS, leading to the se-
lection of the compact ramp as sole can-
didate recommended for testing in
full-scale sea trials. It has also been con-
jectured that structural components sim-
ilar to the compact ramp could, poten-
tially, confer flow-control and load-re-
duction benefits in applications that in-
volve piggyback or other external
attachments to aircraft. 
This work was done by John Lin of Langley
Research Center. Further information is con-
tained in a TSP (see page 1). LAR-17364-1
Ultrasonic/Sonic Anchor
The anchor can be embedded or de-embedded with minimal axial force.
NASA’s Jet Propulsion Laboratory, Pasadena, California
The ultrasonic/sonic anchor (U/S an-
chor) is an anchoring device that drills a
hole for itself in rock, concrete, or other
similar material. The U/S anchor is a re-
cent addition to a series of related de-
vices, the first of which were reported in
“Ultrasonic/Sonic Drill/Corers With In-
tegrated Sensors” (NPO-20856), NASA
Tech Briefs, Vol. 25, No. 1 (January 2003),
page 38. There are numerous potential
uses for U/S anchors, especially in en-
abling walking robots and humans to
climb steep rock faces for diverse pur-
poses, including scientific exploration,
recreational rock climbing, military ma-
neuvers, and search and rescue.
Like the prior devices in this series,
the U/S anchor drills a hole by means of
hammering and chiseling actions of a
tool bit excited with a combination of ul-
trasonic and sonic vibrations. The U/S
anchor also contains an actuator that in-
cludes a piezoelectric stack at the upper
end of a rodlike horn that serves to me-
chanically amplify the piezoelectric dis-
placement. In addition, as in the previ-
ously related devices, the tool bit is
mounted at the lower end of the horn.
The piezoelectric stack is electrically
driven at its resonance frequency (an ul-
trasonic frequency), and a bolt holds the
stack in compression to prevent fracture
during operation. 
In a typical prior related device, the
sonic vibrations are generated with the
help of upper and lower mass that is de-
noted the free mass because it is free to
move axially through a limited range
within the actuator/tool-bit assembly.
In the U/S anchor, there are two free
masses: one above and one below the
lower tip of the horn (see figure). Each
free mass bounces between hard stops
at the limits of its range of motion at a
sonic frequency. The impacts of the
free masses on the hard stops create
stress pulses that propagate along the
horn, to and through the tool bit, to
the tool-bit/rock interface. The rock
becomes fractured when its ultimate
strain is exceeded.
A major advantage of the U/S anchor
(or of any device in this series) is that it
is not necessary to apply a large axial
force to make the tool bit advance into
the drilled material. Similarly, during
operation, only a small force suffices to
extract the tool bit from the drilled hole.
Hence, a human or robotic rock climber
could easily insert and withdraw a U/S
anchor at successive positions during
traversal of a rock face.
This work was done by Yoseph Bar-Cohen
and Stewart Sherrit of Caltech for NASA’s Jet
Propulsion Laboratory. Further information
is contained in a TSP (see page 1).
This invention is owned by NASA, and a
patent application has been filed. Inquiries con-
cerning nonexclusive or exclusive license for its
commercial development should be addressed to
the Patent Counsel, NASA Management Of-
fice–JPL. Refer to NPO-40827.
The Ultrasonic/Sonic Anchor drills its own anchor hole in a rock face.
Horn 
Tip Rock
Tool Bit
Piezoelectric
Stack
Lower Free Mass
Upper Free Mass
Bolt
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Ultrasonic/Sonic Anchor

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