Fall 2003
Galloping Snails
and Gliding Robots
he humble snail, trailing its ribbon of
slime, now has its first robotic
counterpart in research at MIT that
could lead to new forms of locomotion for
future machines.
T
RoboSnails I and II each
consist of electronics aboard
a rubber "foot" about six
inches long by one inch
wide. The robots glide over
a thin film of "mucus," or
silicon oil. The two were
created to test mathematical
simulations describing
forms of snail locomotion.
little information on the
subject. "Most sources said
that snails lay down a layer
of mucus then move with
their foot, but there was no
detail," said Chan. So, he
brought some snails to the
lab and studied them with
tools including a video
camera.
Snails "can maneuver over
a range of complex terrains
– even across ceilings – and
they’re very mechanically
simple," said Assistant
Professor Anette "Peko"
Hosoi of the Department of
Mechanical Engineering,
principal investigator for
the work. They also don’t
have exposed joints, so a
machine based on their
form and covered with
rubber resistant to corrosion
can navigate in chemically
harsh environments.
"Snails have three different
modes of locomotion," he
said. For example, some
travel over the mucus by
undulating their bodies in
tiny waves moving from
the front of the animal to
the back.
When Hosoi and her
mechanical engineering
colleagues (graduate
student Brian Chan, senior
Susan Ji, and junior
Catherine Koveal) first
began exploring snail
locomotion, they found
MIT Professor Anette "Peko" Hosoi, graduate student Brian Chan, and
junior Catherine Koveal demonstrate RoboSnail I (right) and RoboSnail II.
RoboSnail I has since been rebuilt to be the same size as the smaller
RoboSnail II.
kink, at the end of the snail’s
tail, extends forward – and
moves the snail in the same
direction – as the animal
stretches out. RoboSnail II,
which was completed last
month, mimics this
"forward-undulating"
movement.
"By pushing [the fluid]
backwards, they can build
up large pressures in the
thin layer of mucus. The
sum of all these pressures
then pushes the snail
forward," explained Hosoi.
RoboSnail I mimics this
"backward undulating"
form of movement.
The snail’s third form of
locomotion? It actually
gallops. Like an inchworm,
the animal sticks the front of
its foot to a surface (thanks
to suction and friction from
the mucus), and then draws
the rest of its body up
behind it. (The engineers
have no immediate plans to
build a galloping robot.)
Snails can also move
forward by undulating in
the reverse direction, from
back to front. "Imagine a
carpet with a kink in it,"
Chan said. In this case, the
Although the research has
only been underway since
last November, the
engineers are excited about
some initial results. For
1
example, said Hosoi, it was
previously thought that
movement (like that of a
snail) over a fluid requires a
non-Newtonian fluid, or one
that can behave like a solid
or liquid. "We’ve shown that
you don’t need that at all.
It’ll work with any sort of
fluid, so long as the fluid is
viscous enough."
The team also found that
RoboSnail I, which Chan
calls "a little crude," actually
performed well, traveling at
a speed close to that
predicted by the team’s
mathematical models.
Source: Massachusetts
Institute of Technology (MIT)
http://web.mit.edu/newsoffice
/nr/2003/robosnail.html
Photo credit: MIT. Used with
permission.
Hearlihy Tech Times
Fall, 2003
Powerful Recipe
ombine old tires, plastic
bottles, sewage sludge,
paper, agricultural refuse,
and a heaping helping of turkey offal
from ConAgra’s Butterball plants. Add water
and heat under pressure for several hours.
Yield: Oil, gas, carbons, and fuel.
C
While not a mixture you’d expect to find in Julia
Child’s kitchen, it is the process being tested at
Changing World Technology’s Carthage, Missouri,
plant. If successful, the process has the potential to
reduce U.S. dependence on foreign oil while solving
fast-growing, worldwide waste disposal problems.
In April, CWT began using thermal technology to
convert organic and low-value waste products into
clean energy by emulating the Earth’s natural
geothermal activity that converts organic material
into fossil fuel under conditions of extreme heat and
pressure over millions of years. The Missouri plant,
however, reduces the "cooking" time from eons to
hours. The process is 85 percent energy efficient,
requires very low BTUs, uses recycled water
throughout, and even generates its own energy by
utilizing the steam produced by the process.
Above: Low value organic feedstocks (waste streams) are slurried
with water to begin the thermal conversion process which
transforms them into high value energy products. Below: CWT’s
thermal conversion process concludes with simple fractional
distillation, separating the oil and gas from water.
"If the process works as well as its creators claim,
not only would most toxic waste problems become
history, so would imported oil," says Discover
magazine, which featured a full-length article on
CWT’s thermal process in its May 2003 issue.
R. James Woolsey, former director of the U.S.
Central Intelligence Agency, sees even more farreaching ramifications: "This technology offers all
of us an opportunity someday to have a more
peaceful and freer world, a world that is not
dependent on turbulence and chaos."
Source: Changing World Technology
http://www.changingworldtech.com/ newsfr.htm
Photo credits: Changing World Technologies, Inc. &
Affiliate Companies © 2003. Used with permission.
2
Hearlihy Tech Times
Fall, 2003
"Matchbox" Clock
H
ow accurate is your kitchen clock? Probably good enough to get you to work on time,
but perhaps not good enough for extremely precise ship and aircraft navigation, groundto-outer space communications, or missile guidance.
In October 2003, the Office
of Naval Research (ONR)
will unveil the performance
of the next-generation,
super-accurate atomic clock
no bigger than a matchbox.
The Ultra-Miniature
Rubidium (Rb) Atomic
Clock, 40 cubic centimeters
in volume and using a
minuscule one watt of
power, doesn’t weigh much
more than a matchbox
either.
And it will lose only about
one second every 10,000
years.
Dr. John Kim, who oversees
navigation and timekeeping
technology programs at
ONR, points out that while
commercial atomic clocks
already are available, they’re
relatively large and bulky. A
typical Cesium beam atomic
clock is about the size of a
large backpack and
consumes up to 50 watts of
power. The laser-based
Ultra-Miniature Rb Atomic
Clock improves on power
needs by a factor of four,
and its tiny size will permit
new degrees of design
flexibility for systems,
especially aircraft, which
place a high premium on
size and weight.
The "matchbox" clock is
entirely optical in nature – a
key breakthrough for
miniaturizing atomic clocks.
The laser light source is
derived from a new
technology breakthrough
called Vertical Cavity
Surface Emitting Laser
(VCSEL, pronounced
"vixel") developed to meet
the needs of the fiber-optic
communications industry
for extremely compact
The ultra-miniature Rubidium atomic clock is the next-generation,
super-accurate clock no bigger than a matchbox and loses only one
second every 10,000 years.
lasers. The differences
between this new clock
and other atomic clocks
are the size, weight, power
consumption,
transportability, and price.
Source: Office of Naval
Research http://www.onr.
navy.mil/media/tipoff_
display.asp?ID=46#2
Photo credit: Office of Naval
Research
Tech Times Tech Feature
What Is an Atomic Clock Anyway?
cientists have long realized that atoms (and molecules) have resonances: each chemical
element and compound absorbs and emits electromagnetic radiation at its own
characteristic frequencies. These resonances are inherently stable over time and space.
An atom of hydrogen or cesium today is, so far as we know, exactly like one a million years
ago or in another galaxy. Thus, atoms constitute a potential "pendulum" with a reproducible
rate that can form the basis for more accurate clocks.
S
The development of radar in the 1930s and extremely high frequency radio communications in the 1940s made possible
the generation of the kind of electromagnetic waves (microwaves) needed to interact with atoms. Research aimed at
continued on page 4
3
Hearlihy Tech Times
Fall, 2003
What Is an Atomic Clock Anyway?
developing an atomic clock focused
first on microwave resonances in the
ammonia molecule. In 1949, the
National Institute of Standards and
Technology (NIST) built the first
atomic clock, which was based on
ammonia. However, its performance
wasn't much better than the existing
standards, and attention shifted
almost immediately to more
promising atomic-beam devices based
on the metallic element cesium.
First Cesium Clock
The first practical cesium atomic
frequency standard was built at the
National Physical Laboratory in
England in 1955, and in collaboration
with the U.S. Naval Observatory
(USNO), the frequency of the cesium
reference was established or
measured relative to astronomical
time. While NIST was the first to start
working on a cesium standard, it
wasn't until several years later that it
completed its first cesium atomic
beam device. Soon after, a second
unit was built for comparison testing.
By 1960, cesium standards had been
refined enough to be incorporated
into the official timekeeping system
of NIST. Standards of this sort were
also developed at a number of other
national standards laboratories,
(continued from page 3)
leading to wide acceptance of this
new timekeeping technology.
Time is Defined
The cesium atom’s natural frequency
was formally recognized as the new
international unit of time in 1967: the
second was defined as exactly
9,192,631,770 oscillations or cycles of
the cesium atom's resonant frequency,
replacing the old second that was
defined in terms of the Earth's
motions. The second quickly became
the physical quantity most accurately
measured by scientists. As of January
2002, NIST's latest primary cesium
standard was capable of keeping time
to about 30 billionths of a second per
year.
Other Kinds of Atomic Clocks
Other kinds of atomic clocks have
also been developed for various
applications; those based on
hydrogen offer exceptional stability,
for example, and those based on
microwave absorption in rubidium
vapor are more compact, lower in
cost, and require less power.
Source: National Institute of
Standards and Technology (NIST)
"A Walk Through Time: The ‘Atomic
Age’ of Time Standards"
http://physics.nist.gov/GenInt/Time/
time.html
Why Cesium and How Does it Work?
The metallic element cesium is the best choice of atom for time
measurement because all of its 55 electrons – except the outermost ones –
are confined to orbits in stable shells of electromagnetic force. Thus, the
outermost electron is not disturbed much by the others.
A cesium clock operates by exposing cesium atoms to microwaves until
they vibrate at one of their resonant frequencies and then counting the
corresponding cycles as a measure of time.
Source: U.S. Naval Observatory http://tycho.usno.navy.mil/ cesium.html
4
The NIST-F1 Cesium Fountain Atomic
Clock – the primary time and frequency
standard for the United States.
Who uses atomic clocks?
Sailors, truck drivers, soldiers,
hikers, pilots – anyone who uses a
Global Positioning System (GPS)
benefits from atomic time. Each of
the 24 GPS satellites carries four
atomic clocks on board. By
triangulating time signals broadcast
from orbit, GPS receivers on the
ground can pinpoint their own
location.
Tiny instabilities in those orbiting
clocks contribute at least a few
meters of error to single-receiver
GPS measurements. Making the
clocks smaller (so more of them can
fit on each satellite) and increasing
their stability could reduce such
errors to fractions of a meter. And, if
you were a pilot landing on a
narrow airstrip at night, that would
be a welcome improvement!
Source: Science at NASA
http://science.nasa.gov/headlines/
y2002/08apr_atomicclock.htm
Photo credit: NIST Physics Laboratory, Time
& Frequency Division.
http://www.boulder.nist.gov/timefreq/cesium/
fountain.htm
Hearlihy Tech Times
Fall, 2003
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5
Hearlihy Tech Times
Fall, 2003
Puzzle Pages
What is a
cryptogram?
In a cryptogram, each
letter of the alphabet is
represented by
another letter of the
alphabet. For
example, the letter A
may be represented
by the letter T. Using
your knowledge of
English language
construction, you can
break the code and
replace the substituted
letter with the actual
letter to reveal a
message.
CRYPTOGRAM
Break the code and reveal a message inspired by this semester’s Hearlihy Tech
Times. Hint: l = o
Evg
m
lzekze
ezyigd
lh
ur
XCE’a
dlzy
evgyqmw kylxgaa
cuww
kze
emri!
WORD SCRAMBLE
Rearrange the letters to reveal words from Tech Times articles.
1. LUFE
2. LASIN
3. KERUTY
4. COMAIT
5. SCUIME
CROSSWORD
Test your retention of the articles in this issue of Tech Times as well as your general knowledge of
physics, sports, and language. Crossword clues appear on page 7.
1
2
3
4
5
6
7
8
9
10
13
14
16
17
18
19
20
21
22
25
23
26
27
29
28
30
31
32
33
6
24
15
11
12
Hearlihy Tech Times
Fall, 2003
ACROSS
2
A fluid that can behave like a solid or a liquid depending on the force that
is applied to it (2 words)
5
Type of radiation emitted and absorbed by every chemical element and
compound
10
Most frequently used word in the English language
13
Film over which RoboSnail glides (2 words)
16
Decorative pitcher
17
Past tense of tell
19
Pungent gas used in first atomic clock
22
Ascending direction
23
__ Kill a Mockingbird (Harper Lee novel)
25
Frequencies
28
Preposition used to indicate location
29
To have an understanding of
30
Domesticate
32
Light source for matchbox atomic clock
33
A cesium clock operates by exposing cesium atoms to ____________.
DOWN
1
Output of the CWT's thermal technology process
3
Tenacity; viscidity, as of fluids
4
9,192,631,770 oscillations of the cesium atom's resonant frequency
equals one _________.
6
Belonging to the 2003 Super Bowl champs
7
University where RoboSnail was developed
8
Locator device that uses atomic clocks (abbreviation)
9
As the ____ flies (idiom)
11
Informal greeting
12
55 _________ in an atom of cesium
14
Metallic element used in large atomic clocks
15
Laws of motion fellow
17
Fowl ingredient used in CWT's energy-making process
18
Opposite of closed
20
National Institute of Standards and Technology (abbreviation)
21
The smallest particle that defines an element
24
Solitary number
26
__ what?!
27
These nocturnal birds of prey give a hoot
31
An upper limb of the human body
7