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THE LATEST RESEARCH AND DEVELOPMENT NEWS IN MANUFACTURING AND TECHNOLOGY
NASA Fired Up Over 3D-Printed Engine Components
A
NASA team is fired up about getting closer to building
lant of choice, the propellant combination of cryogenic liquid
a completely 3D-printed, high-performance rocket
hydrogen and oxygen tests the limits of 3D-printed hardware
engine. They demonstrated this in December by
because it produces the most extreme temperatures and
assembling additive-made complex engine parts and firing
exposes parts to cryogenic hydrogen, which can cause
them up with cryogenic liquid hydrogen and oxygen to pro-
brittleness. In addition to testing with methane, the team
duce 20,000 pounds of thrust.
plans to add other key components to the demonstrator
“We manufactured and then tested about 75% of the
parts needed to build a 3D-printed rocket engine,” said
engine including a cooled combustion chamber and nozzle
and a turbopump for liquid oxygen.
Elizabeth Robertson, the project manager for the
additively manufactured demonstrator engine at
NASA’s Marshall Space Flight Center in Huntsville,
AL. “By testing the turbopumps, injectors and
valves together, we’ve shown that it would be
possible to build a 3D-printed engine for multiple
purposes such as landers, in-space propulsion or
rocket engine upper stages.”
Over the last three years, the Marshall team has
been working with various vendors to make 3Dprinted parts, such as turbopumps and injectors,
Photo courtesy NASA
and test them individually. To test them together,
they connected the parts so that they work the
same as they do in a real engine.
“What matters is that the parts work the same
way as they do in a conventional engine and
perform under the extreme temperatures and
pressures found inside a rocket engine,” explained
During test firings at NASA’s Marshall Space Flight Center, 3D-printed
rocket engine parts worked together successful under the same conditions
experienced inside rocket engines used in space.
Nick Case, the testing lead for the effort. “The turbopump got its ‘heartbeat’ racing at more than 90,000 rpm
“These NASA tests drive down the costs and risks associ-
and the end result is … over 20,000 pounds of thrust, and
ated with using additive manufacturing, which is a relatively
an engine like this could produce enough power for an upper
new process for making aerospace quality parts,” said Rob-
stage of a rocket or a Mars lander.”
ertson. “Vendors who had never worked with NASA learned
Seven tests were performed, with the longest tests lasting
how to make parts robust enough for rocket engines. What
10 seconds. During the tests, the 3D-printed demonstra-
we’ve learned through this project can now be shared with
tor engine experienced all the extreme environments inside
American companies and our partners.”
a flight rocket engine where fuel is burned at greater than
The 3D-printed turbopump, one of the more complex
3315° C to produce thrust. The turbopump delivers the fuel
parts of the engine, had 45% fewer parts than similar pumps
in the form of liquid hydrogen cooled below -240° C. These
made with traditional welding and assembly techniques. The
tests were performed with cryogenic liquid hydrogen and
injector had over 200 fewer parts than traditionally manufac-
liquid oxygen, mainstays of spaceship propulsion systems.
tured injectors, and it incorporated features that have never
Even if methane and oxygen prove to be the Mars propel-
been used before because they are only possible with addiFebruary 2016
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tech front
tive manufacturing. Complex parts like valves that normally
would take more than a year to manufacture were built in a
few months. This made it possible to get the parts built and
Image courtesy user Materialscientist/Wikipedia Commons
assembled on the test stand much sooner than if they had
been procured and made with traditional methods. Marshall
engineers designed the fuel pump and its components and
leveraged the expertise of five suppliers to build the parts
using 3D-printing processes.
New, Atom-Thick Borophene
in Race with Graphene
T
ech Front has been following the development of
Front-view illustration of Neutral C6v B36 borophene.
graphene, that single-atom-thick material with amazing
properties that may yet revolutionize Lithium batteries (see
A team of scientists from the US Department of Energy’s
below) and other manufactured products. And while progress
(DOE) Argonne National Laboratory, Northwestern University
in making graphene affordable and usable outside the lab
and Stony Brook University announced that it has, for the
has been consistent, it has at times seemed slow. Now there
first time, created a two-dimensional sheet of boron—bo-
is a second horse in the race, however—called borophene.
rophene. It’s an unusual material because it shows many
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February 2016
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metallic properties at the nanoscale even though three-di-
Based on theoretical predictions of borophene’s char-
mensional, or bulk, boron is nonmetallic and semiconducting.
acteristics, the researchers also noticed that it likely has a
“Borophenes are extremely intriguing because they are
higher tensile strength than any other known material—in-
quite different from previously studied two-dimensional mate-
cluding graphene. Tensile strength refers to the ability of a
rials,” said Argonne nanoscientist Nathan Guisinger, who led
material to resist breaking when it is pulled apart. “Other two-
the experiment. “And because they don’t appear in nature,
dimensional materials have been known to have high tensile
the challenge involved designing an experiment to produce
strength, but this could be the strongest material we’ve
them synthetically in our lab.”
found yet,” researcher Nathan Guisinger said.
One of boron’s most unusual features consists of its atomic
As they grew the borophene monolayer, the researchers
configuration at the nanoscale. While other two-dimensional
discovered an advantage within their experimental technique.
materials look more or less like perfectly smooth and even
Unlike previous experiments that used highly toxic gases in the
planes at the nanoscale, borophene looks like corrugated
production of nanoscale boron-based materials, this experiment
cardboard, buckling up and down depending on how the bo-
involved a nontoxic technique called electron-beam evapora-
ron atoms bind to one another, according to Andrew Mannix,
tion, which essentially vaporizes a source material and then con-
a Northwestern graduate student and first author of the study.
denses a thin film on a substrate—in this case, boron on silver.
The “ridges” of this cardboard-like structure result in a
The study will be published in the Dec. 18 issue of the
material phenomenon known as anisotropy, in which a mate-
journal Science. Borophene thus joins graphene in a devel-
rial’s mechanical or electronic properties—like its electrical
opmental race of atom-thick miracle materials. We’ll watch to
conductivity—become directionally dependent, Mannix said.
see which eventually takes a thin lead.
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Lithium-Air Battery
Progress is Breathtaking
S
cientists at UK’s University of Cambridge have developed a working laboratory demonstrator of a lithium-ox-
ygen battery that has very high energy density, is more than
90% efficient, and, to date, can be recharged more than
Microscope image showing charged (left) and discharged
graphene electrodes.
2000 times, showing how several of the problems holding
University of Cambridge researchers have now demon-
back the development of these devices could be solved.
strated how some of these obstacles may be overcome, and
Lithium-oxygen, or lithium-air, batteries have a theoretical
developed a lab-based demonstrator of a lithium-oxygen
energy density that’s ten times that of a lithium-ion battery.
battery which has higher capacity, increased energy ef-
Such a high energy density would be comparable to that of
ficiency and improved stability over previous attempts. Their
gasoline–and would enable an electric car with a battery that is
research was published in the journal Science.
a fifth the cost and a fifth the weight of those currently on the
What Tao Liu, Clare Grey and their colleagues at Cam-
market to drive over 400 miles on a single charge—theoretical-
bridge have developed uses a different chemistry than earlier
ly, that is. However, as is the case with other next-generation
attempts at a nonaqueous lithium-air battery, relying on
batteries, there are several practical challenges that need to be
lithium hydroxide (LiOH) instead of lithium peroxide (Li2O2).
addressed before lithium-air batteries become a viable alterna-
With the addition of water and the use of lithium iodide as
tive to gasoline.
a ‘mediator’, their battery showed far less of the chemical
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tech front
reactions which can cause cells to die, making it far more
iodide, and changing the chemical makeup of the electrolyte,
stable after multiple charge and discharge cycles.
the researchers were able to reduce the ‘voltage gap’ between
By precisely engineering the structure of the electrode,
changing it to a highly porous form of graphene, adding lithium
charge and discharge to 0.2 volts. A small voltage gap equals
a more efficient battery—previous versions of a lithium-air battery have only managed to get the gap
down to 0.5–1.0 volts, whereas 0.2 volts
is closer to that of a Li-ion battery, and
equates to an energy efficiency of 93%.
The highly porous graphene
electrode also greatly increases the
capacity of the demonstrator, although
only at certain rates of charge and
discharge. Other issues that still have
to be addressed include finding a way
to protect the metal electrode so that it
doesn’t form spindly lithium metal fibers
known as dendrites, which can cause
batteries to explode if they grow too
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much and short-circuit the battery.
Additionally, the demonstrator can
only be cycled in pure oxygen, while
the air around us also contains carbon
dioxide, nitrogen and moisture, all
of which are generally harmful to the
metal electrode.
“There’s still a lot of work to do,”
said Liu. “But what we’ve seen here
suggests that there are ways to solve
these problems—maybe we’ve just got
to look at things a little differently.”
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Laser Micromachining
Grows Up
L
aser micro-machining (LMM) is an
attractive manufacturing process
due to its intrinsic machining characteristics such as such as noncontact processing and capabilities to
machine complex free-form surfaces
in a wide range of materials. That’s the
good news.
Nevertheless, state-of-the-art LMM
platforms still don’t offer the repeat-
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ability, reproducibility and operability of
conventional machining centers. That
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is to say they don’t yet offer the flexibility to realize complex
in LMM by creating the necessary prerequisites for achieving
machining configurations and also to combine LMM with
machining ARR better than ±10 μm. The entire paper is avail-
other complementary processes in hybrid manufacturing sys-
able at http://tinyurl.com/JMS-LaserMMS
tems and production lines. For these reasons, LMM isn’t yet
Tech Front is edited by Senior Editor Michael C. Anderson
considered a ‘mature’ process—unlike
rival processes such as micro milling.
Four researchers—Pavel Penchev,
Stefan Dimov, Debajyoti Bhaduri, and
Sein L. Soo—at University of Birmingham’s School of Mechanical Engineering (Birmingham, UK) have published
a paper in Volume 28 of the Journal of
Manufacturing Systems that offers to
bring maturity to LMM processes.
The paper, “Generic Integration
Tools for Reconfigurable Laser Micromachining Systems,” presents the
development of three generic integration tools for improving the system-level
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performance of reconfigurable LMM
platforms. In particular, the research
reports the design and implementation
of a modular workpiece holding device,
an automated workpiece setup routine
and automated strategy for multiaxis LMM machining employing rotary
stages.
An experimental validation of their
accuracy, repeatability and reproducibility (ARR) was performed on a representative state-of-art LMM platform.
The results demonstrate the flexibility
and operability of the proposed tools to
address important system-level issues
Tech Front welcomes your manufacturing
research-related news releases: Please
email them to Tech Front editor
Michael Anderson at [email protected].
SME’s authoritative peer-reviewed research
journals, Journal of Manufacturing
Processes, Journal of Manufacturing
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February 2016
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