LabNews 07/08/2005 — PDF (650KB)
Materials
used
for
NASA’s
future
planetary
exploration
missions
are
being
put
to
the
test
at
Sandia
—
severe
heating
tests
that
is.
For the last two years, tests have been conducted at Sandia’s National Solar Thermal Test Facility to see how material can withstand severe radiant heating. The tests apply heat equivalent to 1,500 suns to spacecraft shields called Advanced Charring Ablators. The ablators protect spacecraft entering planetary atmospheres with significant radiation environments.
Under a Work for Others Agreement, researchers at Sandia and Applied Research Associates, Inc. are conducting the tests for NASA Marshall’s In-Space Propulsion/Aerocapture Program. The R&D effort is tied to NASA’s plan for a future Titan mission with an orbiter and lander. Titan is Saturn’s largest moon.
The
tests
are
led
by
Solar
Tower
expert
Cheryl
Ghanbari
(6218)
and
Bill
Congdon,
project
principal
investigator,
for
Applied
Research
Associates,
Inc.
The
tests
are
designed
to
simulate
atmospheric
heating
of
spacecraft
that
enter
Titan
—
heating
that
includes
low
levels
of
convective
heating
combined
with
relatively
high
levels
of
thermal
radiation.
The primary ablator material for the Titan mission will be low-density silicones and phenolics, all under 20 pounds per cubic foot density.
To date, more than 100 five-inch-diameter cylindrical samples have been tested to the solar environment inside the tower’s wind tunnel using a large quartz window. Congdon says because of Titan’s relatively high radiation environment, some initial concerns had to be put to rest through testing. He said radiation might penetrate in-depth within the ablator, causing an increased “apparent” thermal conductivity and degrading insulation performance.
“Radiation could also generate high-pressure gasses within the ablator leading to spallation,” Congdon says.
“We have been testing at Solar Tower to see how the candidate Titan materials can withstand the expected range of heating conditions,” Cheryl says. “Titan has a nitrogen-rich atmosphere and nitrogen is used in tests to similarly reduce ablator oxidation while energy from the sun-tracking heliostats is focused on the samples.”
Congdon
says
ground
tests
are
necessary
to
understand
and
model
surface
ablation
of
the
materials
that
will
be
severely
heated
during
Titan
entry.
During
thermal
radiation
testing
conducted
in
the
Solar
Tower
all
of
these
concerns
were
addressed
and
found
not
to
be
a
problem
for
the
ablators.
Shots of heat
The Solar Tower consists of an eight-acre field of 220 solar-collection heliostats and a 200-foot- tall tower that receives the collected energy at one of several test bays. A single heliostat contains 25 mirrors that are each four feet square. Total collection area of 220 heliostats is 88,000-square feet. Since the heliostats are individually computer controlled, test radiation can be a shaped pulse as well as a square wave in terms of intensity vs. time.
Test samples are mounted high in the receiver tower, and the heliostats direct the sunlight upward to irradiate the sample surface. The samples are mounted in a water-cooled copper plate inside the wind tunnel with a quartz window that allows entry of the reflected radiation. Exposure is controlled by a fast-moving shutter and by pre-programmed heliostat movement. Radiation flux is calibrated before and after each test by a radiometer installed to occupy the same position as the test sample. Cooling effects from imposed surface flows are calibrated via a flat-plate slug calorimeter.
The materials are subject to square pulse environments at flux levels of 100 and 150 W/cm2 for time periods that far exceed predicted flight durations for such high heating. They are also subjected to “exact” flux vs. time environments (simulating actual flight conditions) using programmed heliostat focusing at the Solar
Tower facility.
The material samples are installed in the Tower’s wind tunnel and exposed to the solar beam at flux levels up to 150 W/cm2, which is approximately 1,500 times the intensity of the sun on earth on a clear day. During the exposure, air blows past the sample at about mach 0.3, and below this, the sample is immersed in a high-speed nitrogen layer.
Cheryl says tests can be conducted only during about four hours midday bracketing solar noon. Haze, clouds, and high winds that affect the heliostats can degrade test conditions.
Current results
“All of the candidate materials showed no spallation and very good thermal performance to these imposed environments,” Congdon says. Recently, five 12-inch by 12-inch panel samples were tested on top of the tower. Up to 20 additional 12-inch panels will be tested late in the summer followed by testing of 2-foot by 2-foot panels later in the year.
Additional tests for convective heating have been conducted on identical material samples at the Interaction Heating Facility (IHF) at NASA’s Ames Research Center. -- Michael Padilla
By Neal Singer
Sandia
has
purchased
a
4,096-node
Dell
high-performance
computer
cluster,
called
Thunderbird,
that
will
provide
more
than
8,000
processors
of
compute
capacity
to
meet
the
laboratory’s
high
demand
for
cluster
computing.
The
aggregated
capacity
of
the
computer
will
have
approximately
24
terabytes
memory
and
60
tera-OPS
(trillion
operations
per
second)
speed.
Sandia, with Dell Professional Services and Albuquerque’s Technology Integration Group, will install the system at Sandia’s Central Computing Facility in Albuquerque. Delivery of Thunderbird should be completed by the end of July and integration and testing will occur over the next several months. The system is expected to be fully operational in early October.
Thunderbird is Sandia’s second installment of an institutionally maintained cluster. Sandia’s first institutional cluster was installed October 2003 and provides approximately seven tera-OPS of capacity to the laboratory.
“Our first institutional cluster was an important investment for the lab, but it has been fully utilized from the first day it was installed,” says Ken Washington, CIO and director of Sandia’s Information Systems and Services Program. “Thunderbird will make a huge impact by more than quadrupling our institutional capacity. The increase allows the Labs to meet a significant fraction of previously unmet institutional capacity computing requirements in one fell swoop.”
Thunderbird is referred to as a capacity cluster because it is ideally suited to perform many mid-sized tasks with extreme rapidity, rather than one huge task across its entire system like Sandia’s highly customized and tightly coupled Red Storm supercompter.
Thunderbird consists of 4,096 Dell PowerEdge 1850 servers, each equipped with two Intel 64-bit (EM64T) processors, for a total of more than 8,000 processors.
A high-performance Infiniband interconnect from Cisco was chosen because it scales more linearly than most proprietary technologies for building large clusters — an important consideration in assembling a large number of processors. Lower cost was another factor in Sandia’s selection of this widely used interconnect.
The procurement also includes a smaller 128-node developmental cluster to be installed in the Distributed Information Systems Lab at Sandia’s California site. It will enable Sandia to develop and test system software solutions required to successfully integrate and deploy Thunderbird for production use.
“Thunderbird makes important strategic connections between Sandia, Dell, and other vendors,” says Bill Camp, director of Sandia’s Computation, Computers, Information and Mathematics Center. “Our purchase opens a venue to them in high-performance cluster computing. Together we will break new ground by deploying a cluster with commodity processors and an lnfiniband interconnect at the scale of thousands of processors.”
“Sandia has been a leader in putting Infiniband on the high-performance computing map,” Ken Washington says. “It is only natural that we be the place where such a large Infiniband cluster is first realized for meeting an institutional computing requirement.”
“Specific
thanks,”
says
John
Zepper
(9320),
“go
to
Facilities
for
power
and
cooling
modifications,
Purchasing
for
rapid
JIT
placement
of
the
order;
for
technical
contributions,
Matt
Leininger
(8961),
Geoff
McGirt,
Carl
Leishman,
and
Kevin
Kelsey
(all
9324),
David
Martinez
and
Archie
Gibson
(9335),
Chris
Maestas
(9326),
Josh
England
(8963),
Sean
Taylor
(9328),
Jerry
Friesen
(8963),
and
Rob
Leland
(9300),
Jim
Ang
(9224),
and
Art
Hale
(9900).
“Expanded
capacity
computing
will
deliver
on
the
modeling
and
simulation
vision
for
the
Sandia
community,”
says
John.
Both the Ethernet Input/Output and the command and control of the Thunderbird cluster are based on the Force 10 E-Series switch/routers. The Force 10 E1200, which supports 1,260 gigabit Ethernet ports, offers the industry’s leading gigabit and 10-gigabit port density — providing the scalable performance required to support the largest cluster computers in deployment. -- Neal Singer
By Erin Gardner
In
October
2005,
libraries
all
over
the
world
will
view
a
revised
cataloging
tag
that
will
broaden
the
scope
for
cataloging
classified
or
restricted
documents.
The newly revised 583 action tag will be published in the MARC 21 Bibliographic Format, October 2005 Edition. What the librarians who receive this reference tool and catalog materials according to MAchine Readable Cataloging (MARC) may not realize is that three Library staff members from Sandia’s Technical Library persevered to create this change.
Teresa Gilbert, Jennifer Miller, and Jessica Shaffer-Gant (all 9536) are the influences behind the changes to this tag, which can now be used to record report classification changes or reviews.
Previously, there was no appropriate MARC tag to record historical classification information. With the new modification to the 583 action tag, catalogers will be able to maintain records of these restriction changes, downgrades, upgrades, reviews, etc.; the authorization; date; and other pertinent information.
In October 2003, during sessions to discuss cataloging procedures of classified reports, conflicting opinions arose about how to record historical classification actions. Jennifer, who was team leader of the Technical Library’s Cataloging Operations, decided to look to the Library of Congress (LC) for guidance.
LC
asked
for
Sandia’s
input,
and
Teresa,
Jennifer,
and
Jessica
wrote
a
proposal
to
create
a
new
MARC
tag.
They
submitted
the
proposal
in
spring
2004.
After
review,
LC
suggested
modification
to
an
existing
tag.
The
Technical
Library
trio
drafted
a
new
proposal
in
May
of
this
year.
They
gave
examples
of
potential
uses
for
the
revised
tag
for
special
libraries
as
well
as
traditional
libraries,
globally.
Within two weeks the Library of Congress accepted the proposal.
“I’m really pleased that we could make an impact by teaming with the Library of Congress,” says Jennifer.
The Technical Library has already started implementing the revised tag into its internal procedures.
“We resolved an issue rather than having to work around it,” says Teresa. “Hopefully this change will be as useful to other libraries as it will be for us.”
“Its really exciting that our hard work paid off,” says Jennifer. -- Erin Gardner
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