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 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.”
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
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.
“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.”
“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.
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