LabNews 04/14/2006 — PDF (650KB)
Multiple electromagnetic qualification measurements have been performed at Sandia on two types of cruise missiles that carry the W80.
The measurements are part of the W80 Stockpile Lifetime Extension Program (SLEP). SLEP is an extensive qualification program to ensure that the W80 meets its operational and nuclear safety requirements in a wide range of environments.
The electromagnetic qualification program includes testing a refurbished W80 under a variety of electromagnetic conditions. These include simulations of friendly and hostile radio frequency transmitters, electromagnetic pulse, nearby and direct-strike lightning, accidental contact with electrical power lines, and electrostatic discharge.
The electromagnetic qualification program started by characterizing the behavior of the cruise missiles that carry the W80.
Project lead Matthew Higgins (1653) says it is important to characterize the payload bays and warhead interface cables of the Air Launched Cruise Missile (ALCM) and Advanced Cruise Missile (ACM) because the W80 spends time mounted in the cruise missiles for logistical operations and remains in the missile from carriage on a B-52 to launch and delivery.
“The transfer function measurements will help define further qualification tests in which W80-3 electrical systems will be tested,” he says.
W80 refers to the current stockpile weapon system. The W80-3 refers to the upgraded system being developed for the Stockpile Lifetime Extension Program. The measurements looked at electromagnetic leakage into the payload bays and interface cables of both missiles. The W80-3 shipping container has also been tested, and the W80-3 itself will be tested next.
The electromagnetic transfer function testing determines the leakage of electromagnetic energy into a test object. Using the external threat environments as defined in the W80 stockpile-to-target sequence, the exact amount of leakage can be calculated over a wide range of frequencies.
“With the cruise missile data, we can calculate the leakage into the W80-3 through the missile,” Matthew says. “While it might seem intuitive that a cruise missile would provide some protection, this is not necessarily the case. People tend to assume that metal structures provide sufficient shielding from electromagnetic environments. In reality, the metal structures typically have penetrations, such as control cables in a missile, and openings, such as engine inlets and outlets.”
In addition, cruise missiles have quite a few cables, which can act as antennas that can pick up energy at certain frequencies. Small details such as cable shield terminations can have a big impact on the leakage into an object.
Shielding effectiveness is measured to determine how much electromagnetic energy gets into the missile payload bays. To do this, Sandia engineers exposed the missile to electromagnetic radiation (EMR) over a wide range of frequencies and measured the electric field strength outside the missile and, simultaneously, inside the payload bay. The ratio of the field strength inside the payload bay versus outside the missile is described as shielding effectiveness. A well-shielded enclosure helps protect internal electronic packages from inadvertent malfunction or damage due to exterior EMR.
Energy can also couple into the missile cabling system, which can then create voltages on internal cable wires. In the right circumstances, this voltage can be delivered straight to the W80. To determine the degree of cable coupling, engineers expose the missile to EMR and measure the cable pin voltages. These types of measurements are called effective height, a quantity similar to the effective area of antennas. The less energy that couples into the missile cable, the lower the voltages induced inside the weapon.
The measurements of shielding effectiveness and effective height are carried out in two of Sandia’s RF facilities, the Electromagnetic Environments Simulator (EMES) in Tech Area 1 and the Mode-Stirred Chamber in Tech Area 4.
Low-frequency testing (100 kHz to 250 MHz) is performed at EMES and high-frequency (220 MHz to 40 GHz) is done in the Mode-Stirred Chamber. The two facilities are needed because of the wide range of frequencies required for weapon testing.
“It has been to our advantage that for weapon-related testing, both facilities are vault-type rooms,” says Matthew.
The Mode-Stirred Chamber is essentially a broadband microwave oven, where the fields are deliberately mixed to uniformly bathe a test object in electromagnetic fields. The advantage of this method is that every penetration in a test object will be exposed in a single test run. The disadvantage is that because all potential leakage points are exposed at once, it is difficult to know sometimes where the dominant leakage point is.
“We will find out if it ‘leaks’ and at what frequency, but we may not be able to say where it is leaking from,” Matthew says.
EMES is essentially a building-sized coaxial cable, called a transverse electromagnetic, or TEM cell. Like a coaxial cable, it has a center conductor and a return conductor surrounding it. At EMES, the center conductor is in the middle of the structure, 13 feet away from the return conductor at its highest point. While the Mode-Stirred Chamber bathes a test object in all directions, EMES produces a vertically polarized plane wave that travels the length of the cell like a two-dimensional sheet across a test object. To get a good characterization of a test object in EMES, it is usually desirable to make measurements of a test object rotated in several orthogonal orientations. The main advantages of EMES are its large size and the ability to test at frequencies all the way down to 0 Hz (DC static fields). -- Michael Padilla
By Neal Singer
Once again defying a world rampant with cost overruns and unmet deadlines, Sandia’s massive MESA project will hold a building dedication at 10:30 a.m., Friday, April 21, to celebrate the formal opening — on-time and on-budget — of its Microfab and Microlab facilities.
Senators Pete Domenici and Jeff Bingaman, Rep. Heather Wilson, NNSA Defense Programs head Tom D’Agostino, and Sandia President Tom Hunter are among those slated to attend.
The Microlab building, attached by a second-floor skywalk to Sandia’s Microelectronics Development Laboratory at the southeastern end of Tech Area 1, is possibly the most architecturally scenic building Sandia has yet built, as well as the most secure.
Ringed by closely spaced boulders to protect against vehicular security incidents and using for the most part only basic materials like cement, steel, and glass, the imaginative, esuriently design — with light coming in from external walls of glass and large skylights three stories above the building’s central corridor — is expected to encourage interactions among groups formerly separate in the Sandia work force.
These include microelectronics workers in both silicon and compound semiconductors as well as computer visualization researchers. The intent is to combine the expertise of the three groups to more quickly imagine and design better microelectronic devices. These, produced in the MESA facility itself, would improve US security and also produce designs and methods that later might be found suitable for the consumer needs of US industry, which could use commercial manufacturing plants to produce products in the large numbers needed to satisfy a mass market.
The MicroFab replaces Sandia’s aging Compound Semiconductor Research Laboratory. The new three-story facility is one of the most modern and complex buildings at Sandia and was the first of three new facilities that make up the MESA complex. Its structure includes sophisticated safety systems and controls because of the hazardous materials used in the production of compound semiconductors.
Still to be completed for the MESA project is the Weapons Integration Facility, expected to be structurally finished later this year and operational in FY 2008.
The Microsystems and Engineering Sciences Applications (MESA) construction project supports the NNSA Defense Programs mission for research, development, and simulation. Upon completion, MESA is expected to provide the essential facilities and equipment to enable the design, integration, and qualification of microsystem technologies for the nuclear weapons complex of the future.
There have been no increases to the total project cost, project schedule, or original scope objectives since the project was originally baselined in October 2002.
Leading the way are Mike Cieslak, MESA Program Director, and Bill Jenkins, MESA construction project manager. -- Neal Singer
By
Nancy Garcia
One of the newer researchers on site, Isabelle Chumfong (8114), gained a new perspective during a recent unique assignment in which she spent six months working with New York City’s Department of Health and Mental Hygiene (DOHMH) to develop an in-depth understanding of and contribute to the city’s bioterrorism response planning and preparedness efforts.
The goal of the collaboration was to develop better strategies for collecting information about the impact of bioterror agent releases in real time, to both support bio-defense systems studies for the Department of Homeland Security (DHS), which partially funded her participation, and to improve New York City’s response activities.
Isabelle first came to Sandia/California in the summer of 2003. She then completed a master’s in chemical engineering at Yale during a year on campus through Sandia’s University Programs. In May 2005 she returned to the East Coast for the temporary assignment, in which she spent three weeks each month in New York and one week in Livermore.
The Sandia-DOHMH team focused on improving methods and approaches for post-incident environmental sampling, which typically would be used to confirm and characterize a bioterror event. Air and surface samples are collected to understand if an actual release has occurred, examine the properties and viability of the agent released, and determine the extent of contamination and population exposure.
“It was really enlightening to be there,” she says, because her exposure to the real-world concerns in the public health department put into perspective some of the issues and priorities of end-users of Sandia research.
She got to see how decisions are made and goals overlap, for instance, with public health officials dedicated to preventing and treating illness and law enforcement being concerned about obtaining forensic evidence of a crime.
She visited areas of the city being considered for sampling, noting the possibility of operational complications due to urban grime and unfavorable weather conditions, as well as the potential reaction of passersby to hazardous materials teams suited up in protective gear, an eye-catching sight that would affect how potential threats are communicated to the public.
She says her New York colleagues’ special expertise is appreciated and they are called by other cities because they are ahead in planning responses to terrorist attacks. “New York City has actually been attacked,” she notes, “so the idea [that a bioterror attack] could happen is much more real to them.”
The preliminary study examined the city’s responsive architecture for bioterrorism events and proposed a methodology, based on modeling, for identifying promising sites for environmental sampling. These sites were chosen by analyzing an extensive set of agent release scenarios deemed most likely by New York City law enforcement and emergency management agencies. Initial conclusions from this work were recently presented to city officials, who were supportive of follow-on analysis and product development.
Part of the work involved modeling different hazard footprints based on different bioagent release scenarios using historical weather data, undertaken with Tony McDaniel (8367) and Todd West (8114). She says the archived footprint data set can be mined for other applications and the study method can be readily applied to other cities.
Collaborators in New Mexico, Gary Brown (6245) and John Brockmann (1517), carried out related experimental work, releasing simulated bioagents in test chambers to approximate the limits of sampling methods on various surfaces, which were then incorporated into the model.
Isabelle says she appreciated learning what day-to-day questions key decisionmakers need answered, based on their goals and responsibilities. The concept of sending someone to the city agency came about early last year in a Bay Area meeting of public health, law enforcement, and environmental officials who wanted to better understand the potential hazards of bioterror releases and how to gather information about them in real time. Decisionmakers at DOHMH were eager for assistance, having heard of Sandia’s initial modeling of plumes that might be generated from releases of a bioterrorism agent.
“Our studies for DHS are ultimately directed toward enhancing the preparedness and capabilities of end-users who are responsible for responding to emergencies,” says Isabelle’s manager, Susanna Gordon. “It is tremendously beneficial to work closely with agencies such as these to better understand needs and priorities that are paramount in creating effective operational plans and tools to deal with new threats, such as bioterrorism.”
Isabelle frequently visited New York City while attending college just 90 minutes away, she says, so it was appealing to spend several months there exploring the city as a resident. Flying back once a month helped maintain continuity with her project team and life here.
During her assignment, she sat in the department’s Bureau of Communicable Disease, in a section devoted to mitigating the consequences of bioterrorism. There she was able to interact with public and environmental health professionals, as well as the New York Police Department and the city’s Office of Emergency Management. -- Nancy Garcia