LabNews 06/23/2006 — PDF (650KB)
By Neal Singer
Airplane travelers addicted to worry sometimes fret about an engine failing or a wing falling off, but they rarely stress about wiring. But they might — if they knew there are miles of aging wiring, intertwined like spaghetti, behind the side panels of a commercial airliner’s fuselage. An intermittent electrical short due to frayed insulation can make lights blink or air conditioning falter, or even cause fatal crashes, as with flights SwissAir 111 or TWA 800.
The challenge to engineers is how to locate a wiring fault before — not after — it becomes a problem. That’s quite a trick. Sandia researchers believe they have helped achieve a solution.
The newly patented method — called PASD, for Pulse Arrested Spark Discharge — relies on a Sandia specialty called pulsed power, developed over decades of research. Usually the public thinks of this research — if it thinks of it at all — in terms of Sandia’s massive Z machine, which sends great bursts of electrical current down conduits as big around as a horse’s girth.
But the PASD device in its experimental state was only the size of a small refrigerator.
Now, licensed in late April to Astronics Advanced Electronic Systems of Redmond, Wash., and combined with that company’s other patented test methods, it’s the size of a small suitcase. It can be plugged into aircraft-installed wire harnesses, 40 wires at a time, to check them for the very small insulation breaks associated with intermittent faults.
These sporadic short circuits occur where two exposed conductors, or a conductor and aircraft frame, make temporary contact during flight. Vibrations caused by turbulence may cause wires to touch, interrupting power to sensitive electronics and possibly damaging wires. These conditions are tricky to diagnose when the aircraft is on the ground because the shorting wires often will have shifted back to a non-shorted state. Sometimes these breaks can barely be seen by the naked eye because missing insulation may be the size of a pinhole, or nearly invisible like a fine cut from a razor blade. Traditional wire-test systems have great difficulty finding these faults.
Location method simple
PASD locates faults by a method simple to understand at its basis.
What Sandia has done, under project lead Larry Schneider (1650), is send a high-voltage pulse down the wire. The pulse is very brief (nanoseconds — a nanosecond is a billionth of a second) so the energy is very low.
The situation is analogous to a waterfall — very high, higher even than Niagara Falls — with only a trickle of water going over it, and even the trickle lasting for only a fraction of a second. Water will certainly fall far and fast, but the tiny amount arriving at the bottom will cause only a tiny splash — not enough to do damage.
But because the voltage is so high, the little bit of harmless energy will jump like a rabbit from the smallest insulation break to the bulkhead or to another nearby damaged wire. That jump — like static electricity leaping from hand to doorknob — in effect lights up the damaged spot like a tracer bullet at night lights up on its trajectory to a target. The amount of time it takes for the current to return to its source is analyzed by the automated test-set to tell within inches how far the break is from the test entry point.
The simple method should make it financially feasible for airlines to quickly diagnose and locate intermittent faults that have plagued the industry and cost millions of dollars in lost revenue due to aircraft downtime.
Is the technique in reality more complicated than that? You bet. That’s why the National Nuclear Security Administration and the US Navy supported the research, followed by the Federal Aviation Administration, to the tune of about $2 million. It’s why it took two years for Astronics to adapt it to its suite of tools, called (fittingly) ArcSafe, a method developed over four years of research to locate wire breaches with the potential for electrical shorting. ArcSafe is expected, by the way, to be on the market by September.
“Rather than ripping apart the fuselage for access to a faulty harness that may run the length of the plane, airline mechanics will be able to use this new tool to efficiently locate and repair the fault,” says Larry.
Says Astronics team leader Mike Ballas, "We really value PASD technology. We licensed it, turned it into a practical portable test unit targeted for the aviation industry to find intermittent faults, and we believe it’s the best way now to do the job. It’s a nice complement to our patented technology.”
Says Robert Pappas, the Federal Aviation Administration’s project manager for aging aircraft research and the first to recognize the value of Sandia’s original research proposal in 1998, “It would have been unfortunate if PASD had been developed and then remained stuck in a lab. Integration of the technique [with those of Astronics’ ArcSafe] is a real success story.”
Faults detected early
“Rather than reacting to a problem, these systems can find a fault before it manifests into a catastrophic event,” says Larry, who predicts PASD will one day become a final test for the wiring harnesses of passenger cars and new homes, as well as for military tanks and the hard-to-reach wiring behind the steel bulkheads of submarines.
There’ll be problems, just the same, in getting the method accepted, says Mike Walz, current FAA overseer of the project. For one thing, he says, “What PASD looks like is an electrostatic discharge [ESD] — something aircraft manufacturers work hard to keep out of their wiring system.”
One researcher responds with humor, “PASD is a little like homeopathy: Uncontrolled ESD can kill you, but a little bit can help cure you.” (Homeopathy holds that dangerous material, extremely diluted in solution, can be helpful in healing.)
Other problems involve the varying resistance of wires over long distances, called electrical impedance, particularly in the branched wiring systems prevalent in aircraft. This was a problem for earlier versions of ArcSafe, which used a DC current to detect breaks. Varying impedance meant it was difficult to accurately locate an intermittent fault, since electrical return signals were inconsistent, especially on complex wire geometries. Still, the DC method is most effective for identifying ordinary faults and has been retained for quick fault screening. To enhance its fault-locating ability, a new Astronics method allows the PASD pulse to ride upon the DC current like a rider on a horse. The DC current provides support for the high-voltage pulse, which then can be effective even a hundred feet from its starting point in accurately locating critical breaches in wire insulators, even those occurring on branched wire harnesses. The distance to a fault is computable, regardless of changes in impedance produced by the wiring as it reacts to the PASD pulse at various voltage levels.
Insulation defects hard to find
“Wiring insulation grown defective over time can cause malfunctions or even fires, but is devilishly hard to spot and even harder [once spotted,] to [exactly] locate,” says Larry. “Other methods have faltered when confronted with the varying impedances of bundles of wires, or the difficulty of providing the exact location of the defect as wiring bundles branch into other bundles. This nondestructive, inexpensive method not only detects cracking or pinholes but also is able to pinpoint the defect’s precise location to facilitate wire replacement.”
The actual location of the defect may require examining several possible branches since the same distance-to-short may exist along several paths, but the problem is minor compared with the alternative.
The hybridized system is an improvement be-cause of its greater robustness on complex systems.
The technique probably would be best used to check those wiring subsystems that are known problem areas, says Larry. To check all the wiring in a plane might take several days.
Involved in the project over the years for Sandia have been Mike Dinallo, Steve Glover, and Gary Pena (all 1654), Kevin Howard (1653), Tom Lockner (5445), and John Barnum (6452).
“We’re advertising the system now and we’d love to take orders,” Mike Ballas says. -- Neal Singer
Related story: Researchers apply energy surety to military bases |
With concerns that energy use will rapidly increase over the next several years while fossil fuels diminish, Sandia is looking at a new way to meet growing energy challenges — energy surety.
“We have taken our surety know-how and applied it to energy,” says Rush Robinett, senior manager of the Energy and Infrastructure Futures Group 6210. “By doing this we are looking at what energy practices can best answer our current needs while not making compromises for future generations.”
Rush, together with Margie Tatro, director of Energy, Infrastructure & Knowledge Systems Center 6200, and others in the center designed the new model and detailed it in a recently-released SAND report, Toward an Energy Surety Future.
Energy surety takes an integrated approach to achieving safety, security, reliability, recoverability, and sustainability objectives for the nation’s civilian and military energy systems. Patterned after Sandia’s many decades of applying surety principles to weapon systems, the approach includes choosing the best mix of fuels and applying conservation principles to all steps, starting with energy production and ending with final use, even using what would normally be characterized as waste heat and mass.
Margie notes that in developing the energy surety approach, “the sustainability model was the most difficult to create because sustainability was not a system requirement in the original weapons system surety approach.”
The energy surety approach is part of Sandia’s effort to support DOE’s National Energy Policy goals, which include diversifying the country’s energy mix and reducing dependence on foreign petroleum; reducing greenhouse gas emissions and other environmental impacts; creating a more flexible, more reliable, and higher-capacity US energy infrastructure; and improving efficiency and productivity.
For the past 100 years this country has been largely dependent on liquid fossil fuels — especially petroleum — for transportation, electricity, and even food production.
Lack of energy isn’t the problem
Today, with the price of oil becoming unpredictable, together with increased energy consumption worldwide — particularly in China and India — and oil being concentrated in volatile countries, it’s time to manage our fuels better, Rush says.
“Energy is all around us — just look at the power of hurricanes and tsunamis,” Rush adds. “It’s not the lack of energy that’s the problem, it’s a knowledge shortage of how to manage and harness that energy. We believe the energy surety approach is the best way to do this. If we don’t follow this model, the whole world, including the US, could find itself living a lifestyle of the Third World.”
The SAND report outlines a three-step strategy for moving toward better matching of energy resources with energy needs.
The first step is to squeeze every unit of available energy from the current supplies. This goes beyond the implementation of higher-efficiency electricity-consuming devices (lighting, appliances, and motors) and vehicles (diesels and hybrids) to include waste-to-energy options such as the extraction of methane from landfills and the conversion of biomass wastes to liquid fuels. Making better use of limited fossil supplies will allow the country to “buy time” while it moves down the path towards energy surety, Margie says.
Holding the world’s population to a level that the earth can sustain and capping energy demand at some point are also parts of Step 1. To address demand, consumer needs for energy must be reduced. The traditional view of an expanding world population and economy must level off or it could surge to the point of “resource exhaustion, social upheaval, disease epidemic, and then collapse,” notes the SAND report. An ultimate plan must have some commitment to hold growing populations in check.
A final part of the initial step is to limit the use of fossil fuel resources — although the magnitude of potentially recoverable fossil fuels may never be known. Conservation must be a major part of the surety plan.
Storing energy a critical component
The second step involves storing energy for later use when there is no wind, the sun is obscured, or an energy supply is disrupted. Currently, energy storage techniques are used in limited ways, ranging from battery-powered units to managing brief interruptions to the Strategic Petroleum Reserve. Examples that could provide expanded energy storage include solar production of hydrogen for fuel cells, solar-powered conversion of carbon dioxide and water to liquid fuels, and energy storage from solar thermal collectors.
Step 3 is to learn how to reproduce the sun’s fusion process on earth in a safe, secure, reliable, and sustainable way. “Though we do not know if fusion can succeed as a practical terrestrial energy source, we believe that its promise is worth extensive investment,” the SAND report says.
“While it might not be possible to fully accomplish all the goals in the energy surety model, striving toward them is far better than blindly marching toward energy depletion, environmental exhaustion, and esthetic despair, only to discover that the scarce remaining resources are inadequate to meet needs,” Rush says. “The big question now is how to make this happen in the real world. The driver may very well be people’s pocketbooks, caused by highly unpredictable fuel prices, coupled with increasing threats of terrorism.”
A Sandia research team headed by Dave Menicucci (6217) has taken a Labs-developed energy surety model to a tangible level by applying it to military bases.
The team, working with the US Army, is looking at how military bases can improve energy generation and transmission through a new system called the Energy Surety Microgrid.
“In today’s grid system, power generators [coal, nuclear, gas] are located far from the load — the place where people live, work, and use power,” Dave says. “This requires much distributed wiring and has a potential for power disruption.”
What the microgrid team envisions for military bases is an energy surety system that uses more small generation units and storage near the load and less generation at big plants. It can operate with or without the grid. In addition to being smaller, the power generators would integrate a diversified fuel mix, include secure on-site fuel storage, and apply sustainable technology, such as renewable energy.
Rush Robinett, senior manager of the Energy and Infrastructures Futures Group 6210, says this model is “like back to the future.”
“Military bases used to comanufacture energy in the same area as is proposed here,” he says. “Now most are totally dependent on the grid for power.”
Funding for the project comes from the US Army and the internal Sandia Laboratory Directed Research and Development (LDRD) program.
Energy systems with high levels of energy surety must be safe — safely supplying energy to end users; secure — using diversified energy sources; reliable — maintaining power when and where needed; sustainable — being able to be maintained indefinitely (“indefinite” is based on the American Indian definition of seven generations or 200 years); and cost-effective — producing energy at an acceptable (and preferably lowest) cost.
Dave says the current grid system meets some of these criteria, while the proposed microgrid system for military bases would meet all.
“The existing [grid] system is generally safe and secure,” Dave says. “The generation and storage are reliable. The problem comes from the fact that generators are far away from people and the power has to be transmitted through thousands of miles of lines.”
If any of these lines go down, either through an act of nature or terrorism, power will be disrupted and the country’s national security could be threatened.
Dave also asserts that current generation methods are not sustainable.
“It’s not that we are running out of oil and coal, it’s that we can’t predict the cost, implying that we can’t afford it,” he says. “The demand for more fuel from China and India are driving prices up. There are also limits to where we can drill.”
While the cost-effectiveness of the current generation system is OK, Dave anticipates it may not stay that way for long.
The team believes the solution is what they are researching for Army bases across the country — a microgrid that reduces the single points of failure by cutting down the number of transmission lines.
In looking at the five criteria of an energy surety approach, the microgrid meets all. It is safe — it’s not introducing any new dangers. It’s secure because it uses a diverse mix of fuels — solar, wind, and oil. It’s reliable because it uses a variety of types of generators. There is a redundancy of generation and storage. It’s sustainable because it is using renewable energies. And, it is cost-effective because it uses energy sources that are readily available and appropriate for the site. (An example is that solar could be used in the Southwest and wind along the nation’s coastlines.)
Dave says there are two reasons Sandia paired with the Army in planning microgrid systems at military bases. Sandia is a national security laboratory and the team members, most of whom have been in the armed forces, understand how the military operates.
The research team is now working with the Army to develop an energy surety microgrid for a soon-to-be selected military base. They are resolving such issues as where to put the smaller generators, how much storage is needed, and microgrid control.
Next spring a test military base will be determined, and a microgrid system will be installed and tested.
“The ultimate goal is to have microgrids at all military bases in the country and eventually in civilian communities,” Dave says. -- Chris Burroughs
By
Nancy Garcia
Loss of traditional foam sources akin to removing lumber from housing industry, says surf sage
When the main manufacturer of blanks used for surfboard construction, Clark Foam, closed shop last year, the nation’s $200 million surfboard manufacturing market appeared headed for a wipeout.
Hearing the news, LeRoy Whinnery (8778), who describes himself as “a warm-water surfer” (as opposed to his wife, whom he says “will surf anywhere”), believed he just might have a solution — a foam initially developed to protect sensitive equipment from harsh mechanical environments, TufFoam™.
Now two licensees are evaluating the Sandia-developed foam for this use and scores of inquiries are being explored about this field and other uses, including insulation and structural core applications.
The material is a water-blown close-cell rigid polyurethane foam that features formulations with densities as low as 2 pounds per cubic foot.
News of TufFoam being considered as a potential replacement for surfboard manufacturing spread rapidly through news agencies, television, magazines, newspapers, and trade journals since the licensing opportunity was announced in February.
“It can be used for thermal and electrical insulation, and potentially as a core material for the automobile and aerospace industries,” says Scott Vaupen, who began the commercialization effort in Business Development Support Dept. 8529, where Jim Wilhelm is now handling TufFoam agreements and inquiries. Jim points out the material is unique in its ability to withstand high-rate impact without fracture or loss of structural integrity. In addition, it’s also being considered for use as industrial thermal insulation for liquefied natural gas storage tanks.
Clark Foam closed its doors suddenly late last year, citing the impact of ever-tightening environmental regulations on the manufacturing of their polyurethane surfboard blanks. The move led to near-panic, particularly in California, by manufacturers and sellers of surfboards who fear they will not be able to find the high strength-to-weight ratio surfboard blanks necessary to make the boards. Surf historian Matt Warshaw, in an article in the Santa Barbara News-Press, said “it’s the equivalent of removing lumber from the housing industry.”
Largely due to its low density, Sandia’s TufFoam might very well fit the bill as a drop-in replacement material. A key feature of TufFoam is that it does not contain toluene diisocyanate (TDI), the chemical used in the production of the polyurethane foam surfboard blanks that is most problematic with respect to environment regulations. Another attractive feature of the Sandia product is that all of the chemicals used to make TufFoam are commercially available in commodity quantities. The material is currently formulated to be processed in a batch mode, but the processing schedule can be modified for machine mixing or injection molding.
So, will a foam developed for America’s nuclear weapons program save the American surfboard industry? Maybe. Leroy hopes so.
“Yeah, I’m really looking forward to surfing on a TufFoam board,” he says. “That would be pretty awesome.” -- Nancy Garcia