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SANDIA LAB NEWS

Lab News -- August 5, 2005

August 5 , 2005

LabNews 08/05/2005PDF (650KB)

Back in space: Sandia assists with NASA Discovery return-to-flight projects

By Michael Padilla

Several Sandia projects have been instrumental in helping NASA with its Space Shuttle Discovery’s return-to-flight mission (STS-114). Discovery has been in orbit on its two-week mission since its successful launch last week (July 26), temporarily ending the hiatus on space shuttle flights caused by the Columbia disaster in 2003.

Sandia’s projects range from creating an orbiter inspection sensor, to analyzing sensors placed on the orbiter’s wing leading edges, to providing peer review reports. Sandia also studied the vibrations caused during the rollout of the space vehicle and developed an ultrasonic nondestructive inspection method.

Sandia was instrumental in analyzing the cause of the accident that destroyed the Columbia during reentry on Feb. 1, 2003. A Labs-wide team effort helped confirm that the accident was caused by foam from the external tank that impacted the wing leading edge on takeoff (Lab News, Sept. 5, 2003).

Orbiter inspection sensor

Sandia provided the primary Thermal Protection System (TPS) inspection system to NASA for the mission of the space shuttle Discovery, successfully launched on July 26 after a long hiatus due to the 2003 Columbia disaster.

Bob Habbit and Bob Nellums (both 2624) led a collaborative effort of nearly 120 Sandians in creating the sensor. Many of the team members worked nights and weekends to meet NASA’s critical need to return to flight ASAP in support of the International Space Station.

Using 3-D imaging, the sensor inspected the orbiter for critical damage to alert astronauts if further investigations are needed to repair the damage. The crew used the orbiter’s robotic arm to scan the front edge of both wings for damage as little as a 0.02-inch crack.

The Sandia-patented 3-D technology uses a modulated laser illuminator coupled with a modulated receiver to image and spatially locate each point in the scene. The intensity data is used to detect damage and the geometric data to assess the damage criticality.

The sensor data was relayed back to the Mission Control Center at Johnson Space Center in Houston. A team of more than 20 Sandians working in the Mission Control Center processed and reviewed the data. The processed data were provided to the NASA Mission Management Team. The Mission Management Team used the Sandia data as well as other data to determine if it is safe for the Orbiter to re-enter.

Bob Habbit said he is proud to be part of the mission. “It’s exciting to be a contributor to the space program,” he says. “This is truly Sandia providing a service to the nation.”

Inspection hardware

NASA funded a Sandia team to develop an ultrasonic nondestructive inspection method (hardware, techniques, and standards) that led to a scientifically rigorous pre-flight shuttle certification process. The team investigated and proposed ways to improve nondestructive inspection methods for certifying the flightworthiness of orbiter wing leading edges (Lab News, March 19, 2004).

The team, led by Dennis Roach and Phil Walkington (both 6252), initially evaluated and refined their inspection methods and hardware using carbon-composite samples with known defects created by the Sandia team. Later, as part of the selection process, a NASA engineer hand-carried orbiter wing samples to all the labs involved in the project and asked that each lab try to find defects known only to NASA
scientists.

The team developed the revised inspection and certification protocols, and the ultrasonic scanning system was integrated into NASA’s Shuttle Orbiter Processing Facility at Kennedy Space Center to monitor the health of the shuttle after each orbiter flight.

Sandia produced an in-situ ultrasonic inspection method while NASA Langley developed the eddy current and thermographic techniques. These groups were the primary players on the NASA In-Situ NDI Team. The NASA In-Situ NDI Team consisted of members from all of the NASA facilities and was assembled to guide NASA as it moves to increased use of advanced nondestructive testing techniques to closely monitor the health of the space shuttle.

In 10 months the Sandia team developed and assembled customized hardware to produce an ultrasonic scanner system that can meet the shuttle wing inspection requirements. Optimum combinations of custom ultrasonic probes and data analysis were merged with the inspection procedures needed to properly survey the heat shield panels. System features were introduced to minimize the potential for human factors errors in identifying and locating the flaws. A validation process, including blind inspections monitored by NASA officials, demonstrated the ability of these inspection systems to meet the accuracy, sensitivity, and reliability requirements.

Team members are Phil, Dennis, Kirk Rackow, and Dick Perry (all 6252). The NASA project manager was Ajay Koshti at Johnson Space Center.

Sensor tests

David Crawford (9116) and Kenneth Gwinn (9126) analyzed tests conducted on sensors that were placed on the leading edge of the orbiter’s wings (Lab News, Feb. 4).

The project focused on validating forcing functions for NASA’s Impact Penetration Sensing system (IPSS) Wing Model. The model was developed at Boeing to predict the accelerometer data collected during ascent and micrometeoroid/orbiting debris (MMOD) impacts on shuttle wing and spar leading-edge materials.
The sensors developed by NASA are significant to the return-to-flight effort. The addition of the sensors to the leading edge was in response to one of the prime objectives identified by the Columbia Accident Investigation Board.

David and Kenneth evaluated test data and were comparing it with structural models of the shuttle and assessing what the signal levels mean. Tasks included defining the forcing functions for foam, pieces of ice (from takeoff), ablator particles, and micrometeorites. Full-scale tests of foam, ice, ablator, metal particle, and MMOD impacts were performed at Southwest Research Institute in San Antonio, Texas. Tests on fiberglass and RCC (reinforced carbon composite) wing panels were conducted at the White Sands Test Facility.

Peer reviews

Members of Sandia’s Aerosciences and Compressible Fluid Mechanics Dept. 9115 contributed two peer reviews on NASA’s development of computational tools that are being used to support rapid damage assessments should anything occur during future flights.

Basil Hassan, manager of Dept. 9115, serves as an external member of NASA’s Engineering and Safety Center’s (NESC) Flight Sciences “Super Problem Resolution Team” (SPRT). NESC was formed shortly after the Columbia accident to oversee any safety issues that might arise in any of NASA’s flight programs.
Basil and two staff members, David Kuntz and Jeffrey Payne (both 9115), participated in several peer reviews as NASA prepared for return-to-flight. They were also part of a larger group of Sandia management and staff who were active in the post-accident investigation.

Two recent reviews focused on Debris Transport Review and Boundary Layer Transition Review.

Debris Transport Review focused on NASA’s development of tools to model external tank foam or ice buildup that may come off during ascent and potentially hit the orbiter. While several efforts have been under way to minimize foam and ice release from the external tank, NASA wants to predict if the released debris will impact the orbiter in critical areas. NASA has used these tools to redesign parts of the external tank so that catastrophes like the Columbia accident will not re-occur.

Boundary Layer Transition Review focused on reentry. During the reentry trajectory the airflow around the orbiter will transition from laminar to turbulent flow. When the flow becomes turbulent, the heat transfer to the vehicle can increase two to four times above the laminar heating. While the thermal protection system (TPS) is designed to absorb the heating rates generated by turbulent flow, damage to the TPS could cause the flow to become turbulent at a higher altitude. The result of this damage could mean higher localized heating rates on the TPS, and ultimately higher than normal integrated heating on the orbiter during reentry.

“Sandia’s participation on these two reviews teams is a one part of a larger effort of the Labs supporting a variety of return-to-flight activities,” Basil says. “We expect additional requests to tap into many of Sandia’s unique capabilities.”

Basil, David, and Jeffrey also reviewed NASA’s rapid damage assessment tools to help the agency ensure that the codes were being applied appropriately and that the relevant assumptions in the codes were not being violated. In general, these tools make use of data from computer codes that model the fundamental physics, wind tunnel test data, and data from previous shuttle flights. Should it be found in orbit that damage occurred during the ascent stage, NASA engineers will use these tools to decide whether the orbiter can safely return or if some in-orbit repair is needed.

Shuttle rollout

To help understand the fatigue caused by vibrations during the rollout, NASA contacted Sandia to assist with a series of tests (Lab News, April 1).
Sandia helped NASA design the test and instrumentation to measure the dynamic vibration environment of the rollout. Sandia also provided additional support to NASA by computing the input forces that the crawler applies to the MLP, which are being used by Boeing and NASA to compute the fatigue life for critical shuttle components.

Tom Carne (9124) assisted with a series of tests beginning in November 2003 to develop the data necessary to understand the environment and the response of the space shuttle vehicle during rollout.

Moving the shuttle from the Vehicle Assembly Building at Kennedy Space Center in Florida to the launch normally takes five to six hours at 0.9 mph. As the equipment ages, emphasis is being given to understanding how the rollout may fatigue the orbiter.

The analyses showed that modifying the speed of the crawler would reduce the fatigue stresses of the critical shuttle components. Merely reducing the speed from 0.9 mph to 0.8 mph would significantly reduce the vibrations in the shuttle by shifting the engagement frequency of the crawler treads. The shuttle’s vibration response can be much reduced when the driving frequencies are shifted away from its own resonant natural frequencies. -- Michael Padilla
John German also contributed to this story.

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Two Sandia microChemLab technologies soon to search for toxins in nation’s water supplies

By Chris Burroughs

Two Sandia technologies, both based on microChemLab, are expected to soon be checking for toxins and harmful bacteria in the nation’s water supplies.

The microChemLab, officially called µChemLab, is a hand-held “chemistry laboratory.” The liquid prototype was designed and built at Sandia/California, while the µChemLab that takes measurements in the gas phase was developed at Sandia/New Mexico.

The µChemLab, electronics, and sample collector weigh about 25 pounds and fit into a box the size of a small suitcase. The only external parts of the two sensor technologies are water collectors. The units are completely portable.

“Our goal is to place these sensors within utility water systems and use them to quickly determine if the water contains harmful bacteria and toxins,” says Wayne Einfeld (6245), who heads the Sensor Development Focus Area within Sandia’s Water Initiative (www.sandia.gov/water). “This on-site monitoring approach would replace current utility monitoring systems that require water samples to be sent to laboratories for analysis, which sometimes takes days for results.”
The United States has more than 300,000 public supply water wells, 55,000 utilities, 120,000 transient systems at rest stops or campgrounds, and tens of millions of hydrants. Up until now, real-time, remote water quality monitoring for toxins has been very limited.

The liquid µChemLab is currently being tested at the Contra Costa (Calif.) Water Utility, says Jay West (8324), California principal investigator. Specifically, the team is testing to determine the steps necessary to identify toxins in drinking water, as well as expanding its capabilities as an autonomous monitor. The device is presently collecting and analyzing a water sample every 30 minutes and reporting results via a real-time data link to researchers at Sandia.
CRADA partners have long experience

Sandia’s cooperative research and development agreement (CRADA) partners in the California endeavor are CH2M Hill, a leading US engineering firm, and Tenix, an Australian engineering services company. CH2M Hill is a global engineering and construction management firm with particular expertise in sewer and wastewater treatment design. Tenix is an engineering services and technology company with more than 30 years’ experience in water supply, sewerage and drainage infrastrucure, and defense.

The California µChemLab identifies proteins by separating samples into distinct bands in seconds to minutes. Separations occur in channels as narrow as a human hair coiled onto a glass chip about the size of a nickel.

Curt Mowry (1764), principal investigator for the New Mexico project, says his team is seeking to develop a device that detects trihalomethanes, undesirable byproducts of the chlorination process used to control the bacterial content of water. Trihalomethanes, which form naturally when surface water is treated with chlorine, are highly carcinogenic and can have adverse liver and kidney effects. The New Mexico project is funded through Laboratory Directed Research and Development (LDRD) resources allocated through Sandia’s Water Initiative.

“The EPA has regulations for water utilities to monitor for trihalomethanes on a regular schedule,” Curt says. “Currently they have to collect samples and send them to labs for analysis. They get numbers back a few days later. This is a scary thing for us as consumers. The way it’s done now, chemists might have measured high levels and there is chance someone has already consumed the water before the results return. Using the µChemLab will provide a way to bring the labs to the site and get results in a more timely manner.”

The µChemLab system is expected to help water utilities control the formation of trihalomethanes by functioning as a component of a process control loop.
New Mexico’s portable unit analyzes a sample of water by bubbling air through it and collecting trihalomethanes from that air. The collector is heated, sending the trihalomethanes through a separation channel and then over a surface acoustic wave (SAW) detector.

“The collector and the separation phase can be purchased off the shelf, but the SAW detector is at the heart of the microChemLab,” Curt says. “The goal by the end of summer is to replace the commercial separation column with a Sandia microfabricated column made using MEMS fabrication technology to reduce the power needed and increase performance.”

Commercial collectors are about four to five inches in diameter. Microfabricated collectors will be half a square inch. They are in development and need further tuning for trihalomethanes.

The Sandia/New Mexico microChemLab uses similar concepts to the California one — collect, separate, and detect. The main difference is at the “front end” of the device, where different capabilities are needed to be able to extract gases such as trihalomethanes from the water.

“Both systems will speed the analytical process and give the utility operator better information in a shorter time period,” Wayne says. “In addition to routine water quality monitoring, both are expected to be part of early warning systems that can alert utility operators to intentional contamination events that might occur at vulnerable locations downstream from treatment plans.”

And finally, he says, “In both of these projects Sandia has successfully leveraged MEMS-based core technologies nurtured by various DOE programs into the water security applications area.” -- Chris Burroughs

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Labs’ engine research aims high: Reduce US oil imports 30 percent while achieving ultra-low emissions

By Nancy Garcia

Among the hardest and most challenging problems facing the national labs are the issues of energy security and environmental quality. Ground transportation consumes the largest share of oil in the US, and to meet the demand, oil imports have reached the highest levels in history.

To help reduce this dependence on foreign oil, promising new combustion strategies for efficient, clean engines are being explored at the Combustion Research Facility (CRF) in Center 8300 through a $6 million engine-combustion research program. The work is funded 90 percent by DOE’s Office of

FreedomCAR and Vehicle Technologies (OFCVT) and 10 percent by private industry.

“Our research is providing the science base needed by industry to develop higher efficiency, emission-compliant engines,” says Dennis Siebers, who manages Engine Combustion Dept. 8362. “There’s a significant potential for improving the fuel efficiency of engines while simultaneously reducing their pollutant emissions.” Moreover, he added, “Such improvements in fuel efficiency will contribute to a direct reduction in greenhouse gas [CO2] emissions.”

To achieve these goals, the engine research at the CRF is focusing on new combustion strategies that will allow high-efficiency, clean engines. Also included is research on fuels for these engines from both traditional and alternative sources. The new combustion strategies fall into a class being referred to as low-temperature combustion (LTC). In simple terms, LTC is combustion under conditions that are fuel-lean enough (or sufficiently dilute with recirculated exhaust gas) to avoid soot formation and the high combustion temperatures that lead to significant nitrogen oxide (NOx) formation.

Unique capabilities, new strategies

Sandia has been conducting engine-combustion research in collaboration with industry for more than 25 years. The research has led to a suite of advanced optical-diagnostic tools for analyzing the combustion in an operating engine, and to the advancement of predictive computer models. This research has impacted industry’s design and development process, contributing significantly to the efficiency and emissions improvements of engines that are currently in production. As Dennis summarizes, “We bring capabilities that are unique in the world for helping industry develop new combustion strategies for high-efficiency engines.”

Patrick Flynn, former vice president of research at the country’s largest diesel engine manufacturer, Cummins, Inc., comments: “I feel that these tools provided by the CRF will play an ever-increasing role in engine design evolution.” The application of these tools and the expertise of CRF researchers, three of whom have been elected fellows of the Society of Automotive Engineers, are central to the new research efforts on LTC.

The low-temperature combustion research at the CRF is being conducted as part of a broader DOE program. Because of its established reputation, Sandia was recently tasked by DOE OFCVT to create and lead a memorandum of understanding (MOU) surrounding the overall research efforts. The MOU involves five national labs (Sandia, Lawrence Livermore, Los Alamos, Oak Ridge, and Argonne) and 10 engine manufacturers (Cummins, General Motors, Ford, DaimlerChrysler, Caterpillar, Detroit Diesel, International Truck, Mack/Volvo, John Deere, and General Electric). The research is conducted in collaboration with several universities (Stanford, MIT, University of California at Berkeley, University of Wisconsin, University of Michigan, Pennsylvania State University, University of Illinois, and Wayne State University).

50 percent better mpg by 2012?

The DOE low-temperature combustion program covered by the MOU targets a 50 percent improvement in fuel efficiency in the light-duty sector (automobiles, SUVs, and pickups) by 2012 and a 30 percent improvement in heavy-duty trucks by 2013. With complete market penetration, these efficiency improvements would reduce US oil use by 4 million barrels per day or oil imports by one-third from their present levels. The improvements would also translate directly to a 9 percent reduction in the total US greenhouse gas emissions. Even greater reductions in oil use are possible through further improvements in engine efficiency and through the use of these high-efficiency engines in hybrid-electric
vehicles.

“Two factors have made the low-temperature combustion techniques practical to consider now: the advent of onboard computers and electronic fuel injection,” Dennis says. “These allow for real-time control of potentially unstable combustion conditions that can arise with the advanced strategies. It’s possible that cycle-by-cycle, or even cylinder-by-cylinder control will be necessary to implement low-temperature combustion,” he says. “This dictates the need for a fairly comprehensive understanding of the in-cylinder processes.” As a national laboratory tackling tough technical problems, Sandia is playing a vital role.

Reducing emissions a challenge

In addition to reducing fuel consumption, the new LTC engine concepts are being driven by the need to reduce pollutant emissions. Stringent new emission regulations call for a factor of 10 reduction in soot and NOx by 2010. “Those regulations are really challenging,” notes John Dec (8362), who is working on clean combustion concepts for high efficiency engines in one of Sandia’s eight engine labs, adding that meeting the current emission regulations on high-efficiency diesel engines “took 20 years and a lot of work.”

Fairly good aftertreatment options exist for controlling soot from high efficiency diesel engines, but NOx aftertreatment for diesel exhaust is difficult. This is because the exhaust contains excess oxygen, which makes conventional automotive catalytic converters ineffective. Special “lean-NOx” catalysts have been demonstrated, but they have reliability problems and are expensive, sometimes costing as much as the engine itself.

“You’d like to take care of the NOx problem at its source,” John said, “and that means lowering the combustion temperature.”

To accomplish this, John’s research centers on a concept that combines some of the advantages of gasoline engines (which have premixed fuel and air with no soot emissions) and diesel engines (which have high efficiencies due to their high compression ratio and lack of throttling losses). The concept, homogeneous charge compression ignition (HCCI), has been known for some time but the operating range was very limited, and the technical challenges could not be overcome without modern computerized controls.

John’s research is conducted in both a conventional, “all-metal” engine used for performance and emissions measurements, and a second engine with quartz windows to allow laser diagnostics to be used to probe the combustion chamber, illuminating various aspects of the in-cylinder processes.

Although much work is still required to perfect the concept, it is efficient and has low emissions. “Market penetration,” John says, “could take several years, but the potential fuel savings are tremendous.”

An approach that has the potential for more rapid market penetration is being explored by Paul Miles (8362). Paul is studying modifications to standard diesel combustion that result in low-temperature combustion in automotive-size diesel engines, greatly reducing NOx and particulate emissions.

Paul is investigating fuel spray and fuel-air mixing to understand in-cylinder geometries that enhance the combustion completeness, and to provide data for the development of computational tools for engine design by colleagues at Los Alamos National Laboratory and the University of Wisconsin. “The fuel injection, mixing, and combustion processes in engines are so complicated, and the physical processes are so convoluted,” Paul says, “you’re not going to design and optimize advanced combustion systems for these engines other than by computer.”

Fuels a focus too

Another part of the research effort is on fuels, especially fuels that enable the full potential of low-temperature combustion. One aspect to be sorted out is what the most appropriate fuel might be. Since gasoline and diesel engines have been around some 100 years, those fuels are now highly optimized for current engine designs, but there is no reason to expect they are ideal for low-temperature combustion.

Another aspect is how to accommodate the changing nature of the feedstocks for fuels. In the future, bio-derived fuels and fuels from heavier crude oils, oil sands, and potentially shale oil will play an increasing role.

Fuels are a specialty in the engine lab of Chuck Mueller (8362), who is studying fuel effects on low-temperature combustion strategies. Chuck began studying oxygenates in 1997 as a prospective way to reduce soot, and more recently to see if they can enable low-temperature combustion technologies. Experiments in his lab have already shown a drop of two orders of magnitude in pollutant emissions with no loss of fuel economy. “It’s really pretty revolutionary,” he says. “You’d think all the breakthroughs would have been made by now, but this is a rich field.”

“There are still many hurdles to overcome in order to make combustion efficient, clean and practical,” he says, “and emissions restrictions typically involve trade-offs between cost and performance. The concepts themselves may be relatively simple,” Chuck adds, “but implementing them will be challenging.” -- Nancy Garcia

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