Technics

The Icy moon Enceladus source of mysterious hot spots

An SwRI researcher, working with scientists from NASA’s Goddard Space Flight Center on data from the NASA Cassini Saturn orbiter, has found heat leaking out of the south polar region of Saturn’s tiny icy moon, Enceladus. This find makes Enceladus only the third place in the solar system, after Earth and Jupiter’s volcanic moon Io, where “hot spots” associated with ongoing geological activity have been detected.

The discovery was made with Cassini’s Composite Infrared Spectrometer (CIRS), which was built by and is operated from the NASA Goddard Space Flight Center in Greenbelt, Md., under the direction of Principal Investigator Michael Flasar. NASA announced the findings in a July 29 press release.

Enceladus has been a puzzle since the first pictures of it were taken by the Voyager spacecraft in the early 1980s. It is only 500 kilometers (300 miles) in diameter — so small that it ought to be cold and dead — yet its surface is torn by innumerable fractures, indicating great geological violence in the relatively recent past. It is also the brightest moon in the solar system, with a surface that is almost pure white, and seems to be the source of a huge ring of dust, called the “E ring,” that surrounds Saturn.

On July 14, 2005, Cassini flew a mere 175 km above the surface of Enceladus, returning unprecedented information about this mysterious place. Following plans devised by NASA Goddard scientist John Pearl and SwRI scientist John Spencer, the CIRS instrument scanned the south polar region, measuring the thermal (heat) radiation from the surface at wavelengths between 9 and 16 microns.

Though the pole, like Earth’s poles, should have been one of the coldest places on Enceladus, at about 75 degrees Kelvin (-324 degrees Fahrenheit), Spencer's analysis of the data found that the south pole was instead the warmest place on the moon, with temperatures in small areas reaching well over 110 degrees K (-261° F) — so “warm” that these temperatures are difficult to explain by solar heating alone. More likely, heat is being generated inside Enceladus and is being released to the surface through fractures near the pole.

“Looking for signs of internal heat on Enceladus was always one of the goals of the CIRS instrument, but it always seemed like a long shot because we couldn’t imagine that an object so tiny could produce enough heat to detect,” said Spencer, a staff scientist in the SwRI Space Studies Department. “We are amazed that we were actually successful.”

Other Cassini instruments discovered a huge cloud of water vapor over the warm south pole, as described in the NASA press release. Cassini’s cameras also showed that the south polar region is one of the youngest parts of Enceladus’ surface. The water vapor cloud is probably continually supplied by evaporation of the warm ice discovered by CIRS.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington. The Cassini orbiter was designed, developed and assembled at JPL.

Contact Spencer at (303) 546-9674 or spencer@boulder.swri.edu.

Fuel cell-assisted truck completes cross-country trek

A tractor-trailer truck with auxiliary systems powered by electricity from a fuel cell has successfully completed a cross-continent trip from California to Washington, D.C.

In laboratory evaluations at SwRI prior to the trip, the truck achieved a 13 percent improvement in fuel economy.

The truck, owned and operated by SunLine Transit Agency in Thousand Palms, Calif., departed on May 17 for a 2,650-mile journey that ended on May 21 at Fort Belvoir, Virginia. The truck made the journey without a trailer.

The truck’s primary propulsion system is a standard production 330-horsepower diesel engine. With funding from the U.S. Army TARDEC National Automotive Center, SwRI engineers converted the truck’s water pump, radiator cooling fan, air compressor, air conditioning compressor and air conditioner condenser fan from engine-powered belts and pulleys to electric power.

Removing these “parasitic” loads from the engine and powering them electrically enables the engine’s full motive power to propel the truck and increases the overall efficiency of the truck.

To power the accessories, SwRI integrated a fuel cell auxiliary power unit (APU) that is independent of the engine and is fueled with hydrogen gas. The proton exchange membrane APU is capable of producing up to 20 kilowatts (kW) of power at 42 volts DC, although the truck typically uses no more than approximately 7 kW for normal operation. Hydrogen for the fuel cell is stored in three compressed gas cylinders aboard the truck. The tanks hold approximately 5 kilograms (11 pounds) of hydrogen, or the equivalent energy of about five gallons of gasoline.

The truck appeared on public display at the U.S. Fuel Cell Council’s Congressional Fuel Cell Exposition in Washington, D.C.

Contact Alan Montemayor at (210) 522-6940 or alan.montemayor@swri.org.

SwRI provides key spacecraft avionics for the NASA Deep Impact Mission

Over a 25-year span, spacecraft computers and avionics built by SwRI have flown on more than 50 missions with no on-orbit failures. The most recent addition to this history, the avionics for the Deep Impact mission to Comet Tempel 1, also marked the first flight of the latest radiation-hardened processor, the RAD750, and SwRI’s first Compact PCI (cPCI) architecture in space. 

Under contract to Ball Aerospace & Technologies Corp., SwRI engineers built six computers for the flyby and impactor spacecraft for the Deep Impact mission. Launched in January 2005, the 800-pound (365-kilogram) impactor spacecraft successfully collided with Comet Tempel 1 on July 4.

Deep Impact is the first mission designed to impact a comet and probe the mysteries beneath its surface, which is believed to contain pristine remnants from the formation of our solar system. NASA’s Discovery program oversees the Deep Impact mission, with overall management provided by the University of Maryland and the California Institute of Technology’s Jet Propulsion Laboratory. Both the flyby and impactor spacecraft were designed and built by Ball Aerospace. SwRI avionics served as the “brains” of the flyby spacecraft and impactor, supporting navigation, propulsion control, image processing, data storage, command reception and execution, telemetry downlink and spacecraft thermal management.

The cPCI open architecture, provided by SwRI’s SC-10 line of spacecraft computers on the Deep Impact spacecraft, increases the throughput and performance of previous bus architectures. This open architecture provides seamless integration of cPCI avionics cards (such as a core line of CCSDS command and telemetry modules) with commercially available processors such as BAE Systems’ RAD750. SwRI is the first to fly the RAD750, the next-generation, high-performance radiation-hardened supercomputer board, supporting NASA, the Department of Defense and commercial spacecraft companies. The Institute was also the first to use its predecessor, the RAD6000, which has provided the computational capability for such programs as NASA’s Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) and the Swift Gamma Ray Observatory.

With SwRI offering non-recurring engineering and expertise along with fabrication and test facilities, clients may focus resources on integration, systems engineering and astrodynamics. Where possible, staff engineers standardize architectures to reduce costs. However, space missions typically need custom science instruments that, in turn, require specially tailored avionics systems. SwRI offers flexibility in producing both standard architecture products and custom products on almost every mission.

In addition to spacecraft avionics and computers, the staff has expertise in spacecraft instruments, theoretical and observational studies, space plasma physics, data analysis and science support, planetary exploration and stellar astronomy. SwRI currently leads the New Horizons mission to Pluto, the IBEX mission to study the interstellar boundary, the MMS mission to study the Earth’s magnetosphere and the Juno Jupiter orbiter mission. The Institute is also providing avionics and electronics support for IBEX, MMS and Juno, as well as instrumentation for the Mars Science Lander and the Lunar Reconnaissance Orbiter.

Contact Buddy Walls at (210) 522-3823 or buddy.walls@swri.org.

Buckingham elected Fellow of American Statistical Association

Janet P. Buckingham, a principal analyst in the Fuels and Lubricants Research Division at Southwest Research Institute (SwRI), has been elected a Fellow of the American Statistical Association (ASA).

The honorary title of Fellow is conferred upon ASA members who have made outstanding contributions in the field of statistics. Buckingham was cited for “excellence in fostering good statistical practice and in the application of statistical methods in the engineering and physical sciences, and for outstanding leadership and service to the profession, especially in committee and section activities.”

Buckingham joined the Institute staff in 1978 after receiving a bachelor’s degree in computing and information sciences and mathematics from Trinity University. At SwRI, she has provided statistical support in experimental design, reliability, quality control, sampling techniques, regression analysis, statistical modeling, analysis procedures, data interpretation and data representation for a number of research projects ranging from engine and vehicle research to bioengineering.

The author of 25 papers and publications, Buckingham also holds a master’s degree in statistics from The University of Texas at San Antonio and is a member of the American Society for Quality.

Contact Buckingham at (210) 522-2407 or janet.buckingham@swri.org.

SwRI develops low-emission natural gas truck engine

As part of the U.S. Department of Energy’s (DOE) Next Generation Natural Gas Vehicle Program, SwRI has developed a low-emissions, heavy-duty natural gas engine that more than meets stringent U.S. Environmental Protection Agency (EPA) 2010 emissions standards. The next-generation engine emits greatly reduced levels of oxides of nitrogen (NOx) and particulate matter (PM), allowing production of heavy-duty trucks that restrict release of pollutants to the atmosphere.

SwRI engineers modified a standard production Mack E7 natural gas-fueled engine to reduce regulated emission levels. Test results with a “degreened,” or seasoned, catalyst showed NOx emissions at 0.049 gram per brake horsepower hour (g/bhp-hr), less than one-quarter of the 2010 standard, and PM at 0.002 g/bhp-hr, one-fifth of the future standard. A degreened catalyst is one that has been operated briefly before testing to achieve a stable emissions reduction.

The DOE’s Next Generation Natural Gas Vehicle Program funds developing technologies for alternative fuels. The National Renewable Energy Laboratories and the South Coast Air Quality Management District (a California air pollution control agency), through separate agreements, funded the program with Mack Trucks Inc. to develop the next-generation, stoichiometric heavy-duty natural gas engine and to evaluate the prototype in a fleet of refuse hauler trucks. As subcontractor to Mack, SwRI was tasked to develop the engine and perform emissions evaluations.

Natural gas engines operate on a gaseous fuel and are typically spark-ignited, which emits lower PM. However, the engines are normally adjusted to run with a lean air-fuel ratio, which prevents using a simple catalytic aftertreatment device to reduce NOx emissions. 

“The key to decreasing emissions,” said James Chiu, program manager and a principal engineer in the SwRI Engine, Emissions and Vehicle Research Division, “is to allow the engine to run under stoichiometric, or chemically correct, conditions. Then a three-way catalytic converter can significantly reduce engine emissions.”

In addition to the catalyst, other changes to the engine included adding a cooled exhaust gas recirculation (EGR) system and modifying an engine controller with algorithms to control the EGR and to maintain proper air-fuel ratio control with varying EGR rates. Use of the EGR improved engine efficiency, lowered temperatures, reduced engine-out NOx emissions and decreased the tendency to knock.

SwRI, which operates the world’s largest independent emissions laboratory, performed emissions evaluations on the newly developed engine, including the 13-mode steady-state emission procedures and the more revealing U.S. transient emission assessment. In the transient operations, the composite Federal Test Procedure values, in g/bhp-hr, included NOx, 0.049; carbon monoxide (CO), 4.153; and PM, 0.002. The 2010 standards mandate NOx, 0.2; CO, 15.5; and PM, 0.01. The 13-mode series showed similar results.

Contact Chiu at (210) 522-2570 or james.chiu@swri.org.

Lunar “dark spots” point to upheaval in planetary orbits 

People of every culture have been fascinated by the dark “spots” on the Moon. With the Apollo missions, scientists found that these features are actually huge impact basins that were flooded with now-solidified lava. One surprise was that these basins formed relatively late in the history of the early solar system — approximately 700 million years after the formation of the Earth and Moon. Many scientists now believe that these lunar impact basins bear witness to a huge spike in the bombardment rate of the planets — called the late heavy bombardment (LHB). The cause of such an intense bombardment, however, is considered by many to be one of the best-preserved mysteries of solar system history.

In a series of three papers published in the journal Nature, an international team of planetary scientists, Rodney Gomes (National Observatory of Brazil), Harold Levison (Southwest Research Institute, United States), Alessandro Morbidelli (Observatoire de la Côte d’Azur, France) and Kleomenis Tsiganis (OCA and University of Thessaloniki, Greece) — brought together by a visitor program hosted at the Observatoire de la Côte d’Azur in Nice — proposed a model that not only naturally solves the mystery of the origin of the LHB, but also explains many of the observed characteristics of the outer planetary system.

This new model envisions that the four giant planets, Jupiter, Saturn, Uranus and Neptune, formed in a very compact orbital configuration, which was surrounded by a disk of small objects made of ice and rock (known as “planetesimals”). Numerical simulations by the Nice team show that some of these planetesimals slowly leaked out of the disk due to the gravitational effects of the planets. The planets scattered these smaller objects throughout the solar system, sometimes outward and sometimes inward. Numerical simulations show that, on average, Jupiter moved inward while the other giant planets moved outward.

The Nice team argues that this evolution of Uranus’ and Neptune’s orbits caused the LHB on the Moon. Their computer simulations show that these planets very quickly penetrated the planetesimal disk, scattering objects throughout the planetary system. Many of these objects entered the inner solar system where they peppered the Earth and Moon with impacts. In addition, the whole process destabilized the orbits of asteroids, which then would have also contributed to the LHB. Finally, the gravitational effects of the planetesimal disk caused Uranus and Neptune to evolve onto their current orbits.

Contact Levison at (303) 546-0290 or hal@boulder.swri.edu.

Published in the Summer 2005 issue of Technology Today®, published by Southwest Research Institute. For more information, contact Joe Fohn.

Summer 2005 Technology Today
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