Thursday, July 14, 2011

Marshall Center's Bassler Leads NASA Robotic Lander Work

Growing up on a working farm in rural Breese, Ill., NASA engineer Julie Bassler constantly found her attention drawn away from the tranquility of farm life by the thunder of jets from nearby Scott Air Force Base, and she knew early on that her heart's ambition was not in the soil, but among the stars.

Today, as manager of the Robotic Lunar Lander Development Project at NASA's Marshall Space Flight Center in Huntsville, Ala., she is fulfilling that ambition -- and helping to create some unprecedented thunder herself. Bassler and her team have spent the past 21 months designing, developing and testing a sophisticated robotic lander prototype for a new generation of automated spacecraft capable of exploring and conducting science on the surface of the moon, near-Earth asteroids and other airless planetary bodies in the solar system.

In a U.S. Army propulsion test facility on Redstone Arsenal in Huntsville, Bassler gives the word, and a hissing roar fills the chamber as the latest robotic lander prototype lifts off. It's a three-legged construct 4 feet tall and 8 feet in diameter, weighing roughly 700 pounds when fueled. It's powered during this test series by an environmentally friendly propellant that's 90 percent hydrogen peroxide -- a substitute for a monomethylhydrazine and nitrogen tetroxide blend called MMH/MON-25, which has an extremely low freezing point suited for long missions in the icy reaches of space.

The lander, a blocky metal tripod, rises more than six feet into the air. It's putting out nowhere near the 750 pounds of maximum thrust the final version will deliver, but it nonetheless hangs effortlessly in space. After just 33 seconds of controlled, autonomous flight, it descends. A short test run -- but the assembled engineers and onlookers applaud. Bassler looks pleased.

"Big science in a very small, very smart package," she says. "That's our goal." She says the team -- small and efficient, like the prototype itself -- remains on a record-setting development pace to deliver a practical, low-cost, highly versatile lander that will expand the frontiers of automated research and discovery across the solar system. It took them just 17 months to go from the drawing board to the first powered flight test of the lander prototype, which the team has nicknamed "MightyEagle." This prototype is a warm-gas, peroxide-fueled test article; a cold-gas version was completed and tested in only nine months. Since then, the team has conducted approximately 160 flight tests on its prototypes, and Bassler says they still clap at the end of nearly every one. It's hard not to.

"This is the most rewarding project I've worked on in my years at NASA," she says -- and it's evident in her voice why she traded farm life for a chance at a legacy in space, an opportunity to touch -- even remotely -- the soil and rock of worlds other than ours.

Progress on the Path to Other Worlds
Bassler credits much of the excitement -- and the project's success to date -- to a strong team, which includes Marshall Center engineers and partners at Johns Hopkins University's Applied Physics Laboratory in Laurel, Md., and the Von Braun Center for Science and Innovation in Huntsville. The latter includes two Huntsville-based contributors: Teledyne Brown Engineering, which integrated the lander's structure and avionics systems; and Dynetics Corp., which developed its innovative altitude-control thrusters and a unique, "Earth gravity canceling" thruster which counteracts up to 5/6ths of normal Earth gravity.

The lander project also has conducted component level testing on heritage descent thrusters initially developed by the U.S. Missile Defense Agency. Tests were conducted at NASA's White Sands Test Facility in Las Cruces, N.M.

The Planetary Science Division of NASA's Science Mission Directorate in Washington directs the project.

Even as they assess the prototype in flight, work is under way on other fronts. The team is tackling inventive new solutions for the lander’s thermal protection system, which will protect its components while traveling through space. Conventional NASA multilayer insulation stands up well to the rigors of space flight, but in this instance would inhibit the lander's ability to make mid-flight course corrections using its array of thrusters, so the team is investigating efficient, low-mass alternatives suitable for the lander's complex flight configuration.

The lander team also is working on thermal management of the lander once it has set down on another celestial body, and for the duration of its multi-year mission. On the lunar surface, for example, the lander would be exposed to widely varying thermal conditions. Lunar surface temperatures can climb as high as 260 degrees Fahrenheit during the day -- then plummet to minus-279 degrees Fahrenheit overnight. The lander’s electronics, batteries and other sensitive equipment must be protected from this widely varying environment, while maintaining its ability to support continuous operations.

On-board batteries are another source of innovation on the project. To sustain the lander's electrical power and energy storage systems in extreme environments for long months or years, the team is studying two types of lithium ion batteries at the Marshall Center. Advanced, lightweight lithium iron phosphate batteries have proven themselves capable of supplying high power levels at sub-freezing temperatures, increasing the inherent safety of the energy storage system and permitting the team to devote more mass to payload. Meanwhile, energy-dense lithium cobalt oxide batteries are being tested to prove whether they're up to a six-year mission to another world, braving temperatures similar to those documented at the moon's equator while maintaining power system requirements. Battery testing at Marshall is expected to be completed in October.

Upon completion of the latest prototype tests -- the project's fourth major series of autonomous, closed-loop, free-flight tests since September 2009 -- the team will pass another major milestone on the robotic lander's promising journey to space. Over the hot summer months, it will go higher and for longer durations, glide horizontally over and around the test floor and descend 100 feet under its own power from an overhead crane, all the while permitting the team to assess its sensors, avionics and software systems and integrated structures. Testing will conclude in late summer with a series of more complex, autonomous free flight tests, lasting up to 60 seconds each, on the Army's Redstone Arsenal test range.

The lander is proving itself capable of handling all aspects of closed-loop, autonomous descent and landing, Bassler says -- preparing to find its way unaided around surfaces far stranger and less forgiving than the gray concrete of the test chamber.

The spaceflight version of the lander will be expected to take on a variety of science and exploration excursions in a wide range of airless alien environs. Nimble enough to touch down in craters or other harsh geological formations that could foil traditional aerobraking systems or parachutes, the lander also will be robust enough to operate for more than six years -- performing equally well in the frigid darkness of the moon's night side, or under the punishing glare of a sun unshielded by Earth's atmosphere.

"Our approach to designing the final robotic lander has been incremental," Bassler said. "During testing, we're running through an actual mission-sequence scenario, training a team capable of building and executing an actual lunar mission in less than two years if we got the go-ahead today."

More About the Team Leader
Bassler was a natural choice to lead the lander effort at Marshall. A 1988 graduate from Parks College of St. Louis University in St. Louis, Mo., where she received an undergraduate degree in aerospace engineering, she went on to earn a master's degree in space science in 1992 from the University of Houston in Texas.

She conducted a variety of software integration and engineering tasks for two NASA contractors in Clear Lake, Texas -- Rockwell Space Operations from 1988-1990 and McDonnell Douglas from 1990-1994 -- before accepting a full-time position at NASA's Johnson Space Center in Houston in 1994. There, she led a team of engineers in the International Space Station Program Office for three years before transferring to the Marshall Center in 1997.

Among numerous key management posts at Marshall over the next 14 years, she was deputy manager of the Lunar Precursor Robotic Program and supervisor of the Lunar Precursor Robotic Office at Marshall from 2006 to 2008. In that post, Bassler helped set the stage for a number of successful lunar missions including NASA's Lunar Reconnaissance Orbiter and Lunar Crater Observation Sensing Satellite -- which flew to the moon in tandem in 2009 to map the surface and search for water ice, respectively -- and laid the groundwork for the new lander development effort, which began in 2009.

Her prime advantage, though, may have come much earlier -- as far back, she says, as those years as an Illinois farm girl with an eye on the stars. She credits her parents, Lucille Beckmann Loepker and the late Wendell Loepker of Breese, Ill., for setting her on a path to win the future.

"Living on a dairy farm, the clock never stopped on things to do," she remembers. "My parents taught me that if you work hard and expect good things, you will achieve the goals you set for yourself."

That work ethic has served her well as she juggles her demanding NASA position with her other busy vocation -- mothering four active children, which often means transitioning quickly from test site to ball field, from laboratory to gymnasium. She changes hats deftly; she has to.

Bassler is handed a sheet of data. She calls to her team to start their post-test tasks, already thinking ahead to the lander's next scheduled flight, and another step toward space.

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