Cleveland, OH—Imagine having to change your car's battery on a very
cold February morning.
Now imagine doing it dressed in a spacesuit. Astronauts might have faced a similar challenge if they had needed to change the batteries in the Hubble Space Telescope (HST) as it orbited the Earth. Michelle Manzo, winner of the first Design News Women in Engineering Achievement Award, played a key role in ensuring the HST flew with batteries that would work well and have a long life without requiring frequent maintenance.
Poles Apart: Bipolar batteries - really
power systems - rely on the positive electrode in one cell to form the
negative electrode in the adjoining cell. This type of configuration saves
space and simplifies power source of design.
She continues her engineering work today as acting chief for the electrochemistry branch at the Glenn Research Center in Cleveland, and leads a program for the development of lithium-based polymer electrolyte batteries for future use by NASA. Like all NASA employees—and, indeed, the nation at large—she mourns the loss of the Columbia astronauts.
During work on the Hubble, Manzo was the only NASA representative on a government-and-industry team formed to evaluate and recommend the electrical 'storage' system. NASA designed the HST to use nickel-cadmium (Ni-Cd) batteries. But the temporary halt of space-shuttle launches after the Challenger incident meant the Ni-Cd batteries built for the HST would approach or exceed their recommended shelf life before the telescope ever got into orbit. Manzo noted that original plans included a space-shuttle mission to replace the Ni-Cd batteries with nickel-hydrogen (Ni-H2) batteries two to three years after the HST went into space.
But contractors were already manufacturing newer Ni-H2 batteries and could have them ready in time to meet the HST's launch date. "There was a catch, though," says Manzo. "The Ni-H2 batteries had never flown in a low-earth-orbit (LEO), other than as an experiment, so trusting a new battery technology to work properly on a high-profile mission was risky."
After a thorough assessment of the risks involved, the team recommended NASA use the Ni-H2 batteries. Those batteries have performed flawlessly since the HST was launched in April 1990. They've required only minimal attention during service missions that repaired or replaced other systems in the orbiting telescope. Without the need to replace batteries, NASA saves money and astronauts can spend time on other tasks.
As a result of her efforts related to the development and use of Ni-H2 batteries on the HST, Manzo received a NASA Exceptional Achievement Medal in August 1998.
Full House: Lithium-ion batteries on the
commercial market come in a variety of shapes and sizes that fit in cell
phones, PDAs, and laptops. Their high power density makes them excellent
choices for portable electronic equipment. Courtesy of Valance Technology.
All of which points to the wisdom of Dean Sheibley, who took Manzo under his wing during her time as a co-op student at the Glenn Research Center in 1974. Sheibley helped convince her to make a career at NASA, where part of her current duties include addressing battery-safety issues.
Although Manzo always had an interest in science and math, she didn't always have her eyes on the sky. As best she can recall, she had little interest in space flight while growing up in Ohio. And no teacher in high school stands out in Manzo's recollections as encouraging the future battery expert to think about a career in science or engineering. Although Manzo's parents never attended college, they actively encouraged their children to take advantage of higher education. Michelle was the first in the family to pursue a college degree.
After reaching Alderson-Broaddus College (Philippi, WV), Manzo caught the attention of faculty, who recognized her interest in math and science and recommended she pursue a double major. She graduated with a B.S. in chemistry and mathematics in 1976. During her co-op sequences at NASA's Glenn Research Center (Cleveland, OH), she worked with a materials group and an electrochemistry group. She quickly decided research looked like more fun than running routine analyses, so she gravitated to electrochemistry and battery research. After she received her degree, she joined NASA full time.
Early in her career she had to wrestle with problems involving Ni-Cd batteries, the type NASA had used on satellites since the 1960s. But in the mid 80s, the agency began to experience severe problems with standard Ni-Cd cells. "The separator material in the cells caused problems," says Manzo. "The vendor stopped making the material 10 years earlier. And stockpiles of it had degraded due to improper storage, so cells performed poorly."
Manzo served on the team that addressed the problems with the Ni-Cd batteries. The team developed standard tests that ensured quality, uniformity, and reliability of separator materials. As a result, she helped make recommendations for the separator material used in the cells that flew on Mars Observer in 92 and 93.
Manzo continued her work with Ni-H2 batteries after participating in the HST program. "We studied how cells failed and found ways to modify cell designs to overcome problems, extend cell life, and improve battery performance," she says. Vendors implemented a number of the team's modifications.
Those modifications included adjusting cell design to improve heat removal, using a spring-like washer to accommodate electrode expansion, and changing the concentration of the electrolyte. Testing has shown these modifications to the basic nickel-hydrogen cell design resulted in a 4-10X improvement in cycle life over standard cell designs. NASA and commercial satellite manufacturers now incorporate many of these features in their cells.
For its innovations, the Nickel-Hydrogen Development team received an R&D 100 Award. Manzo goes out of her way to distribute credit to that team and to members of the NASA Aerospace Flight Battery Systems Steering Committee and to those in NASA's Aerospace Flight Battery Systems Program. These groups advise NASA and handle tasks that ensure the availability, reliability, and quality of batteries for NASA's missions.
Manzo also worked on bipolar-battery designs for Ni-H2 and nickel-metal hydride (Ni-MH) battery systems. "Bipolar battery designs approach energy storage from a systems perspective," said Manzo. "For normal battery cells, you can increase the voltage by connecting individual cells in series, plus-to-minus, plus-to-minus, and so on. In a bipolar cell, you no longer have those connections. Instead, the plus electrode in one chemical cell also acts like the negative electrode in the adjoining cell. You still have separate cells, but now the design incorporates everything in one array or package."
But the bipolar nickel-hydrogen batteries just don't offer volume efficiencies because they generate hydrogen as they charge, which requires vessels to store the gas. (Discharging a Ni-H2 battery consumes the hydrogen.) Although research groups at NASA have demonstrated that bipolar Ni-H2 power systems can go through 15,000 charge/discharge cycles, NASA has never flown one on a mission. In all likelihood, Li-ion batteries will replace Ni-H2 batteries before bipolar-technology power sources qualify for space flight.
"We're doing extensive work on Li-ion batteries now," explains Manzo. NASA has research underway that involves several forms of lithium in several cell configurations. The performance advantage of Li-ion batteries include higher specific energy, higher energy density, and a higher cell operating voltage compared to Ni-H2 and Ni-Cd batteries.
To illustrate how much time it can take to fully develop and characterize a new battery type, Manzo offers an example: In 1970, Intelsat began development of Ni-H2 batteries that would have a longer life than Ni-Cd cells then in use. The company wanted to use the new battery in geosynchronous satellites. Seven years later, Ni-H2 batteries went on an experimental flight, and in 1983 they flew on Intelsat V in a geosynchronous orbit. Only in 1990—20 years after developments commenced—did Ni-H2 batteries go into a low-earth-orbit satellite, the Hubble Space Telescope.
In addition to her prestigious Exceptional Achievement Medal, Manzo also received a local award at the Glenn Research Center that included an all-expenses-paid trip to Cape Canaveral to watch a space shuttle launch. As luck would have it, that shuttle mission carried the first Ni-H2 batteries to the International Space Station.