More than just scratching the surface
By Brian Fitzgerald
Last spring Matt Heverly waved farewell to identical robotic arms he helped design for Spirit and Opportunity, two exploration rovers that NASA was sending to Mars. Then he prayed that they would make it to the red planet without being damaged.
They did, surviving a rough ride into Mars' atmosphere at 12,000 miles per hour, and successfully landing on January 3 and January 24, respectively. Never before have two mobile robots explored the surface of another planet simultaneously.
Heverly (ENG'05) has had further cause for celebration lately: he has seen his devices for the first time in nine months. Spirit is now running fine and is sending back images of the planet after more than a week of computer memory problems, and a February 2 webcast showed Opportunity extending its arm, unveiling it to both the human and Martian worlds. “It was both exciting and stressful to watch,” Heverly says. “If the arm didn't deploy, there would be no chance to fix it.”
NASA is two for two on this mission: both rovers and their arms are intact. Not only are the rovers' panoramic cameras sending back the highest resolution pictures ever taken of Mars, their robotic arms are also busy examining the planet's soil, analyzing its minerals and chemistry. The ultimate goal is to provide scientists with enough information about rock and soil structure to determine if water once evaporated from the planet, which will give them a better indication of whether Mars might have been suitable for sustaining life in the past.
Heverly was a mechanical engineer for Alliance Spacesystems, Inc., (ASI) in Pasadena, Calif., before coming to BU last fall to further study robotics and controls. At ASI, he worked with three other engineers for almost two years on the robotic arms, formally known as instrument deployment devices.
Each arm has roughly the size and motion capabilities of a human arm, allowing it to position its four instruments in contact with rocks and soil. “My duties included portions of the structural design and analysis of the arm,” says Heverly. He also made most of the mechanical drawings of the arm and was responsible for design portions of the actuators and contact sensors.
“None of my work was very glamorous,” he says. “But it was amazing to be part of a space hardware project, and it certainly is fun to turn on my computer and look at the footage of the rovers, and see the parts that I designed. There they are, right on Mars.”
A microscope on Opportunity's arm has examined a patch of soil, revealing structures as thin as a human hair, and a Moessbauer spectrometer has collected information to identify minerals by spraying gamma rays at them and measuring the fraction of atoms that don't recoil. The arm has also examined soil with another instrument, the alpha particle X-ray spectrometer, which reveals chemical elements. From February 5 to 7, Opportunity rolled 16 feet to investigate a slab of rocks, focusing on a protruding geological feature NASA scientists have nicknamed “Snout.” The rover will soon turn its attention to more of the pebbly Martian soil, which so far has been found to contain very little iron oxide, a mineral that typically forms in water.
On the other side of Mars, Spirit's arm dusted off a rock with an abrasion tool, and used a microscope and two spectrometers to examine it. At present, Spirit is moving toward a crater 800 feet away — a trip that could take a month.
“The most stressful time during the Spirit and Opportunity webcasts was watching the small pyrotechnic devices fire and release the arms from the cables that are holding them,” says Heverly. “Up to that point, the mission had been a success — the rovers came off the landers fine and started driving around. But it really wasn't a total success until the arms deployed. A thousand thoughts were going through my mind at once. So many things could have gone wrong. I was asking myself, did I check all those calculations right? Is dirt going to get into the motor? We had only one shot to get it right. I was so relieved when the arms worked.”
Heverly's team had to work quickly and effectively in designing the arm: the launches couldn't be postponed because Mars' and Earth's orbits were so closely aligned last summer. “If there was a delay,” Heverly says, “Mars would have just been getting further and further away.” If NASA hadn't had the rovers ready in time, there would have been a minimum of a four-year wait for another chance.
From outer to inner space
Heverly was thrilled to be part of the design team for a NASA rover, and he hopes to lead such efforts in the future. To gain a broader perspective in robotics as well as expertise in dynamics and controls, he joined the master's degree program in ENG's aerospace and mechanical engineering department. Because of Heverly's proven ability to work well under pressure, Pierre Dupont, an ENG associate professor of aerospace and mechanical engineering, recruited him to join a research project on image-guided fetal cardiac surgery.
Funded by the National Institutes of Health, Heverly and Dupont are teaming with cardiologists from Children's Hospital and engineers from Philips Medical Systems of Andover, Mass., to develop technology for delicate surgical procedures in which doctors can correct malformations of the heart prior to birth. This research will involve the integration of engineering techniques from robot navigation, control systems, and acoustics.For Heverly, going from outer space to inner space — perfecting medical technology involved in fetal congenital heart surgery — is equally rewarding. For Dupont, the opportunity to work with a student like Heverly holds great appeal. “Matt's work on the robotic arm for the Mars rovers shows that he has a lot of potential to substantially contribute to a new surgical method,” says Dupont. “He comes to the College of Engineering highly motivated. What more could I ask for in a graduate student?”