DEPARTMENT NEWS engineering, who figured out how to calculate the impact the suit must tolerate if the astronaut fell down on the moon or on Mars. How fast would the astronaut fall? What would happen if the astronaut fell onto a sharp rock? What if the impact was on the astronaut’s chest? Hips? Back? “That is a great computational challenge,” Haque said. Defending the astronaut against micrometeoroids that might arrive at speeds greater than 2,237 miles an hour was another high-level problem to address. Using state-ofthe-art MAT162 software, Haque was able to calculate and show the kind of damage that would occur in a range of scenarios, and the team came up with a composite material and a process that would perform in every situation. With Haque’s precise analysis, ILC, UD and NASA chose a hybrid structure of carbon and glass in a matrix of epoxy that David Graziosi, ILC principal engineer, calls “the most advanced composite structure ever deployed in space” for the Z-2’s Hard Upper Torso (HUT). The HUT is a fiberglass-strengthened shell that protects the body and also bears the weight of a life-support system, communication devices and attachments for tethers and assorted connections. The project unfolded over a three-year period, as ILC and UD experts explored material options, worked on designs, determined necessary stiffness and tensile strength of materials, tested the load they could bear and the strain they could withstand, figured out 30
how they should fit together and how they would react to sometimes-extreme changes in temperature and pressure. They designed tools and processes to produce what was needed. They met with many challenges, as you might expect. For example, wrapping a flat fabric around a cylinder is not usually a problem, said Dan Molligan, CCM assistant director for application development. Wrapping it around a sphere requires shearing —a definite complication. There are no flat spaces on the torso piece, he said, and that makes it more difficult to lay out the materials, especially in areas where the carbon fiber epoxy material goes from thin to thick. The thickness can range from an eighth of an inch to 2 inches in some places. The material in the Z-2—carbon fiber with 1 million pounds per square inch of tensile strength—is impregnated with resin and cut to precise specifications using a computer-controlled ply cutter. The pieces are then positioned using a laser system that projects the patterns— hundreds of unique patterns were involved— onto the Z-2 part tool. A layer of S-glass is incorporated to increase impact resistance. The Z-2 was subjected to months of rigorous testing at NASA’s Neutral Buoyancy Lab near the Johnson Space Center in Houston. There, astronauts were submerged in a giant tank filled with a million gallons of water, in which they practiced the maneuvers they will perform in space and put the suit through its paces. Testing continued into last
UD MECHANICAL ENGINEERING summer, and as materials and designs are evaluated, NASA will make decisions about the next step for the Mars spacesuit. “Sending a human to Mars will answer some of the major questions that humanity has,” Scarborough said. “Is there life there? Is life on our planet the only place in the universe or the solar system where it exists? And being able to put a human there instead of a robot allows the research to happen so much faster.” As with so many NASA-led developments, the technological advances and innovations that are part of this mission are likely to have applications in many other areas. “The idea of hybrid carbonglass composites can have application in high-performance vehicles,” Scarborough said, “potentially with impact resistance and militarytype impact performance. Some things developed for the military are now being qualified to be used in space.” And the Z-2 has performed well. “There have been no issues with the suit and nothing with the composite structure, which is really good on a prototype like this,” Graziosi said. “They’re hanging simple things—mockup life support systems—but those are a lot of stressing interfaces to the hatch and the HUT, while the crew goes into the water to do things. “They have had zero issues, zero leakage, zero structural problems. And that’s a really big deal."