Tough Textiles Protect Payloads and Public Safety Officers
- Sunday, 01 November 2009
Originating Technology/NASA Contribution
Special textiles have been mission-critical components for successful space missions since the early years of NASA’s first parachutes and space suits in the late 1950s. One of the Agency’s more recognizable uses for textiles, the Mars Pathfinder airbags, provided a cushioned, instrument-friendly landing in 1997. This same technology also successfully protected the Mars Exploration Rovers when they landed on the Red Planet in 2004.
These were not the ordinary airbags found in automobiles. Because the success of the missions depended on the payloads remaining undamaged, NASA had specific, exacting requirements for the airbag design. A lightweight fabric that could maintain inflation was required, but that fabric would have to be tough enough to withstand extreme temperatures (both in space and in the Martian atmosphere). The fabric balloons would have to inflate after passing through the atmosphere and then maintain inflation during impact on the rocky, sharp, and unpredictable Martian terrain. In July 1997, when the Mars Pathfinder landed on Mars, 24 interconnected, inflated spheres protected the vehicle and its delicate payload as the craft bounced 15 times after an initial impact speed of 18 meters per second (40 mph).
In order to create Pathfinder’s mission-critical airbags, NASA’s Jet Propulsion Laboratory (JPL) collaborated with Frederica, Delaware’s ILC Dover, which solicited a bid from New Ipswich, New Hampshire’s Warwick Mills Inc. to weave the textiles. Founded in 1888, Warwick Mills has a long history in weaving textiles and a long history with NASA as well, having woven fabrics for reentry parachutes and the Apollo recovery floats in the 1960s. The company began developing high-performance flexible composites in 1991 in order to address needs in the military, industrial, marine, and aerospace markets.
According to John Cronin, one of Warwick’s public safety equipment program managers, the company was one of the first weavers of Vectran, a liquid-crystal polyester fiber noted for its strength as well as its resistance to impact and abrasion. After receiving a request from JPL to weave a lightweight and yet strong fabric for the Mars airbags, Warwick, in collaboration with the engineering team at ILC Dover, decided to use a blend of coated Vectran fibers, due to Vectran’s strength and reliability in cold temperatures. Warwick’s team also engineered a process to apply thin coatings to the woven Vectran, which added strength while remaining lightweight.
After Warwick wove the fabric, the completed airbag prototypes first underwent tests at ILC Dover and then at Glenn Research Center’s Plum Brook Station Space Power Facility in a simulated Martian atmosphere. According to Chuck Sandy, chief engineer at ILC Dover, “Warwick provided valuable insight to the team as a number of iterations of candidate materials (different weaves, weights, and layup combinations) were fabricated and subjected to customized rock impingement testing at ILC.” During this testing, the JPL team discovered that the most effective design would incorporate multiple layers (up to four, depending on the location of the airbag) of lightweight fabric. The outer layers could tear and absorb more energy from impact while protecting the inner layers.
Charlie Howland, Warwick’s chief engineer and CEO, explains that the collaborative design and testing with NASA and ILC Dover yielded several benefits for Warwick, including new enthusiasm for design possibilities. “What this project provided for us was this innovative spark,” he says. “This was able to really get our engineering staff excited and looking at high-performance fibers that were emerging.” In addition, the company also learned new techniques for improving the fiber’s tear resistance and refining test methods.