NASA Reinvented Wheels

The red planet has now become a tire-destroyer for the NASA’s Curiosity rover. The Mars’ lonely resident, Curiosity rover, has suffered a tremendous amount of adverse conditions in the past five years. However, NASA is more concerned about its tires as Mars’ uneven and rough terrain has broken its wheels. Addressing the issue, NASA has reinvented the wheels by giving it a ‘memory’. NASA has used shape-memory alloys (SMAs) to develop these tires, which one day will be used to in the rovers of Mars. The new tires are created from a woven-mesh metal, which remembers its original shape, and returns to it after a deformation. A team of engineers led by Colin Creager at the NASA Glenn Research Center in Cleveland, Ohio has been working on “spring tires”. They came across an unsolvable problem of tire dents. When Colin came across SMAs and their applications, they collaborated to come up with a new technology which can sustain heavy weight and does not burst after a long run.

NASA has been a developing “space-grade” tires since 1960’s Apollo moon mission. However, Mars puts forth several challenges that are hard to overcome. It is covered in sand, gravels, and littered with rocks. It costs way too much to launch anything on Mars, thus every penny counts. Furthermore, every electro-mechanical system must have solar panels for its operation, and it should sustain any harsh weather and temperature swings. After a five-year long fight against such adverse conditions, Curiosity rover has shown small holes, tears, and rips in its wheels.

According to Colin, such challenges can be overcome by nickel-titanium (NiTi) alloy. Spring steel can withstand only about 0.3 percent of strain before its permanent deformation; the NiTi alloy can suffer up to 10 percent strain–30 times more elasticity. These new wheels can bear heavy weight, about 10 times the capacity than Curiosity rover. It can function in the temperature from -202 to 194-degree Fahrenheit, has improved grip, and can climb steeper surfaces. Although the invention will not be used in follow-on mission to Curiosity as NASA takes a lot of time and tests to approve new updates. Nevertheless, if not on Mars, people will see such wheels roaming on the Earth for sure.

The use of SMAs is not new to the scientists of NASA. Researchers have been developing wing wrapping technology using SMAs. The aim is to be able to bend and fold wings without causing them a permanent damage. With the use of SMAs, the outer portions of the wings can be manipulated to control the angles in flight.

Othmane Benafan, a material engineer at NASA research center, said “SMAs are materials that can produce ‘work energy’ by a reversible, solid-state phase transformation activated by thermal stimuli. It gives a large reversible deformation ability, which can be used to move objects including actuators. The changes that happen to these alloys are at an atomic level, and it can be trained to deform to a certain shape and return to its original shape after heating.”

He pointed out that they are using F/A-18 wing as a test article to demonstrate the actuation concept, and they need to understand if scaling up is possible from all aspects including material performance and work densities.

While there is still a long way to go in the field of shapeshifting metals, scientific researchers are keen on developing such smart materials. Furthermore, there has been a while since humanity saw the invention of wheels. NASA’s “wonder wheels” is a nice throwback to the ancient history.

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