A bizarre kind of metal called nitinol, which can be trained to remember its own shape could also shape our future Mars missions.
NASA is one of the most successful space exploration agencies. Since its inception, the agency has successfully landed rovers on Mars, tested the atmosphere around Jupiter, explored the planets Saturn and Mercury, and successfully landed humans on the moon. Missions like Pioneer, Voyager, Spitzer, Apollo etc., have been the most crucial for studying space and its elements.
Therefore, when NASA’s Perseverance rover landed on Mars successfully, studying the rover and its working became imperative as it would be helpful for future explorations. The wheels of Perseverance are 20.7 inches in diameter, made of aluminium and fitted with special cleats for traction. To make rovers more efficient, NASA is now working with a shape memory alloy that can help in the future mission to Mars.
Innovating Space Memory Alloys
The wheels that are now on the rover have curved titanium spokes that help the rover roam on the uneven Mars terrain. It is equipped with separate drive motors for all six wheels, and four of these can steer so that the rover can spin on the spot. Even though this provides great stability to the rovers, NASA did not stop there. It is now looking at innovative space memory alloys (SMAs) to be used in future expeditions to Mars and other planets. These alloys have the ability to expand and contract but eventually retain their original shape.
This metal is called Nickel-titanium or Nitinol. As the name suggests, it consists of Nickel and Titanium in almost the same proportions. Nitinol has a unique property called shape memory effect and superelasticity. Shape memory enables nitinol to undergo deformation at a certain temperature, stays in the shape that is forced upon them for a while and recovers its original shape. Super elasticity, on the other hand, is the ability of the metal to undergo even larger deformations and still go back to the original state immediately.
The Distinctive Properties Of Nitinol
Nitinol has the capacity to deform 10-30 times more than ordinary metals and still regain its true shape. The shape memory effect and elasticity of the alloy depends on whether it is above the alloy’s transformation temperature. If the temperature is below the transformation temperature, it exhibits the shape memory effect, and if it is above the temperature, it gains superelasticity.
To “train” a paper clip made out of nitinol, the alloy needs to first be heated at 500 degrees Celsius in the desired shape, after which water is splashed on it. After this process, if you bend it out of shape and expose it to the same heat source, the alloy falls back into its original form.
The Uses Of Nitinol
The engineers can make changes in the ratio of the metals so that the alloy can adapt to a wide array of conditions. This makes it very useful in situations where even machines can’t fit, like blood vessels surrounding a human heart or a hook that positions a solar panel.
Dentists commonly use it as the wires and brackets that connect the teeth. It is also used by endodontics during root canals while cleaning and shaping the root canals. This material is used in various devices for reconnecting the intestine after a pathology is removed.
Nitinol On Mars
NASA is using this metal to make new tires at the Glenn Research Center. The tires made by this alloy could contour to the terrain underneath, maximize the grip and even envelope rocks and other such obstacles without getting a puncture. The deforming ability of the alloy could provide a smoother ride for the rovers and other such gadgets.
The new tires that are made using this alloy look like “ghost” wheels due to their mesh-like bubbles attached to a wheel hub. Even though they look less sturdy than Perseverance’s wheel, they are much more resilient.
NASA says, “The more capable tires allow for a rover design using four tires as opposed to the past six-tire configuration. So, in the case of future human exploration or robotic missions, these tires can provide valuable flexibility in the vehicle and spacecraft design.”
These tires are being conducted at the Simulated Lunar Operations Lab at Glenn, which has replicas of Martian landscapes. The results are as expected. The SMA tires show better grip and traction than the existing tire versions.
Reducing Potential Failures
By cutting down the number of wheels on a rover or any such vehicle for the future operation of the surface of Mars, the mission can be more straight-forward and can reduce the potential failures. These tires can be used on Earth as well. Glenn has already used these wheels on regular vehicles for a complete puncture-resistant alternative instead of traditional rubber tires.
The only drawback is that the alloy is expensive and a difficult thing to process. Due to its superelasticity, shape memory, biocompatibility, and fatigue resistance, it makes up for the money spent. As we have seen above, the many uses of this alloy continue to help humanity and its never-ending need for finding a way to make life easier.