When exploring another planet, the last thing you want to deal with is tire damage when AAA is millions of miles away. It’s a concern that prompted NASA one airless titanium band that is flexible like rubber, but almost indestructible. As has been the case with many of NASA’s inventions over the years, so will space-age tire technology will be available to consumers soon
Using air-filled rubber tires on a vehicle is simply not a practical solution for exploring nearby celestial bodies whose natural terrain is covered with rocks and sharp objects. So for the handful of wheeled vehicles that NASA has sent to the Moon and Mars, metal wheels are a better alternative. For the Lunar Rover, which brought Apollo 15 to the moon, wheels were made of hollow metal springs that could absorb bumps to make the ride more comfortable for astronauts. But most metals lose their shape over time and become brittle when bent repeatedly, resulting in misshapen wheels that don’t roll as well, and worse, severe damage that prevents them from rolling at all.
Alternatively, NASA has spent millions of dollars over the past seven years developing Nitinol, a metal alloy of aluminum and titanium that behaves differently. Metal springs eventually lose their ability to spring back to their original shape because the connections between their atomic structures become so stretched that they are no longer able to return to their original order. But Nitinol has a more ordered atomic structure and exhibits something known as the shape memory effect, which allows it to be deformed but return to its original manufactured shape over and over again without permanent damage. This allows the creation of metal tires that can deform to absorb the impact of uneven terrain such as rubber, without the possibility of a puncture.
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It’s an incredible technology that will soon be available in the years to come for a vehicle that is unlikely to ever leave Earth’s atmosphere: your bicycle. A startup called The Smart Tire Company has announced that it is making a metal bicycle tire using NASA’s Nitinol alloy that will never need to be inflated, will never cause a puncture, and will likely survive much longer than the bike itself.
Named METL (Martensite Elasticized Tubular Loading) tire, its makers hope it will be available as early as 2022 as an alternative to premium bicycle tires. It remains to be seen how much a titanium alloy bicycle tire will cost, but you can bet it will be a long time before kids find a bike with Nitinol wheels under the Christmas tree. For cyclists eager to spend tens of thousands of dollars on their bikes, the METL tires could be the last set they should ever buy, although they still require regular maintenance.
The most common problem with airless tires is that they often have an open structure that allows dirt to enter and throw off the balance of the wheel. Using a structure of metal instead of rubber complicates things further, as the smooth finish means the tire doesn’t have much grip. To solve this, the METL tires will also be finished with a rubber-like tread made from a material called polyurethane that provides traction and makes them suitable for riding on all terrains, including pavement, gravel and dirt. Over time, the tread will wear out and will need to be reapplied, but that maintenance is expected to be a lot cheaper than replacing a set of tires on a regular basis.
The METL tires are not suitable for every rider. After all, they are made of metal and are expected to be heavier than the premium lightweight tires used by professional cyclists and athletes. But for most other uses, including athletes using larger bikes on off-road terrains, the tires won’t feel any different on a ride.
The Smart Tire Company makes a lot of promises about the advantages of its Nitinol tires over rubber tires – see this in detail FAQ on its website showcase the virtues of the technology – and there is good reason to be excited about the technology. Clearly, NASA felt it was important enough to spend millions of dollars on its development. But we have been promised airless tires for many years, from industry giants like Bridgestone who have the manufacturing capabilities to make them happen. However, they still don’t exist, even for bicycles, which is just about the least demanding application for the technology.
There’s no question that punctures will one day be a thing of the past, but will that be thanks to the efforts of this startup? If it can deliver the METL tires as it plans in the coming years, there is good reason for Michelin, Goodyear and Bridgestone to be concerned.