When you’re exploring another planet, the last thing you want to deal with is tires damaged when the AAA is millions of miles away. It is a concern that led NASA to develop a airless titanium tire which is flexible like rubber, but almost indestructible. As has happened with many of NASA’s inventions over the years, space age tire technology will soon be available to consumers.
Using rubber tires with air in a vehicle is simply not a practical solution for exploring nearby celestial bodies, whose natural terrain is covered by rocks and sharp objects. So for the handful of wheeled vehicles that NASA sent to the Moon and Mars, metal wheels are a better alternative. For the Lunar Rover, which Apollo 15 brought to the moon, wheels were created made of hollow metal springs that could absorb bumps to make the trip more comfortable for astronauts. But most metals lose their shape over time and become brittle when flexed repeatedly, resulting in deformed wheels that don’t roll as well and, even worse, severe damage that prevents them from rolling.
Alternatively, NASA has spent several million dollars over the past seven years developing Nitinol: a metal alloy made of aluminum and titanium that behaves differently. Metal springs eventually lose their ability to return to their original shape because the bonds between their atomic structures become so stretched that they are no longer able to return to their original arrangements. But Nitinol has a more orderly atomic structure and exhibits something known as the shape memory effect, which allows it to be deformed, but return to its original form of manufacture over and over again without permanent damage. It allows the creation of metal tires that can be deformed to absorb the impact of uneven terrain such as rubber, without the possibility of a flat tire.
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It is an incredible technology that will soon be available in the coming years for a vehicle that will probably never leave Earth’s atmosphere: your bicycle. A startup called The Smart Tire Company announced that it is creating a metal bicycle tire using NASA’s Nitinol alloy that never needs to be inflated, will never have a leak and will probably survive much longer than the bicycle itself.
Called the METL (Martensite Elasticized Tubular Loading) tire, its creators are hopeful that it will be available as an alternative to premium bicycle tire options as early as 2022. It remains to be seen how much a titanium alloy tire will cost, but you can suppose it will be a long time before children find a bicycle with Nitinol wheels under the Christmas tree. For cyclists who like to spend tens of thousands of dollars on their bikes, however, METL tires may be the last set they will have to buy, although they still require regular maintenance.
The most common problem with airless tires is that they often feature open-frame designs that can allow debris to enter and impair wheel balance. Using a metal frame instead of rubber further complicates things because the smooth finish means that the tire doesn’t have much grip. To address this, METL tires will also be finished with a rubber-like tread made of a material called polyurethane that adds grip 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 maintenance is expected to be much cheaper than regular replacement of a set of tires.
METL tires are not suitable for all drivers. After all, they are made of metal and are expected to be heavier than the premium light tires used by cyclists and professional athletes. But for most other applications, including athletes who use larger bikes on off-road terrain, the tires will have no different feeling during a ride.
Smart Tire Company is making many promises about the advantages of its Nitinol tires over rubber tires – see this extensive FAQ on your website touting the virtues of technology – and there is good reason to be excited about technology. Obviously, NASA felt it was important enough to spend millions of dollars on its development. But we have been promised airless tires for many years now, from industry giants like Bridgestone, who have the manufacturing resources to make them a reality. They are not here yet, not even for bicycles, which is the least demanding application for technology.
There is no doubt that one day flat tires will be a thing of the past, but will it be thanks to the effort of this startup? If she can deliver METL tires in the years to come as she wants, there are good reasons for Michelin, Goodyear and Bridgestone to be concerned.