The US National Aeronautics and Space Administration (Nasa) and Goodyear Tire & Rubber Company have deve- loped an airless, rubberless tyre to transport large, long-range vehicles across the surface of the moon.

The new Spring Tyre, with 800 load-bearing springs, is designed to carry heavier vehi- cles over greater distances than the wire-mesh tyre used previously on the Apollo lunar roving vehicle.

The new tyre will allow for broader exploration and the eventual development and maintenance of a lunar outpost. But the tyre may also, event- ually, migrate to earth.

According to Nasa principal investigator at the Glenn Research Centre, in Cleveland, Vivake Asnani, the new moon tyre demanded quite a degree of innovation.

“With the combined requirements of increased load and life, we needed to make a fundamental change to the original moon tyre,” he explains.

“What the Goodyear-Nasa team developed is an innovative, yet simple, network of interwoven springs that does the job.

“The tyre design seems almost obvious in retrospect, as most good inventions do.”

The Spring Tyre has been installed on Nasa’s lunar electric rover test vehicle, and put through its paces at the Johnson Space Centre’s Rock Yard, in Houston.

“The spring design contours to the surface on which it is driven to provide traction,” notes Jim Benzing, Goodyear’s lead innovator on the project. “But all of the energy used to deform the tyre is returned when the springs rebound. It doesn’t generate heat like a normal tyre.”

According to Goodyear engineers, development of the original Apollo lunar mission tyres, as well as the new Spring Tyre, was driven by the fact that tradi- tional rubber, pneumatic (air-filled) tyres used on earth have little utility on the moon.

This is because rubber proper- ties vary significantly between the extreme cold and hot temperatures experienced in the shaded and directly sunlit areas of the moon.

Further, unfiltered solar radiation degrades rubber, and pneumatic tyres pose an unacceptable risk of deflation.

According to Asnani, the Spring Tyre does not have a “single point failure mode”.

What this means is that a hard impact that may cause a pneumatic tyre to puncture and deflate will only damage one of the 800 loadbearing springs on the new tyre.

The tyre also has a combination of overall stiffness and flexibility, that allows off-road vehicles to travel fast over rough terrain with relatively little motion being transferred to the vehicle.

To subscribe to Engineering News's print magazine email subscriptions@creamermedia.co.za or buy now.