The National Aeronautics and Space Administration (NASA) and tyre and rubber company Goodyear have developed an airless tyre to transport large, long-range vehicles across the surface of the moon.

Everybody involved in the project has been so impressed with its performance that they are mulling over finding ways to use the technology in tyres for cars and other Earthbound vehicles.

The new Spring Tyre with 800 load-bearing springs is designed to carry much heavier vehicles over distances greater than the wire mesh tyre previously used on the Apollo Lunar Roving Vehicle (LRV). The developers say the new tyre will allow for broader exploration and the eventual development and maintenance of a lunar outpost.

According to Vivake Asnani, Nasa's principal investigator at the Glenn Research Center in Cleveland, this was a significant change in requirements that required innovation.

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

Retrospect

"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 was installed on Nasa's Lunar Electric Rover test vehicle and put through its paces at the Johnson Space Centre's "Rock Yard" in Houston where it performed successfully.

"This tire is extremely durable and extremely energy efficient," said Jim Benzing, Goodyear's lead innovator on the project.

"The spring design contours to the surface on which it's driven to provide traction. 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."

No air needed

According to Goodyear engineers, development of the original Apollo lunar mission tyres, and the new Spring Tyre were driven by the fact that traditional rubber, pneumatic (air-filled) tyres used on Earth have little use on the moon.

This is because the properties of rubber vary significantly in the extremes of temperature experienced in the environment moon.

Unfiltered solar radiation also 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 that means," he said, "is that a hard impact that might cause a pneumatic tyre to puncture and deflate would only damage one of the 800 load bearing springs. "Along with having this ultra-redundant characteristic, the tyre has a combination of overall stiffness yet flexibility that allows off-road vehicles to travel fast over rough terrain with relatively little motion being transferred to the vehicle."

Future use

Nasa has been so impressed with the tyre that it decided to highlight the project during a meeting with members of Congress in Washington, DC.

"I spoke with 10 to 15 members of Congress and about sixty staffers," noted Asnani. "Virtually everyone I spoke with was blown away by the idea that this technology may one day be used, not only for extraterrestrial vehicles, but also, perhaps, for vehicles here on Earth."