With NASA hoping to put Americans back on the moon within 10 years, Goodyear and Michelin are racing to build airless tires for the next generation of moon rover vehicles. Undertaking such an endeavor isn't easy: moon vehicle tires can't employ air and rubber. This is partially because of the moon's extreme temperatures -- dropping below about minus 250 degrees Fahrenheit at night and rising above plus 200 degrees in the day.
Since the new lunar rovers will be very similar to those employed in the early 1970s, Goodyear reverse-engineered the wire-mesh tires used on the original Apollo Lunar Roving Vehicle. Goodyear even borrowed moon rover tires from the Smithsonian museum and brought in retired engineers who worked on the project as well. The Goodyear tire uses mesh woven from piano wire with a tread of metal strips to provide flotation in the moon's soft soil.
Michelin's entry is a version of its Tweel, first revealed in 2004. The Michelin Lunar Wheel (pictured) uses a fabric tread to maintain traction and the function of air is replaced with a series of flexible composite spokes. Michelin currently makes the tires for the soon-to-be discontinued space shuttle.