If you have ever watched footage of the Apollo Moon missions of the early 1970s, you probably saw the "Moon buggy" that astronauts used to move themselves, their equipment, and samples across the lunar surface. This was NASA's first rover designed for an environment other than Earth.

Tomorrow’s Moon missions will explore much broader territory. For these longer missions, NASA plans to construct habitats for its astronauts and a next-generation rover. New rover designs will still have to meet the particular challenges of the lunar environment—low gravity, no atmosphere, extreme temperatures and radiation, and varied topography. The rovers will also need to be specially equipped to support updated mission goals that will demand reliability, climbing ability, remote control, and self-contained electrical power.

One design being considered is called the All-Terrain Hex-Limbed Extra-Terrestrial Explorer (ATHLETE). At its core, ATHLETE is a mobile platform that can be operated by astronauts on the Moon or personnel on Earth to transport heavy cargo from a landing vehicle to wherever it’s needed. But ATHLETE has been designed to help with exploration and construction as well.

To perform these varied roles, the rover has six identical limbs, each with six degrees of freedom. In robotics, “degrees of freedom” refers to the number of different ways in which a limb can move or pivot. Six degrees of freedom means each limb can move forward–backward, up–down, and left–right and pivot around three perpendicular axes (pitch, yaw, and roll). Attached to the end of each limb is a wheel that can be used to drive ATHLETE and its cargo over gentler terrain at a top speed of just under 2 mph (3 kph). The wheels can also be locked so that the limbs become more like legs, able to walk over uneven terrain.

ATHLETE’s design meets mission goals in other ways, too:

• The unique limbs enable ATHLETE to use tools.
• Cameras are positioned along its body to see around and directly under the vehicle.
• ATHLETE’s body has six flat faces that can either be used to dock to similar ATHLETE vehicles and coordinate work, or to other systems, such as refueling stations.
• Lastly, because transporting large bulky objects into space can be problematic, ATHLETE can fold into a flat ring. This means several ATHLETEs can be stacked for transit.

Because many of the challenges presented by the lunar environment are common to Mars, ATHLETE’s design and capabilities would make it suitable for use in future Mars missions as well.

Print Background Essay