NASA published their rock climbing robot project. The robots called TRESSA. TRESSA is a group of three autonomous robots that work together to climb steep slopes. And by steep we mean up to 90 degree slope angles. Two of the robots, called Anchorbots, remaining at the top and support the third robot, named Cliffbot, with tethers as it negotiates the rocks. The Anchorbots dynamically adjust the tension of the tethers, allowing Cliffbot to go up, down, or across the slope. This is more complicated than it sounds as the Anchorbots have to combine the amount of tether tension needed to offset gravitational forces with anticipation of desired motion of Cliffbot. The robots also monitor themselves and each other for faults and communicate any potentially unsafe conditions to each other.

The TRESSA (Teamed Robots for Exploration and Science on Steep Areas) system, previously cited in the literature as Cliffbot (Pirjanian et al., 2002; Mumm,Farritor, Huntsberger and Schenker, 2003; Schenker et al., 2003b; Mumm, Farritor, Pirjanian, Leger and Schenker, 2004), is designed to allow access to steep slopes that are not feasible for traditional wheeled rovers.