Half Dome, Tis-Sa-Ack Climbed by a Paraplegic. Mike Corbet and paraplegic climber Mark Wellman, who serves as a Yosemite Park Ranger, climbed the Tis-Sa-Ack route on Half Dome, reaching the top on September 16 after 13 days on the wall. They suffered from bad weather and lack of food. Wellman had been injured in a climbing accident in 1982 but refuses to consider himself disabled.