Weapons maker Lockheed Martin Corp
Walker joins the world's largest defence contractor from the U.S. Department of Defense's future warfare and technology agency DARPA, where he was a director.
In his new role, Walker will act as the company's liaison to science and technology communities and help in the development of advanced weapons technologies.
Walker's efforts to develop hypersonic weapons and low-earth orbit satellites while at DARPA will help Lockheed as it pursues hypersonic weapons and to win future defence contracts.
In October, Lockheed said it expects $1 billion in sales from hypersonic weapons in 2020.
Walker will replace Keoki Jackson, who was appointed chief engineer and vice president for the engineering and program operations at Lockheed.