Former space shuttle operator United Space Alliance, Google Lunar X Prize contender Moon Express, and aerospace crew equipment maker David Clark Co. have joined the Commercial Spaceflight Federation (CSF) as associate members, the Washington-based advocacy organization announced Sept. 22.

The news comes as the organization launches a search for a new president. Craig Steidle, the retired U.S. Navy rear admiral and former NASA official who took the helm of the Commercial Spaceflight Federation in May, stepped down Sept. 9 following a heart attack.

Eric Anderson, the Commercial Spaceflight Federation’s chairman, said in a statement that Steidle would “continue to serve as an advisor to ensure a smooth transition as his successor is selected.

“The entire commercial spaceflight industry recognizes Admiral Steidle’s tremendous work during his service to CSF,” Anderson continued. “He has been able to accomplish much since taking the helm and the Federation wishes him well and thanks him for all his hard work.”

With the addition of the new companies, the Commercial Spaceflight Federation’s membership stands at 47.