Six more firms joined the Commercial Spaceflight Federation in July, boosting the Washington-based advocacy organization’s number of corporate members to 31.

Among the largest of the crop of new members are rocket-engine builder Pratt & Whitney Rocketdyne of Canoga Park, Calif., and SRA International, a Fairfax, Va.-based technology consulting firm employing 7,000 people worldwide.

The other new members are: Andrews Space of Seattle; DCI Services and Consulting of Houston; MEI Technologies of Houston; and Space Aerospace Services of Boulder, Colo.