In connection with the national defense program, the Departments of the Navy, Army, and Air Force and the Secretary of Housing and Urban Development are authorized to cooperate in making necessary housing available for persons engaged in national defense activities, as provided in this subchapter. “Persons engaged in national defense activities” (as that term is used in this subchapter) shall include (i) enlisted men with families, who are in the naval and military service and officers of the Army, Air Force, and Marine Corps not above the grade of captain, and officers of the Navy and Coast Guard, not above the grade of lieutenant and employees of the Departments of the Navy, Army, and Air Force who are assigned to duty at naval or military reservations, posts, or bases, and (ii) workers with families, who are engaged or to be engaged in industries connected with and essential to the national defense program. No project shall be developed or assisted for the purposes of this subchapter except with the approval of the President and upon a determination by him that there is an acute shortage of housing in the locality involved which impedes the national defense program.