Technically, that facility is the Udvar-Hazy Center. The Fairfax Connector bus # 983 connects the museum and the airport every 20 minutes for $1.75 cash fare. Senior fare (65+) is $.85 - just show the driver your Medicare card. The bus uses Curb 2E at Dulles.

Information desks in the Dulles baggage claim area next to claim 6 and claim 11 can steer you in the right direction.