The museum's fundraising campaign, specifically focused on building the Dulles annex, contacted Udvar-Hazy, Moeser said. The donation brings the total for the campaign to roughly $90 million, Moeser said. Its goal is $130 million.

Work will start on the annex next spring and is scheduled to open in December 2003, to coincide with the 100th anniversary of the Wright Brothers first flight.

The huge annex, much larger than the current museum, will house over 180 aircraft and 100 spacecraft.

The Enterprise was the prototype Space Shuttle used for landing-approach tests in the 1970s. It was attached to the top of a Boeing 747 and then released at a high altitude to test the shuttle's lifting body characteristics and handling.

The SR-71, though officially retired from active service, remains the fastest plane in existence with a top speed above Mach 3. The model donated to the museum was retired just after it broke the coast-to-coast supersonic speed record (once held by astronaut John Glenn before he joined the space program) averaging 2,124.05 miles per hour.

The Goddard rocket was from the scientist's A series, a liquid oxygen and gasoline rocket which reached a maximum altitude of 4,000 feet.

The museum plans an official announcement on October 7, when Udvar-Hazy will return from a business trip from Asia.

"Nobody here has really met him," Moeser said. "He's sort of our mystery man."