One of aviation’s most fascinating marvels is nearing the end of its life in the sky. After operating for just eight years out of its expected 20-year lifespan, the Stratospheric Observatory for Infrared Astronomy’s (SOFIA) sole aircraft, a retrofitted 747 with a 17-ton reflecting telescope on board, takes his retirement.
The aircraft first flew in 1977. Originally built as a commercial aircraft for Pan Am, the Boeing 747SP was christened as the Lindbergh mower in tribute to Charles Lindbergh, the famous American aviator who made the first non-stop solo flight across the Atlantic in 1927. The machine was then sold to United Airlines, before being acquired by NASA in 1997.
Using the nearly 9-foot-diameter infrared telescope that sits inside a cavity in the tail section, or rearmost part of the aircraft, the airborne observatory has since discovered water on the surface of the moon, revealed new planetary systems, and found the first kind of molecule to form as a result of the big bang. Not bad for an airliner originally built to transport people.
Not your typical 747
A variant of the classic 747 aircraft that many aviation fans know and love, the SOFIA is a much shorter, “chunkier” version of the jumbo jet, specifically designed for long-distance flights. The result of a collaboration between NASA and the German Space Agency (DLR), SOFIA operates from an agency hangar in Palmdale, California. The craft logged more than 980 hours of observation each year, an average of about seven to nine hours of scientific observation per flight.
It sports a wingspan of 196 feet and can also reach around 450 knots, or about 520 miles per hour when at its preferred height of 41,000 feet above sea level. of a 747,” says Ting Tseng, NASA’s chief engineer for the SOFIA mission.
Tseng, who has worked on the craft since 2006, led the team that made it the engine of scientific discovery that it is today. But before SOFIA could take flight, the craft underwent serious modifications and maintenance to optimize its potential for collecting scientific data.
A unique modification was to make the fuselage, or the main body of the aircraft, thicker than normal gear to ensure the telescope could operate safely. But to create a cavity large enough to fit in, the team had to drill a hole in the side of the plane – a solution as problematic as it sounds.
“If you drill a hole in an aircraft, it is possible that the airflow will enter that hole and exert a considerable force on the airframe inside,” says Bernhard Schulz, deputy director of operations for the SOFIA science mission. and representative of the DLR. side of the project. “Basically, he can rip off the whole tail.”
[Related: Explore the gauges, levers, and history of a 747′s iconic cockpit]
The team’s engineers solved this problem by creating a special door for the telescope’s cavity. “The door system is one of a kind,” says Tseng. “You won’t see any of this type of system in any other aircraft.” The rigid structure weighs over 3,000 pounds and helps minimize airflow into and over the telescope cavity, ensuring turbulent weather does not affect instrument measurements.
With a range of around 6,625 nautical miles, SOFIA is able to depart and return from its missions on the same day. “Depending on the observations we make for a particular instrument, we can fly anywhere in the United States and sometimes in Canada,” Tseng says. But to do this, the plane needs a ton of fuel; it can carry a maximum of 300,000 pounds.
In 2012, SOFIA’s analog gauges and hardware were upgraded, and many of its current science and communications systems are now automated, linked together by a series of computers and integrated devices.
It was a decision that promised to propel it into the future, but unfortunately for 747 nostalgics in general, the craft may soon be resigned to the annals of history.
A last farewell
Although SOFIA will continue to carry out scientific missions until September 30, no other observatory is planned to take its place or to provide the space community with the same wavelength of data that it collects.
NASA’s decision to retire the mission cited community concerns about the productivity and cost of the project. Compared to a space mission, SOFIA tends to cost more due to the pilots, fuel and maintenance needed to fly it. But Schulz says the difference in cost is worth it when you consider the kinds of science the craft enabled.
“It will probably be the last type of aircraft observatory that works this way,” Schulz says. “It’s a great asset [and] it works perfectly. It’s a shame to close it now and put it in a museum.
But SOFIA’s fate is not yet sealed: in fact, it’s not even the first time that the mission has been canceled. Although that would require congressional action to save the mission and its funding, Schulz says “it’s happened before.” And at a town hall meeting on astrophysics on May 3, Paul Hertz, director of NASA’s astrophysics division, answered questions about the future of the plane, a topic that many members of the general public seemed to support.
But for scientists and engineers intimately familiar with the mission, some recognize that, while bittersweet, stopping the mission early isn’t the end of the world.
“NASA programs don’t last forever and we’ve come to the end of the road,” says Tseng. “I’m just happy to have been part of this incredible observatory and to have been able to make a great plane out of it.”