Farewell from SOFIA, NASA 747 with telescope

One of the most fascinating wonders of aviation is nearing the end of its life in the sky. After operating for just eight years from its planned 20-year lifespan, the unique Stratospheric Observatory for Infrared Astronomy (SOFIA) aircraft, subsequently equipped with a 747 with a 17-tonne reflective telescope on board, is retiring.

The aircraft first took off in 1977. Originally made as a commercial aircraft for Pan Am, the Boeing 747SP was christened as Clipper Lindbergh in recognition of Charles Lindbergh, a famous American aviator who completed the first solo non-stop flight across the Atlantic in 1927. The aircraft was later sold to United Airlines, before being bought by NASA in 1997.

Using an infrared telescope nearly 9 feet in diameter lying inside a cavity in the back of the plane, the aerial observatory has since discovered water on the moon’s surface, discovered new planetary systems and found the first type of molecule to form after a big bang. Not bad for an aircraft originally made to only transport people.

Not your typical 747

A variant of the classic 747 aircraft that many aviation enthusiasts know and love, the SOFIA is a much shorter, “stubborn” version of the jumbo jet, made especially for long-haul flights. A collaboration between NASA and the German Space Agency (DLR), SOFIA operates from an agency hangar in Palmdale, California. The spacecraft recorded more than 980 hours of observation each year, averaging about seven to nine hours of scientific observation per flight.

It has a wing span of 196 feet and can also reach about 450 knots or about 520 miles per hour when at a desired altitude of 41,000 feet above sea level. “Think of it as the hot rod of the 747,” said Ting Tseng, NASA’s chief engineer for the SOFIA mission.

Tseng, who has worked in the craft since 2006, led a team that turned it into a powerhouse of scientific discovery as it is today. But before SOFIA could take off into the sky, the spacecraft underwent major modifications and maintenance to optimize the potential for collecting scientific data.

One unique modification involved making the fuselage, ie the main body of the aircraft, thicker than a conventional vessel to ensure that the telescope could work safely. But to create a cavity large enough to fit, the team had to cut a hole in the side of the aircraft – a solution that is as problematic as it sounds.

“If you cut a hole in an airplane, there’s a chance that air currents will enter that hole and exert significant force on the aircraft frame from the inside,” says Bernhard Schulz, deputy director of operations at SOFIA’s scientific mission and DLR side project representative. “Basically, it can rip off an entire tail.”

[Related: Explore the gauges, levers, and history of a 747′s iconic cockpit]

A team of engineers solved this by creating special doors for the telescope. “The door system is unique,” ​​says Tseng. “You won’t see that kind of system in any other aircraft.” The rigid structure weighs over 3,000 pounds and helps minimize airflow inside and above the telescope cavity, ensuring that turbulent weather does not affect instrument measurements.

With a flight range of about 6,625 nautical miles, SOFIA is able to depart and return from its missions on the same day. “Depending on what observations we have for a particular instrument, we can fly all over the United States and sometimes Canada,” Tseng says. But for that, the plane needs a ton of fuel; can carry a maximum of £ 300,000.

In 2012, SOFIA’s analog meters and hardware were modernized, and many of its current scientific and communication systems are now automated, connected by a range of integrated computers and devices.

It was a move that promised to move him into the future, but unfortunately for those generally nostalgic for the 747, this craft could soon recede into the annals of history.

Sofia 747
SOFIA in March 2021 at NASA’s Armstrong Flight Research Center. NASA / Ken Ulbrich

Final farewell

Although SOFIA will continue to fly on scientific missions until September 30, there is no other observatory that should take its place or provide the space community with the same wavelength of data it collects.

NASA’s decision to withdraw the mission cited community concerns about the project’s productivity and cost. Compared to a space mission, SOFIA usually costs more because of the pilots, fuel, and maintenance required to fly. But Schulz says the difference in price is worth it when you consider the types of science the craft has made possible.

“It will probably be the last type of aircraft observatory to work this way,” says Schulz. “It’s a great advantage [and] works perfectly. It’s a shame to close it immediately and put it in a museum. “

But SOFia’s fate has not yet been sealed: in fact, this is not even the first time the mission is ready to cancel. Although Congress would call for action to save the mission and its funding, Schulz says “it has already happened.” And during City Hall Astrophysics on May 3, Paul Hertz, director of NASA’s Department of Astrophysics, asked questions about the future of the aircraft, a topic that many members of the general public seemed to support.

But for scientists and engineers who are closely acquainted with the mission, some admit that while it is bitter-sweet, the early withdrawal of the mission is not the end of the world.

“NASA programs don’t last forever and we’ve come to the end of the road,” Tseng says. “I’m just happy to have been a part of this amazing observatory and to have been able to make this a great aircraft.”

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