X-37B Air Force space plane.
Credit: Boeing/Inside Outer Space Screengrab

The U.S. Air Force’s robotic space drone, the X-37B, has flown more than 600 days circuiting the Earth.

This craft is labeled Orbital Test Vehicle (OTV-6), also called USSF-7 for the U.S. Space Force, and was launched on May 17, 2020 by an Atlas-V 501 booster.

As for the vehicle’s primary agenda that remains classified, although some of its onboard experiments were identified pre-launch.

Air Force X-37B space plane.
Credit: Boeing

Known payloads

One experiment onboard the space plane is from the U.S. Naval Research Laboratory (NRL), an investigation into transforming solar power into radio frequency microwave energy. The experiment itself is called the Photovoltaic Radio-frequency Antenna Module, PRAM for short.

In addition, the X-37B also deployed the FalconSat-8, a small satellite developed by the U.S. Air Force Academy and sponsored by the Air Force Research Laboratory.

Naval Research Laboratory (NRL) has pioneered “sandwich” modules that are used in space solar power experiments.
Credit: NRL/Jamie Hartman

Also onboard are two NASA experiments, one to study the effects of the space environment on a materials sample plate and a payload of seeds.

OTV-6 is the first to use a service module to host experiments. The service module is an attachment to the aft of the vehicle that allows additional experimental payload capability to be carried to orbit.

Track record

There’s no official word on when the military space plane mission will return to Earth, but the craft might be headed for a record-setting duration in orbit, eclipsing 780 days in space.

X-37B breaks record, lands after 780 days in orbit
The Air Force’s X-37B Orbital Test Vehicle Mission 5 successfully landed at NASA’s Kennedy Space Center Shuttle Landing Facility Oct. 27, 2019.
Credit: U.S. Air Force

Originally designed for missions of 270 days, the X-37B has set endurance records during each of its five previous flights.

Earlier flights in the X-37B program are:

OTV-1: launched on April 22, 2010 and landed on December 3, 2010, chalking up over 224 days on orbit.

OTV-2: launched on March 5, 2011 and landed on June 16, 2012, spending over 468 days on orbit.

OTV-3: lofted on December 11, 2012 and landed on October 17, 2014, spending over 674 days on-orbit.

OTV-4: launched on May 20, 2015 and landed on May 7, 2015, spending nearly 718 days on-orbit.

OTV-5: placed into orbit on September 7, 2017 and landed on October 27, 2019, spending nearly 780 days on-orbit.

OTV-1, OTV-2, and OTV-3 missions landed at Vandenberg Air Force Base, California, while the OTV-4 and OTV-5 missions landed at the Kennedy Space Center, Florida.

The unpiloted mini-shuttle has a height of 9.6 feet (2.9 m), a length of 29.3 feet (8.9 m), a wingspan of 14 feet, 11 inches (4.5 meters) and weighs roughly 11,000 pounds (4,990 kg). There are two vehicles that constitute the X-37B program, designed and built by Boeing.

Reusable technologies

According to a Boeing fact sheet, “the X-37B is one of the world’s newest and most advanced re-entry spacecraft, designed to operate in low-Earth orbit, 150 to 500 miles above the Earth. The vehicle is the first since the Space Shuttle with the ability to return experiments to Earth for further inspection and analysis. This United States Air Force unmanned space vehicle explores reusable vehicle technologies that support long-term space objectives.”

According to Boeing, the autonomous vehicle features many elements that mark a first use in space, including:

  • Avionics designed to automate all de-orbit and landing functions.
  • Flight controls and brakes using all electro-mechanical actuation; no hydraulics on board.
  • Built using a lighter composite structure, rather than traditional aluminum.
  • New generation of high-temperature wing leading-edge tiles and toughened uni-piece fibrous refractory oxidation-resistant ceramic (TUFROC) tiles.
  • Advanced conformal reusable insulation (CRI) blankets.
  • Toughened uni-piece fibrous insulation (TUFI) impregnated silica tiles.

“The X-37B has a lifting body-style and landing profile that is similar to the Space Shuttle, but the vehicle is one-fourth the size. The X-37B design combines the best of aircraft and spacecraft into an affordable system that is easy to operate and maintain,” states Boeing.

Space test platform

The X-37B program is flown under the wing of a U.S. Space Force unit called Delta 9, established and activated July 24, 2020.

Credit: U.S. Air Force/Boeing

“Delta 9 Detachment 1 oversees operations of the X-37B Orbital Test Vehicle, an experimental program designed to demonstrate technologies for a reliable, reusable, unmanned space test platform for the U.S. Space Force,” according to a fact sheet issued by Schriever Air Force Base in Colorado.

Credit: U.S. Air Force/Boeing

“The mission of Delta 9 is to prepare, present, and project assigned and attached forces for the purpose of conducting protect and defend operations and providing national decision authorities with response options to deter and, when necessary, defeat orbital threats,” the fact sheet explains. “Additionally, Delta 9 supports Space Domain Awareness by conducting space-based battlespace characterization operations and also conducts on-orbit experimentation and technology demonstrations for the U.S. Space Force.”





Go to this new video of OTV-6 flying overhead on January 11, 2022 by satellite tracker, Kevin Fetter, at:


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