Spaceflight Insider

USAF’s secretive X-37B spacecraft’s AFSPC-5 mission passes one year mark

USAF X-37B space plane at Edwards Air Force Base in California photo credit USAF posted on SpaceFlight Insider - Copy

Photo Credit: USAF

CAPE CANAVERAL, Fla. — The U.S. Air Force’s secretive X-37B spaceplane has launched four times since its first flight in 2010; it has only landed three times. The current mission, OTV-4, has been in space for more than a year, having been launched from Cape Canaveral Air Force Station on May 20, 2015. Little is known as to what the vehicle is doing in orbit.

The OTV-4/AFSPC-5 mission is the second flight of the second X-37B vehicle. One of the few experiments that has been publicly announced as taking place on this flight was a test of the Hall effect thruster as part of the Advanced Extremely High Frequency (AEHF) communications satellite program. Also on board the automated shuttle is a test of more than one hundred materials samples in space using NASA’s Materials Exposure and Technology Innovation in Space (METIS) experiment.

OTV Orbital Test Vehicle AFSPC 5 X_37B diagram image credit Nathan Moeller / SpaceFlight Insider

Image Credit: Nathan Moeller / SpaceFlight Insider

The AEHF Hall thrusters were developed by Aerojet Rocketdyne and use electricity to accelerate xenon propellant for thrust. The U.S. Air Force Research Laboratory produced the orbital experiments with the Hall thruster, which include not only the measurement of the operation of the thruster but also the amount of thrust imparted to the X-37B.

The METIS experiment is based on NASA’s Materials on International Space Station Experiment (MISSE). Between 2001 and 2013, MISSE flew more than 4,000 samples in space. METIS is composed of a number of polymers, composites, and coatings.

The X-37B was launched by a United Launch Alliance Atlas V 501 rocket from Space Launch Complex 41 at Cape Canaveral Air Force Station. The uncrewed mini-spaceplane measures some 29 feet (8.84 meters) in length and is equipped with a small cargo bay. Its maneuvering engine runs on hydrazine and nitrogen tetroxide.

Much about the X-37B remains secret, but it is known that its thermal protection system is different from the Space Shuttle’s silica tiles.

There has been much speculation about the purpose of the X-37B, but James Andrew Lewis, director and senior fellow in the Strategic Technologies Program at the Center for Strategic and International Studies, believes it’s likely meant for advanced orbital surveillance.

“I think that’s probably what they’re not telling you,” Lewis said in a report appearing on Air&Space, “that there are payloads in there that might be part of the design for future reconnaissance satellites.” He said that the Air Force is “looking to figure out how to transition from big, expensive satellites to smaller but equally capable satellites.”

Brian Weeden, a technical adviser for the Secure World Foundation, thinks the Hall thrusters are being tested in order to develop capabilities of planning low-orbit satellites to take higher-resolution photographs of objects on the ground. He cites the X-37B’s low altitude, under 200 miles (320 kilometers), which is lower than the International Space Station (at approximately 260 miles or 418 kilometers). Hall thrusters could significantly lighten surveillance satellites.

“One of the reasons that the traditional exquisite imaging satellites are so hard to launch is because they’re big and they’re heavy,” Weeden said. “My guess would be that [the X-37B] itself would probably not move into an operational-type role, but that a lot of the technologies that it’s demonstrating, like the Hall effect thrusters, or whatever the sensor payloads are, are going to move into the operational role. That’s how it went with the X-planes of the 1950s and 1960s.”

Todd Harrison, a defense budget analyst at the Center for Strategic and International Studies, thinks that an operational fleet would enable satellites to be captured and returned to Earth for maintenance or repairs, then relaunched.

“They could add different versions of the vehicle, larger versions in particular,” Harrison said.

The X-37B program is run by the Air Force’s Rapid Capabilities Office.

Video courtesy of SpaceFlight Insider


Collin R. Skocik has been captivated by space flight since the maiden flight of space shuttle Columbia in April of 1981. He frequently attends events hosted by the Astronaut Scholarship Foundation, and has met many astronauts in his experiences at Kennedy Space Center. He is a prolific author of science fiction as well as science and space-related articles. In addition to the Voyage Into the Unknown series, he has also written the short story collection The Future Lives!, the science fiction novel Dreams of the Stars, and the disaster novel The Sunburst Fire. His first print sale was Asteroid Eternia in Encounters magazine. When he is not writing, he provides closed-captioning for the hearing impaired. He lives in Atlantic Beach, Florida.

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