Credit: Boeing

 

The U.S. Air Force X-37B mini-space plane has winged past 340 days of flight performing secretive duties during the program’s fifth flight.

Labeled the Orbital Test Vehicle (OTV-5), the robotic craft was rocketed into Earth orbit on September 7, 2017 atop a SpaceX Falcon 9 booster from Launch Complex 39A at NASA’s Kennedy Space Center in Florida.

Payload bay

On this latest clandestine mission of the space plane, all that’s known according to Air Force officials is that one payload flying on OTV-5 is the Advanced Structurally Embedded Thermal Spreader, or ASETS-11. Developed by the U.S. Air Force Research Laboratory (AFRL), this cargo is testing experimental electronics and oscillating heat pipes for long durations in the space environment.

Credit: Boeing

The X-37B space plane has a payload bay about the size of a pickup-truck bed, which can be outfitted with a robotic arm. X-37B has a launch weight of 11,000 lbs. (4,990 kilograms) and is powered on orbit by gallium-arsenide solar cells with lithium-ion batteries.

Record setting history

Each X-37B/OTV mission has set a new flight-duration record for the program:

OTV-1 began April 22, 2010, and concluded on Dec. 3, 2010, after 224 days in orbit.

OTV-2 began March 5, 2011, and concluded on June 16, 2012, after 468 days on orbit.

OTV-3 chalked up nearly 675 days in orbit before finally coming down on Oct. 17, 2014.

OTV-4 conducted on-orbit experiments for 718 days during its mission, extending the total number of days spent in space for the OTV program to 2,085 days.

Last Air Force’s X-37B Orbital Test Vehicle mission touched down at NASA ‘s Kennedy Space Center Shuttle Landing Facility May 7, 2017.
Credit: Michael Martin/USAF

Tarmac touchdown

After eclipsing 11 months in orbit, how long the unpiloted, reusable craft will stay aloft is unknown. The robotic vehicle is likely to land at Kennedy Space Center’s Shuttle Landing Facility, as the OTV-4 mission did back on May 7, 2017. That was a first for the program. All prior missions had ended with a tarmac touchdown at Vandenberg Air Force Base in California.

The classified X-37B program “fleet” consists of two known reusable vehicles, both of which were built by Boeing. Looking like a miniature version of NASA’s now-retired space shuttle orbiter, the military space plane is 29 feet (8.8 meters) long and 9.6 feet (2.9 m) tall, with a wingspan of nearly 15 feet (4.6 m).

The first X-37B Orbital Test Vehicle waits in the encapsulation cell of the Evolved Expendable Launch vehicle on April 5, 2010 at the Astrotech facility in Titusville, Fla. Half of the Atlas V five-meter fairing is visible in the background.
Credit: U.S. Air Force

Ground tracks

Ted Molczan, a Toronto-based satellite analyst, told Inside Outer Space that OTV 5’s initial orbit was about 220 miles (355 kilometers) high, inclined 54.5 degrees to the equator. “Its ground track nearly repeated every two days, after 31 revolutions.”

On April 19, the space drone lowered its orbit by 24 miles (39 kilometers) which caused its ground track to exactly repeat every five days, after 78 revolutions, Molczan said – a first for an OTV mission.

“Repeating ground tracks are very common,” Molczan added, “especially for spacecraft that observe the Earth. That said, I do not know why OTV has repeating ground tracks.”

Space force 

Does the X-37B program fit into the Trump Administration’s call for a Space Force?

Responds Joan Johnson-Freese, a professor in the National Security Affairs Department at the Naval War College in Newport, Rhode Island: “Ironically, the X-37B is exactly the type of program — toward giving the U.S. flexibility of operations in space — that seems to be prompting the current push for a Space Force, yet are already underway.”

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