The US military’s X-37B robotic spaceplane is nearing a mission record.
That X-37B was launched into Earth orbit on May 17, 2020 on the program’s sixth mission, a flight dubbed Orbital Test Vehicle-6 (OTV-6).
That space forces Minishuttle has now been in the air for 773 days. That’s just a week short of the X-37B record of 780 days set on OTV-5. (This program record is nowhere near the overall mark for an orbital stay; for example, the Landsat 5 satellite observed Earth from orbit for 29 years.)
Related: 10 Surprising Facts About the US Military’s X-37B Spaceplane
experiments on board
While the Boeing-built robotic spaceplane’s primary orbital agendas are classified, some of its onboard experiments have been disclosed prior to launch.
One such experiment by the US Naval Research Laboratory (NRL) investigates the conversion of solar energy into high-frequency microwave energy. The experiment is called Photovoltaic high frequency antenna moduleor PRAM for short.
We also know that OTV-6 involved the use of FalconSat-8, a small satellite developed by the US Air Force Academy and sponsored by the Air Force Research Laboratory, to conduct several in-orbit experiments.
In addition, two NASA experiments are on board the spaceplane to study the effects of the space environment on a material sample plate and seeds used to grow food.
OTV-6 is the first X-37B mission to use a service module to host experiments. The service module is an attachment at the rear of the vehicle that allows additional experimental payload capacity to be transported into orbit.
Here is a list of previous X-37B missions, each of which lasted longer than its immediate predecessor:
- OTV-1 was launched on April 22, 2010 and landed on December 3, 2010 and spent over 224 days in orbit.
- OTV-2 was launched on March 5, 2011 and landed on June 16, 2012 and spent over 468 days in orbit.
- OTV-3 was launched on December 11, 2012 and landed on October 17, 2014 and spent over 674 days in orbit.
- OTV-4 was launched on May 20, 2015 and landed on May 7, 2017 and spent nearly 718 days in orbit.
- OTV-5 was launched on September 7, 2017 and landed on October 27, 2019 and spent nearly 780 days in orbit.
It is unclear when and where OTV-6 will come to Earth. OTV-1, OTV-2 and OTV-3 landed at Vandenberg Space Force Base in California, while OTV-4 and OTV-5 landed at NASA Kennedy Space Center in Florida.
The X-37B program will be flown under the auspices of a US Space Force entity called Delta 9, formed in July 2020.
“Delta 9 Detachment 1 oversees the 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,” Space Force officials wrote in a Data sheet for Delta 9 (opens in new tab).
“Delta 9’s mission is to prepare, present and project assigned and attached forces to conduct protective and defensive operations and provide response options to national decision-making agencies to repel and, if necessary, defeat orbital threats,” the fact sheet explains. “In addition, Delta 9 supports Space Domain Awareness by conducting space-based combat space characterization operations and also conducting in-orbit experiments and technology demonstrations for the US Space Force.”
The Space Force is said to have two X-37B vehicles in its fleet, both built by Boeing. The X-37B takes off vertically on a rocket and lands horizontally on a runway, like old NASA Space Shuttle orbiter.
The military spaceplane looks very similar to the now-decommissioned shuttle, but is much smaller — just 29 feet (8.8 meters) long compared to 122 feet (37 m). There is another important difference: the NASA shuttle was manned, while the X-37B is a robot.
Boeing has noted that the X-37B has many elements that mark a first in-orbit deployment for a spaceplane, including fully automatic de-orbit and landing capabilities, flight controls and brakes all using electromechanical actuation (no hydraulics), and a body made of a relatively light composite structure instead of traditional aluminum.
“The X-37B is one of the newest and most advanced reentry spacecraft in the world, designed to operate in a 150- to 500-mile low Earth orbit [240 to 800 kilometers] above the earth”, Boeing wrote in a vehicle description (opens in new tab). “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 [Space] Force Unmanned Space Vehicle explores reusable vehicle technologies that support long-term space goals.”
The X-37B was designed to fly missions lasting up to 270 days, Boeing noted. But every flight except the first has far exceeded that supposed limit.
Leonard David is the author of Moon Rush: The New Space Race, published by National Geographic in May 2019. A longtime writer for Space.com, David has covered the space industry for more than five decades. Follow us on Twitter @spacedotcom (opens in new tab) or on Facebook (opens in new tab).