Space force

US Space Force’s X-37B spaceplane nears orbital record

The US Army’s X-37B robotic spaceplane is closing in on a mission duration record.

The X-37B launched into Earth orbit on May 17, 2020 on the program’s sixth mission, a flight known as Orbital Test Vehicle-6 (OTV-6).

The space force minishuttle has now been airborne for 773 days. This is just one week before the X-37B record of 780 days, which was set on OTV-5. (This program record does not come close to the overall rating for an orbital stay; for example, the Landsat-5 Satellite observed the Earth from orbit for 29 years.)

Related: 10 surprising facts about the US Army’s X-37B spaceplane

Embedded experiences

While the main orbital programs for the Boeing-built robotic spaceplane are classified, some of its onboard experiences have been leaked before launch.

One of these experiments, conducted by the US Naval Research Laboratory (NRL), studies the transformation of solar energy into radio frequency microwave energy. The experience is called Photovoltaic radio frequency antenna moduleor PRAM for short.

It is also known that OTV-6 included the deployment of FalconSat-8, a small satellite developed by the US Air Force Academy and sponsored by the Air Force Research Laboratory to conduct several experiments in orbit.

Additionally, two NASA experiments are onboard the spaceplane to study the effects of the space environment on a sample plate of materials 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 to the rear of the vehicle that allows additional experimental payload capacity to be carried into orbit.

Previous flights

Here is a list of previous X-37B missions, each of which lasted longer than its immediate predecessor:

  • OTV-1 launched on April 22, 2010 and landed on December 3, 2010, spending over 224 days in orbit.
  • OTV-2 launched on March 5, 2011 and landed on June 16, 2012, spending over 468 days in orbit.
  • OTV-3 launched on December 11, 2012 and landed on October 17, 2014, spending over 674 days in orbit.
  • OTV-4 was launched on May 20, 2015 and landed on May 7, 2017, spending nearly 718 days in orbit.
  • OTV-5 was launched on September 7, 2017 and landed on October 27, 2019, spending nearly 780 days in orbit.

It is unclear when and where OTV-6 will descend 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.

Operations supervision

The X-37B program is flown under the auspices of a US Space Force unit called Delta 9, which was created in July 2020.

“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 “, Space Force officials wrote in a statement. Delta 9 Fact Sheet (opens in a new tab).

“The mission of Delta 9 is to prepare, present and project assigned and attached forces for the purpose of conducting protective and defensive operations and providing national decision-making authorities with response options to deter 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 conducts in-orbit experimentation and technology demonstrations for the US Space Force.”

Vehicle Features

The Space Force is believed to have two X-37B vehicles in its fleet, both built by Boeing. The X-37B launches vertically atop a rocket and lands horizontally on a runway, like NASA’s old one spaceship orbiter.

In fact, the military spaceplane looks a lot like the now-retired Shuttle, but it’s much smaller – just 29 feet (8.8 meters) long, down from 122 feet (37 m). There’s also another key difference: NASA’s shuttle was manned, whereas the X-37B is robotic.

Boeing noted that the X-37B features many elements that mark a first use in orbit for a spaceplane, including fully automated deorbit and landing functions, flight controls and brakes that all use electromechanical actuation. (no hydraulics) and a body made of a relatively light composite structure, rather than traditional aluminum.

“The X-37B is one of the world’s newest and most advanced re-entry spacecraft, designed to operate in low Earth orbit, from 150 to 500 miles [240 to 800 kilometers] Above the Earth”, Boeing written in a vehicle description (opens in a new tab). “The vehicle is the first since the Space Shuttle with the ability to return experiments to Earth for further inspection and analysis. [Space] The Force unmanned space vehicle explores reusable vehicle technologies that support long-term space goals.”

The X-37B was designed to perform missions that last up to 270 days, Boeing noted. But every flight, except the first, has exceeded this supposed limit.

Leonard David is the author of the book “Moon Rush: The New Space Race”, published by National Geographic in May 2019. A longtime author for, David has been reporting on the space industry for more than five decades. Follow us on twitter @Spacedotcom (opens in a new tab) Or on Facebook (opens in a new tab).