USSF's X-37B space plane lands, ending record-breaking mystery mission

Jan 27, 2020
By Mike Wall

The X-37B circled Earth for 908 days on its OTV-6 mission.

The U.S. Space Force's X-37B space plane is seen shortly after landing at NASA's Kennedy Space Center on Nov. 12, 2022, bringing an end to its OTV-6 mission. (Image credit: Boeing/US Space Force)

The record-breaking sixth mission of the U.S. military's X-37B space plane is finally over.

The robotic X-37B touched down at NASA's Kennedy Space Center (KSC) in Florida today (Nov. 12) at 5:22 a.m. EST (1022 GMT). The winged vehicle had spent 908 days in orbit — more than four months longer than any previous X-37B flight.

The Boeing-built space plane also carried a service module on the newly completed mission, a first for the U.S. Space Force's X-37B program.

"With the service module added, this was the most we've ever carried to orbit on the X-37B, and we're proud to have been able to prove out this new and flexible capability for the government and its industry partners," Jim Chilton, senior vice president at Boeing Space and Launch, said in a statement today(opens in new tab).

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Technicians work with the recently landed robotic X-37B space plane at NASA's Kennedy Space Center in Florida on Nov. 12, 2022. (Image credit: Boeing/US Space Force)

The X-37B resembles NASA's now-retired space shuttle but is much smaller, measuring just 29 feet (8.8 meters) from nose to tail. The space shuttle was 122 feet (37 m) long and was piloted — another key difference, as the X-37B is autonomous.

The U.S. Space Force is thought to own two X-37B vehicles, both of which were provided by Boeing. To date, the duo has flown six orbital missions, each of which is known by the signifier OTV ("Orbital Test Vehicle"):
  • OTV-1: Launched on April 22, 2010 and landed on Dec. 3, 2010 (duration 224 days).
  • OTV-2: March 5, 2011 to June 16, 2012 (468 days).
  • OTV-3: Dec. 11, 2012 to Oct. 17, 2014 (674 days).
  • OTV-4: May 20, 2015 to May 7, 2015 (718 days).
  • OTV-5: Sept. 7, 2017 to Oct. 27, 2019 (780 days).
  • OTV-6: May 17, 2020 to Nov. 12, 2022 (908 days).
Space Force and Boeing describe the X-37B as chiefly a testing platform; the vehicle allows researchers to see how payloads work in the space environment and then examine them afterward on the ground.

"Since the X-37B's first launch in 2010, it has shattered records and provided our nation with an unrivaled capability to rapidly test and integrate new space technologies," Chilton said.

Many of these payloads are classified, as are most of the X-37B's activities; the Space Force doesn't announce details of the vehicle's orbit, for example, or tell us in advance when each OTV mission is going to end.

But military officials do reveal information about some of the hardware the X-37B totes aloft. For example, we know that OTV-6 tested the U.S. Naval Research Laboratory's Photovoltaic Radio-frequency Antenna Module. This device, about the size of a pizza box, is designed to convert solar energy into microwaves, which can then be beamed down to Earth. Its work could help bring space-based solar power closer to reality, experiment team members have said.

OTV-6 also carried FalconSat-8, a satellite designed by cadets at the U.S. Air Force Academy that carries five experimental payloads of its own. The X-37B deployed FalconSat-8 in October 2021, and the satellite remains in orbit today, Boeing representatives said in today's statement.

OTV-6 carried a few known NASA experiments as well. One tested how space radiation affects plant seeds, and another gauged how various materials respond to the space environment.

"This mission highlights the Space Force's focus on collaboration in space exploration and expanding low-cost access to space for our partners, within and outside of the Department of the Air Force," Gen. Chance Saltzman, the Space Force's chief of space operations, said in the same statement. (The Space Force is part of the U.S. Air Force, much as the Marine Corps is part of the Navy.)

While OTV-6 set a new mission-duration record for the X-37B program, it didn't come close to the overall spaceflight mark.

Some Earth-observation and communications satellites operate in Earth orbit for a decade or more, for example. The International Space Stationhas been continuously occupied by rotating astronaut crews since November 2000, and NASA's Voyager 1and Voyager 2 probes remain operational in interstellar space more than 45 years after lifting off.

Follow Mike Wall on Twitter @michaeldwall (opens in new tab).


X-37B Orbital Test Vehicle

The X-37B Orbital Test Vehicle, or OTV, is an experimental test program to demonstrate technologies for a reliable, reusable, unmanned space test platform for the U.S. Air Force. The primary objectives of the X-37B are twofold; reusable spacecraft technologies for America’s future in space and operating experiments which can be returned to, and examined, on Earth.

The X-37B Orbital Test Vehicle is the newest and most advanced re-entry spacecraft. Based on NASA’s X-37 design, the unmanned OTV is designed for vertical launch to low Earth orbit altitudes where it can perform long duration space technology experimentation and testing. Upon command from the ground, the OTV autonomously re-enters the atmosphere, descends, and lands horizontally on a runway. The X-37B is the first vehicle since NASA’s Shuttle Orbiter with the ability to return experiments to Earth for further inspection and analysis, but with an on-orbit time of 270 days or greater, the X-37B can stay in space for much longer.

Technologies being tested in the program include advanced guidance, navigation and control, thermal protection systems, avionics, high temperature structures and seals, conformal reusable insulation, lightweight electromechanical flight systems, advanced propulsion systems, advanced materials and autonomous orbital flight, reentry and landing.

The Department of the Air Force Rapid Capabilities Office is leading the Defense Department’s Orbital Test Vehicle initiative, by direction of the under secretary of defense for acquisition, technology and logistics and the secretary of the Air Force. The Air Force OTV effort uses extensive contractor and government investments in the X-37 program by the Air Force, NASA and the Defense Advanced Research Projects Agency to continue full-scale development and on-orbit testing of a long-duration, reusable space vehicle.

NASA’s original X-37 program began in 1999 and was transferred to DARPA in 2004. NASA envisioned building two vehicles, an Approach and Landing Test Vehicle, or ALTV, and an Orbital Vehicle. DARPA completed the ALTV portion of the X-37 program in 2006, executing a series of captive carry and free flight tests. DARPA successfully validated the flight dynamics and extended the flight envelope beyond the low speed/low altitude tests previously conducted by NASA on the X-40A, a sub-scale version of the X-37 developed by Air Force Research Labs. NASA’s X-37 Orbital Vehicle was never built, but it's design was the starting point for the Air Force’s X-37B Orbital Test Vehicle program.

The Air Force has successfully flown five X-37B missions, OTV-1 through OTV-5. All five missions launched from Cape Canaveral Air Force Station, Fla., beginning with its first launch on April 22, 2010. OTV-1 through OTV-3 all landed at Vandenberg Air Force Base, Calif., while OTV-4 and OTV-5 landed at Kennedy Space Center, Fla. Through five completed missions, the X-37B has spent a total of 2,865 days on orbit, successfully checking out the X-37B’s reusable flight, reentry and landing technologies as well as operating experiments to benefit the national space community. The current mission, OTV-6, was launched on May 17, 2020 from Cape Canaveral on an Atlas V.

General Characteristics
Primary Mission: Experimental test vehicle
Prime Contractor: Boeing
Height: 9 feet, 6 inches (2.9 meters)
Length: 29 feet, 3 inches (8.9 meters)
Wingspan: 14 feet, 11 inches (4.5 meters)
Launch Weight: 11,000 pounds (4,990 kilograms)
Power: Gallium Arsenide Solar Cells with lithium-Ion batteries
Launch Vehicles: United Launch Alliance Atlas V (501) and SpaceX Falcon 9

(Current as of August 2020)



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.

The 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.

The on-orbit duration of the X-37B will vary based on flight requirements but has the ability to perform flights lasting up to 270 days.


While we don’t know everything that the X-37B was carrying on its payload adapter and inside its payload bay, we do know the basics of at least some of the items.

Of these, we're familiar with the Naval Research Laboratory’s Photovoltaic Radiofrequency Antenna Module. According to Space Force, “This experiment successfully harnessed solar rays outside of Earth’s atmosphere and aimed to transmit power to the ground in the form of radio frequency microwave energy (RFME).”

The service module sounds like it has a lot in common with another item, the Evolved Expendable Launch Vehicle Secondary Payload Adapter Augmented Geosynchronous Laboratory Experiment, or EAGLE, from the Air Force Research Laboratory. Tested in 2018, EAGLE is a ring-shaped payload adapter that can maneuver by itself once reaching orbit and is capable of hosting six fixed or deployable payloads. We don’t know if EAGLE is also designed to be launched by the X-37B, but it’s notable that both EAGLE and the X-37B come under the jurisdiction of Space Force’s Space Delta 9, the unit tasked with performing a mission set described as orbital warfare.