The X-37B Orbital Test Vehicle is a Boeing-built, uncrewed autonomous spaceplane operated for U.S. government orbital experimentation by the Department of the Air Force and U.S. Space Force. Public mission reporting describes it as a returnable test platform that has launched on Atlas V, Falcon 9, and Falcon Heavy rockets, landed autonomously at runway sites, and flown eight missions as of the OTV-8 launch in August 2025.
The X-37B sits at the end of a public reusable-spaceplane development line rather than at the start of a standalone battlefield weapon family. NASA began X-37 work in 1999, transferred the program to DARPA in 2004, and retained technical participation while Boeing and government teams matured autonomous landing and reusable orbital-vehicle technologies.
Subscale approach-and-landing flights reduced risk for autonomous runway recovery before orbital X-37B missions.
DARPA completed captive-carry and free-flight testing of the approach-and-landing vehicle before the Air Force orbital program.
The operational vehicle carries experiments to orbit, returns them to Earth, and is refurbished for later missions.
The public X-37B program grew out of NASA, DARPA, Air Force, and Boeing reusable-spaceplane demonstrators; precursor vehicles are lineage context rather than separate operational catalog records.
| Variant | Configuration | Designation notes |
|---|---|---|
| X-40A | Subscale autonomous approach-and-landing demonstrator | NASA describes X-40A as an 80-percent subscale X-37 demonstrator used for seven approach-and-landing test flights in 2001. Sources: NASA X-40A at Armstrong |
| X-37A ALTV | Approach and Landing Test Vehicle | The Air Force fact sheet says DARPA completed the X-37 Approach and Landing Test Vehicle portion in 2006 after captive-carry and free-flight testing. Sources: DVIDS X-37B Fact Sheet |
| X-37B OTV | Operational orbital test vehicle | The Air Force version built on NASA, DARPA, Air Force, and Boeing work and became the reusable orbital test vehicle flown for Department of the Air Force and Space Force missions. |
Official program and launch sources document X-37B missions using Atlas V, Falcon 9, and Falcon Heavy launch vehicles as part of U.S. national-security space-launch activity.
| Launcher | Launcher type | Launch evidence |
|---|---|---|
 | Expendable orbital launch vehicle | Atlas V launched the first X-37B orbital mission and later USSF-7/OTV-6, tying early X-37B missions to United Launch Alliance's Atlas V launch service. Sources: DVIDS X-37B Fact Sheet, ULA USSF-7 launch |
 | Reusable two-stage orbital rocket | Falcon 9 launched OTV-5 in 2017 and USSF-36/OTV-8 in August 2025, making it the Falcon-family vehicle used for both the first SpaceX X-37B launch and the eighth X-37B mission. Sources: DVIDS X-37B Feature, USSF OTV-8 Launch |
 | Heavy-lift orbital launch vehicle | USSF-52 carried X-37B Mission 7 on Falcon Heavy, the first X-37B mission launched by that rocket and the mission that later demonstrated aerobraking from a highly elliptical orbit. Sources: USSF OTV-7 launch, USSF OTV-7 Landing |
Public X-37B mission descriptions emphasize returnable orbital experimentation. Named examples include NASA and Naval Research Laboratory experiments on OTV-6, space-domain-awareness and radiation-effects work on OTV-7, and laser-communications plus quantum inertial-sensor demonstrations on OTV-8. Many payloads and mission details remain undisclosed in public releases.
NASA's original X-37 program began in 1999 before the program transferred to DARPA in 2004.
Sources: DVIDS X-37B Fact Sheet, NASA NTRS X-37 Lessons
NASA says the 80-percent-scale X-40A demonstrator flew seven approach-and-landing test flights at what is now Armstrong Flight Research Center.
Sources: NASA X-40A at Armstrong
NASA transferred X-37 program ownership to DARPA in 2004, with NASA continuing technical participation.
Sources: NASA NTRS X-37 Lessons, DVIDS X-37B Fact Sheet
The Air Force fact sheet records the first X-37B launch from Cape Canaveral Air Force Station in April 2010.
Sources: DVIDS X-37B Fact Sheet
United Launch Alliance launched the sixth X-37B mission for the U.S. Space Force on an Atlas V 501 rocket, and Boeing later identified OTV-6 as the first X-37B mission with a service module.
Sources: ULA USSF-7 launch, USSF OTV-6 Landing
The sixth X-37B mission landed at Kennedy Space Center after 908 days on orbit, the program's longest completed mission in public reporting.
Sources: USSF OTV-6 Landing, Boeing X-37B Program Page
The U.S. Space Force launched X-37B Mission 7 on Falcon Heavy from Kennedy Space Center Launch Complex 39A.
Sources: USSF OTV-7 launch
The Space Force announced that OTV-7 would use aerobraking to change orbit while conserving propellant after conducting experiments in a highly elliptical orbit.
Sources: USSF OTV-7 aerobraking
Mission 7 landed at Vandenberg Space Force Base after more than 434 days in orbit and after demonstrating aerobraking and space-domain-awareness experiments.
Sources: USSF OTV-7 Landing
The Space Force launched the eighth X-37B mission on a Falcon 9 from Kennedy Space Center Launch Complex 39A, with public objectives including laser communications and quantum inertial-sensor experimentation.
Sources: USSF OTV-8 Launch, USSF OTV-8 Preparation
