The X-37B is an uncrewed spaceplane. Boeing builds it. The United States Space Force has flown it on eight missions since 2010, most recently launching in August 2025 to test a laser communication link and a navigation sensor built for environments where GPS does not reach. It launches vertically on a conventional rocket and lands horizontally on a runway, the same profile the Space Shuttle once flew.
It is the only reusable spaceplane flying today. The Space Shuttle retired in 2011. The Soviet-era Buran flew once before its program was shelved. That leaves the X-37B without an active counterpart apart from China’s newer Shenlong, a vehicle it closely resembles.
What the X-37B Is
The X-37B is a robotic spaceplane about the size of a small bus. It is built to fly long missions in orbit and then return intact for inspection. Boeing builds and maintains it, and the United States Space Force owns and flies it. Two known airframes exist. That is how the Space Force overlaps missions: a new flight can launch within months of the previous one landing, because a second vehicle is already available.
A conventional rocket carries the X-37B to orbit. Once there, it operates on its own for months or years at a time. When the mission ends, it re-enters the atmosphere and glides to a runway landing, first at Vandenberg Space Force Base in California and, on at least one mission, at NASA’s former Space Shuttle runway at Kennedy Space Center in Florida. Recovering the vehicle intact lets engineers inspect flown hardware directly, instead of relying only on the telemetry a satellite radios down before it eventually burns up or goes silent.
How the Program Started
NASA began the X-37 project in 1999. It was a technology-demonstration vehicle, built with Boeing to test reusable spacecraft components. The Defense Advanced Research Projects Agency took the project over in 2004, and the US Air Force flew the first orbital mission in 2010 under a renamed Orbital Test Vehicle program. The Space Force stood up as its own military branch in 2019 and formally organized in 2020. The X-37B moved with it, and the program has flown under Space Force ownership ever since.
That lineage explains the vehicle’s NASA-derived designation, X-37B, even though NASA has not operated a mission in more than fifteen years. The letter B distinguishes it from an earlier, unflown X-37A prototype used only for atmospheric drop tests.
Mission History and the Duration Record
Eight missions have flown since 2010, each one numbered as an Orbital Test Vehicle (OTV) flight, and the durations have grown sharply over that span. The table below lists the confirmed record for each completed flight.
| Mission | Launch | Duration | Notes |
|---|---|---|---|
| OTV-1 | April 2010 | About 225 days | First orbital flight |
| OTV-2 | March 2011 | About 469 days | |
| OTV-3 | December 2012 | About 675 days | |
| OTV-4 | May 2015 | About 718 days | |
| OTV-5 | September 2017 | About 780 days | |
| OTV-6 | May 2020 | 908 days | Program duration record; first to carry a service module |
| OTV-7 | December 2023 | 434 days | First flight in a highly elliptical orbit, launched on a Falcon Heavy |
| OTV-8 | August 2025 | Ongoing as of September 2026 | Laser-communication and quantum-navigation demonstration |
OTV-6 set the standing record at 908 days, nearly two and a half years, after launching on an Atlas V rocket in May 2020 and landing at Kennedy Space Center in November 2022. OTV-7 broke a different kind of ground instead of chasing that record. It launched on a SpaceX Falcon Heavy in December 2023, the first time the Space Force used that more powerful rocket for the program, and flew in a highly elliptical orbit reaching roughly 38,800 kilometers at its farthest point, far higher than any prior mission. It landed at Vandenberg after 434 days.
OTV-8 launched on a Falcon 9 from Kennedy Space Center in August 2025 and remains in orbit as of this writing. The Space Force has named two of its objectives: a laser communication demonstration meant to improve how satellites relay data to each other, and a quantum inertial sensor meant to help a spacecraft track its own position and motion precisely without a GPS signal, a capability with obvious value if GPS is jammed or spoofed. The how GPS jamming works page covers why that alternative matters.
Across its first seven completed missions, the Space Force says the X-37B logged more than 1.3 billion miles and spent thousands of cumulative days in orbit, a record built almost entirely on the strength of the later, much longer flights.
What the X-37B Carries
Disclosure has grown a little over time, though most of what any given flight actually holds stays classified. Earlier missions carried named NASA experiments testing how spacecraft materials hold up to long radiation exposure, and a Naval Research Laboratory payload that tested converting solar energy into radio-frequency power in orbit, a small-scale precursor to the space-based solar power concepts covered on the space-based solar power page. OTV-8’s laser-communication and quantum-navigation payloads are the most specific set of objectives the Space Force has named for any single mission.
What is not disclosed matters just as much. The Space Force has never published a complete manifest for any flight, never confirmed how many payloads a given mission carries, and rarely says anything about a mission’s status once it is underway beyond periodic updates. That silence is the main reason outside analysts spend as much energy tracking the vehicle’s orbit as speculating about its cargo.
Is the X-37B a Weapon
No disclosed payload, and no observed maneuver, shows the X-37B carrying or using a weapon. The Space Force describes the program as an experimental test bed, not an operational combat system, and every named payload to date has been a sensor, a communications experiment, or a materials test. Russian officials have called the vehicle’s eighth mission a potential orbital bomber, a claim that Western commercial space-tracking firms, which publish the X-37B’s orbit continuously, have not corroborated with any observed behavior consistent with a weapon.
The ambiguity is structural rather than accidental. A vehicle that can loiter in orbit for years, change its own orbit, and return to Earth for inspection is useful for almost any military purpose, from testing a sensor to rehearsing satellite servicing. The Space Force’s silence about specific payloads leaves room for speculation on all sides. Tracking exactly this kind of long-duration, low-disclosure mission is why the sensor networks on the space domain awareness page exist.
How the X-37B sits alongside the systems the Space Force has actually acknowledged as weapons is laid out in our Space Force weapons inventory.
Compared to China’s Shenlong
The clearest comparison is China’s own uncrewed spaceplane, widely known as Shenlong, which China has flown four times since 2020.
| Measure | X-37B | Chinese spaceplane (Shenlong) |
|---|---|---|
| Operator | United States Space Force | Chinese government |
| Crew | None | None |
| First flight | April 2010 | September 2020 |
| Missions flown | 8 | 4 |
| Longest mission | 908 days | 276 days |
| Launch vehicle | Atlas V, Delta IV, Falcon 9, Falcon Heavy | Long March 2F |
| Landing | Horizontal, on a runway | Horizontal, on a runway |
| Payloads disclosed | Partially, some experiments named | Almost none |
The X-37B has the longer operating history and has named more of what it carries, though “more” is relative. Neither government publishes a full manifest for any mission, and both vehicles have drawn the same basic question from analysts: a platform this flexible could support almost any mission a military space program might want, and the public record cannot rule most of them in or out.
What Would Change the Assessment
A disclosed weapon test or a confirmed close approach to another nation’s satellite would move the X-37B from ambiguous to specific, and neither has happened on the public record. Naming a complete mission payload, something the Space Force has never done, would narrow the guesswork considerably in the other direction, showing the vehicle doing exactly what it says it does and nothing more.
Until one of those things happens, the most reliable way to follow the program is the same one that applies to Shenlong: watching where the vehicle actually goes. Commercial trackers publish X-37B orbital data throughout each mission, and the Space Force’s own newsroom posts a release at launch and another at landing, which remains the most direct public record the program provides.