It’s about 9 meters long, looks like a miniature space shuttle and stayed in space for 2½ years during one of its eight missions. The stated purpose of the X-37B spaceplane is conducting tests and experiments to advance reusable space capabilities.
The work of the autonomous spacecraft, full name X-37B Orbital Test Vehicle (OTV), has remained largely classified since its first deployment in 2010. But details emerging from the U.S. Space Force have provoked widespread interest and speculation, especially after the Chinese Communist Party (CCP) followed 10 years later by orbiting its own spaceplane, the Shenlong.
United States Space Force Gen. B. Chance Saltzman, chief of space operations, has hinted during public presentations at the importance of this space drone to the service’s mission. “When I have a platform like the X-37B, my mouth starts to water,” Saltzman told the news site Aviation Week in January 2025. A year earlier, at a conference in Orlando, Florida, during a period when both nations’ spaceplanes were deployed, Saltzman told an audience, “These are two of the most watched objects on orbit while they’re on orbit.”
The secrecy is one reason. But so are considerations about what capabilities the orbit-hopping spacecraft could bring to space operations that are largely limited to satellites locked into one path for life. The modular design and maneuverability of a spaceplane are seen as a potential game changer.
“With each successive flight, the X-37B has demonstrated adaptability and flexibility by hosting diverse experiments and pioneering new orbital regimes,” Michelle Parker, then vice president of manufacturer Boeing Space Mission Systems, said before the launch of the eighth spaceplane mission in August 2025.
That mission still was underway in 2026. In a news release, the Space Force revealed two of the capabilities OTV-8 would test: laser communications to replace radio frequencies for moving data around a growing network of low Earth orbit satellites, and a quantum inertial sensor for space navigation at a time of emerging threats to GPS.
Launched vertically into space atop a rocket, the X-37B lands horizontally like an airplane upon its return to Earth. It’s about a quarter the size of the crewed U.S. space shuttle and is designed for low Earth orbit missions from 240 kilometers to 800 kilometers altitude. Past experiments that have been made public include aerobraking maneuvers — to aid in safe debris disposal and in changing orbit using minimal fuel — and the release of objects from its bay door, including a U.S. Naval Research satellite to beam solar power as microwaves back to Earth, a U.S. Air Force Academy-designed spacecraft carrying five payloads and NASA tests of radiation’s effects on plant seeds.
Not for warfighting
The U.S. and CCP say their spaceplanes are not intended as space weapons, though online speculation — including the idea of outfitting the U.S. spaceplane with a high-energy laser — has raised the prospect. “I don’t think that either has a whole lot of military utility, to be honest,” Victoria Samson, chief director of space security and stability at the Secure World Foundation think tank in Washington, D.C., told Reuters in January 2024. “I am guessing that both are technology demonstrators.”
Still, the state-owned agency developing Shenlong is closely tied to the People’s Liberation Army under the CCP’s Military-Civil Fusion structure. In the U.S., the military took over development of the X-37B from NASA in 2004 through the Defense Advanced Research Projects Agency. The program was transferred to the Air Force Rapid Capabilities Office in 2010. After its formation in 2019, the Space Force partnered in the program. Boeing has provided continual upgrades to X-37B components, including batteries and solar cells, and developed a collision avoidance device that enabled the spaceplane to identify some 1.7 million avoidance opportunities on orbit.
These are two of the most watched objects on orbit while they’re on orbit.”
U.S. Space Force Gen. B. Chance Saltzman, chief of space operations
The potential warfighting implications of a spaceplane are detailed in an essay about the CCP’s Shenlong, published in January 2024 in the Indo-Pacific affairs magazine The Diplomat. They include the secrecy afforded the cargo that a spaceplane is carrying — “the adversary would not even know what they are facing until the spaceplane opens its payload bay doors” — and its ability to conduct close-in rendezvous and proximity operations. These operations could involve repair or refueling on a cooperative satellite or some kind of mischief against an adversary’s spacecraft, the essay said. “Reusability enables an entirely different and faster tempo of operations, making one less predictable.”
Secrecy surrounding Shenlong has been greater than for X-37B, said essay co-author Namrata Goswami, professor of space security with the Space Force’s Schriever and West Space Scholars Program at Johns Hopkins University in Washington, D.C. At least eight objects have been released into orbit from Shenlong but have yet to be identified in open-source reports, Goswami told Apogee. “China has not said anything about those objects. When you see an unidentified object come out, you ask, ‘Is it an object that could be threatening?’” First launched in 2020, Shenlong — divine dragon in English — deployed for the fourth time in February 2026, meaning both spaceplanes were operating simultaneously again.
Like the Space Force, the CCP has said that its spaceplane is testing reuse capabilities, as if to declare, “We want to showcase that we can do this, too,” Goswami said. Determining the real purpose of the Shenlong will require tracking its movements. “It’s so difficult to understand intent.” One military goal may be as simple as gray zone operations, she said: “You are going to target the adversary’s strategy but not necessarily engage in a conventional fight. So any showcasing of capability that can deter or target the deterrence strategy of your adversary is a good place to go.”
Outpacing Shenlong
With a decade-long head start, and the number and duration of its missions, the X-37B program continues to outpace Shenlong. The U.S. spaceplane remained on orbit without refueling for 908 days before landing in November 2022 at NASA’s Kennedy Space Center in Florida. Shenlong has not exceeded 280 days. “Where China is trying to catch up with the X-37B is that ability to stay a much longer time in space,” Goswami said. “They are trying to achieve that multiyear presence, I think, with the fourth mission.”
Catching up in maneuverability is likely a goal, too, she said. “The X-37B is more advanced in that capability, at least what we know based on open-source information.”
Maneuverability is determined by Delta V, or difference in velocity — a change in acceleration that affects both speed and direction and enables a spacecraft to move between orbits. Delta V is determined, in part, by how much fuel a spacecraft carries and the efficiency of its propulsion. “The most important capability for a spaceplane to be able to move is that it is able to have enough fuel, that it can lift up,” Goswami said. “That can help it to do those burns that allow this.”
India also is developing a reusable, autonomous spaceplane and completed a series of tests in July 2024 aimed at demonstrating horizontal landing, according to the Indian Space Research Organisation (ISRO). The body and flight systems of the Pushpak spaceplane were used as is from an earlier landing test, the ISRO said, “showcasing advanced autonomous capabilities under challenging conditions.” Other spaceplanes, including a single-stage-to-orbit version requiring no booster rocket, are under development in countries including France, Germany and the United Kingdom. Sierra Space in the U.S. is developing the Dream Chaser commercial spaceplane to carry cargo and crews.
Aside from their level of achievement, the strategic purpose of the U.S. and CCP spaceplanes so far appears similar, Goswami said. “Both planes can loiter, to the extent possible. And they have a secret capability, so that unless they’re willing to talk about it, we don’t know what’s inside.” While the U.S. has revealed certain details about X-37B missions, “on the Chinese side, they are not making things public. They’re saying, ‘Oh, this is to study the orbital mechanics, this is to study how we can maneuver, this is to study debris removal, the rendezvous and proximity operation and grabbing.’ But they’re not making it as transparent. That’s why I think it’s critical to see what it’s actually doing and identify intent,” Goswami said.
Understanding intent
The same rendezvous and proximity operations (RPO) that can be used in refueling, Goswami said, can be used against an adversary’s spacecraft and “put those particular assets at risk.” The Space Force has not said whether the X-37B can perform RPO, but it’s possible, Goswami said, since Shenlong seems to be trying to copy the U.S. spaceplane’s capabilities. The U.S. Space Command has announced it conducted RPO involving other satellites, operated by the U.S. and its allies. The only open-source images of Shenlong appear to be from a private space watcher in Austria, who described it as having a delta or triangular wing like the X-37B.
Understanding the intent of a secretive spaceplane, and the fuel it carries, involves watching closely, Goswami said. “Which orbit is it going to, which will tell us its capacity. And where is it not able to go? When you’re designing any spacecraft, you have to design it with a mission in mind and you have to put in that amount of fuel for Delta V changes. So the moment we can see, ‘Oh, the spaceplane is going from this particular altitude to that particular altitude, but it’s not moving beyond that,’ then we can decipher, ‘So, it’s designed for this mission.’”
The mission is unlikely to include the kind of air-to-air combat associated with nimble fighter planes on Earth. Each maneuver in space, “to be able to be in a particular orbit at a particular time,” requires planning and careful calculations using a data table known as the Delta V budget. Chemicals such as hydrazine help fuel spacecraft today. But the next game changer could come from a switch to nuclear propulsion, a goal of both the U.S. and the CCP. “It could well be that nuclear propulsion systems are faster,” Goswami said.
Meantime, watching closely as the mysterious Shenlong develops will require greater space domain awareness (SDA) capabilities, she said — fielding sensors and analytical capability in the right places in space and on Earth. SDA gaps often emerge as top concerns during open-source space war gaming.
“They’re game changers,” she said of the spaceplanes. “In some sense, our entire thinking on force posture, response, anticipation — it affects all that. It affects doctrine, thinking about how space warfare might play out.” Whatever their stated purpose, Goswami said, it’s important “to think through the implication for warfighting that spaceplanes can actually contribute to.”