There’s a mystery unfolding on the outskirts of Earth’s atmosphere.
Last week, the U.S. Space Force launched the seventh mission of the X-37B: a secretive spaceplane or orbital test vehicle (OTV) project intended to prepare the country for the next era of space travel.
Almost nothing is known about the Boeing-built spacecraft’s specific purpose, payload, or final destination. But we do know that the most recent launch had more juice than any other, perhaps enough to send X-37B into deep orbit—or even to the neighborhood of the moon.
“The technological advancements we’re driving on X-37B will benefit the broader space community, especially as we see increased interest in space sustainability,” said Michelle Parker, vice president of space mission systems for Boeing Defense, Space & Security. “We are pushing innovation and capability that will influence the next generation of spacecraft.”
The mission, known as USSF-52 or OTV-7, departed Kennedy Space Center Launch Complex 39A last Thursday evening in Florida after a few weeks of delays because of weather and technical issues. SpaceX shut down its livestream of the launch at the request of the Space Force once X-37B reached orbit.
“My memories go back to the Gemini and Mercury programs,” said Frank Kendall, secretary of the U.S. Air Force. “This is an incredible event, and I think about the teamwork over all those decades that has led to what has been a revolutionary improvement in space travel capability. We have come so far, and it’s been teamwork by the government, the Air Force, and now the Space Force, which didn’t exist until a few years ago, NASA, industry teams, and so many others that all contributed to what we saw.”
For the first time, the reusable, self-flying spaceplane left the launchpad coupled to a SpaceX Falcon Heavy rocket—one of the most powerful launch vehicles in existence. The rocket’s three first-stage boosters are also reusable.
X-37B’s first five missions used Atlas V rockets made by United Launch Alliance, a joint venture between Boeing and Lockheed Martin, while the sixth flew on SpaceX’s Falcon 9 booster. Each trip was confined to below 1,200 miles in altitude. Falcon Heavy, meanwhile, can reach 22,000 miles, fueling speculation that X-37B’s seventh mission may go deeper than ever before. But the Space Force has not disclosed the spaceplane’s flight plan.
The X-37B project—a collaboration between the Space Force and U.S. Air Force’s Rapid Capabilities Office under the National Security Space Launch program, with support from Boeing—is shrouded in secrecy.
Speculation on X-37B’s purpose ranges from new spying and reconnaissance capabilities to a weapons delivery system, the latter of which the Pentagon has denied. According to a Space Force statement, USSF-52 specifically will test operations in new “orbital regimes” and explore the effects of radiation on NASA payloads. Seeds, for example, will be exposed to the bitterness of space, perhaps to understand how humans could sustain interplanetary bases.
“The X-37B government and Boeing teams have worked together to produce a more responsive, flexible, and adaptive experimentation platform,” said William Bailey, director of the Rapid Capabilities Office. “The work they’ve done to streamline processes and adapt evolving technologies will help our nation learn a tremendous amount about operating in and returning from a space environment.”
In addition, the orbital test vehicle will experiment with “future space domain awareness technology,” which the Space Force explained is designed to enable safe and secure space operations for government and commercial users alike.
What Do We Know?
U.S. agencies have largely kept the details of X-37B under wraps, but there are a few clues as to its intended use.
The spaceplane has been in development for decades. Originally, it was a NASA-led project. In 1999, the agency enlisted Boeing’s Phantom Works—the manufacturer’s prototyping arm responsible for such cutting-edge designs as the A160 Hummingbird—to build the ambitious concept.
According to Boeing’s website, the design is an advanced reentry spacecraft geared for operations in low Earth orbit, about 150 to 500 miles above the ground. It’s the first vehicle since NASA’s space shuttle capable of returning experiments to Earth for analysis, landing on the runway like an airplane. Its goal, Boeing says, is to explore reusable technology for “long-term space objectives.”
X-37B introduced a handful of technologies that had previously never been used in spaceflight. Its state-of-the-art avionics, for example, automate de-orbiting and landing, considered some of the trickier maneuvers to make. The spaceplane’s flight controls and brakes replace hydraulics with electromechanical actuation, while a lighter composite structure stands in for traditional aluminum. The design also includes a new generation of high-durability tiles.
Not everything is new, however. The mysterious spacecraft’s landing profile and lifting body architecture—a fixed-wing configuration wherein the body itself provides lift for subsonic, supersonic, or hypersonic flight or spacecraft reentry, à la Sierra Space’s Dream Chaser—resemble the space shuttle’s.
Yet X-37B is only one-fourth as large, about the size of a small bus. It’s also much harder to track than its predecessor, capable of quickly changing orbit or “hiding” in the glare of the sun to keep its position secret.
Since its maiden voyage in April 2010, the spaceplane has spent more than 3,750 days in space, traveling an astounding 1.3 billion miles. In 2019, it won the Robert J. Collier Trophy, awarded by the National Aeronautic Association for the greatest American aeronautical or astronomical achievements of the year prior.
Another Space Race?
With each voyage, X-37B has flown farther and for longer. But at the same time, a foreign superpower is ramping up its own mysterious, state-of-the-art spaceplane project.
Boeing’s model was initially designed for a mission duration of 270 days. But since OTV-2 in 2011, each test flight has been longer than the last.
Its sixth and most recent mission, which touched down in November 2022, lasted a record 908 days. If that’s any indication, OTV-7 will fly even longer. The mission was also the first to introduce an expanded service module that allowed the spacecraft to host more experiments than ever before, including payloads from the Naval Research Lab and more seeds from NASA.
X-37B’s seventh mission could be its last, according to comments from General B. Chance Saltzman, chief of space operations for the Space Force, in 2020. That could be consequential given activity across the Pacific.
Earlier in December, China launched its Shenlong “Divine Dragon” on its third mission since 2020 aboard a Long March 2F rocket, which is less powerful than SpaceX’s Falcon Heavy. There are no photos available of the secretive spacecraft, but it’s thought to be similar to the X-37.
Like its American counterpart, not much is known about Shenlong’s purpose. But a few weeks ago, it reportedly deployed six mysterious objects into orbit. Though the project is covert, U.S. officials are already drawing links between it and the Space Force initiative. The close timing of the two launches, in particular, has raised eyebrows—if not for delays, X-37B and Shenlong would have reached orbit within days of each other.
“It’s no surprise that the Chinese are extremely interested in our spaceplane,” Saltzman told Air & Space Forces Magazine last month. “We’re extremely interested in theirs. These are two of the most watched objects on orbit while they’re on orbit. It’s probably no coincidence that they’re trying to match us in timing and sequence of this.”
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