Overview
The X-37B is not a secret. It is photographed on runways, its dimensions are published, its contractor is named, and the Space Force issues a press release when it lands.
What is secret is what it does. The target orbit of a launch is classified. On-orbit activities are not described. Landings are not announced in advance. The programme's budget is not public.
That combination — a visible object on an invisible errand — is what the speculation grows in, and the speculation has included heads of foreign space agencies. It is not a fringe question, and the honest answer is not that there is nothing to ask. It is that the people who have watched the vehicle most closely have recorded things that fit the official account better than they fit the alternatives.
What is on the record
The programme began at NASA in 1999, with Boeing selected to design the orbital vehicle. It moved to DARPA in 2004, and the Air Force announced the military X-37B in 2006. NASA's own orbital vehicle was never built; its design was the starting point.
The Air Force fact sheet gives the vehicle as 29 feet 3 inches long with a wingspan of 14 feet 11 inches, standing 9 feet 6 inches, with a launch weight of 11,000 pounds, powered by gallium arsenide solar cells and lithium-ion batteries. It is designed for on-orbit time of "270 days or greater" and lands itself on a runway.
One widely repeated figure is not in any official document: the payload bay is usually given as about 2.1 by 1.2 metres, roughly the size of a pickup truck bed. That number comes from analysts who track the vehicle, not from the Air Force, and it should be attributed accordingly.
The flight record
Seven missions have flown and returned.
| Mission | Launched | Landed | Days |
|---|---|---|---|
| OTV-1 | April 2010 | December 2010 | 224 |
| OTV-2 | March 2011 | June 2012 | 469 |
| OTV-3 | December 2012 | October 2014 | 675 |
| OTV-4 | May 2015 | May 2017 | 718 |
| OTV-5 | September 2017 | October 2019 | 780 |
| OTV-6 | May 2020 | November 2022 | 908 |
| OTV-7 | December 2023 | March 2025 | 434 |
An eighth launched in August 2025.
The durations are the part that unsettles people. A vehicle that stays up for two and a half years is doing something, and "testing reusable spacecraft technologies" is a thin answer to occupy that much time.
What it has actually been carrying
Since 2020 the Space Force has named payloads, and the named ones are mundane in a way that is itself informative.
The most misreported is the Naval Research Laboratory's Photovoltaic Radio-frequency Antenna Module, flown on OTV-6. The Space Force's own release says the 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," and a great many secondary accounts compressed that into the X-37B beaming power down to Earth.
It did not. Paul Jaffe, who leads the Naval Research Laboratory's power-beaming work, said plainly that the experiment was not beaming microwave energy anywhere. It was a twelve-inch tile measuring how efficiently sunlight could be converted to radio-frequency power in orbit, and how it handled the heat. The published result was about eight percent module efficiency, consistent with what the same hardware had done on the ground.
OTV-5 and OTV-6 carried NASA materials-exposure plates — coatings, printed electronics, candidate radiation shielding — left in vacuum for hundreds of days and compared afterwards against ground simulations. OTV-6 also carried seeds, to see how long-duration radiation exposure affects them.
The Air Force Academy's FalconSat-8, a 136-kilogram satellite with five experiments, was deployed from OTV-6 and remains in orbit. Its deployment date is genuinely unresolved: the Space Force's 2022 release says October 2021, while Jonathan McDowell's independent tracking logged a subsatellite release around 28 May 2020, catalogued under the cover name USA 300. Those may be two different events, and it is not always clear whether small satellites on these missions come out of the payload bay or off the launch vehicle's upper stage.
The claims, and who actually made them
This is the part most often gotten wrong, so it is worth being exact about who said what.
Xinhua, China's state news agency, 17 June 2012, the day after OTV-2 landed: the craft "could be a precursor to an orbiting weapon, capable of dropping bombs or disabling enemy satellites as it circles the globe" — a framing the agency attributed to industry analysts.
Dmitry Rogozin, then director general of Roscosmos, 23 April 2022, on Rossiya 24: the vehicle "may carry some kind of reconnaissance tools or weapons of mass destruction. This is a new category of carriers of mass destruction weapons." He added that Russia had no "intelligible information from the United States about the purpose and technical capabilities of this device."
Researchers at China's Space Engineering University, writing in PLA Daily in September 2025, described it as a potential "space killer."
What does not exist, as far as the available record shows, is a statement from the Chinese foreign ministry or defence ministry calling the X-37B a weapon. The distinction between a state news agency quoting analysts, a military university's researchers writing a commentary, and a named government official speaking on television is worth preserving, because summaries tend to flatten all three into "China and Russia say it is a space bomber."
What the trackers found
The X-37B is watched by an amateur network — the SeeSat-L mailing list and the observers around it — which has tracked every mission. This is not casual: the archives contain fitted orbital elements posted by observers like Ted Molczan for others to point their telescopes at.
Marco Langbroek, who observes from Leiden, published plots of inclination and altitude across the first five missions and used them to test the most quotable claim about the vehicle. Heather Wilson, then Secretary of the Air Force, had said it "can do an orbit that looks like an egg and, when it's close to the Earth, it's close enough to the atmosphere to turn where it is," which "means our adversaries don't know" where it will come up next.
The tracking data show something different. Across five missions there were only minor inclination changes, with one exception — a temporary shift of about 0.6 degrees on OTV-4 — which an ordinary engine burn accounts for. What the vehicle does repeatedly change is altitude and eccentricity, using thrusters. Langbroek's summary of the aerodynamic-manoeuvring idea is blunt: "in space, the wings of the X-37B are useless." And on the claim that it slips its watchers: "Nor of course, are the X-37B that difficult to track as is claimed."
The trackers also produced the numbers for OTV-7's unusual orbit. The Space Force said only "highly elliptical orbit"; the figures that circulated — roughly 323 by 38,838 kilometres at 59.1 degrees — came from an amateur observer, Tomi Simola, locating it in February 2024.
The physics problem with the bomber theory
The Secure World Foundation, a space-policy institute, assessed the weapons claims against the flight record in 2025 and reached a conclusion worth quoting because it is mechanical rather than political: the vehicle has "near-zero feasibility as an orbital weapons system for attacking targets on the ground."
The reasoning is about the vehicle's own characteristics. The payload bay and available power are small. Anything dropped from it would need its own substantial deorbit burn to hit a target, and there is not obvious room for that. And the X-37B re-enters slowly — its own re-entry speed is nothing like a ballistic warhead's — so a weapon delivered this way would arrive as, in the foundation's phrase, "a slow moving, not-very-maneuverable glide bomb, easy prey for any air defense system."
On the satellite-inspector and satellite-killer versions, the same assessment offers something stronger than an absence of evidence. Across fifteen years of tracking, the X-37B "has never approached or rendezvoused with any other known space object," and it generally orbits well below most operational satellites. That is a positive finding from the observational record, not a failure to find one.
The foundation's overall conclusion is the shape of the honest answer: "The actual activities the X-37B has carried out indicate its mission is likely exactly what the Space Force claims it is" — while, in the same document, criticising the programme's opacity and noting that its budget is unknown.
What secrecy does and does not imply
The most recent mission complicates the picture in the opposite direction. On OTV-7 the Space Force performed a novel aerobraking manoeuvre, using atmospheric drag to lower the orbit so that service-module components could be discarded safely — and announced it in advance. General Chance Saltzman's stated reason was that they wanted other nations to observe it and wanted to share the data.
That is not the behaviour of a programme trying to conceal a weapon. It is the behaviour of one demonstrating a capability it wants observed, while continuing to classify the orbit it operates in.
Both things are true at once, and the article's honest position is to leave them both standing. The secrecy is real, officially acknowledged, and gives anyone reasonable grounds to ask what a vehicle does with 908 days in orbit. The specific weapons claims are not merely unproven; several are contradicted by the tracking record and by the vehicle's own dimensions. A programme can be genuinely opaque and still be doing roughly what it says.