More than 25 months after it lifted off on a SpaceX Falcon 9 rocket, the US Air Force’s secretive X-37B spaceplane successfully returned to Earth on October 27th, breaking its own record for time spent in orbit.

As always, the specifics of what exactly the X-37B spaceplane does in orbit remain as obscure as ever.

SpaceX’s Falcon 9 rocket launched X-37B on its fifth mission – OTV-5 – on September 7th, 2017, just a handful of months after successfully launching a similarly secretive mission (NROL-76) for the National Reconnaissance Office (NRO) and a handful of months prior to the company’s even more mysterious ‘Zuma’ launch. SpaceX’s OTV-5 launch had to race against the clock to beat Hurricane Irma’s forecasted landfall and the company managed to launch just a few days prior, while the booster’s post-landing operations had to be similarly expedited.

Falcon 9 B1040 returns to Landing Zone-1 after launching the X-37B spaceplane. The booster was reused roughly 9 months later. (SpaceX)

Thankfully, all went as planned and SpaceX recovery technicians had Falcon 9 booster B1040 safely stored inside a nearby hangar before Hurricane Irma impacted the Florida coast. B1040 was reused for the second and final time during the June 2018 launch of the SES-12 communications satellite and marked the second to last launch of a pre-Block 5 variant of Falcon 9.

In the interim, the USAF X-37B was quietly stationed in low Earth orbit (LEO), performing any number of tasks. Over the course of the 779 days it spent in orbit, the spaceplane modified its orbit several times before finally reentering Earth’s atmosphere to land at Kennedy Space Center’s Shuttle Landing Facility (KSC SLF) runway.

During the OTV-4 mission that preceded OTV-5, the same X-37B spacecraft spent 717 days in orbit – just shy of two years. OTV-5 surpassed that endurance record on August 26th and remained in orbit for another two months, breaking its own record by a bit less than 10%. For the most part, the USAF’s most consistent cover story for the X-37B paints the spaceplane as a platform for testing reusable spacecraft hardware, but that explanation has never made a huge amount of sense alongside the fact that each mission has averaged more than 570 days in orbit.

“[The X-37B is the] Air Force’s premier reusable and unmanned spacecraft providing the performance and flexibility to improve technologies in a way that allows scientists and engineers to recover experiments tested in a long-duration space environment.”



USAF, October 27th, 2019

In reality, it’s largely assumed that X-37B serves as a kind of flexible, on-call spy satellite, featuring a payload bay with plenty of room for signals intelligence or imaging hardware and a level of orbital endurance that makes it comparable to satellites. For example, OTV-5’s orbital parameters meant that the spacecraft routinely overflew Russia for much of the 25 months it spent in space.

An artist’s impression of X-37B in orbit. (Adrian Mann)

Aside from the “experiments” and likely espionage-related payloads X-37B can stow inside its payload bay, the spacecraft also brings along a small solar array and radiator and features a hydrazine maneuvering system with substantial delta-V reserves, allowing it to significantly change its orbit.



In an unexpected twist, the USAF press release suggested that X-37B also provided “a ride for small satellites”, unusual because the US never registered those satellites with the UN if they were actually deployed from the spacecraft – a potential violation of international spaceflight treaties.

The statement that this @usairforce X-37 flight deployed small satellites is alarming, since the US has not reported those deployments in its UN Registration Convention submissions. This would be the first time that either the USA or Russia has blatantly flouted the Convention. https://t.co/mpLWuvsECV — Jonathan McDowell (@planet4589) October 27, 2019

Following its successful October 27th recovery, Boeing and USAF teams will begin the process of refurbishing X-37B and preparing it for its sixth orbital mission as soon as possible. Known as OTV-6, the spacecraft is scheduled to head to orbit once more on a ULA Atlas V rocket that is scheduled to launch no earlier than Q2 2020.

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