Completing its seventh mission, the military’s secret spaceplane returned to Earth late Thursday night, generating sonic booms heard around Vandenberg Space Force Base.  

The X-37B Orbital Test Vehicle successfully deorbited and landed on Vandenberg’s 3-mile-long runway at 11:22 p.m. as a sonic boom sounded its arrival.

Some residents took to social media to ask about the source of the sound, with some suspecting an explosion.

“Mission 7 broke new ground by showcasing the X-37B’s ability to flexibly accomplish its test and experimentation objectives across orbital regimes,” said Gen. Chance Saltzman, the chief of space operations for U.S. Space Force.

“The successful execution of the aerobraking maneuver underscores the U.S. Space Force’s commitment to pushing the bounds of novel space operations in a safe and responsible manner.”

The uncrewed X-37B has orbited Earth since arriving in space in late 2023 following a Falcon Heavy launch from Florida. In total, the small orbiter spent more than 434 days in space for the program’s latest mission.

This wasn’t the first X-37B landing at Vandenberg, which welcomed home the small spaceplane early in the program’s history. 

At 29 feet long and boasting a wingspan of 14 feet, the spaceplane is much smaller than the space shuttle orbiter Vandenberg’s runway originally expected to serve decades ago. The West Coast program was canceled before any launches or landings occurred at the base.

Space Force officials said the X-37B landing demonstrated the program’s rapid ability to launch and recover its systems across multiple sites. 

Since the beginning, military officials have remained mum about the specifics for the program’s Mission 7 while in orbit.

After landing, Space Force representatives said X-37B accomplished a range of test and experimentation objectives demonstrating its robust maneuver capability. 

While in orbit, Mission 7 tested space domain awareness technology experiments aiming to improve the military’s knowledge of the space environment. 

“These technologies are critical to the U.S. Space Force’s ability to conduct space operations in an increasingly congested and contested environment of space, to the benefit of all users of the domain,” according to Space Force representatives. 

After aerobraking to a low-Earth orbit and completing its test and experimentation objectives, Mission 7 successfully performed its autonomous return. 

“Mission 7’s operation in a new orbital regime, its novel aerobraking maneuver, and its testing of space domain awareness experiments have written an exciting new chapter in the X-37B program,” said Lt. Col. Blaine Stewart, X-37B program director. 

“Considered together, they mark a significant milestone in the ongoing development of the U.S. Space Force’s dynamic mission capability.”

The inaugural mini space shuttle first launched in 2010, and that mission lasted 224 days in orbit before returning to Vandenberg. 

After conducting the first three landings of X-37B, the next three missions between 2015 and 2020 ended in Florida before the program’s return this week to the West Coast.