Leonard David's INSIDE OUTER SPACE

Artist rendering of the X-37B performing an aerobraking maneuver using the drag of Earth’s atmosphere.
Image credit: Boeing Space

That secretive U.S. Space Force X-37B Orbital Test Vehicle (OTV-7), now some 345 days in orbit, is engaged in performing aerobrake maneuvers, a technique to alter its orbit around Earth and safely dispose of its attached service module.

Lofted back in late December of 2023, the military spaceplane was placed in an orbit higher than any spaceplane, in a highly elliptical high Earth orbit. From that orbit, the United States Space Force, supported by the Air Force Rapid Capabilities Office, conducted radiation effect experiments and tested Space Domain Awareness technologies.

X-37B (OTV-7) is also referred to as United States Space Force-52 (USSF-52). Image credit: SpaceX

This OTV-7 flight marks the first time the U.S. Space Force and the X-37B have attempted to carry out a dynamic aerobraking maneuver.

Expending minimal fuel

“The Boeing-built X37B will perform ground-breaking aerobraking maneuvers to take the dynamic spaceplane from one Earth orbit to another while conserving fuel. Partnered with the United States Space Force, this novel demonstration is the first of its kind,” Boeing explains.

Image credit: Boeing/Inside Outer Space screengrab

The use of the aerobraking maneuver requires the heat-tiled spacecraft to conduct a series of passes using the drag of Earth’s atmosphere. That technique enables the spacecraft to change orbits while expending minimal fuel.

There are no details as yet on whether the aerobrake maneuvering is complete. If so, the X-37B was slated to resume its test and experimentation objectives until they are accomplished. At that point, the vehicle is to de-orbit and execute a safe return to Earth, likely at the Kennedy Space Center.

OTV-6 return at Kennedy Space Center. Image credit: Boeing/Inside Outer Space screengrab

Apollo, Zond programs

“I wouldn’t exactly call it ground breaking. Aerobraking occurs every time something re-enters. If the object has a heat shield, it survives, if not – it breaks up,” explains Bob Christy of the informative Orbital Focus website at https://www.orbitalfocus.uk/

As far as using aerobraking for trajectory control goes, Christy told Inside Outer Space that you can look back as far as the 1960s to the U.S. Apollo and former Soviet Union Zond programs.

“Zond used aerobraking to modify the incoming extremely elliptical orbit to a sub-orbital trajectory. Original perigee was within the atmosphere, above the Indian Ocean. Encounter with the atmosphere shaved off sufficient velocity to result in a ballistic arc with a second atmosphere entry point above Russia,” Christy advised.

Image credit: Boeing Space/Inside Outer Space screengrab

“I believe Apollo had a plan to do something similar. There was a fear that a small error could strand the CM [command module] in low Earth orbit so it was modified to keep the aerobraked trajectory within the atmosphere,” Christy said, recalling Voice of America coverage of the re-entries and the danger of “skipping off into space” that was often mentioned.

Lowering orbital height

A recent reported orbit of the X-37B came November 2 by an amateur observer, Toni Simola, who observed the craft in an orbit of about 100 x 30,000 kilometers, nearly 9,000 kilometers down from its original height, Christy said. “There was never any way for the craft to return to Earth using a retro-rocket as it cannot carry sufficient propellant for the job,” he said.

OTV-6 was the first mission to introduce a service module that expanded the capabilities of the spacecraft.
Image credit: Staff Sgt. Adam Shanks

“It probably continued with the low perigee, with a plan to raise it once apogee reached 400-500 kilometers so it can continue its mission in low Earth orbit. I notice that the Boeing press release mentions disposal of the [vehicle’s] Service Module so maybe it was planned to be released before the X-37B raised perigee, to re-enter above the southern hemisphere,” said Christy. “We’ll not know whether the maneuver is complete or successful until either Boeing/Space Force announces it or an amateur observer detects it again.”

Go to this Boeing video at: