Image credit: SpaceX

That secretive mission of the U.S. Space Force X-37B, lofted into a classified orbit by a SpaceX Falcon Heavy booster last December has been spotted by eagle-eyed satellite trackers.

This novel space trek of the winged craft is dubbed Orbital Test Vehicle-7 (OTV-7).

U.S. military’s X-37B space plane is encapsulated in launch faring and features the United States Space Force (USSF) logo for the first time.
Image credit: Boeing

Classified doings

A recent posting by Tomi Simola, a sky watching hobbyist in Finland, captured the craft’s whereabouts.

“OTV 7 found!” Simola wrote, sharing his observations with a global family of equipment-running members of the SeeSat-L community.  SeeSat-L is a mailing list for visual satellite observers.

The classified doings of the maneuverable X-37B has apparently reached new heights, zooming from 200 miles at its closest to Earth, outward to over 24,000 miles at its highest point – at least for now.

This X-37B craft is in a 59.1 degree inclined highly elliptical orbit. 

Image credit: Tomi Simola

For an excellent story on this sighting, go to Stephen Clark’s article at Ars Technica at:

Also, go to this earlier informative video from Shelby Holliday at the Wall Street Journal at:

Image credit: Tomi Simola

Distinctive mission

This mission of the U.S. military’s unique X-37B robotic space plane is decidedly distinctive.

For the first time, the Boeing-built craft was hurled spaceward atop a SpaceX Falcon Heavy booster, “with a wide range of test and experimentation objectives,” explains a U.S. Space Force press statement. Reportedly OTV-7 is the fourth flight of this particular craft; there are believed to be only two vehicles for the program.

OTV-6 in-space photo. Image credit: Boeing/Inside Outer Space screengrab

The past flights of an X-37B made use of the Atlas V 501 launcher for the most part, although OTV-5 was placed in orbit via a SpaceX Falcon 9 Block 4 launcher.

New orbital regimes

The Department of the Air Force Rapid Capabilities Office, in partnership with the United States Space Force, launched the vehicle on December 28 from Kennedy Space Center, Florida.

Image credit: Boeing/Inside Outer Space screengrab

Designated USSF-52, the space plane tests include operating in new orbital regimes, experimenting with future space domain awareness technologies, and investigating the radiation effects on materials provided by NASA.

A previous flight, OTV-6, was the first mission to introduce a service module that expanded the capabilities of the spacecraft.

“We are excited to expand the envelope of the reusable X-37B’s capabilities, using the flight-proven service module and Falcon Heavy rocket to fly multiple cutting-edge experiments for the Department of the Air Force and its partners,” said Lt. Col. Joseph Fritschen, the X-37B Program Director.

Hotfooting back to Earth

Given the X-37B’s jaunt to high orbit, what about its return and the speed the vehicle is cruising? In particular, is the craft outfitted with a different reentry tile system than earlier flights?

I asked noted space tracker Marco Langbroek what’s up with this craft getting back down to Earth. He’s a lecturer in optical Space Situational Awareness (SSA) at Delft Technical University, the Netherlands.

Reentry tiles as seen from earlier X-37B mission.
Image credit: Boeing

Previous OTV missions in Earth orbit are slower than its velocity at high Earth orbit.

“It is about 2.5 kilometers per second above the speed of previous missions, so definitely significantly higher,” Langbroek told Inside Outer Space. “We do not know if the X-37B heat-shield and structural integrity can handle that – perhaps it can, perhaps it cannot.”

But one way for this X-37B vehicle to de-orbit for landing on Earth, Langbroek said, would be to first do a burn to lower apogee around Earth and circularize the orbit, before de-orbiting.

“That brings the speed down to the speed of earlier missions. A vehicle like the OTV can use aerobraking once in perigee and at the top of the atmosphere, making use of atmospheric drag, to circularize the orbit at low Earth orbit altitude, and then de-orbit from there,” Langbroek said.

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

Details: skimpy and classified

Since the X-37B first launched in 2010, Boeing has empowered the reusable spaceplane “with more capability, new technology, and pushed the boundaries of what’s possible with each ensuing mission,” the company points out.

OTV-6, after circling Earth for a record-setting 908 days — completed that mission with a successful landing at Kennedy Space Center on November 12, 2022.

As in previous missions, details of the OTV-7’s in-space agenda are skimpy and classified.

A Space Force statement did note that the NASA experiment onboard will expose plant seeds to the harsh radiation environment of long-duration spaceflight. Known as “Seeds-2,” that investigation is paving the way for future crewed space missions.

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

Service module

As explained in the Air Force statement, the last space plane flight, OTV-6, was the first mission to introduce a service module that expanded the capabilities of the spacecraft.

That module hosted more experiments than any of the previous space plane missions. In the OTV-6 flight, the service module was detached in orbit from the space plane before its landing, necessary due to the aerodynamic forces seen by the X-37B vehicle upon re-entry.

Once detached, the free-floating service module was later disposed of “in compliance with best practices,” according to the Air Force.

First use technologies

In past Boeing-supplied information, the company says the X-37B is designed to operate in low-Earth orbit, 150 to 500 miles above the Earth.

Additionally, the vehicle makes use of several “first use in space” technologies including:

— Avionics designed to automate all de-orbit and landing functions.

— Flight controls and brakes using all electro-mechanical actuation; no hydraulics on board.

— Use of a lighter composite structure, rather than traditional aluminum.

— New generation high-temperature wing leading-edge tiles and toughened uni-piece fibrous refractory oxidation-resistant ceramic (TUFROC) tiles and advanced conformal reusable insulation (CRI) blankets.

X-37B handout.
Credit: Boeing

Flight roster

Here’s a listing of previous flights of the space plane:

OTV-1: launched on April 22, 2010 and landed on December 3, 2010, spending over 224 days on orbit.

OTV-2: launched on March 5, 2011 and landed on June 16, 2012, spending over 468 days on orbit.

OTV-3: launched on December 11, 2012 and landed on October 17, 2014, spending over 674 days on-orbit.

OTV-4: launched on May 20, 2015 and landed on May 7, 2015, spending nearly 718 days on-orbit.

OTV-5: launched on September 7, 2017 and landed on October 27, 2019, spending nearly 780 days on-orbit.

OTV-6: Launched on May 17, 2020  and landed on November 12, 2022, circling Earth for 908 days.

This size chart shows how the Boeing-built X-37B robot space plane compares to NASA’s space shuttle, a larger version of the spacecraft called the X-37C and an Atlas 5 rocket.
Image: © AIAA/Grantz/Boeing/povided to Inside Outer Space via AIAA

Derivative plan?

There are known to be at least two X-37B vehicles.

Curiously, back in late 2011, a technical paper popped up at a major aerospace conference. It outlined new plans for the spacecraft and a scaled-up version to support space station cargo deliveries or even haul astronauts into orbit.

An X-37B OTV and derivatives plan assessment sketched out a variety of scaled-up versions of the X-37B space plane.

What is not known, however, is whether such a plan was advanced within Boeing or the Air Force.

Go to this informative Boeing video released last April, complete with head-banging, heavy metal music that offers a look at the OTV-6 mission at:

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