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Envisioning The Future Of Dynamic Spaceborne Operations

Centaur V upper stage

“It’s time to be able to move through space at will and defend ourselves when we are attacked,” ULA CEO Tory Bruno says.

Credit: ULA

Rockets that intercept adversarial satellites; spaceplanes maneuvering around low Earth orbit; and multiuse platforms that can host, refuel and otherwise service on-orbit assets.

These assets could be the future of dynamic space operations as envisioned by the U.S. Space Force, supporting sovereign space capabilities and serving as a powerful deterrent to competitors in the domain.

The irony of space, according to the commander of U.S. Space Command, Gen. Stephen Whiting, is that every object operating within it is constantly in motion. “But normally, rarely do we use maneuver as a way to gain positional advantage,” he said at the Space Force Association’s Spacepower Conference in Orlando, Florida, in December.

Dynamic space operations would be supported by what the Defense Department calls “sustained space maneuver,” or the ability to keep a space platform operating almost continuously over time.

  • Optimized ULA upper stage could serve as an in-space interceptor
  • Sustained space maneuvering still limited by fuel availability

The U.S. is not alone in its pursuit of this concept: China and Russia “are rapidly advancing their own versions of [dynamic space operations] that entail sophisticated on-orbit operations, such as maneuver, concealment and deception,” the National Security Space Association states in an April 2024 report. In response to these developments, U.S. military leaders increasingly are expressing the need to invest in counterspace technologies—ideally, ones that can easily maneuver among the stars.

Satellites already are capable of orbital maneuvers, but when United Launch Alliance (ULA) CEO Tory Bruno considers dynamic space operations, he is not thinking about those assets. He is envisioning rockets that operate in space—for example, his company’s Centaur V upper-stage vehicle, enhanced to crisscross orbits as needed to counter, and if needed, dispose of threats.

In a Dec. 5 Medium post, Bruno called for the Space Force to hone a two-pronged strategy for advanced resiliency in space. On one hand, it should continue plans to field a vast array of satellites positioned in multiple orbits, as the service is pursuing across its space-based mission areas, he wrote. On the other hand, it should also field platforms that could intercept a satellite-killer before it attacks, then patrol the space domain looking for the next interdiction, he added.

X-37B orbital transfer vehicle
The X-37B Orbital Test Vehicle began executing a series of aerobraking maneuvers during its current mission. Credit: ULA

They would need to be “lightning-fast, long-range and, if necessary, very lethal,” he said at the Spacepower Conference on Dec. 12. If an adversary spacecraft were to approach a U.S. asset in a concerning manner, this platform could intercept the spacecraft within hours, “and if necessary, remove their assets off the board,” he noted.

The Centaur, which is the upper stage of ULA’s new Vulcan heavy-lift launch vehicle, could one day serve that purpose. The company is planning incremental improvements to the platform over the next couple of years that offer additional duration on orbit and will baseline each increment into the upper stage as it is completed, Bruno told reporters at the conference.

The upper stage that supported the Vulcan’s Oct. 4 certification mission for the Space Force’s National Security Space Launch (NSSL) program can last about 12 hr. on orbit. The goal is to last for days, “and longer,” he said, without elaborating on the specific improvements.

“It’s time to be able to move through space at will and to be able to defend ourselves when we are attacked,” Bruno said. “Then, we’ll truly be able to deter that aggression in space, which in turn deters an attack on the ground.”

Centaur V upper stage
The Centaur V upper stage was built for ULA’s Vulcan medium-lift launch vehicle. Credit: ULA

The U.S. military has long kept its space capabilities shrouded in secrecy, but officials are increasingly disclosing more information both to draw awareness to the threat space and to advocate for precious funding dollars.

The Space Force is looking to its own experimental platforms as inspiration for future maneuverable assets in space.

The service on Oct. 10 announced that the Boeing-built X-37B Orbital Test Vehicle would begin executing a series of “first-of-its-kind” aerobraking maneuvers, to dispose of service module components in low Earth orbit (LEO) before continuing with its mission. The two uncrewed, reusable X-37B space vehicles have completed six missions since the first launch in 2010, with the ongoing seventh mission launching Dec. 29, 2023, conducting radiation effect experiments and testing space domain awareness technologies in a highly elliptical orbit.

Aerobraking is a standard way for spacecraft to switch orbits without using up a lot of fuel, and the technique is particularly useful for maneuvering in LEO. This was the first time the Space Force and the spacecraft would attempt to carry out such an action while in orbit around the Earth, the service said in October. During the maneuver, the spaceplane uses the drag of the Earth’s atmosphere to drop its service module off to burn up, in accordance with space debris mitigation standards, and then it moves on.

Whiting applauded the X-37B’s novel maneuvering technique at the Spacepower Conference.

“We think this is exactly the kind of maneuverability we’d like to see in future systems, which will unlock a whole new series of operational concepts,” he said, adding that the X-37B is a test vehicle and as such does not fall under Space Command authorities.

The U.S. military already operates some maneuverable assets on orbit. The Northrop Grumman-built Geosynchronous Space Situational Awareness Program (GSSAP) satellites collect space situational awareness data from their position in near-geosynchronous orbit, and the satellites are capable of rendezvous proximity operations (RPO) that allow the spacecraft to approach an object of interest while also maintaining flight safety.

Six GSSAP spacecraft have been launched since 2014, one of which was deactivated in 2023 after reaching the end of its lifespan. Two new GSSAP spacecraft are due to fly on ULA’s Vulcan rocket under USSF-87, once the launch vehicle is certified for NSSL missions. Two additional satellites are scheduled to launch around 2027.

Fully realized dynamic space operations remain technically challenging, mainly hindered by the limitations of in-space propulsion.

Thomas Roberts, a postdoctoral fellow at the Georgia Institute of Technology and an adjunct fellow at the Center for Strategic and International Studies in Washington, writes in a December debate paper published by The Aerospace Corp. that such operations, where spacecraft are constantly transferring between orbits, would require “massive amounts of propellant.”

For an LEO-based satellite to raise its altitude from 400 km (250 mi.) above the Earth’s surface to 1,000 km using chemical propellant, about 10% of its mass must be propellant, he writes. For a geosynchronous-orbit-based satellite to maneuver to a 30-deg. inclination and back would require twice its mass in propellant just to perform those two actions.

“In reality, burning propellant at such exceptionally high rates introduces new regrets for operators,” such as time spent waiting to perform RPO, propellant expended to reach a refueler or launch costs associated with reconstituting satellite constellations, Roberts writes. He called for the Space Force to adopt “strategic” or “tactical” maneuver capabilities, rather than “sustained” space maneuvers, that can serve the nation’s needs on orbit while preserving costly energy.

DARPA and NASA are developing a nuclear thermal propulsion engine ultimately to support on-orbit maneuvering and enable humans to travel to Mars. But progress is slow, thanks to the challenges inherent to ground-testing a nuclear reactor.

Whiting, for his part, sees in-orbit refueling as the most viable option to keep satellites pivoting through space.

“There’s a trade-off there between performance and endurance that seems to exist in the technology, but we’re open to new technologies that may give us both endurance and velocity at the same time,” he said.

Meanwhile, commercial capabilities are increasingly coming online to support on-orbit mobility in ways similar to what the Space Force envisions.

When Blue Origin’s New Glenn heavy-lift launch vehicle lifted off for the first time on Jan. 16, it carried Blue Ring to orbit—a large, multiuse platform the company developed to host, deploy and refuel spacecraft from Earth orbit, cislunar space and beyond.

Blue Ring was developed to host and/or deploy 1,100-lb.-class satellites over a dozen docking points, while the top deck can anchor a 2-ton payload. A single Blue Ring can carry more than 6,660 lb. to a range of orbits, powered by a hybrid chemical and solar-electric system that uses chemical propulsion to maneuver and electric propulsion for station-keeping or to save on energy when transferring orbits. The spacecraft is also refuelable and capable of serving as a refueling depot for other satellites.

Jeff Bezos’ company unveiled the Blue Ring platform in October 2023, along with a new business unit called In-Space Systems.

Vivienne Machi

Vivienne Machi is the military space editor for Aviation Week based in Los Angeles.