The US military develops "upper atmosphere" to change satellite orbits, hoping to significantly reduce fuel consumption

The U.S. Space Force's unmanned space plane X-37B landed at the Kennedy Space Center in Florida on October 27, 2019. (Picture taken from U.S. Space Force)

Satellites change their orbits in space, usually consuming propellant. The U.S. Defense Advanced Research Projects Agency (DARPA) is developing a new technology that hopes to allow space vehicles to use the Earth's atmosphere to change orbits, reduce fuel consumption, and improve on-orbit maneuverability.

The military website "Defence Blog" reported that DARPA announced the Anzio project on November 9 and is scheduled to hold an industry briefing in Virginia from December 16 to 17 to find American companies interested in participating in research and development. The goal of the plan is to allow space vehicles to use the resistance or lift of the atmosphere to complete rapid and precise orbit transfers.

Generally, satellites must consume propellant to change their orbits; if the upper atmosphere can be used to assist in slowing down or changing flight direction, there is an opportunity to reduce fuel requirements. Traditional aerodynamic deceleration usually requires multiple passes through the thin atmosphere to gradually lower the orbit; another aerodynamic capture technology reduces the speed through a deeper atmospheric pass.

The key to this technology is to allow space vehicles to enter the Earth's upper atmosphere and use air resistance or lift to help change their flight path, rather than relying entirely on their own propulsion system. Traditional aerodynamic deceleration is to allow the space vehicle to pass through the thin atmosphere multiple times and gradually lower the orbit; another aerocapture technology is to reduce the speed and enter the orbit through a deeper atmosphere pass. Another way is to use lift in the atmosphere to change the orbital inclination.

X-37B used atmospheric resistance to change orbit

The U.S. Space Force's unmanned space plane, the X-37B, has tested similar technology. During its seventh mission, the space plane used atmospheric resistance to adjust its orbit several times. It returned to Vandenberg Space Force Base in California on March 7, 2025, ending a space mission of more than 434 days.

However, the X-37B is a space plane with wings that can withstand the high temperatures of re-entry into the atmosphere. DARPA has listed heat-resistant protection, control systems, atmospheric sensing and lightweight aerodynamic shells as research and development priorities this time, hoping to develop technologies that can be used by other space vehicles.

The four research and development directions listed by DARPA include heat-resistant protection systems, control systems and algorithms, atmospheric sensing, and lightweight aerodynamic shells; communications, power management, space vehicle platforms, payloads, propulsion systems, and existing orbital transfer vehicles are not within the scope of the plan.

DARPA has not yet announced which satellites will be used in the future, project budget, implementation schedule and winning bidders. The draft of the official solicitation document will be released as soon as December 9.