X-37B's Power Beaming Payload A Reminder Of Potential Orbital Microwave Anti-Satellite Weapons

Technology related to sending power via a microwave beam down to Earth could potentially be applied to taking out hostile targets in space.


The U.S. Navy has announced the first test of its on-orbit power-beaming system on the U.S. Air Force's X-37B mini-space shuttle, just a day after the successful launch of that vehicle on its latest mission to space. These experiments could have game-changing implications for power generation on Earth, especially for facilities in remote areas and for unmanned aircraft, but they also underscore the potential applications of high-powered microwaves and other directed energy beams as weapons in space to jam, blind, or even destroy critical sensors and other components on opponents' satellites.

The U.S. Naval Research Laboratory's (NRL) Photovoltaic Radio-frequency Antenna Module (PRAM) is one of a number of publicly disclosed payloads onboard the X-37B, which blasted off from Cape Canaveral Air Force Station in Florida on top of a United Launch Alliance Atlas V rocket on May 17, 2020. This is the reusable space plane's sixth trip into orbit since 2010 and it had just completed its fifth mission, which lasted a record-setting 780 days, in October 2019. Much about the craft and its missions remain highly classified.

PRAM is a self-contained module that is a foot long, a foot wide, and around two inches tall. The system uses a solar panel on top to collect sunlight and then converts that into a microwave beam. In principle, a receiver on Earth could then take the beam and convert it back into energy that could be used to power traditional electric devices. You can read more about the history of this concept and the science behind it in this past War Zone piece.


The Naval Research Laboratory's Photovoltaic Radio-frequency Antenna Module that is now on that X-37B in orbit.

"PRAM converts sunlight for microwave power transmission. We could’ve also converted for optical power transmission," Chris Depuma, the PRAM program manager at NRL, said in a statement. "Converting to optical might make more sense for lunar applications because there’s no atmosphere on the Moon. The disadvantage of optical is you could lose a lot of energy through clouds and atmosphere."

The Navy team plans to test how efficiently PRAM converts energy and its associated thermal performance in space, rather than in a terrestrial laboratory setting. NRL hopes these experiments will inform the development of future prototypes and could lead to a full system installed on a dedicated spacecraft.

In principle, a constellation of solar-energy-collecting power-beaming satellites could provide near-limitless, clean power anywhere on Earth. This could completely transform how power is supplied for both military and civilian activities in the most remote areas. It could potentially power propulsion systems on long-endurance drones, allowing them to stay aloft indefinitely, something The War Zone has previously explored in detail

"To our knowledge, this experiment is the first test in orbit of hardware designed specifically for solar power satellites," Paul Jaffe, PRAM principal investigator at NRL, said in his own statement. This "could play a revolutionary role in our energy future."

However, if a power-beaming system can take solar energy, convert it into a microwave beam, and direct that beam at a specific location, one has to wonder if that concept could not also be adapted into a space-based weapon. The idea of using high-powered microwaves to disrupt, or even destroy, electronic systems in space, as well as on Earth, is hardly new

The U.S. military alone has already explored various types of high-powered microwave weapons that can scramble or damage electronic systems and is evaluating new designs, right now. These include systems that can disrupt enemy computer networks, knock down small drones, and fry the electronics in incoming missiles to throw them off course, among others. A sufficiently powerful burst of microwave energy could cause enough damage to cause a mission kill on satellites.

A 2019 report from the U.S. Defense Intelligence Agency (DIA) specifically highlighted ground and space-based high-powered microwaves, as well as other directed energy weapons, including lasers, as potential future threats to American assets in orbit. It also listed a slew of other possible dangers, including jamming and "killer satellites" capable of launching various types of kinetic and non-kinetic attacks.


A graphic from a 2019 Defense Intelligence Agency report on present and future challenges in space showing the means by which one satellite might attack another.

The Russians and the Chinese both already have various anti-satellite capabilities, including air-launched and ground-based kinetic interceptors, and are continuing to develop new capabilities given the traditional advantage that the United States has in space-based capabilities, including intelligence gathering, early warning, communications and data sharing, navigation, and more. The U.S. military itself has a number of other highly-classified counter-space capabilities and other countries, such as India, are also developing their own means to challenge opponents assets' in orbit.

There is also renewed discussion about space-based weapons, mostly as a means to counter anti-satellite threats or for missile defense, in recent years. "Directed energy weapons (high energy lasers or particle beam) or space-based interceptors provide the best overall hope of a hard kill" to destroy future hypersonic weapons, according to a report the NATO Science & Technology Organization released in March. In 2019, France also notably announced plans to eventually deploy small laser-armed satellites to protect other space-based assets. 


A portion of the section on hypersonic defense from the March 2020 NATO Science & Technology Organization report.

As NRL's researchers noted with regards to PRAM, the vacuum of space removes many of the obstacles that deflect and diffuse directed energy beams on Earth. This means it could require less starting power to generate a beam with sufficient energy to disrupt or damage another target in space, even if it were shielded from common solar radiation. Many military-grade weapons and other systems are also hardened against electromagnetic radiation, but are still vulnerable to a suitably powerful microwave attack.

Highly maneuverable satellites or other spacecraft – the X-37B would be an ideal platform itself – could also maneuver the system very close to its target. This could, in turn, reduce the power and range requirements for high-powered microwave or other directed energy weapons. A high-powered microwave also has the benefit of not needing to physically break up the target to destroy it, meaning that an attack would not cause a cloud of dangerous space debris that could threaten friendly assets in space.

Of course, there is no indication that NRL has plans to transform PRAM, specifically, into a weapon. At the same time, the technology, or at least related technology, seems to have clear applications as a weapon. In addition, the U.S. military has been researching new space-based weapons in recent years, including plans for a particle beam system, which it announced it had shelved in September 2019. This is in addition to the anti-satellite capabilities that the Air Force is already known to have, which the U.S. Space Force has now begun to inherit, the full scope of which remains largely unknown.

All told, the PRAM experiments onboard the X-37B are exciting steps forward toward potentially revolutionary systems for providing power down here on Earth. Work along similar lines could have important implications for possible future American space-based weapons as competition in orbit and beyond continues to heat up.

Contact the author: joe@thedrive.com