Our planet’s magnetic field shields us from the harmful radiation of space, but it also acts as a trap for highly charged particles. These particles, accelerated to near light speed, pose a significant threat to our increasingly reliant satellite infrastructure. Imagine a scenario where a nuclear weapon detonates in space, releasing a torrent of energetic particles capable of frying a significant portion of our satellites. This isn’t science fiction, but a growing concern in the age of space militarization.
The historical record underscores this threat. In 1859, a massive solar storm known as the Carrington Event triggered fires at telegraph stations, while in the 1960s, a nuclear test called Starfish Prime led to the disabling of a third of the satellites in orbit. These events highlight the devastating consequences of energetic particles on our technological assets.
These harmful particles, often called ‘hot’ or ‘killer’ electrons, are trapped within the Earth’s magnetic field, forming two doughnut-shaped radiation belts. For decades, scientists have sought ways to clear these belts on demand, a process known as Radiation Belt Remediation (RBR). Recent years have seen a surge in RBR research, with encouraging progress, much of it undertaken by the US Department of Defense and Energy, often under secrecy.
The urgency behind this research stems from growing anxieties about potential space warfare. In early 2024, allegations emerged of Russian plans to deploy a nuclear weapon in space, posing a direct threat to our vital satellite infrastructure. The potential consequences of such an attack could dwarf those of Starfish Prime, as the majority of today’s satellites are commercial and lack the military hardening needed to withstand a nuclear detonation’s particle storm.
Professor Emeritus Dennis Papadopoulos of the University of Maryland has been appointed advisor to a new, secretive RBR initiative at the Naval Research Laboratory (NRL) in response to these concerns. The concept of RBR is not as outlandish as it may seem. Lightning, for instance, acts as a natural RBR, generating radio waves that push hot electrons down into the atmosphere, where they collide with air molecules and rapidly lose energy. This effect, known as precipitation, effectively wipes out nearby radiation belts.
The challenge lies in replicating this effect on a larger scale. To precipitate energetic particles, radio waves with wavelengths ranging from 10 to 100 kilometers are needed. While generating such long wavelengths (low frequencies) is challenging, it’s not impossible. Several navies utilize ‘very low frequency’ (VLF) radio waves for communication with submarines, employing antennas hundreds of meters high. However, even if the US Navy were to shift its VLF transmitters to optimal RBR frequencies, the process would be too slow to save satellites in a nuclear attack.
The ionosphere, a layer of charged particles beginning roughly 80 kilometers above the Earth’s surface, poses a significant hurdle. The ionosphere weakens radio waves significantly, especially during the day. Researchers are exploring innovative solutions to overcome these limitations.
One promising approach involves using experimental antennas designed to hop between different frequencies, allowing for targeted removal of particles at different energy levels. Morris Cohen and his team at Georgia Tech built a 275-meter antenna, laying it horizontally in a field in Oklahoma. The flexibility of frequency-hopping allows for targeting particles across a range of energy levels and optimizing particle removal in key orbits.
Others are seeking to bypass the ionosphere altogether. The Air Force Research Laboratory (AFRL) launched a unique satellite called DSX, equipped with an 80-meter, 10,000-volt transmitting antenna. This satellite, orbiting between 6,000 and 12,000 kilometers above Earth, generated VLF radio waves for nearly two years, successfully knocking energetic particles into the Earth’s atmosphere.
More ambitious ideas are also on the horizon. The Department of Energy’s Los Alamos National Laboratory envisions using a space-based electron beam to manufacture lightning, while the NRL is developing a rocket that would release barium into the ionosphere. The resulting barium ions, spiraling under the influence of Earth’s magnetic field, would generate an electric current capable of producing electron-precipitating radio waves.
These advanced approaches come with inherent risks. The precipitation of high-energy particles can deplete the stratospheric ozone layer, which shields Earth from harmful ultraviolet radiation. The potential environmental impact of large-scale RBR operations remains a subject of ongoing research.
Despite the challenges, the goal of developing effective countermeasures against a nuclear attack on satellites is paramount. The hope is that by demonstrating the ability to neutralize these threats, America can deter potential adversaries from taking such drastic action. However, solar storms, a natural source of energetic particles, pose a more enduring challenge and require different approaches for mitigation.
