One scientist has produced a detailed model which proposes a way to verify that no government or rogue actors are secretly hiding nuclear weapons in the Earth’s orbit. Currently, international laws prevent the use of nuclear weapons in orbit, but it also presents a problem. International space law was created by the Outer Space Treaty, which was drafted in 1966 and has been ratified by 117 nations, including the USA, China, and Russia, since then. It explicitly bans nuclear weapons from being used in space, which is reassuring, because a nuclear explosion launched from an orbiting object could destroy most of the satellites in low Earth orbit, creating havoc with vital satellite communications, imaging and weather forecasting, to say the least. Angela Di Fulvio, associate professor in nuclear engineering at the University of Illinois, said: “The power of such a treaty to deter space-based nuclear detonations, which could sabotage key satellite-reliant infrastructure, is limited if compliance with the treaty cannot be readily verified.” To attempt to crack this problem, Areg Danagoulian, associate professor of Nuclear Science and Engineering at MIT, modelled the interaction between high-energy sub-atomic particles in the Earth’s magnetic field and disclosed the details in a paper published in Nature this week. Di Fulvio explained that the study modelled nuclear weapons at 2,000 km altitude where the Earth’s magnetic field traps electrons with energies in the megaelectronvolt (MeV) range and protons up to gigaelectronvolt (GeV). “When GeV protons interact with heavy nuclei, such as those of uranium and plutonium, which are the most common fissile materials in nuclear weapons, they can induce a process called nuclear spallation. This produces secondary radiation that can include neutrons, charged particles and gamma rays,” Di Fulvio said in an accompanying article. The study, published in Nature today, found that satellites carrying nuclear weapons emit a tell-tale neutron signal caused by interactions with high-energy protons trapped in the Earth’s magnetic field. “The author finds that this signal could be detected by nearby ‘inspector’ satellites,” Di Fulvio said. Danagoulian’s modeling showed calculations suggesting a CubeSat made of commercially available equipment weighing up to 18kg could detect the tell-tale signals emitted by nuclear weapons in space. Such a satellite could identify a thermonuclear weapon at a distance of 4 km after around a week of observations, the study found. But more work was needed to test whether the modelled approach was feasible, the paper said. “Future engineering proof-of-concept studies are needed to test the practicality of this approach. The purpose of this study is to inform policy and provide the theoretical basis for future research in this field. There are many challenges and open questions that need to be addressed for the proposed concept to achieve a high technical readiness level,” he said. ®
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