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This Article reviews the recent emergence of the space-cyber nexus as a distinct warfighting domain, solidified during the Russian invasion of Ukraine, and analyzes the (missing?) laws of space-cyber warfare. The Article further suggests a roadmap for the development of norms and rules under the constraints of contemporary geopolitics and difficulties in multilateral rulemaking. As space-based infrastructure became critical to modern militaries and economies, it has, as a result, become a prime target. While only four countries possess antisatellite missiles (United States, Russia, China, and India), cyberattacks require much less in terms of funds and technological sophistication and can also be launched by nonstate organizations. They are powerful asymmetric weapons that allow an attacker to cover their tracks, leaving the attacked country uncertain about attribution, thus rendering retaliation and deterrence challenging. The war in Ukraine, dubbed by some as “the first space-cyber war,” saw, for the first time, the targeting of space-based services as part of a military campaign. Significantly, this was achieved through cyberattacks—a telling choice given that Russia, to which the attack was attributed, also possesses antisatellite missiles. This Article suggests that current multilateral regimes are insufficient to address the new space-cyber nexus and that there is an urgent need to develop an integrated, flexible, multilateral regime. Considering the gridlock in traditional international lawmaking and the rise of nonbinding international agreements, the Article suggests a polycentric approach to regime building. Advocated by Nobel Laureate Elinor Ostrom for commons governance, polycentric governance is increasingly used to address a diverse range of global collective action challenges. The Article thus envisions multi-track diplomacy in which multiple forums introduce a series of nonbinding international agreements that together would amount to a feasible and flexible, albeit imperfect, corpus of the laws of space-cyber warfare. 

This paper describes the fabrication and assembly of tessellated precast reinforced concrete shear walls. These walls are being constructed and tested as part of an NSF-funded research project designed to demonstrate the concept of Tessellated Structural-Architectural (TeSA) systems. The over-arching goal of this research is to explore tessellation patterns that can be implemented on a large scale, are architecturally appealing, and provide structural function. TeSA systems are comprised of individual tiles arranged in tessellations, or repeating geometric patterns. Tiles are topologically interlocking, which means that they transfer forces due to their interlocking geometry rather than through a bonding adhesive. The benefit of such a system is the ability to localize failure and rapidly repair the individual damaged tiles, rather than the entire system. The specimen discussed in this paper is a precast concrete shear wall constructed from individually cast I-shaped tiles. Shear wall tests are forthcoming; this paper focuses instead on documenting technical solutions to difficulties faced during design, fabrication, and assembly of the test specimen. This paper is intended to provide lessons learned to others who are designing and building TeSA walls and thereby facilitate the benefits of these novel systems. 

Abstract The Australian, Chinese, European, Indian, and North American pulsar timing array (PTA) collaborations recently reported, at varying levels, evidence for the presence of a nanohertz gravitational-wave background (GWB). Given that each PTA made different choices in modeling their data, we perform a comparison of the GWB and individual pulsar noise parameters across the results reported from the PTAs that constitute the International Pulsar Timing Array (IPTA). We show that despite making different modeling choices, there is no significant difference in the GWB parameters that are measured by the different PTAs, agreeing within 1σ. The pulsar noise parameters are also consistent between different PTAs for the majority of the pulsars included in these analyses. We bridge the differences in modeling choices by adopting a standardized noise model for all pulsars and PTAs, finding that under this model there is a reduction in the tension in the pulsar noise parameters. As part of this reanalysis, we “extended” each PTA’s data set by adding extra pulsars that were not timed by that PTA. Under these extensions, we find better constraints on the GWB amplitude and a higher signal-to-noise ratio for the Hellings–Downs correlations. These extensions serve as a prelude to the benefits offered by a full combination of data across all pulsars in the IPTA, i.e., the IPTA’s Data Release 3, which will involve not just adding in additional pulsars but also including data from all three PTAs where any given pulsar is timed by more than a single PTA.