Launch vehicle “ridesharing” has redefined access to and use of outer space. Today, rockets carry satellites from dozens of countries on shared journeys towards the stars. To ensure that these diverse payloads pose no threat to the overall space mission, safety controls have emerged to protect against mechanical and electrical failure. While these protections were designed to mitigate the risk of probabilistic physical effects, they also have implications for cyber attackers seeking to abuse the trusted status of secondary payloads to harm launch missions. This paper considers such dynamics through a multidisciplinary lens. It begins by drawing on the perspective of security studies and international relations to characterize what motivates an attacker to target satellite launches. This is combined with a technical analysis which leverages model-based engineering techniques to assess the threat of electronic warfare (EW) and radio frequency interference (RFI) attacks against missile range safety technologies on modern launch vehicles. Through dynamic physical simulation, we demonstrate that even inexpensive nanosatellite platforms have the potential to threaten shared launch vehicles in the hands of motivated cyber adversaries. The paper concludes with a brief discussion of the implications of these findings for both policymakers and technical researchers interested in cyber-physical threats in orbit.