The predawn darkness on a cool Florida night was shattered by the ignition of nine Merlin engines on a SpaceX Falcon 9 rocket. The thrust of the engines shook the ground miles away. From a distance, the rocket appeared to slowly rise above the horizon. For the cargo onboard, the launch was anything but gentle, as the ignition of liquid oxygen generated more than 1.5 million pounds of force. After the rocket had been out of sight for several minutes, the booster dramatically returned to Earth with several sonic booms in a captivating show of engineering designed to make space travel less expensive and more sustainable.

Long-duration missions with limited solar exposure need a reliable power source to operate. This makes nuclear power sources (NPSs) an attractive alternative to solar energy for such missions. The implementation of the ESA Safety Policy on the Use of Nuclear Power Sources by the European Space Agency’s Independent Safety Office (ISO) provides a framework for ensuring the safe use of NPSs and sets a standard for future ESA missions. This article provides an overview of how the ISO is implementing the policy in the development and operation of the Argonaut mission, which serves as a valuable case study for understanding the practical application of the ESA safety policy and the importance of ensuring the safe use of NPSs in space.