Developed Fission Power Systems
Astronuclear fission power systems have flown more than any other system save radioisotope thermoelectric generators (RTGs), the true bread and butter of astronuclear engineering.
However, only a few systems have flown: two for the Soviet Union, one for the United States. This doesn’t mean that many systems haven’t undergone significant development, involving both thermal and nuclear testing, some of which were ready to fly – but unfortunately either mission requirements changed, political winds shifted, or in some cases the time is coming soon, but hasn’t happened yet.
This page covers both the systems that have flown, either on experimental or operational missions, or those that have undergone significant development. The definition of “significant development” is fuzzy, because of the vagarities of astronuclear development means that many of the most important tests of a system change based on the technological development of the materials, thermal behavior, nuclear behavior, or (often most especially) power conversion mechanisms of a system.
This page will be an intermittent work in process, adding more systems over time both as brief summaries here as well as individual pages for more notable reactors (or those that I cover in the blog as I continue my personal research).
Soviet/Russian Astronuclear Systems
The country with the undisputed crown of “most experienced astronuclear power” is the former Union of Soviet Socialist Republics. They have flown 35 nuclear reactors, all for fission power systems, in two core designs. A third, more advanced design was certified by flight not only by the Soviet Union, but Russia and the United States, but sadly never achieved flight.
Additionally, Russia continues to lead in high-power fission power systems, with their YaDEU reactor, useful as both an interplanetary stage and an orbital tug.
While the United States has ever flown one reactor (sadly the spacecraft failed due to a non-nuclear part), the US has developed many reactors to a degree that, even if flight capability was not achieved, the level of research and development offers many lessons in astronuclear design and development.
Additionally, one system is being prepared for use on the lunar surface as part of the Artemis Program, although it also has both orbiter and Martian applications as well/