The nuclear powered reconnaissance drone was a piece of technology created by the Russians during their Stargate Program.
The Russians managed to have built several of them, for the purpose of leaving them on planets for long term observation. They can remain operational for as long as ten years. When one such drone went to the Water planet, the Water-based life form was able to use the drone placed on the planet to hold the Stargate open, while the beings themselves provided the necessary power needed to maintain an active wormhole for longer than 38 minutes. This stopped the Beta Gate, currently being used by Stargate Command, from being used, as you cannot activate a Stargate on a planet where there is already an active Stargate. Fortunately, SG-1, assisted by Dr. Svetlana Markov, were able to shut down the drone. (SG1: "Watergate")