Rocheworld
Robert Forward
 In Rocheworld, a small group of civilian and military personnel crew humanity's first manned exploration of another star system. Using a laser-pumped light sail spacecraft, the journey to their destination of Barnard's star lasted 40 years. The crew used a drug called "No-Die" which slowed their aging process, whilst proportionately lowering their effective I.Q., and arrived only a decade physically older than when they left. A fraction of the crew visit the double planet Rocheworld, landing on the water-free lobe, dubbed Roche (French for rock as well as the name of the French mathematician who worked on Roche limits). After exploring Roche, they again split up, and one group journeys via the space-plane Dragonfly to the other lobe, Eau (French for water), which is covered almost entirely by ocean. The crew are caught in a violent storm that causes their plane to experience a crash water-landing. The flooded propulsion systems of the space-plane are unable to provide enough thrust to break free and take off from the ocean surface. The crew decide to use the plane's lift fans as propellers to make their way to the inner pole of the double planet, where the gravitation from the other lobe of the double planet should help them to break free and allow rendezvous with the remaining crew in the lander at the zero point between the two lobes. While making this journey, the space-plane attracts the attention of one of the native species of the planet: the very intelligent, but technologically lacking, Flouwen. The Flouwen and the artificial intelligence aboard the space-plane establish communications and the two species begin to exchange cultural and scientific knowledge. The Flouwen realize the humans are travelling to the pole and warn the humans that they are approaching a period where the configuration of the star and planets of the system allow for a phenomenon where the ocean on the water lobe of Rocheworld can partially flow to the rocky lobe, due to the change in the gravitational equipotential. They try to stop the humans from continuing into this violent event by pinning the spacecraft to the ammonia-water ocean floor with ice as ballast (water ice sinks in the less dense ammonia-water solution of the ocean). However, the humans realize that the interplanetary waterfall poses a threat to the crew remaining on Roche. Fortunately, the tidal stresses cause nearby dormant volcanoes to become active again. This melts an underwater glacier and floods the area with warm water, upon which the ice floats off the plane. The crew manages to get airborne and takes advantage of the changing equipotential to return to Roche. They rendezvous with the lander just as water is reaching it.