Flight of the Dragonfly (Rocheworld) by Robert L. Forward (1984). A hard sf book about a one way expedition to Barnard’s Star, the second closest star system to Earth. A team of sixteen travels to the star by way of a light sail pushed by a terawatt laser originating from Mercury. The trip takes forty years and the crew’s aging is retarded during the journey by a drug. Even with the drug, the trip is one way. One of the planets around Barnard’s Star is a Roche world–a pair of co-rotating planets close enough to share atmosphere.
The crew arrives at Barnard’s Star and first explores the moons of the largest planet, a large gas giant. This is just a teaser, as most of the book describes the exploration of the Roche world. Intelligent aliens are found, and they are friendly and quite alien in form.
The book is a bit of a mismash, and it seems too short for all the elements crammed in. First, it’s a hard sf description of the engineering of a light sail trip to a nearby star. Second, it’s a hard sf look at the exploration and potential discoveries in the Barnard’s Star system, including the bizarre and wonderful Roche double planet with it’s unique physics and geography. The first two elements here feel rushed.
The most jarring part of the book is the set up in the beginning. The description of how the crew is chosen for a lifelong expedition, and why people would choose to go isn’t realistic. The crew choice seems unbelievably cavalier and the decisions of the crew aren’t really part of the book, just papered over with ‘adventure, wheee!’.
Finally, the book is an great tale of first contact and the dangerous adventure of exploring a new planet. This is the heart of the book and is well-told. This isn’t the best written book, but it has so many unique elements that it succeeds as great hard sf.