|This article relies on references to primary sources. (May 2010)|
|Author(s)||Robert L. Forward|
|Original title||The Flight of the Dragonfly|
|Publisher||Simon & Schuster|
|Followed by||Return to Rocheworld|
Rocheworld (first published in serial form in 1982; first book publication, under the title The Flight of the Dragonfly, 1984) is a science fiction novel by Robert Forward in which he uses a light sail propulsion system to set the crew on an interstellar mission. The spaceship and crew of 20 have to travel 5.9 light-years (ca. 34 trillion miles; ca. 56 trillion km) to the double planet that orbits Barnard's Star, which they call Rocheworld.
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.
Forward's Light-Sail Propulsion System 
The light-sail system consists of three functional parts: a powerful laser, a large focusing lens, and a giant space-sail. The idea behind the solar sail is that the laser provides a small force on the sail when the sail reflects the light. This small force provides the acceleration of the spaceship. With the ship's primary source of energy coming from the outside, it would not be limited to traveling distances that it had enough fuel for.
The light used in the system was an array of a thousand laser generators, which were focused through lenses and aimed at the sail. The lasers provided up to 1,500 terawatts of power. Two different lenses were used to magnify the laser beams. The acceleration lens was 100 km in diameter and was able to accelerate the ship at 0.01g; the deceleration lens was 300 km in diameter and was able to decelerate the ship at 0.1g. Although these accelerations are relatively small, over time they result in enormous speeds.
To catch the energy, Forward used a 1,000-km-diameter, circular aluminum sail. The sail resembled a flattened disk with a 300-km diameter removable center portion. When traveling to Rocheworld, the entire sail was used. When the ship needed to decelerate, the smaller sail was separated from the larger outer sail. The large sail was used as a reflecting lens, focusing light onto the smaller sail, slowing the craft.
Using the Light-Sail Propulsion system, the spaceship Prometheus continued to accelerate for 20 years, traveling 2 light years' distance toward Barnard's Star before going into coast mode and traveling an additional 20 years' time at a constant speed of .2 c, covering the remaining 4 light years (ca. 23 trillion miles; 38 trillion km).
Flouwen (the Middle English word for 'flow') are the alien creatures in the book. They are the sole inhabitants of the planet Eau, which makes up the watery half of Rocheworld. Flouwen are blob-like, happy-go-lucky aliens that spend their days surfing waves and working on difficult mathematical problems.
Flouwen appear to be giant, colored jellyfish in the ammonia oceans of Eau. Like Earthly jellyfish, they are amorphous, colored blobs of jelly. Flouwen are highly intelligent, sexless, and do not appear to physically age. They are able to communicate and see in the water by means of sonar. They are also able to see outside the water by morphing their jelly bodies into crude lenses, which they use to methodically track the stars. Flouwen are also capable of morphing themselves into a hard, rock-like substance when they feel the need to think about a difficult problem for an extended period. They do this by excreting much of their body water, thereby bringing their silica-gel-based cells closer together, which allows quicker processing of information.
Flouwen can grow quite large over time. This excess bulk can be shed during a peculiar breeding ritual where large Flouwen gather in a circle and spin off pieces of themselves to create a new Flouwen. Because they are created out of indistinguishable pieces of their parents, they are born fairly intelligent. One of the aliens, Warm@Amber@Resonance, is said to be over five hundred Eau seasons in age. Warm@Amber@Resonance refers to other Flouwen that are much older than it, such as Sour#Sapphire#Coo.
Flouwen possess mathematical abilities far exceeding our own. Despite their intellect, they lack any desire to make real use of it, other than to work on math problems or to study the stars; they just don't see the point in studying anything else. They do not have any concept of technology. They refer to the spaceship Dragonfly as a 'giant talking rock' or "Floating Rock".
Flouwen do not appear to have a strong social structure. They tend to treat one another equally, though mathematics proficiency appears to confer a heightened social status. Mathematics is one of the few subjects in which Flouwen show interest and concern. While younger Flouwen seem to have large amounts of free time, their elders spend long periods of time in rock form, contemplating and solving mathematical problems. As a result, the older Flouwen often hold higher social status as a result of their perceived higher knowledge in mathematics.
Although Flouwen do not seem to physically age, they reveal that it's possible that their ages are reflected in the amount of time they spend contemplating in rock form. Perhaps the actual population of the Flouwen is much larger than it appears, because there are many off working on problems. Some may never find solutions to their problems, so they will never return (thus completing their life cycle). (The Flouwens' time to solve a problem is limited because they will slowly weather away as time passes).
Rocheworld Shape 
Rocheworld itself is a double planet in which the two elements are close enough that they share an atmosphere. Each element is also deformed into an egg shape by the gravity of the other.
James (The Christmas Bush) 
Rocheworld's human explorers are aided by the Dragonfly's artificial intelligence system, James. The physical extension of James is the Christmas Bush. The Christmas Bush is both a modular robot and a bush robot which both communicates through and is powered by a network of laser transceivers on its body. The Christmas Bush is similar to some recursive fractal structures where the large scale shape of the robot is repeated a number of times in progressively smaller size. A main rod divides into six smaller jointed rods which also divide into six. This is repeated again and again so that the Christmas Bush can manipulate both large and small objects. The end of each rod is where the laser transceivers are located. The Christmas Bush nickname for the robot is due to that when all the rods are fully expanded the robot has a bushy texture, and is lit up like a Christmas tree.
Each rod and its children rods can separate from its parent rod and each carry a certain amount of computational power. The Bush or its pieces move by crawling while experiencing acceleration due to gravity or thrust, or by flying in low gravity environments. To fly, the smallest rods work together like the cilia of single celled organisms to provide thrust in any direction. The cilia also allow James to play audio and record sound through the bush.
The crew all wear a small piece of James (referred to as an imp) near their ear, which allows them to communicate with James and the other crew members. James will always keep some portion of the imp in contact with the crew's skin to allow it to monitor their health by recording their temperature, pulse, etc.
Publication History 
Rocheworld was first published in slightly shorter form as a serial in Analog Science Fact/Science Fiction magazine in December 1982 through February 1983. (Cover image with illustration by Rick Sternbach available here ). It won the Analog "Analytical Laboratory" award for Best Serial Novel or Novella in 1983. The first book version, slightly lengthened, came out under the title Flight of the Dragonfly from Timescape Books (a publishing line of Pocket Books/Simon and Schuster). A Baen Books paperback edition in 1985, also titled Flight of the Dragonfly was slightly lengthened. The British version was published by New English Library in their "SF Master Series" in 1985. A revised and lengthened version was released in 1990 from Baen Books under the original title Rocheworld, marked "At Last The Complete Story!".
Four sequels, written in collaboration with Forward's family members Julie Forward Fuller and Martha Dodson Forward, were published in 1993, 1994, and 1995.
See also 
- Barnard's star in fiction
- Roche lobe for an explanation of the underlying gravitational principle.
- Correspondence between Forward and Hans Moravec regarding the use of Moravec's bush robot in the novel.