Anderson Poul We Have Fed Our Sea

In the scientific speculation that underlies the story, humanity has reached out to the stars in ships that move at half the speed of light. At that speed the ships will take years, decades, even centuries to reach their destinations. And yet the ships' crews serve month-long tours of duty, teleporting to and from their bases on Earth and other worlds instantaneously through what Anderson calls a mattercaster. At the end of Chapter 5 Anderson provides a description of how a mattercaster works.
The first ship that Humanity sent into interstellar space was the Southern Cross, sent on a four-and-a-half century voyage to Alpha Crucis. On autopilot she accelerated at over one hundred gees until she was flying away from Sol at half the speed of light. Then the autopilot shut down the ion drive, the ship went into free fall, and the first crew went into the mattercaster on Earth's moon to be teleported aboard the ship for their month-long tour of duty. Ten generations later, when she is one hundred light years from Sol, Southern Cross receives her last crew, though the four men who come through the mattercaster do not know that they are the last crew.

Terangi Maclaren, an astrophysicist of Polynesian ancestry, has convinced officials of the Protectorate, the dictatorship under which he lives, to take a great risk. Previous crews have made observations indicating that Southern Cross will pass close enough to a burnt-out star that she could be diverted, decelerate, and go into orbit around it in order that the crew can make further studies. The risk comes from the fact that if the crew cannot find a roughly asteroid-sized body to provide feedstock for the mattercaster, the Exploration Authority will not be able to teleport enough mercury to the ship to provide enough propellant for Southern Cross to resume her journey to Alpha Crucis. More playboy than scientist, Maclaren is assigned to the mission he had promoted.

David Ryerson is a graviticist/tachyonicist born and raised in Scotland's Outer Hebrides. He has just married an Indonesian woman, Tamara Suwito, and has brought her home to meet his father, Captain Magnus Ryerson. The couple are preparing to emigrate to a planet just opened for colonization, but Magnus demands that David first serve a tour on the Southern Cross. Reluctantly David agrees, if only for the extra pay.

Seiichi Nakamura lives on Sarai, an Earth-like moon of a gas-giant planet in the 40 Eridani system. He has been selected to serve as Southern Cross's pilot and captain on this particular tour. Old traumas haunt him and his Zen discipline cannot relieve him of his fear of the dark star.