h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

I finished reading a fantastic book the other day. ‘The Depths of Time’ by Roger MacBride Allen. A great science fiction novel.

Man has spread out across the galaxy, settling on terraformed worlds. Faster than light travel isn’t possible, but they have gotten around it by using timeshafts. Timeshafts are ingenious. As an example; a ship will travel 50 years ‘uptime’ with its crew in cold sleep. The captain is then woken to pilot the ship through a timeshaft, which takes them back in time (downtime)100 years. The ship then travels a further 50 years ‘uptime’ and arrives at its destination only a few days or weeks after it left.

The chronologic patrol guards these timeshafts, so they cannot be misused. Their main mission is not to let anything from the future go back and contaminate the past time line.
Things get tricky when some intruders come uptime through the timeshaft, killing the crew of the CP ship at one end. They then try to go back, so the commander of the other CP ship is forced to permanently close the timeshaft, stranding his crew almost 80 years into the future. The commander’s name, though he did everything right, becomes cursed because he closed the shaft. This is only the beginning, of a much longer and more intriguing story.