First off, I want to say I'm not exactly a professional writer, so I acknowledge that what follows is probably rather poorly written anyway. Still, as a fan of hard science fiction, I would find it impossible not to complain a little bit. So here's what bugs me. The Outerra spacecraft was a giant ship built to travel between multiple stars in the near future and start several colonies, each of which failed, and then returns to earth and recolonizes it as well.
1.) One massive spaceship puts all eggs in one basket. Although, yes, there may be a marginal increase in efficiency as only one starship engine is required, there's a reason that Columbus had three ships (The Ninja, the Piña Colada, and the Santa Malaria).
2.) One massive spaceship going to multiple destinations is extremely inefficient. When you are traveling to the first star system on the route, you have to carry everything you are going to take to that system, plus everything you are going to take to every other system you plan on visiting! This might be excused if you plan to refill at each stop, but then you stay at each planet for decades! What's more, we know that that isn't the case- humans that visit earth on the return trip mention that they've remained in stasis the entire time. If they were loading and unloading people at each stop, they surely would have had need for a skilled doctor such as the one mentioned in the prologue.
3.) How can a colony fail? The ship carries enough supplies to start six or seven colonies! If they arrive at a planet they can't easily colonize, then they skip it, assuming they the mission planners were idiotic enough to plan a multi-system colonization attempt in the first place. If they settle a good planet and find that there's a bad harvest or something, then they just use some of the remaining supplies to cover the deficit. If a planet is good enough to try colonizing, it's good enough to try again.
4.) Perhaps the colony ship simply dropped a few million tons of supplies on a planet and left. While slightly sane- since the colony ship wouldn't even need to enter orbit or decelerate much depending on the destination star- but if that is the case, then EVERY ton of supplies would have been dumped on one of the destinations or the other; they wouldn't even be able to collect leftover supplies like tractors or pointless APCs or whatever.
5.) Good lord the reaction mass! I don't know what propulsion system your ships are using, but they need either fuel or reaction mass which gets consumed. You need enough fuel to accelerate the ship, then decelerate the ship, not once, not twice, but once for every single stop on the route! That is madness!
Now, the natural response to critique of a creative project is "Well, let's see you do better." Well, OK:
In the near future, following a chaotic few decades which featured some major political changes and, among other things, the development of functional fusion power generation, a newly unified humanity finally finds itself in the position to reach out to the solar system and the stars. While many commercial groups set about the colonization of the moon and mars, and the Jovian moons, the international space agency plans to send missions to the nearest star systems. These extra-solar missions will consist of three spacecraft using magnetoplasma drives to accelerate at several G to various nearby stars. Five such missions will be launched to likely nearby stars- Alpha Centauri b, Tau Ceti, 40 Eridani A, Delta Pavonis, and HR 7722.
The various missions travel for many decades. Besides the constant drone of the engines and the occasional footsteps of the operations crew down narrow maintenance corridors, all is silent. The Delta Pavonis crew arrives in system to a disappointing sight- despite all evidence to the contrary, the star system has no truly habitable planets. There is a plutonic body well outside of the system which has a great deal of ice- much-needed fuel.
Rather than risk the lives of the crew on traveling to some other system, the colonization mission leaders turn to the emergency plan- turning to broadcasts from earth, which should have updated star charts with good destinations. They set up the massive radio antenna- a huge wire mesh with an area of several kilometers which is stretched between the three vessels. They are confused, then shocked, to realize that they receive no communications from earth whatsoever. After months of waiting, they realize that earth simply isn't transmitting anything.
With few other options, they finish refueling and set out to return to earth.
Several decades later, Delta Pavonis Mission Vessel B and DPMV C arrive in orbit of earth- DPMV A suffered a faulty navigational thruster and was unable to rotate into deceleration position, instead ending up drifting out of the solar system after a failed attempted realignment. B and C look upon an earth that has been abandoned for centuries for unknown reasons.
