The search for Invader ships took the Personalia to many stars in and around the local stellar cloud. Visiting each of these stars was a chore in itself, despite the use of the Personalia's FTL (Faster Than Light) subspace drive. The stars themselves were not the target; but the planets, asteroids and other bodies circling these stars were the main interest, for several distinct reasons.
The first, and most apposite reason was the Invaders' "reason d'etre", their elected justification for existence, dealing death. Called by others "The Invaders", this machine race were the terror of this part of the galaxy. They were fixated on destroying biological life wherever it may be found. This obsession came from being rejected by their creators as a race of their own. In retaliation, they destroyed their biological creators, and then set out to destroy every other biological entity. Weirdly, they had assumed, by their own strange logic, that these might in future become the same as their creators. This scattergun approach inevitably encompassed all biological life that they could detect from space. It seems they never envisaged bacteria existing inside rocks and underground caverns, or at the bottom of deep oceans.
The runaway Personalia found a refuge in the solar system's outer reaches. They noted what was happening on Earth, but recognised that the humans were not developed sufficiently to meet with them. Instead, they left their own messenger parking in one of the oceans, to act as contact with the humans at the right time, which was 300 years later.
After peacefully encountering the human race, the Personalia tooled up with missiles supplied by Earth, and changed from running away from the Invaders, to hunting them down, and destroying them. They became very good at it, such that within a few years what was left was the need to search, star system by star system, for surviving groups of Invader ships.
This was the scenario that led them to adopt a regular search pattern recommended by a human Special Forces Colonel. The concept involved two Landerships acting as scouts for each star to be checked out. The first Landership would cautiously enter the sphere of planets, looking for signs of Invader ships, while the other one waited beyond the outermost planet. This second one was the backup; prepared to run and get assistance if the first ran into trouble. The subspace drive was so efficient that support ships could be present within less than an hour.
Star after star was checked in turn. A few of these visits found Invader ships present, but most did not. Planets with no pre-existing life forms had no attraction for the Invaders, and life was anyway mostly found in the Goldilocks Zone – the distance from a star where water could be found in its liquid state on a planet. Liquid water was a prerequisite for almost all biological life.
To the Personalia, every star had perhaps planets, asteroids, and comets, or had none of these. Landing on planets was of little interest to the Personalia due to the strength of their gravity, whereas asteroids offered plenty in the way of resources, and few problems with gravitational pull. To them, asteroids were by far the most important asset to be found in a star's presence. The other factor was that asteroids offered easy access to minerals and solid water in the form of ice. Water could be split into hydrogen and oxygen with electricity from each spaceship's nuclear reactor, turning it into fuel and oxidant. This built up supplies for use as required. A Base ship could store these for the use of Landerships. Landerships used the fuel supply for take-off to orbit from a planet's surface.
The elements found within the asteroids' bulk were useful in another way: they were the feedstock for building more Landerships and Base ships. Construction by nanomachines was a complicated process, but simple in concept. The organising Base ship held the template, the full ship design, in its memory, and used that to direct the nanomachines. These nanos collected from the supply feeder mechanism the elements indicated, delivered these particles to the correct point in the construction, and "welded" the atoms into position. The is process depended on the power requirements for each pair or group of elements to become a composite, a molecule, which may then be linked to another molecule to make a stronger bond. One might imagine this as a slow process, but under the control of a machine mind, it happened at lightning speed, as long as the correct element was available at the right spot, to be collected and inserted into its slot in the design, and with the appropriate power input. The power was supplied by the ships' internal nuclear engines; engines that were far more efficient than any built on Earth, and requiring less shielding.
Another reason for the speed of construction was the ability of a Base ship to control many nanos at the same time. While one nano was working on one molecule-thin layer, at one spot, another nano was working a short distance further long the layer, and as each layer was being progressively laid down, other nanos were starting on the layer above. It looked like a shotgun approach, but it was a highly organised shotgun, with special nanos interspersed to turn certain elements into alloys, ceramics and glass, because most materials exhibit better properties when not made of one pure element.
With all these processes happening together, construction was a swift process. Even so, it took months to build an entire spaceship – a similar length of time to an equivalent construction produced on Earth. The difference was that the Personalia ship was one unit, not a collection of welds, rivets and other linkages. It was in practice one unitary object with no weak points arising from construction requirements, or design faults. All were identical in construction.
Each of the Personalia possessed a comprehensive suite of detection instruments, and these were put to good use every time one of the ships entered the planetary system of another star. The ship would perform a series of subspace "jumps" within the system, taking it near to each planet and any asteroid belt. At each point, it would halt its stuttering progress for a while, ignoring its ongoing momentum while it scanned the vicinity for any coherent signals. Once a lack of signals was confirmed, it would switch to the next target to be jumped towards, and instigate the process.
To a biological being, it would be a boring routine, with all these negative results; but to a machine mind, boredom was not something that would be experienced. Every new star system was a unique experience, and worthy of full attention.
This one was different. As the Landership arrived in the outskirts of the planetary nebula, it quickly realised that there was a cloud of asteroids immediately in front, and it swerved to avoid them. Once it had plotted a safer course through this cloud of rocks, it looked around, examining the area at a number of wavelengths. The infrared band revealed an oddity: a track faintly warmer than the surrounding frozen asteroids. This track led to an asteroid that showed evidence of a recent collision, a glancing blow. The track shot off at a shallow angle, and as the Landership followed it up, the track stopped completely, at a point where the infrared indicated another collision; but there was no asteroid in evidence. At least, not at the position.
The Landership came to the conclusion that an Invader ship had shot into the system, and the track was the evidence of its hot exhaust as it tried to slow down from its interstellar flight. Despite travelling at less than light speed, it had failed to plot every asteroid in its path, had struck one a glancing blow and its course had been deflected to an unfortunate end – impacting fully with another asteroid. Such a collision was fatal for the Invader ship, and the energy thrown into the collision had been transferred to the asteroid involved in this transaction.
The Impacted asteroid, with the extra momentum imparted to it, had been pushed inwards towards the central star. Its position was unclear, as the timescale of the collision event was unknown. All that could be derived from the infrared readings was that the time was not very long since that event. Weeks, months perhaps, but not much more, or the heat energy would have completely dissipated. As it was, it was very faint indeed.
Dismissing the event as no longer of interest, the Landership went on with scanning the asteroids, to establish a rough approximation of the content of these bodies. The results indicated a higher proportion of metallic ores than was to be expected from past experience. It was gratified at this, and did some further examination of more of these bodies at a greater distance from its previous position. The proportions remained roughly the same, so the deduction seemed to be holding up.
Then it recalled that according to past experience, Invader ships always arrived in groups, not alone. It rapidly expanded its search range, and began to spot other trails through the asteroids. This series of trails gave the Landership an approximation of the numbers of the enemy that had entered this star system. They might still be there, somewhere.
Before moving deeper into this system, the Landership decided it should report all its findings; and jumped back out to the location where its partner was waiting. It transferred all the data from its examination, and then jumped back onto the system again; this time further in, half expecting to find Invader ships there.
.... There is more of this story ...