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Despite its name, the ACM 113, as it was officially titled, was a formidable craft and remained one of Alpha Centauri's standard interceptors throughout the war. Its flight speed was unremarkable even by earlier standards and to our eyes this ship looks a most unlikely vessel, but what it lacked in straight line performance it more than made up for in manoeuvrability and strength.
It was seeing this ship perform in Alpha One's atmosphere that led our first representatives there to realize that their hosts had the technology to produce an antigravity device. Even to this day, having been assisted by the Alpha Centaurians themselves in developing a similar device, we have been unable to duplicate the performance of the Fatboy.

This bulbous craft has been constantly improved over a considerable period of time and it is not known when the first version was flown. Several vintages were employed during the war but all shared a similar appearance and were easily identified. Due to their restricted operational range they served only as defensive ships and as a result saw little action during the last few years of the war.

Two or three squadrons were shipped to Proxima for use as ground support craft but for some reason did not perform so well in the atmospheres of Proxima Centauri's home planets, and they sustained heavy losses before being withdrawn. Although obviously perfectly at home on their own worlds they appear to be highly sensitive to gravitational conditions and have not produced comparable performances elsewhere.

Without doubt the most heavily armoured ship of its size, the Fatboy could withstand the most extraordinary amount of punishment. Probably 40% of its mass was Plastisteel armour built up in layers, Between each layer was a unique system of cellular energy absorbent material which meant that the damage could be progressively contained with the minimum contribution to the inert mass. The Alpha Centaurians had never developed the technology for generating an energy absorbent field as we had, with the result that they were further advanced than we in the field of physical armour. When we exchanged our expertise in generated protective fields for their knowledge of gravity resist, they equipped Fatboy with a field system in addition to the Plastisteel armoured hull. The result was a ship that could survive most attacks and could only be destroyed through a sustained barrage of hits.
One of these dual protected ships appears in the foreground of the accompanying illustration and is distinguishable from the earlier models shown by two lozenge shaped generators on the upper surface of the hull.
Fatboy is still Alpha's main defence ship but the armour specification has been reduced. This, together with the installation of modern high output power plants, has contributed to an improvement in the speed of this distinctive craft.