Salvo

A salvo is a collection of spaceships (usually gliders) that are all coming from the same direction. A salvo is generally aimed at a target to produce a specific reaction -- for example, in a sliding-block memory or a slide gun, a salvo might move a block or other still life a step closer to the salvo source, or a step farther away. Or two or more salvos may collide with each other to construct a complex object.

A slow salvo is a salvo in which the spaceships are far enough apart that any collision reaction affecting the n^th spaceship has settled down by the time the (n+1)^st spaceship arrives.

A P1 slow salvo is a slow salvo in which the intermediate settled-down stages are all period 1 (i.e., stable.) It is conjectured that any glider-constructible object can be produced by a P1 slow salvo aimed at a single block or other small still life -- though the number of gliders needed may be very large.

Conversely, a P2 slow salvo may have intermediate stages containing P2 oscillators, allowing constructions with significantly fewer gliders on average. P3 and higher slow salvos are technically possible, but higher periods do not appear to make much difference to construction efficiency in Life, where higher-period oscillators only appears rarely.

A monochromatic slow salvo is a slow salvo which contains only gliders of a single color. For example, half-baked knightships reconstruct their glider seed constellations using monochromatic slow salvos.

Similarly, a monoparity slow salvo is a slow salvo which contains only gliders of the same shape -- i.e., even or odd parity). The intermediate targets for this type of slow salvo can be P1 or P2, but P2 targets have two completely separate and non-interchangeable phases. A phase-0 blinker is a different target than a phase-1 blinker, for example, and the two targets would require completely different construction recipes. Even-step variants of the engineless Caterpillar use slow salvos that are both monochromatic and monoparity.