Construction an object by a "slow salvo" of
gliders all coming from the same direction, in such a way that
timing of the gliders does not matter as long as they are not too
close behind one another. This type of construction requires an
initial seed object, such as a block, which is modified by each
glider in turn until the desired object is produced.
In May 1997, Nick Gotts produced a slow glider construction of a
block-laying switch engine from a block, using a slow salvo of 53
gliders. Constructions like this are important in the study of
sparse Life, as they will occur naturally as gliders created in the
first few generations collide with blonks and other debris.
Slow glider constructions are also useful in some designs for
universal constructors. However, in this case the above definition
is usually too restrictive, and it is desirable to allow
constructions in which some gliders in the salvo are required to have
a particular timing modulo 2 (a "p2 slow salvo"). This gives much
greater flexibility, as blinkers can now be freely used in the
intermediate construction steps. The Snarkmaker is a very large p2
slow salvo. A much smaller example is the following edgy
construction of an eater1 starting from a block.
Adam P. Goucher's slmake search program, made available in May
2017, makes it much easier to find a slow glider construction for a
wide variety of stable circuitry.