The p42 glider shuttle is a period 42 shuttle oscillator discovered by Noam Elkies in 1994. It was the first non-trivial period 42 oscillator to be discovered and is based on a period 66 oscillator discovered by Robert Wainwright in September 1984. It works by using two copies of eater 3 and four copies of unix to shuttle two gliders back and forth. By increasing the distance between the two reflectors, oscillators of periods 42 + 24n can be created. Dean Hickerson found that the distance between the reflectors could be decreased using a custom period 6 oscillator to create a period 18 glider shuttle. In April 1992 Hickerson created another related oscillator by crossing two pairs of gliders using rephasers, which allowed the construction of oscillators of periods 246 + 24n.
A p18 glider shuttle using a custom period 6 oscillator by Dean HickersonRLE: here
A related p246 oscillator discovered by Dean HickersonRLE: here