The following p4c/2spaceship with a minimum population of 36 cells, which is the smallest known p4 c/2 spaceship. In terms of minimum population, it is tied with the dust mite ship as the smallest known spaceship that travels slower than c, although the dust mite ship has a smaller bounding box. Discovered by glider_rider.

x = 10, y = 24, rule = s0/b2
3bo$8bo$7bo$5bo$7bo$3bobo$8bo$5bo2bo$2bo5bo$bo4bobo$o5b2o$5bo$5bo$6bob
o$bo5bobo$9bo$6bo2bo$9bo$4bobo$8bo$6bo$8bo$9bo$4bo!

x = 10, y = 24, rule = s0/b2

3bo$8bo$7bo$5bo$7bo$3bobo$8bo$5bo2bo$2bo5bo$bo4bobo$o5b2o$5bo$5bo$6bob

o$bo5bobo$9bo$6bo2bo$9bo$4bobo$8bo$6bo$8bo$9bo$4bo!