Ok i had the same problem to, I made the connected the salvage cannnonsto my ship and they worked fine, i decided to change them closer to my core to make it more accurate, but when I came back I dident see any beams, while i was chainging my Salvage cannons i was next to a station, i decided to go their and try it out, it turns out they where invisable for me, but I was breaking blocks. Since its in alpha it might be a glitch,
Hope this answered your problem, their invisiable.