I'm reminded of Feynman's bit about the Challenger O-rings. They were not designed to be eroded, so the fact that they survived the erosion was indicative of a

I'm reminded of Feynman's bit about the Challenger O-rings. They were not designed to be eroded, so the fact that they survived the erosion was indicative of a design flaw, rather than a safety margin. Similarly, while the design may have redundancies built in, the thrusters are not designed to fail. Two of them failing on the *second launch* is not "redundancy". Each launch had 12 thrusters (if I understand correctly). Out of 24 thrusters launched into orbit, 2 have failed, or 8.3%. If I was heading to the ISS, I'd be taking a Dragon or Soyuz for sure.