I think calling it a 50% success rate is disingenuous. The "failure" they had was because the satellite wasn't the primary mission, it was piggy-backing on the

I think calling it a 50% success rate is disingenuous. The "failure" they had was because the satellite wasn't the primary mission, it was piggy-backing on the primary mission. It didn't make its orbit because after a recoverable mishap NASA didn't want to take any chances with the orbit of the ISS. That's not a failure of the rocket. It's just the operator of the primary mission calling the shots, and the secondary mission suffering as a result of that. That's the sort of risk you assume when you piggy-back on the primary payload when launching on any rocket.