Yet even with cars, even with the fact that they have experienced designers, when you build a new car model and put it out, you don't always get it right. You don't know what you did wrong. Which is why we regularly see safety recalls issued on cars - even from the best companies - for everything from software updates to changing the floor mat.
Until you see a model in use in the real world you simply don't know. Even if you have experience on a related model, there is the possibility of something new going wrong. Something you would have never thought of. Like the gas pedal getting stuck on a floor mat.
You take into account everything you know about. You run every feasible test that you think is useful. You run tests in simulators, on isolated components, on the whole model. You review and double review your work. You set up safety checklists to verify everything on the spot. But until you actually see the accident data, you don't really know whether you missed something important.
This is true for cars. It is true for airplanes. It is true for rockets. But the critical differences are that rockets are inherently more dangerous, it isn't feasible to do the same number of tests on them, and we don't get nearly as much accident data.
You have to options:
Option 1: Ride in a car with a single button labeled "press to start engines, you will not be able to stop until they run out of fuel". This car has been driven about a hundred times.
Option 2: Ride in a car with a "start engine" button and a "stop engine" button, plus a throttle. This car has been driven several times plus extensive testing on the ground.
"Option 2 is a safer setup" seems like a fair statement.
Given that the shuttle's SRBs were "once they start, they don't stop until they're empty", sometimes more complicated is a good thing.
> Until you have actual experience with the weird stuff that goes wrong in the field, you do not really know what is going to go wrong. And the more complicated the system is, the more true this fact is.
I'm fairly certain SpaceX has been employing people with actual experience.
> Incidentally I had the opportunity at one point to ask the first software developer ever hired at SpaceX whether he would trust his own software. His answer was enlightening, I wouldn't want to put my life in the hands of someone who trusted his own software, so I'm going to say no.
That's why they probably have more than one developer plus QA team.
> There is always SOMETHING that can go wrong. You want the person who created your safety system to be a paranoid freak. And you have to pray that they didn't miss something. You hope and pray for the best, but until you have actual data, you don't know how it is going to turn out.
True, certainly, but the same argument can be used on cars. Things still go wrong, but we can also safely say they're safer than a car from the 1970s.