I’ve worked with major US car crash testing facilities. I used to think that crash testing was just a video of the car crashing and an opportunity to walk arou

I’ve worked with major US car crash testing facilities. I used to think that crash testing was just a video of the car crashing and an opportunity to walk around the car afterwords to how the car did. Maybe it would pass, and maybe it would not. The reality is that before crash time, a team of guys spend three days wiring hundreds of accelerometers and other sensors onto the car’s structure at precise places. During the crash these sensors are recorded at high data rates, and 3D dataset of the moment by moment deformation of the car’s internal structure is reconstructed. This reconstruction is then compared against previous software crash simulations, and if needed the simulator is updated. Because the crash simulators are refined across hundreds of crashes, when a big manufacturer sends a car to be tested, they not only have a pretty good idea that it will pass, but to a fraction of an inch how much each piece of metal will bend. The real design work happens against the simulator, and reality just validates the simulator. Similarly, SpaceX has enormous amounts of sensors flying on each launch. This data lets SpaceX ensure that the simulator version of the rocket matches the behavior of the real one.