The reason why we have failures so often is because the technology and the physics are incredibly complex. When you’re launching a rocket, you need to make sure that the three ignition systems are working perfectly, that there isn’t a single screw out of the tens of thousands loose, that the weather could not possibly pose a problem. There is so much that could go wrong, and so much at stake (even if there aren’t people on board, launches are unbelievably expensive) that launches get cancelled quite frequently. However, there are so many variables that sometimes one gets missed, something goes wrong, and the launch fails
Part of the issue is that NASA is involved. Any time a government agency gets involved, the project costs 100x more and always has issues. Not saying the people doing the actual work are bad, but communication between outsourced parties is horrendous.
Now imagine SpaceX. All their fabrication and building is in house, meaning everyone involved can meet with everyone else involved. The only reason they talk to NASA is because… well I don’t know why they even keep talking to them. But you can’t go wrong with their rockets these days.
Rockets are extremely restricted by weight, much more than most other technologies. IIRC the Saturn V was something around 3000tons and only delivered a payload of a few single or double digit tons. If the rocket was 1% more heavy it would have basically lost all its cargo potential.
The result is that rockets operate on much lower safety margins than other means of transport. Everything is designed to be just barely strong enough for the expected loads and redundant systems aren’t always possible or particularly practical. A single sensor failure can lead to the loss of the entire vehicle. IIRC there was a proton rocket that just flipped upside down and exploded because a sensor was mounted the wrong way around.
Another aspect is that there is only limited ways to test your product in realistic scenarios. Rockets are crazy expensive and until recently they were entirely expendable devices. „Test flights“ aren’t really a thing when your vehicle has no way to land. The engineers must rely on in flight telemetry which makes it hard to spot faults unless you have a sensor specifically monitoring that part. There was an arianna rocket which exploded because its control software was partially copied from an earlier generation of the rocket. The newer rocket was faster and as a result a sensor ( I think it was an altimeter) exceeded its range of valid values during the early phases of the launch. This wasn’t an issue on the old slower rocket because the system was shut of before it ever flew that high. It never happened during tests because all tests were performed on the ground.
And lastly rocket failures are always spectacular because rockets are basically a giant fuel tank with some high tech strapped on the top and bottom. If it goes wrong it goes wrong with a big boom. In retrospect it’s often a small „silly“ thing, but every part is critical in the rocket.
Rockets are very complex and operate as close to the limit of their materials as we can. That means there are both more things that can break and they’re more likely to break since they’re under a lot of stress. That’s why we have so many launch aborts. If there’s a minor failure that mission control can’t work around, it’s better to scrub the mission and try again later. Otherwise, it risks a failure in flight which is often catastrophic. A rocket isn’t like an airplane that can fly with an engine out or an instrument failure.
When/if you watch programs showing factories producing things you rarely, if ever, see anything going wrong. In reality, there are problems ALL the time, and things are having to be corrected on a regular basis.
Stands to reason things will go wrong with rockets aswell. Only difference is, instead of a small pile of food on the floor, you get an impressive big bang.
For uncrewed launchers, you wouldn’t want extremely high reliability. Extremely high reliability means making things more robust and heavier. It means adding redundant systems that weigh a lot. Weight that you add to the launcher is weight you have to remove from the payload.
I’ve no idea how the economics pay out for any specific launcher, but if they just plain never fail you’ve built them too strong.
Obvs all this goes out the window for crewed launchers.
Global / planetary entropy means there are always variables independent to the launch parameters, which cannot all fully and explicitly be accounted for ahead of launch.
Because there is so much data available at the time of launch and we only know where to apply human focus when a problem arises.
One of the reason humans consider hindsight 20:20; you only get the complete data set when you are observant
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