WhipGhostrider's comments

I have recently worked on software testing for a roughly analagous project to Starliner. The answer is thorough simulations and ground testing. Flight code should have essentially 100% coverage in unit tests as well.

You can do a pretty decent simulation of a space mission on a powerful cluster. You then plug in your simulated spacecraft and run the real flight software. Reentry is easily the most critical phase of flight for a crewed spacecraft, and they should have absolutely tested and caught this flaw in simulation. Ground testing could have also checked on the actual spacecraft that the correct valves were actuated when commanded to.

If I were to speculate, this suggests a pretty large disconnect between the software and hardware engineering teams. The software team should have been able to identify that the wrong valves were being actuated.

I've used it near daily for 2 years to learn Spanish. Can confirm it actually helps, but only if you put in additional effort beyond the bare minimum the app requires. The app suggests that you speak out loud every sentence it presents you, and I usually do that, sometimes multiple times. I listen to them spoken by the app with my eyes closed to train my ear. I try to visualize the meanings behind words and sentences rather than just translating mentally to English. And I then seek out opportunities to practice Spanish in real life. I have the opportunity to travel to Latin America a few times a year, and I always go out of my way to use Spanish as much as possible there.

I had no Spanish background before Duolingo, or any spoken language other than English. I took Latin in HS, which helps somewhat with vocab and reading but not at all with speaking and listening. With solely Duolingo plus the additional practices I mention, I've gotten to the level where I can survive in a Spanish speaking country. I can't speak or listen well, my grammar isn't good, but I know enough to ask for what I want and understand basic information being told to me. I can also read enough to understand at least the key information from most written sources. I think I'll definitely need a more dedicated class and/or a longer full immersion experience to get towards my goal of being conversationally fluent, but Duolingo has been a great starting point.