mikegarrison

Yeah, but mistakes get made. You can't build something as complicated as an airplane or a spacecraft and expect everything to always be perfect every time. The important thing is to always fix them using approved repairs. Concealing defective workmanship is an automatic firing offense where I work, and I assume it would be at any aerospace manufacturer. Deadline or no deadline.

I can't pretend I don't know what you mean by "a deadline patch", but that's exactly the kind of thing we try very hard to convince people to never, ever do. No matter what.

This slightly high. The worldwide number of scheduled flights per day in May 2018 was 89,638 (based on some analysis I did recently). Still, the point remains -- a fatal accident every 1000 flights would mean there were almost 90 fatal air crashes EVERY DAY. Long-haul airplanes are designed for 30-40 thousand flights. Shorthaul airplanes for even more than that.

Dunno. Obviously it's not a normal situation. Generally speaking, ICAO rules govern all air travel between states or that crosses over the airspace of any state (like say a flight from New York to Anchorage that crosses over Canada). ICAO has no jurisdiction on flights that are purely inside one state. (They also have no jurisdiction over military or state aviation -- International CIVIL Aviation Organization.)

I'm sure there are approved repair procedures.

Continuing on with that, type certification is usually done in what is called the State Of Design. That is to say, the FAA certifies Boeing or Gulfstream airplanes, EASA certifies Airbus airplanes, etc. And then agencies have bi-lateral agreements to accept each other's certifications (possibly with reservations in certain areas). Ultimately to fly in the US an airplane needs to be certified by the FAA or to fly in China it needs to be certified by the CAAC. But generally these agencies accept the original certification that was done in the state of design. Some countries completely delegate the role of certification and simply accept an FAA or EASA certification as-is without having a national agency of their own. International aviation also has to follow the rules set up by ICAO. These ultimately derive from what is called The Chicago Convention and dates back to just after WW2. ICAO doesn't so much certify airplanes as they certify the states to certify airplanes.

OK, drilling out damaged fasteners is a legit reason to need a high speed drill in the ISS.

Diesel producing soot is not really a property of the fuel so much as how a diesel cycle engine works. However, it is known that in gas turbine engines the aromatic content of the fuel is correlated with the amount of particles in the exhaust -- apparently those carbon rings just can't break down quite fast enough to get complete combustion like the chain molecules can.

Reminds me of one weekend at the racetrack where some people left their truck idling the entire weekend. I asked why, and it turned out they had converted it to run entirely on used cooking oil. They got it for free from a restaurant. But it would freeze up in the fuel system if it got cold, and the ambient temps were well below freezing (of water). So they had to keep the engine running 24/7 to make sure their free fuel didn't freeze up. (The part of me that is an emissions engineer cringed at running an engine at idle 24/7, but I didn't give them a lecture about it.)

It's obviously really embarrassing if a spacecraft passed all inspections with a hole drilled through it. I can see why there is some appeal to the idea that just maybe it was done by someone on the crew. It was clearly done from the inside. Do they even have drills up there? I assume they have power screwdrivers and such, but that was made by a high speed drill.

One reason diesel fuel is relatively cheap is because it's a fairly wide cut fuel. Diesel motors are not as picky about what they burn as gasoline motors -- this is why you can run a diesel engine on 100% peanut oil or sunflower oil if you want to. (Not saying the rest of the fuel system would like that, though.) Some gas turbines are designed to be pretty tolerant too. They can run on almost any liquid hydrocarbon. But for aerospace applications they are usually designed with tighter tolerances for the fuel spec.

It's pretty hard to hide something like that when it was later investigated as thoroughly as this incident was.

Maybe that toothache you have will just go away if you skip the dentist and pretend it isn't there.

I suppose if some crew member desperately wanted to go home, a slow hidden leak could be a way to force them to abandon the mission. But drilling it into one of the spaceships that the crew would abandon in is problematical for that scenario.

[snip] A) English is obviously not his first language. Cut him some slack. B) They didn't "know" for sure there was damage. But they did know for sure that there had been an impact, and they suspected damage. But they decided that since they couldn't do anything about it in any case, there was no point to telling the astronauts.

What would be worse than going months without pizza? Going months without pizza and then being offered some of that stuff Pizza Hut claims is pizza.

Did you ever see the mythbusters episode where they made a rocket powered by pepperoni?

Hydrogen is a very non-optimal fuel for airplanes. It has terrible energy per volume characteristics. If you look at all the reasonably common fuels on a map of energy density by weight v. energy density by volume, you see why kerosene is so popular. You want to be high on both axes. The only conventional fuels higher than kerosene on both axes are gasoline and diesel. But diesel tends to freeze up and gasoline is too dangerously volatile.

If you (and SpaceX) are going play in this realm, you need to start thinking about cycles. One flight = one cycle. It's not going to be significantly different no matter how far you fly (Mars versus Hong Kong). Long distance airplanes are good for something like 30,000-40,000 cycles. That's how many trips the capital cost is amortized over. The most ambitious numbers I've seen for BFR is 1000 cycles. So the airplane gets 30-40 times as many trips to pay for itself.

No no no. Each passenger (plus luggage) on a plane today is on average over 100kg. That does not count for any cabin furnishings. And 1500 per flight? Airlines seriously struggle to fill A380s with 500 people. More than half of those 500 are flying economy and their ticket price is maybe $2000 for anywhere in the world.

Let's put is another way. SpaceX themselves said the cost of a launch will be $7M. Let's say it held 350 people (like a 777). That's $20,000/passenger.

You are comparing the cost per volume of a gas and a liquid? What's the cost per pound?

No it's not. That's just ridiculous. A full fuel load on an A380 is 570,000 lb. A Falcon F9 first stage has 270,000 lb of kerosene. Are you saying that BFR is going to have no more than twice as much fuel as an F9? Sure, I know it's liquid methane rather than kerosene, but still.

We already talked about this. Here's why it won't work: Way too expensive. Musk keeps going on about how gloriously cheep it will be if it's fully reusable, but guess what is already fully reusable? Airplanes. He would have to get the per trip costs down to something close to what current airplane tickets cost. People will pay for speed, which is they take airplanes and not boats, but they won't pay all that much for speed, which is why there are no supersonic airliners anymore.

Musk running into trouble again. This time it was smoking a joint on a TV show, which seems to have led to a couple of his top Tesla executives quitting.