What I’ve learned about airplanes (from disaster literature at least) is that the safest time to fly is at daylight with clear skies and good weather. Most accidents appear to be caused by or exacerbated by adverse weather and darkness. But I’d love to know the actual stats on this, since mechanical failure for example could happen at any time. What exactly is the breakdown between day/night, or sunny/adverse weather? How much safer is a daylight flight in clear skies to a nighttime flight in the sleet or a thunderstorm? And are certain routes more prone to problems dues to either their weird and wacky airports or perhaps the conditions on the flight path itself? I’m sure some FAA nerd knows the stats on that, so if anyone who reads this knows an FAA nerd, tell them to get in touch so I can ask them :).

The FAA nerds who keep our skies safe have a particular philosophy and process for ensuring continued safety and improvement. Whenever an adverse event happens, they open an investigation into not only the background and causes of the event, but in how all the systems leading to the event can be improved in the future. NASA I believe has a similar system, but I think NASA’s system is entirely in house, not under the jurisdiction of the FAA. So it raises the thought for me: who investigates or will investigate adverse events (crashes, loses) that happen in Space? If next year a Blue Origin flight blows up killing 10 people, who rights the rules and regs that make sure this never happens again? Obviously the market solution will be that Blue Origin takes such a hit to their reputation that only improved safety by themselves and other space-liners will entice customers back to space, but I don’t think we can rely on a market solution here, as customers probably don’t have the knowledge or capacity to accurately discern the actual quality of safety of a space-travel package, especially with such a low-probability event as a death in space. So does the FAA regulate these jokers, or someone else? I’d like to know.

I think some people don’t really understand the challenge of “skipping off” the atmosphere as was presented in Apollo 13. I’ve spoken to people who seemed to think that it was akin to skipping a stone off of water (understandable), where a space craft’s momentum is somehow redirected due to contact with the atmosphere. As I understand it however, skipping off
the atmosphere is a failure to slow down. On a return orbit from the moon (or Mars, or what have you), a spacecraft’s velocity relative to the earth is tremendous. Landing on the earth is basically akin to bringing your velocity relative to the earth to 0 m/s, and with a huge velocity, these spacecraft has a lot of speed they need to lose. If they come in too steeply, then they will lower their relative velocity in a way that is unsafe, either by burning up in the atmosphere or by lithobraking (crashing) into the ground below. If they
come in too shallow then they will simply not lose enough velocity to land. What does it mean to not lose enough velocity? Well a return orbit from the moon is basically a very long oval orbit. If the earth had no atmosphere, then it would take several days or weeks for a craft to complete an orbit along that oval. Because the earth has an atmosphere, the craft will slow down and the obit will shrink, but if the craft doesn’t slow down enough then it will simply continue to ride along that oval for the days or weeks that it takes to complete one full orbit, at which point it returns into earth’s atmosphere and gets another chance for the atmosphere to slow it down. This isn’t actually that bad except that spacecraft don’t have the provisions necessary for such a long trip, and so the astronauts would die of water/food/air deprivation by the time their craft had slowed sufficiently to fall to earth.

The craft could still make it back to earth in tact (if the parachutes could deploy), but the astronauts wouldn’t make it. That was the “skipping off” fear for Apollo 13, that the astronauts would slowly die aboard their craft while NASA could do nothing but watch helplessly.

What is the fuel efficiency of travel by plane vs travel by rocket? On the black-and-white TV show “you bet your life,” one of Groucho’s guests was supposedly an aerospace engineer engineering rockets as the future of long-distance transportation saying that “you could get to Australia in less than 4 hours.” This led Groucho to quip “so the Soviets are going to the moon and we’re going to Australia?” which was hilarious but did speak to the feeling at the time that America was losing the race despite post-1991 evidence showing that the USSR never had any sort of capacity to get a manned mission to the Moon. Anyway, over 50 years ago rockets were seen as a fast alternative to airplanes but they still aren’t used. Why is that? I guess the time saved (4 hour flight vs 24 hr?) isn’t enough to make up for the added cost, but I’d like to know how those added costs break down and in particular, how much of an added cost is fuel? In my playthroughs of Kerbal space program I’ve often marveled at the seeming efficiency of turbojet engines compared to liquid fuel rockets. Turbojets seem capable of getting incredibly high Delta-V on incredibly small amounts of propellant, and furthermore a plane seems capable of visiting any spot on the planet for a small fraction of the fuel cost of a rocket ship. But how true is this really? Certainly the ability to use oxidizer from the air instead of bringing it on board is a weight saver, but are the jet engines also so much more efficient in a Delta-V/weight calculation? Probably, or else rocket travel would have taken off by now.