Quote from: AS-503 on 05/11/2018 01:40 pmQuote from: Jim on 05/11/2018 01:13 pm40% margin is not a requirementJim, I thought 1.4 structure margins were a requirement for manned rating.You are showing requirements for pressurized vessels and not structures.
Quote from: Jim on 05/11/2018 01:13 pm40% margin is not a requirementJim, I thought 1.4 structure margins were a requirement for manned rating.
40% margin is not a requirement
F9 can take a single engine out at any time in the mission and still complete the mission.
Quote from: lonestriker on 05/11/2018 05:52 amF9 can take a single engine out at any time in the mission and still complete the mission. No, it can't. It flies 60-70% of the flight on one engine
Depends on what is defined as Mission....I guess Elon's remark is relevant for the payload's mission... Not so much the booster's mission of returning in one piece...
There are about 1400 seconds of engine run time covered by engine out capability, 600 seconds or less not covered. So 60-70% is in error. Also compare to competitors who offer exactly zero seconds of engine out coverage.Matthew
Quote from: matthewkantar on 05/11/2018 03:39 pmThere are about 1400 seconds of engine run time covered by engine out capability, 600 seconds or less not covered. So 60-70% is in error. Also compare to competitors who offer exactly zero seconds of engine out coverage.MatthewMultiplying the first stage firing time by the number of engines is completely irrelevant.
Quote from: matthewkantar on 05/11/2018 03:39 pmThere are about 1400 seconds of engine run time covered by engine out capability, 600 seconds or less not covered. So 60-70% is in error. Also compare to competitors who offer exactly zero seconds of engine out coverage.Matthewwrong, total engine run time is meaningless, especially in light of quotes like this:Quote from: lonestriker on 05/11/2018 05:52 amF9 can take a single engine out at any time in the mission and still complete the mission.
This is arguably Falcon 9 version 6, in sort of normal vernacular. Because we had version one, version 1.1 which was really like version 2, arguably a version in between that, and then a bunch of blocks. So we should probably just go back, I'm sure the internet's already done this, and have a more sensible description of the versioning. But think of it as like, at least version 6 of the rocket.
Quote from: gongora on 05/11/2018 12:49 amActive water cooling of the base heat shield during reentry?!Yeah that was perhaps the biggest surprise. But cool!
Active water cooling of the base heat shield during reentry?!
But the reason I picked the heat shield, it's also a big improvement. And we replaced the old composite structure with a high- temperature titanium structure to support rapid reuse. The base heat shield will also somewhat actively cooled with water. So we're finding things some things are really just, during the very high-energy phases of re-entry, ascent does not require them, but during the high-energy phases of re-entry, where you have a hypersonic shock-shock impingement, it generates a very hot spot, and you kind of have to use a high-melting point material, a high-temperature material, plus active water cooling in certain places on the base of the heat shield.
The 40% number sounds like a pretty clear reference to structural margin. I’m guessing that on previous versions of F9 the majority of the structure was designed to something like 1.25 ultimate FoS. And now for human rating they are designing to 1.4 ultimate FoS. Of course, this would not necessarily apply to all types of structure, because different types of structure/components have different margin requirements.As for any kind of fault tolerance / reliability requirements (which engine-out would fall under) that would be completely different from a 40% structural margin.
Quote from: Jim on 05/11/2018 03:57 pmQuote from: matthewkantar on 05/11/2018 03:39 pmThere are about 1400 seconds of engine run time covered by engine out capability, 600 seconds or less not covered. So 60-70% is in error. Also compare to competitors who offer exactly zero seconds of engine out coverage.Matthewwrong, total engine run time is meaningless, especially in light of quotes like this:Quote from: lonestriker on 05/11/2018 05:52 amF9 can take a single engine out at any time in the mission and still complete the mission. Wrong
edit: Although I wonder what Musk meant by "somewhat actively cooled". What qualifies as semi-active water cooling? Perhaps the water reservoir is in contact with the heat shield, and it just boils away through a vent without circulating.
Although I wonder what Musk meant by "somewhat actively cooled". What qualifies as semi-active water cooling? Perhaps the water reservoir is in contact with the heat shield, and it just boils away through a vent without circulating.