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> Except SpaceX’s failure rates are similar with every other successful launch system. Falcon 9 has the record for most consecutive successful orbital launches

by ggreer 4y ago

> Except SpaceX’s failure rates are similar with every other successful launch system. Falcon 9 has the record for most consecutive successful orbital launches. Their last failure was AMOS-6 in September of 2016. Since then they've had 189 successful launches in a row.[1] In that same time Soyuz has had 113 launches with 3 failures. Soyuz's longest success streak was 100 launches from 1983 to 1986.[2] The US's Delta II had 100 consecutive successes from 1997 to 2018, though it has since been retired. A total of 155 Delta IIs were launched with 2 failures. Falcon 9's current successful landing streak of 110 missions exceeds the competition's best launch streak. By any metric one can measure, SpaceX has the most reliable rocket. 1. See https://en.wikipedia.org/wiki/List_of_Falcon_9_and_Falcon_Heavy_launches_(2010%E2%80%932019) https://en.wikipedia.org/wiki/List_of_Falcon_9_and_Falcon_He... and https://en.wikipedia.org/wiki/List_of_Falcon_9_and_Falcon_Heavy_launches https://en.wikipedia.org/wiki/List_of_Falcon_9_and_Falcon_He... for the list of launches and outcomes. 2. https://arstechnica.com/science/2022/02/spacexs-falcon-9-rocket-has-set-a-record-for-most-consecutive-successes/ https://arstechnica.com/science/2022/02/spacexs-falcon-9-roc...

Retric 4y ago
You can always slice and dice data to make one side look better. The actual number of successes vs partial successes vs launch failures vs fatalities are the best data we have. Throwing away any of that data because it makes you look worse isn’t a good idea. Similarly we needs to understand that there’s a huge difference between risk and what actually happens. People get lucky in Vegas every day, what matters to most of us is the accuracy of the estimate of underlying odds not just the exact outcomes out to seven decimal places.
- JumpCrisscross 4y ago
  > actual number of successes vs partial successes vs launch failures vs fatalities are the best data we have Current vehicles are vastly different from the originals. What we’re trying to do is predict the probability of the next launch failing. Equally weighting far historicals and recents is bogus statistics.
  - Retric 4y ago
    > What we’re trying to do is predict the probability of the next launch failing. I thought we were comparing methods. Unless the next payload is yours then the odds of the next launch failing is meaningless to most of us, but we can learn something from the methods used. But sure, if you have a bet in Vegas or something then feel free try and calculate things as closely as possible. Just understand that several of Soyuz failures didn’t kill the crew so there’s other metrics people might care about.
    - JumpCrisscross 4y ago
      > we were comparing methods What does this mean? The question most of us care about is which method resulted in a more reliable rocket. And SpaceX’s track record shines uniquely in that respect. The frequency, moreover, makes the results robust. Legacy rockets like Ariane will never reach that confidence because the likelihood of fluke successes won’t have been minimised when the rocket is retired.
      - Retric 4y ago
        As to why their methodology is important this isn’t the Falcon 9 this is a new launch system which is likely going to have multiple failures before it’s own streak can begin. So sure, we can reasonably assume that Starship will get to a state of reliability similar to current Falcon rocket, eventually. We can’t assume the first few commercial Starship launches are going to even approach that level of reliability. And in fact the best point of comparison may be the early days of Falcon 9.
        nunuvit 4y ago
        Speaking of methodology, it's incorrect to relate a development test result to reliability or risk. Source is my personal experience doing reliability calculations for a NASA rocket component and working with the statisticians incorporate my numbers into their risk model.
- nunuvit 4y ago
  You have it mixed up. I've worked with the stats at NASA. Mission success and failure counts. Test quantity and quality count, test freedom counts, how they learn from test counts, but the test result does not count. This isn't a mission.
  - Retric 4y ago
    Where did I suggest this was a mission? This was a partially successful test nothing more and nothing less. I get people really really think SpaceX had done an excellent job and I don’t disagree but people who are comparing the end result of a long process Aka the current state of falcon 9 with a new system like Starship are going to be disappointed. Starship is extremely likely to fail repeatedly before achieving anything close to the same streak as the Falcon 9 has. That’s not an issue with SpaceX that’s an inherent aspect of doing something really difficult.
    - nunuvit 4y ago
      I don't think you realize this, but when you said that we can't exclude the test failure from the risk/reliability assessment, that's exactly what you're saying. I didn't realize until just now that you're actually defending the test failure as being acceptable.

by ggreer 4y ago

Retric 4y ago

You can always slice and dice data to make one side look better. The actual number of successes vs partial successes vs launch failures vs fatalities are the best data we have. Throwing away any of that data because it makes you look worse isn’t a good idea. Similarly we needs to understand that there’s a huge difference between risk and what actually happens. People get lucky in Vegas every day, what matters to most of us is the accuracy of the estimate of underlying odds not just the exact outcomes out to seven decimal places.

JumpCrisscross 4y ago
> actual number of successes vs partial successes vs launch failures vs fatalities are the best data we have Current vehicles are vastly different from the originals. What we’re trying to do is predict the probability of the next launch failing. Equally weighting far historicals and recents is bogus statistics.
- Retric 4y ago
  > What we’re trying to do is predict the probability of the next launch failing. I thought we were comparing methods. Unless the next payload is yours then the odds of the next launch failing is meaningless to most of us, but we can learn something from the methods used. But sure, if you have a bet in Vegas or something then feel free try and calculate things as closely as possible. Just understand that several of Soyuz failures didn’t kill the crew so there’s other metrics people might care about.
  - JumpCrisscross 4y ago
    > we were comparing methods What does this mean? The question most of us care about is which method resulted in a more reliable rocket. And SpaceX’s track record shines uniquely in that respect. The frequency, moreover, makes the results robust. Legacy rockets like Ariane will never reach that confidence because the likelihood of fluke successes won’t have been minimised when the rocket is retired.
    - Retric 4y ago
      As to why their methodology is important this isn’t the Falcon 9 this is a new launch system which is likely going to have multiple failures before it’s own streak can begin. So sure, we can reasonably assume that Starship will get to a state of reliability similar to current Falcon rocket, eventually. We can’t assume the first few commercial Starship launches are going to even approach that level of reliability. And in fact the best point of comparison may be the early days of Falcon 9.
      - nunuvit 4y ago
        Speaking of methodology, it's incorrect to relate a development test result to reliability or risk. Source is my personal experience doing reliability calculations for a NASA rocket component and working with the statisticians incorporate my numbers into their risk model.
nunuvit 4y ago
You have it mixed up. I've worked with the stats at NASA. Mission success and failure counts. Test quantity and quality count, test freedom counts, how they learn from test counts, but the test result does not count. This isn't a mission.
- Retric 4y ago
  Where did I suggest this was a mission? This was a partially successful test nothing more and nothing less. I get people really really think SpaceX had done an excellent job and I don’t disagree but people who are comparing the end result of a long process Aka the current state of falcon 9 with a new system like Starship are going to be disappointed. Starship is extremely likely to fail repeatedly before achieving anything close to the same streak as the Falcon 9 has. That’s not an issue with SpaceX that’s an inherent aspect of doing something really difficult.
  - nunuvit 4y ago
    I don't think you realize this, but when you said that we can't exclude the test failure from the risk/reliability assessment, that's exactly what you're saying. I didn't realize until just now that you're actually defending the test failure as being acceptable.