5 ms·

The Soyuz-FG which has been used since 2001 has had a 100% success rate till today. Seems pretty good to me.

by nhoss2 8y ago

Tossrock 8y ago
I agree that the Soyuz has been very reliable historically, but two major incidents involving it within a few weeks has the appearance of a trend.
- zaarn 8y ago
  Soyuz is literally the most reliable launch vehicle and two datapoints are not a trend. Any two datapoints form a line, ie a trend.
  - Tossrock 8y ago
    "Once is happenstance, twice is coincidence, three times is enemy action." Maybe it's a coincidence, maybe it's not. I think it's very reasonable to want alternatives in any case.
    - zaarn 8y ago
      Even with three failures I would not consider it a trend unless they are related in nature. For the current trend of "basically no failures" to go to "some failures" you'd need a couple dozen failures at minimum. The alternative is to fix whatever broke Soyuz.
    - varjag 8y ago
      Russia at this point is largely deindustrialized and rapidly losing its tech know-how. The recent string of failures in space programme is only one (but certainly high profile) manifestation of it.
  - DanBC 8y ago
    > Any two datapoints form a line, ie a trend. Two datapoints are not a trend. People who use run charts (control charts,time series charts) talk about trends being a set of five points all going the same way. http://www.qihub.scot.nhs.uk/media/529936/run%20chart%20rules.pdf http://www.qihub.scot.nhs.uk/media/529936/run%20chart%20rule...
    - zaarn 8y ago
      While I generally agree, I'm being more generic. A single data point doesn't establish any direction or trend at all. With two data points you can establish a trend and make a prediction about the next data point. However, any two data points form a line, so any two results can be used to make a trend, however wrong it may be. Only when more points are used can you confirm the trend and reduce the probability of being (un)lucky.
      - katrotz 8y ago
        Two in a row is a coincidence, three in a row might be a rule
    - mch82 8y ago
      For what it’s worth, control chart sensitivity rules are selected based on economic considerations. So the decision to use five points is influenced by both statics and how affordable it is to investigate why the control chart alerted. Sensitivity rules can be adjusted, applied, or ignored based on the specific situation and the analysts tolerance for false positives/negatives.
  - azernik 8y ago
    If the worry is about the manufacturer rather than the design, then we have more than two data points. The Soyuz-2 launch vehicle, which is replacing Soyuz-FG, has about a 10% failure rate (including an ISS resupply mission in 2015). This was as far as I know the second-to-last -FG flight planned, as manufacturing has been discontinued and the -2 is the main production line now.
  - userbinator 8y ago
    This reminds me of the fact that if you give most people the output of a true random number generator, they'll think it's rigged because there appears to be more clustering than is intuitive.
    - zaarn 8y ago
      I recommend making a playlist and making a self-blind study which feels more random: your native music player shuffling it or a true random shuffling of the list. You'll be surprised.
      - ams6110 8y ago
        That's because most people don't really want a "random" playlist. They want a random shuffle: A set of songs played in random order with no repeats until all have been played. That's not the same as making independent random picks from a list, but that's what most people want when they "randomize" their playlist.
        zaarn 8y ago
        I was more thinking about taking a list and shuffling it instead of picking songs at random. In both cases, people complain because, for example, the same artist might be picked twice in a row. Most shuffle functions aren't random but try to make distance between similar songs.
- deleted 8y ago
  [deleted]
haarts 8y ago
They might have been swapping out parts for cheaper ones: https://arstechnica.com/science/2017/01/russia-recalling-dozens-of-rocket-engines-sacks-head-motor-builder/ https://arstechnica.com/science/2017/01/russia-recalling-doz...
- huhtenberg 8y ago
  This needs to be taken with a grain of salt. Bashing Russian space program is one of the Ars' favorite pastimes. Just look at their front page now - A Soyuz crew makes an emergency landing after rocket fails. *** It is not clear how long the Soyuz vehicle will be grounded. *** It's been less than an hour since the incident, but let's focus on Soyuzes being grounded rather than on if the crew is OK.
  - rory096 8y ago
    Suppose you'll have to say the same about the Russian space official who said as much to the AP. >11:02Z: BREAKING: Senior official says Russia suspending manned space launches pending investigation into rocket failure. https://twitter.com/jeff_foust/status/1050341565388996609?s=19 https://twitter.com/jeff_foust/status/1050341565388996609?s=...
    - eps 8y ago
      It would've been the same if it were Roscosmos' only comment on the accident.
    - zaarn 8y ago
      I don't think that's particularly much news. I would expect any space agency to ground every single part of a rocket until they are 100% ruled out as source of a failure.
  - vatueil 8y ago
    > A Soyuz crew makes an emergency landing after rocket fails. > It is not clear how long the Soyuz vehicle will be grounded. How is that "bashing"? The article reports the crew escaped without harm, a fact that was quickly established: https://arstechnica.com/science/2018/10/a-soyuz-crew-makes-an-emergency-landing-after-rocket-fails/ https://arstechnica.com/science/2018/10/a-soyuz-crew-makes-a... That Soyuz rockets have been grounded pending investigation is also a fact, and a natural course of action for any responsible space agency. Other rockets have also been grounded after accidents. The implications for the ISS crew if future Soyuz flights do not resume on schedule are a question that many are asking, so it's hardly unusual to address it. Given that everyone knew the astronauts were safe and nobody died, the idea that people shouldn't discuss the causes and consequences of an incident when it's still fresh in people's minds makes even less sense than usual.
PeterisP 8y ago
The parent post argument wasn't about the quality of Soyuz-FG design, we know that this has been tested, tweaked, verified and is very reliable. The quality control of the current manufacturing team, on the other hand, seems not the same as it was for the earlier Soyuz vehicles.

The Soyuz-FG which has been used since 2001 has had a 100% success rate till today. Seems pretty good to me.

by nhoss2 8y ago

The Soyuz-FG which has been used since 2001 has had a 100% success rate till today. Seems pretty good to me.

I agree that the Soyuz has been very reliable historically, but two major incidents involving it within a few weeks has the appearance of a trend.

zaarn 8y ago
Soyuz is literally the most reliable launch vehicle and two datapoints are not a trend. Any two datapoints form a line, ie a trend.
- Tossrock 8y ago
  "Once is happenstance, twice is coincidence, three times is enemy action." Maybe it's a coincidence, maybe it's not. I think it's very reasonable to want alternatives in any case.
  - zaarn 8y ago
    Even with three failures I would not consider it a trend unless they are related in nature. For the current trend of "basically no failures" to go to "some failures" you'd need a couple dozen failures at minimum. The alternative is to fix whatever broke Soyuz.
  - varjag 8y ago
    Russia at this point is largely deindustrialized and rapidly losing its tech know-how. The recent string of failures in space programme is only one (but certainly high profile) manifestation of it.
- DanBC 8y ago
  > Any two datapoints form a line, ie a trend. Two datapoints are not a trend. People who use run charts (control charts,time series charts) talk about trends being a set of five points all going the same way. http://www.qihub.scot.nhs.uk/media/529936/run%20chart%20rules.pdf http://www.qihub.scot.nhs.uk/media/529936/run%20chart%20rule...
  - zaarn 8y ago
    While I generally agree, I'm being more generic. A single data point doesn't establish any direction or trend at all. With two data points you can establish a trend and make a prediction about the next data point. However, any two data points form a line, so any two results can be used to make a trend, however wrong it may be. Only when more points are used can you confirm the trend and reduce the probability of being (un)lucky.
    - katrotz 8y ago
      Two in a row is a coincidence, three in a row might be a rule
  - mch82 8y ago
    For what it’s worth, control chart sensitivity rules are selected based on economic considerations. So the decision to use five points is influenced by both statics and how affordable it is to investigate why the control chart alerted. Sensitivity rules can be adjusted, applied, or ignored based on the specific situation and the analysts tolerance for false positives/negatives.
- azernik 8y ago
  If the worry is about the manufacturer rather than the design, then we have more than two data points. The Soyuz-2 launch vehicle, which is replacing Soyuz-FG, has about a 10% failure rate (including an ISS resupply mission in 2015). This was as far as I know the second-to-last -FG flight planned, as manufacturing has been discontinued and the -2 is the main production line now.
- userbinator 8y ago
  This reminds me of the fact that if you give most people the output of a true random number generator, they'll think it's rigged because there appears to be more clustering than is intuitive.
  - zaarn 8y ago
    I recommend making a playlist and making a self-blind study which feels more random: your native music player shuffling it or a true random shuffling of the list. You'll be surprised.
    - ams6110 8y ago
      That's because most people don't really want a "random" playlist. They want a random shuffle: A set of songs played in random order with no repeats until all have been played. That's not the same as making independent random picks from a list, but that's what most people want when they "randomize" their playlist.
      - zaarn 8y ago
        I was more thinking about taking a list and shuffling it instead of picking songs at random. In both cases, people complain because, for example, the same artist might be picked twice in a row. Most shuffle functions aren't random but try to make distance between similar songs.
deleted 8y ago
[deleted]

haarts 8y ago

They might have been swapping out parts for cheaper ones: https://arstechnica.com/science/2017/01/russia-recalling-dozens-of-rocket-engines-sacks-head-motor-builder/ https://arstechnica.com/science/2017/01/russia-recalling-doz...

huhtenberg 8y ago
This needs to be taken with a grain of salt. Bashing Russian space program is one of the Ars' favorite pastimes. Just look at their front page now - A Soyuz crew makes an emergency landing after rocket fails. *** It is not clear how long the Soyuz vehicle will be grounded. *** It's been less than an hour since the incident, but let's focus on Soyuzes being grounded rather than on if the crew is OK.
- rory096 8y ago
  Suppose you'll have to say the same about the Russian space official who said as much to the AP. >11:02Z: BREAKING: Senior official says Russia suspending manned space launches pending investigation into rocket failure. https://twitter.com/jeff_foust/status/1050341565388996609?s=19 https://twitter.com/jeff_foust/status/1050341565388996609?s=...
  - eps 8y ago
    It would've been the same if it were Roscosmos' only comment on the accident.
  - zaarn 8y ago
    I don't think that's particularly much news. I would expect any space agency to ground every single part of a rocket until they are 100% ruled out as source of a failure.
- vatueil 8y ago
  > A Soyuz crew makes an emergency landing after rocket fails. > It is not clear how long the Soyuz vehicle will be grounded. How is that "bashing"? The article reports the crew escaped without harm, a fact that was quickly established: https://arstechnica.com/science/2018/10/a-soyuz-crew-makes-an-emergency-landing-after-rocket-fails/ https://arstechnica.com/science/2018/10/a-soyuz-crew-makes-a... That Soyuz rockets have been grounded pending investigation is also a fact, and a natural course of action for any responsible space agency. Other rockets have also been grounded after accidents. The implications for the ISS crew if future Soyuz flights do not resume on schedule are a question that many are asking, so it's hardly unusual to address it. Given that everyone knew the astronauts were safe and nobody died, the idea that people shouldn't discuss the causes and consequences of an incident when it's still fresh in people's minds makes even less sense than usual.

PeterisP 8y ago

The parent post argument wasn't about the quality of Soyuz-FG design, we know that this has been tested, tweaked, verified and is very reliable. The quality control of the current manufacturing team, on the other hand, seems not the same as it was for the earlier Soyuz vehicles.