4 ms·

Now we are picking timeframes and deconstructing the meaning of "failure" (BTW, that too is not that much more favorable to Ariane 5). The upshot is that their

by blago 8y ago

Now we are picking timeframes and deconstructing the meaning of "failure" (BTW, that too is not that much more favorable to Ariane 5). The upshot is that their reliability is not dramatically different, they are comparable.

hef19898 8y ago
In terms of percentage, yes. But also mean time to failure, in that case to launch failure, is the really interesting point. So the better comparison would be the last 60+ launches. And then you get 3 failure for SpaceX vs. 0 for the Ariane 5. I did not double check the numbers myself, just the values stated above.
- blago 8y ago
  Picking n = 60 compares Falcon's first n attempts with Ariane's best stretch. It conveniently ignores Ariane's initial mis-steps that every complex system is prone to. By the same token I can cherry-pick n=30 and claim victory :-) Neither is a fair comparison. Honestly, I think it's remarkable that Falcon has had only 5% failure rate considering that the launch vehicle has undergone constant tweaking for reusability. I am not familiar with Ariane's evolution but I would be surprised it it's seen similar amount of change. Maybe we should wait until Falcon catches up with the total number of launches and compare apples to apples then?
  - hef19898 8y ago
    No disagreement there, just pointing out that a) a simple failuee rate percentage is insufficient and b) one should not discard Arian out of hand based on SpaceX hype alone. Again, SpaceX did an incredible job, no doubt there. Doesn't change the reliability numbers of the last launches. And yes, ultimately SpaceX will catch-up. And then we can have discusion about the reliability of the Falcon Heavy or BFR vs. the new Ariane rocket. Hopefully giving Ariane the same benfit of doubt in case SpaceX is further down in the rocket life cycle for a comparable rocket. ;)

4 ms·

Now we are picking timeframes and deconstructing the meaning of "failure" (BTW, that too is not that much more favorable to Ariane 5). The upshot is that their

by blago 8y ago

hef19898 8y ago
In terms of percentage, yes. But also mean time to failure, in that case to launch failure, is the really interesting point. So the better comparison would be the last 60+ launches. And then you get 3 failure for SpaceX vs. 0 for the Ariane 5. I did not double check the numbers myself, just the values stated above.
- blago 8y ago
  Picking n = 60 compares Falcon's first n attempts with Ariane's best stretch. It conveniently ignores Ariane's initial mis-steps that every complex system is prone to. By the same token I can cherry-pick n=30 and claim victory :-) Neither is a fair comparison. Honestly, I think it's remarkable that Falcon has had only 5% failure rate considering that the launch vehicle has undergone constant tweaking for reusability. I am not familiar with Ariane's evolution but I would be surprised it it's seen similar amount of change. Maybe we should wait until Falcon catches up with the total number of launches and compare apples to apples then?
  - hef19898 8y ago
    No disagreement there, just pointing out that a) a simple failuee rate percentage is insufficient and b) one should not discard Arian out of hand based on SpaceX hype alone. Again, SpaceX did an incredible job, no doubt there. Doesn't change the reliability numbers of the last launches. And yes, ultimately SpaceX will catch-up. And then we can have discusion about the reliability of the Falcon Heavy or BFR vs. the new Ariane rocket. Hopefully giving Ariane the same benfit of doubt in case SpaceX is further down in the rocket life cycle for a comparable rocket. ;)