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Frequency and cost yes, but reliability is more complicated. ULA has 148 launches with NO accidents. SpaceX has put up more, but had an accident in flight wit

by btilly 4y ago

Frequency and cost yes, but reliability is more complicated. ULA has 148 launches with NO accidents. SpaceX has put up more, but had an accident in flight with the Falcon 9 in June 2015, and another on the pad in September 2016. Mind you, ULA started with a known rocket design. While SpaceX has been iterating as it goes. But still, we don't have significant statistical evidence about which is actually more reliable.

panick21_ 4y ago
As you said, ULA when it started already had mature rockets. You need to compare rocket families not operators. And ULA had a number of issues in that time. For example a failure in an Atlas first stage and the only just managed to deploy the sat because the upper stage had just enough margin. And ULA had major delays, way longer then what SpaceX could afford for things like their Delta 4 Heavy launches. ULA of course also got 1 billion $ in subsidies per year to ensure launch safety, a luxury SpaceX never had. > But still, we don't have significant statistical evidence about which is actually more reliable. Actually we do. It you look at the launch rates and how often Falcon 9 has launched already the statistical significant of the results gets bigger and bigger. Unfortunately I can't find the list that shows this data and explains the methods used right now. But Falcon 9 is very clearly on top of the list.
- philistine 4y ago
  Every time they do a run-of-the-mill Starlink launch that goes without a hitch, Falcon 9 becomes safer and more valuable. Every time Falcon 9 flies, the necessity for Starship to succeed soon decreases.
  - MichaelCollins 4y ago
    I doubt Starlink is commercially viable in the long run if they don't get Starship operational. The Starlink constellation requires continuous maintenance, replacement of old satellites that have expended their fuel and fall out of LEO a few months later. To do this with Falcon 9 instead of Starship, they need something on the order of 10x more launches, and each time they throw away the second stage. Furthermore the Starlink constellation 'only' has 3,000 satellites so far, but SpaceX has sought approval for 30,000 more than the 12,000 already approved. To launch and maintain a constellation that huge with Falcon 9? It might be commercially viable, but I doubt it, they already have a very rapid launch cadence with Falcon 9 starlink launches and they evidently think they need much more.
- btilly 4y ago
  No, we really don't have significant statistical evidence. Even for the rocket family. And there is no need to look for the reference you can't find since this is all verifiable from public data. The ULA workhorse was the Atlas 5. Over its whole lifetime, both under Lockheed and ULA, it had 95 launches of which one was a partial failure (declared success). Wikipedia is good enough for that. The SpaceX workhorse is the Falcon 9. https://www.spacex.com/launches/ https://www.spacex.com/launches/ puts it at 176 launches with 1 failure and 1 partial failure. This is not counting one that blew up on the pad with the satellite aboard. The measured failure rate of the Atlas 5 is 0/95. Of Falcon 9 is 1/176. Note that 0/95 < 1/176. The measured "not perfect success" rate of the Atlas 5 is 1/95. Of Falcon 9 is 2/176 = 1/88. Note that 1/95 < 1/88. Also anyone with basic statistical knowledge will immediately see that the sample size is sufficiently low that we cannot draw any conclusion at 95% confidence. Now what Falcon 9 does have the crown on is the longest string of uninterrupted successes of any rocket family. They are now at 148. (Not counting, of course, the one that blew up on the launch pad with the satellite on board.) But not enough to be statistically strong evidence that they are best. Also ULA has over 150 launches across their rocket platforms without any being declared a failure - which exceeds SpaceX's current winning streak. That said, I agree with you about ULA's advantages, and I agree that SpaceX is the future. But I'm not going to lie about the math. And the math says that there isn't significant statistical evidence that SpaceX is better on safety.
  - panick21_ 4y ago
    The statistical measure I was talking about does some more complex calculation and takes into account the different iteration of the rocket as well. In low sample size cases such measures are a better predictor of the future. Insurance rates also reflect this same reality, as SpaceX has industry leading safety rating. If I can find this document again I will send it, but somehow I can't find the damn thing.

by btilly 4y ago

panick21_ 4y ago

As you said, ULA when it started already had mature rockets. You need to compare rocket families not operators. And ULA had a number of issues in that time. For example a failure in an Atlas first stage and the only just managed to deploy the sat because the upper stage had just enough margin. And ULA had major delays, way longer then what SpaceX could afford for things like their Delta 4 Heavy launches. ULA of course also got 1 billion $ in subsidies per year to ensure launch safety, a luxury SpaceX never had. > But still, we don't have significant statistical evidence about which is actually more reliable. Actually we do. It you look at the launch rates and how often Falcon 9 has launched already the statistical significant of the results gets bigger and bigger. Unfortunately I can't find the list that shows this data and explains the methods used right now. But Falcon 9 is very clearly on top of the list.

philistine 4y ago
Every time they do a run-of-the-mill Starlink launch that goes without a hitch, Falcon 9 becomes safer and more valuable. Every time Falcon 9 flies, the necessity for Starship to succeed soon decreases.
- MichaelCollins 4y ago
  I doubt Starlink is commercially viable in the long run if they don't get Starship operational. The Starlink constellation requires continuous maintenance, replacement of old satellites that have expended their fuel and fall out of LEO a few months later. To do this with Falcon 9 instead of Starship, they need something on the order of 10x more launches, and each time they throw away the second stage. Furthermore the Starlink constellation 'only' has 3,000 satellites so far, but SpaceX has sought approval for 30,000 more than the 12,000 already approved. To launch and maintain a constellation that huge with Falcon 9? It might be commercially viable, but I doubt it, they already have a very rapid launch cadence with Falcon 9 starlink launches and they evidently think they need much more.
btilly 4y ago
No, we really don't have significant statistical evidence. Even for the rocket family. And there is no need to look for the reference you can't find since this is all verifiable from public data. The ULA workhorse was the Atlas 5. Over its whole lifetime, both under Lockheed and ULA, it had 95 launches of which one was a partial failure (declared success). Wikipedia is good enough for that. The SpaceX workhorse is the Falcon 9. https://www.spacex.com/launches/ https://www.spacex.com/launches/ puts it at 176 launches with 1 failure and 1 partial failure. This is not counting one that blew up on the pad with the satellite aboard. The measured failure rate of the Atlas 5 is 0/95. Of Falcon 9 is 1/176. Note that 0/95 < 1/176. The measured "not perfect success" rate of the Atlas 5 is 1/95. Of Falcon 9 is 2/176 = 1/88. Note that 1/95 < 1/88. Also anyone with basic statistical knowledge will immediately see that the sample size is sufficiently low that we cannot draw any conclusion at 95% confidence. Now what Falcon 9 does have the crown on is the longest string of uninterrupted successes of any rocket family. They are now at 148. (Not counting, of course, the one that blew up on the launch pad with the satellite on board.) But not enough to be statistically strong evidence that they are best. Also ULA has over 150 launches across their rocket platforms without any being declared a failure - which exceeds SpaceX's current winning streak. That said, I agree with you about ULA's advantages, and I agree that SpaceX is the future. But I'm not going to lie about the math. And the math says that there isn't significant statistical evidence that SpaceX is better on safety.
- panick21_ 4y ago
  The statistical measure I was talking about does some more complex calculation and takes into account the different iteration of the rocket as well. In low sample size cases such measures are a better predictor of the future. Insurance rates also reflect this same reality, as SpaceX has industry leading safety rating. If I can find this document again I will send it, but somehow I can't find the damn thing.