edkyle99 - 7/9/2007 7:23 PMQuotemr.columbus - 7/9/2007 2:31 AMQuoteedkyle99 - 6/9/2007 9:50 PMI hate to mention it, but these failure things even out over time. Arianespace seems to be flying high right now, since it hasn't had a failure since 2002. Good for Arianespace, but with 19 consecutive successes (if I'm counting right), Ariane 5 is now starting to race against the statistics of launch vehicle failure. Ariane 5 could fly without error for years more before the next failure, but it is still a race that no launch vehicle has ever won.- Ed KyleEd, the Long March rocket family has had 59 consecutive successful rocket launches (since 1996). The chance of another failure of Ariane 5 is remote, of course there is a chance at every launch, however I would not be suprised if we see another 50 launches before another failure. Ariane is a very reliable rocket.Ariane 5 has had 4 failures in 33 flights. That is a 12% realized failure rate, with enough samples to be able to state, with 90% confidence, that Ariane 5 is no more than 95% reliable. A 95% maximum reliability level means that, on average, at least one out of every 20 launches will fail. Ariane 5 could very well extend its string of successes well beyond 20, or 50, etc., but the odds are against it. There is less than an 8% chance that Ariane 5 will reach 50 consecutive successes, assuming 95% reliability, and less than a 0.2% chance if 88% reliability is assumed. - Ed Kyle
mr.columbus - 7/9/2007 2:31 AMQuoteedkyle99 - 6/9/2007 9:50 PMI hate to mention it, but these failure things even out over time. Arianespace seems to be flying high right now, since it hasn't had a failure since 2002. Good for Arianespace, but with 19 consecutive successes (if I'm counting right), Ariane 5 is now starting to race against the statistics of launch vehicle failure. Ariane 5 could fly without error for years more before the next failure, but it is still a race that no launch vehicle has ever won.- Ed KyleEd, the Long March rocket family has had 59 consecutive successful rocket launches (since 1996). The chance of another failure of Ariane 5 is remote, of course there is a chance at every launch, however I would not be suprised if we see another 50 launches before another failure. Ariane is a very reliable rocket.
edkyle99 - 6/9/2007 9:50 PMI hate to mention it, but these failure things even out over time. Arianespace seems to be flying high right now, since it hasn't had a failure since 2002. Good for Arianespace, but with 19 consecutive successes (if I'm counting right), Ariane 5 is now starting to race against the statistics of launch vehicle failure. Ariane 5 could fly without error for years more before the next failure, but it is still a race that no launch vehicle has ever won.- Ed Kyle
sammie - 7/9/2007 9:59 PMCan anyone elaborate on McDew's comment on the near failure of Fregat during the Globestar Mission, it's the first time I heard of it
pippin - 7/9/2007 12:37 PMFact 1: you don't know the long term success rate yet.
Fact 2: assuming your assumption (95% success rate) is correct (see also: Fact 4), that means the chance a flight will fail is 5% for each flight.
Realized success rates in the past have no influence of the chances for failure.
Fact 3: Since you only deduct your success rate from the success/failure sample a long success streak could also mean, your initially assumed success rate was too low. You can't know whether the failures you did see were a cluster not consistent with the underlying success rate.
Fact 4: Statistically speaking, a confidence level of 90% is equal to "I don't know". Useful confidence levels start at 95% at least (and here you need twice the sample, first).Fact 5: That was all only on statistics and did not include fundamental aspects like things that lead to failure in the past getting fixed or more experience being gained with the LV.
edkyle99 - 7/9/2007 10:21 PMQuotepippin - 7/9/2007 12:37 PM Realized success rates in the past have no influence of the chances for failure.'Gotta disagree with this assertion. The past does provide lessons for the future. NASA and DoD both use reliability estimating methods that initially are based on "a comparison to historical data from previous launches of vehicles developed and launched in similar circumstances". http://www.faa.gov/about/office_org/headquarters_offices/ast/media/FAA_AST_Guide_to_Reliability_Analysis_v1.pdf- Ed Kyle
pippin - 7/9/2007 12:37 PM Realized success rates in the past have no influence of the chances for failure.
anik - 7/9/2007 2:45 PMQuotesammie - 7/9/2007 9:59 PMCan anyone elaborate on McDew's comment on the near failure of Fregat during the Globestar Mission, it's the first time I heard of itThere was problem with sensor (or telemetry), which showed zero gas pressure in tanks of pressurization system after performing of the first burn by Fregat upper stage... The second and third (deorbit) burns were performed successfully...
McDew - 8/9/2007 2:16 AMNot sure if your comments are implying that the pressure was fine and it was just a sensor error
McDew - 8/9/2007 2:16 AMMy sources informed me that the "actual" pressure for second burn was only about 25% of the mininum specification for operation of the engine
McDew - 8/9/2007 2:16 AMInformation identifying that an anomaly occurred on the mission become public about a month ago and was linked to the continued delay of the Fregat stage for next Globalstar mission
anik - 8/9/2007 3:42 AMQuoteMcDew - 8/9/2007 2:16 AMInformation identifying that an anomaly occurred on the mission become public about a month ago and was linked to the continued delay of the Fregat stage for next Globalstar missionI was told that the postponing of this launch (from July to September and then to October) is related to explosion of chemical battery during testing of Fregat upper stage in NPO Lavochkin...
Seer - 10/9/2007 8:46 PMSpacex have just announced a launch order for falcon 9. Does anyone know whether this was connected to the Proton failure?