17% chance of death ?

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radarredux

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(oops, the title should be "17% chance of death")<br />A CNN article references Michael Stamatelatos, NASA's director of safety and assurance requirements, as saying that the Shuttle crew has a 1-in-100 chance of dying. If this number is correct (my guess is that this is a crude guesstimate), and that probability stays consistent for the next 17 flights, the odds of losing another crew before completing ISS is about 17%.<br /><br />1 - (0.99^18) =0.165.<br /><br />Shuttle crew faces 1-in-100 chance of dying<br />http://www.cnn.com/2006/TECH/space/06/27/shuttle.risk.ap/index.html
 
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themanwithoutapast

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Don't get it, 2 losses in appr. 100 launches = 1:50 chance of dying = 34% chance of crew loss during the next 17 flights.
 
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radarredux

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> <i><font color="yellow">Don't get it, 2 losses in appr. 100 launches = 1:50 chance of dying</font>/i><br /><br />I think the assumption is that the Shuttle is now twice as safe as it was before (especially when including the Safe Haven option).</i>
 
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j05h

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The Safe Haven only works for survivable Abort-to-Orbit. A forgotten wrench in an engine bay, fuel line cracks, bad O-Rings, Tin Whiskers, etc all have a chance of making a Bad Day. Foam is a big issue, but NASA may have focused to much on that one failure mode while age-related issues sneak in. <br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>
 
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edkyle98

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Yes, and when you throw in a confidence interval (or use Baysian methods), the chance that the real reliability is only 0.97 can't be ignored, which would push the chance for a failure during one of 17 missions up to 40%.<br /><br /> - Ed Kyle
 
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elguapoguano

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If we are talking straight numbers here. <br /><br />Soyuz is generally considered the most reliable manned space craft in the world today. The Soyuz rocket was first launched in November 1963 and has since flown more than 1500 times. It is one of the most reliable launch vehicles in the world, with a 98% success rate.<br /><br />Shuttle has launched 114 times with 2 failures. That is a 98.2% success rate. <div class="Discussion_UserSignature"> <font color="#ff0000"><u><em>Don't let your sig line incite a gay thread ;>)</em></u></font> </div>
 
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themanwithoutapast

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Only that the fatality rate of crewed launches with Soyuz is not as low as 98% - rather there were 2 fatal flights in 1967 and 1971 (both have nothing to do with the Soyuz rocket (R-7), but were due to failures of the Soyuz spacecraft).<br /><br />That said, the overall rate of losses for crews due to rocket failures is 0%.<br /> <br />The problem with the STS system really is, that it is highly likely to have a crew loss if something goes wrong, while today for Soyuz flights, if something goes wrong crew loss is not very likely, there would be only mission failure due to crew abort systems. <br /><br />
 
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qso1

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Statistics are good indicators of probabilities, they flaw lies in the fact that in actual practice, they sometimes mislead. If shuttle flies 17 missions to retirement with no more fatalities, then the verified actual stat would be 0 percent fatality for the period beginning July 1st or thereabouts.<br /><br />If another fatal accident occurs, then we will never know the actual stat because shuttle will in all likelihood be grounded for good and there would be no way to know if another accident would occur or would not. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>
 
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edkyle98

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I view Soyuz and Shuttle as, for the most part, statistical equals when in comes to crew survival. There have been 94 crewed Soyuz missions, with two fatal reentries and two launch aborts that crews survived, so the demonstrated Soyuz crew survival rate is about 0.98 and a predicted rate (Bayesian - think of it as the lower bound of a 50% confidence interval) of 0.97. Shuttle has had two fatal missions in 114 flights, for a demonstrated crew survival rate of about 0.98 and a predicted rate of about 0.97.<br /><br />Likewise the Soyuz-U and STS launch systems both have predicted reliability rates of about 0.97. The newer Soyuz-FG launcher has only flown 11 times so far, with no failures, so its predicted rate is only up to 0.92 so far, but climbing quickly.<br /><br />If you include unmanned Soyuz missions and test flights, including those performed under the "Kosmos" banner, and count the two launch aborts, there have only been a total of 113 successful Soyuz flights in 118 attempts, a 0.96 demonstrated rate and a 0.95 predicted rate. Both of these numbers trail the Shuttle results to date.<br /><br /> - Ed Kyle
 
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geminivi

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Ok, lets cut to the chase. If you were offered the opportunity to fly to space on a Soyuz or a shuttle, which would you pick ?<br /><br />Not to be unpatriotic as the July 4th day arrives, I think in all cases I'd go Soyuz. <br />
 
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rocketwatcher2001

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I'd take the Shuttle. <div class="Discussion_UserSignature"> </div>
 
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j05h

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> Ok, lets cut to the chase. If you were offered the opportunity to fly to space on a Soyuz or a shuttle, which would you pick ? <br /><br />Soyuz. Only because I can (theoretically) buy that ride. As Ed Kyle posted earlier, they are basically the same safety-wise. I do like Soyuz operational philosophy better and think as a "product" that it will long outlive the STS. <br /><br />The main non-economic reason I'd choose Soyuz: Launch Escape Tower.<br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>
 
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vogelbek

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My guess is that these 98% reliability (per flight) numbers are probably going to pretty standard for manned launch vehicles untill we can get our structures and propulsion good enough for single stge to orbit vehicles. Staging events are ugly, and they introduce tons of uncertainty into the launch events.
 
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geminivi

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Mr. Kyle, the statistics are valid but are deceptive. The Soyuz can plausible be projected to be just as safe today as it was 10 years ago. The Shuttle can not. The Shuttle is unique in that is it reused every time it lights. Just like a car. My now 6 year old car isn't as reliable as it was just off the lot. <br />A Soyuz is rebuilt using pretty much the same template as it was 10 years ago. Its always brand new. The Shuttle gets a major overhaul every time its driven but its still far from brand new each time it launches. <br />So the point is these statistics don't reflect the reality we've seen of the vehicle's aging symptoms.
 
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edkyle98

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"Mr. Kyle, the statistics are valid but are deceptive. The Soyuz can plausible be projected to be just as safe today as it was 10 years ago. The Shuttle can not. The Shuttle is unique in that is it reused every time it lights. Just like a car. My now 6 year old car isn't as reliable as it was just off the lot.<br />A Soyuz is rebuilt using pretty much the same template as it was 10 years ago. Its always brand new. The Shuttle gets a major overhaul every time its driven but its still far from brand new each time it launches.<br />So the point is these statistics don't reflect the reality we've seen of the vehicle's aging symptoms."<br /><br /><br />I don't see aging failures involved with shuttle failures yet. Neither of the fatal accidents were due to aging - both of the failed parts (an SRB joint and an ET foam ramp) were essentially brand new. The orbiters are now equipped with new flight decks and fairly new, upgraded, safer main engines. This is not to say that the orbiters might not run into aging problems down the road, as maintenance work tails off.<br /><br />As for Soyuz, it can be argued that it is as suspect (or more suspect) than a shuttle orbiter *because* it is brand new. You have no doubt read about "infant mortality" and life cycle failure analysis. Google "Bathtub curve" or "Weilbull life cycle curve" to see more.<br /><br /> - Ed Kyle
 
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