Statistically, both have a 2% rate of Loss of Crew.
If you're given the option to be a space tourist on either vehicle, it's Shuttle hands down. It has the greatest internal volume of any spacecraft and more window space than Soyuz. Crew comforts are noteably superior.
That's because the Shuttle is given an almost unlimited degree of scrutiny to insure it is opperating properly. Everything about the Shuttle makes the news lately because STS-115 is only the 3rd post-Columbia flight.
And really, there has never been a better time to fly the Shuttle. It's the safest it has ever been.
Had you passed your assumption in November 2002 when Endeavour flew the last mission before Columbia was lost, you would have likely said that the Shuttle was a safe vehicle with no losses since Challenger in 1986. Likewise, just prior to Challenger STS-51L, the Shuttle had flown 24 successful missions.
Would you rather have flown before those incidents marred the Shuttle's safety record, or would you rather fly now that they have been fixed? Believe me when I say Soyuz has had some very close calls over the years as well.
Thorny From , joined Dec 1969, posts, RR: Reply 8, posted (6 years 8 months 6 days 4 hours ago) and read 13414 times:
Quoting DfwRevolution (Reply 7): There was also an SSME failure on STS-51F that caused an Abort-To-Orbit
Yes, STS-2 and STS-44 both returned early, but the lion's share of the mission's objectives were accomplished nevertheless, as were STS-51F's, so they aren't considered failures. STS-83 however, was a Spacelab flight that accomplished very little and really must be considered a failure.
Lnglive1011yyz From Canada, joined Oct 2003, 1588 posts, RR: 17 Reply 9, posted (6 years 8 months 6 days 4 hours ago) and read 13414 times:
While the logic says to go with the Soyuz, simply due to the number of flights, and the low-mortality rate when compared with the Shuttle, I must say that the Shuttle looks like it's much more 'fun' going into orbit on..
Thorny From , joined Dec 1969, posts, RR: Reply 15, posted (6 years 8 months 5 days 15 hours ago) and read 13311 times:
Quoting Bobster2 (Reply 11): There were five aborts within three seconds of launch. If you count those as failures the statistics get worse.
Yes they would, but why on earth would you count a launch scrub as a mission failure? That's not the mainstream definition of a mission failure.
Generally, a mission failure is when a vehicle flies but does not complete its mission. The only exception I know of, and even that is often argued, is Apollo 1, destroyed during a Plugs-Out Test a few weeks before scheduled launch. In all the other cases of a post-ignition abort (Gemini 6, STS-41D, etc.) the mission did eventually launch and was successful.
I should point out that Soyuz 15, Soyuz 33, and Soyuz T-8 should probably also be classified as mission failures, since all three failed to dock with a Salyut space station as intended.
Thorny From , joined Dec 1969, posts, RR: Reply 19, posted (6 years 8 months 5 days 5 hours ago) and read 13199 times:
Quoting Bobster2 (Reply 18): Technically, anytime the SSME's are ignited is counted as a launch.
No it isn't, as demonstrated by the six Flight Readiness Firings.
Launch is motion off the pad, not engine ignition. Note that firing up the SSMEs 6.6 seconds before liftoff is done for the express purpose of making sure everything is working right before committing to launch. At the very least, I would say launch begins with Hold-Down Post release, not SSME ignition. The RSLS computer makes sure the three SSMEs are burning properly and if they are, they command SRB ignition and Hold-Down Post release. If they're not, the RSLS halts the launch attempt (the narrowest abort was at T-1.8 seconds.)
And they didn't always roll back to the VAB after the post-ignition aborts. STS-51F didn't. STS-55 didn't.
Quoting Bobster2 (Reply 18): I agree it's not a mission failure, it's only a launch failure.
No, it's a launch scrub, albeit more dramatic than most.
Bobster2 From , joined Dec 1969, posts, RR: Reply 21, posted (6 years 8 months 5 days 3 hours ago) and read 13171 times:
Let me clarify what I've been arguing. My objective is to have a meaningful statistic for the reliability of the shuttle. So my argument is based on the somewhat arbitrary definition that the SSME's should be 100% reliable when they ignite, and I want a statistic that measures how much less than 100% reliable they actually are. I forgive them statistically for problems detected before ignition (scrubs), but I penalize them for problems detected after ignition.
I realize that an abort before the hold-down posts release is not a launch, but for the purpose of keeping meaningful statistics I propose counting the abort after ignition as a launch failure, because it indicates a serious reliability issue.
So NASA gets credit for successful FRF's, but they also get penalized for aborts at T-2 seconds. It's just statistics.
We can also count the STS-51F abort to orbit as a launch failure for statistical purposes even thought the mission was 100% succesful. I hope that doesn't sound totally insane.
Thorny From , joined Dec 1969, posts, RR: Reply 23, posted (6 years 8 months 5 days 2 hours ago) and read 13153 times:
Quoting Bobster2 (Reply 20): My reference is the NASA web site. They say: "The procedure that has been used on previous aborts treats an RSLS abort after SSME ignition as a launch and to require a complete engine reinspection."
Nonsense. If NASA considered the FRF flights, they would today have announced the safe landing of the 122nd Shuttle mission, not the 116th. But all NASA references say this week's mission was No.116.
Quoting Bobster2 (Reply 21): I realize that an abort before the hold-down posts release is not a launch, but for the purpose of keeping meaningful statistics I propose counting the abort after ignition as a launch failure, because it indicates a serious reliability issue.
Of what? The Shuttle system? The system did exactly what it was intended to do... when an engine isn't meeting parameters, it safely aborted the launch sequence. It is a mystery to me how you can lump this in the same category as the Falcon 1 launch, which left the pad with a leaky propulsion system because its brains didn't know any better.
Quoting Bobster2 (Reply 21): Let me clarify what I've been arguing. My objective is to have a meaningful statistic for the reliability of the shuttle. So my argument is based on the somewhat arbitrary definition that the SSME's should be 100% reliable when they ignite, and I want a statistic that measures how much less than 100% reliable they actually are.
Then failures in flight is the logical measure. The failure rate is 1 in 348.
Quoting Bobster2 (Reply 21): Let me clarify what I've been arguing. My objective is to have a meaningful statistic for the reliability of the shuttle. So my argument is based on the somewhat arbitrary definition
Very arbitrary. So abitrary that it is used to describe the success rate of absolutely no other launchers in the world. NASA and nearly all historians consider both Gemini and Apollo to have been 100% successful from a launch standpoint. But Gemini 6 aborted on the pad after engine ignition and rising a few inches off the pad. Apollo had engines out on Apollo 6 and Apollo 13. Many launch vehicles use multiple engines precisely to give them engine-out performance and improve the odds of a successful launch. However, your definition penalizes vehicles which have multiple engines for redundancy and other vehicles which bring up the engines to full thrust before committing to flight.
Cutting off engines before committing to flight is not a launch failure or a mission failure, it is a pre-flight launch abort.
Thorny From , joined Dec 1969, posts, RR: Reply 25, posted (6 years 8 months 4 days 9 hours ago) and read 13053 times:
Quoting CURLYHEADBOY (Reply 14): One of the two fatal Soyuz accidents was due to human error, I'm talking about the one that got depressurized on re-entry, am I right?
No, Soyuz 11 was mechanical failure, not human error. A vent valve opened accidentally when the Soyuz's Orbital Module was jettisoned prior to re-entry. The crew tried to save themselves by closing the vent valve, but didn't have enough time to get to it before they lost consciousness. They were not wearing spacesuits and died of decompression/asphyxiation.