posted 09-01-2012 09:52 AM               

• Number of individual space shuttle astronauts/cosmonauts: 355
  
• Number of space shuttle fatalities: 14
  
• Chance of dying on a shuttle if you were a shuttle astronaut: 1 in 25

• Number of individual Soyuz astronauts/cosmonauts: ~173
  
• Number of Soyuz fatalities: 4
  
• Chance of dying on a Soyuz if you are a Soyuz astronaut/cosmonaut: 1 in ~50

Back to the original answer:

More important than the difference in fatality rates Soyuz' fatalities occurred in the first 10% of the program — the 41 years and 103 nonlethal flights since then suggest that the most lethal bugs have been worked out. Fatal shuttle accidents were evenly spaced through the program. The Columbia Accident Investigation Board judged that the shuttle could not be made into a safe, operational vehicle, and that the right way to manage risk was to fly only essential missions.

The key lesson is the difference between safety and survivability. Rockets are unsafe. They "explode" about 1% of the time. The key is to build a system that allows people to survive a catastrophic failure of the launcher. This usually requires putting people on top of the rocket, not to one side, and this has the added benefit of protecting your heatshield from debris. shuttle had incredible accomplishments but was an unusually lethal experimental space vehicle. The future's safer operational human space exploration vehicles will not look like the shuttle.

posted 09-01-2012 10:30 AM               

Spaceflight will never be an everyday event if you plan to drop into the ocean. Flying to a runway is a much better way of coming home.

But, for right now getting ones feet wet may be the safe and sure way. A small shuttle on top of a rocket?

posted 09-01-2012 11:23 AM               

A more meaningful statistic might be to divide by the 14 fatalities the total number of crew spots launched (somewhere in the 700s, if I'm correct, although I don't know the exact number). That would give you the chance that any particular astronaut would be killed on a single mission. You could then multiply that by however many missions a person actually flew if you wanted to figure out that particular individual's "odds."

Just as an extreme example of what I mean, suppose NASA only maintained a pool of 30 astronauts and just kept recycling all of those folks over and over throughout the whole history of the shuttle program. You would still have the same number of fatalities, but now the "chances" of any single astronaut dying would be 14 out of 30, or almost 50 percent. This would not mean that the system was any more "dangerous" than it was in our real-world experience--just that fewer people overall flew on it.

posted 09-01-2012 12:24 PM               

Remember that some people flew more than once.

• Columbia: 160
  
• Challenger: 60
  
• Discovery: 252
  
• Atlantis: 207
  
• Endeavour: 148

posted 09-02-2012 02:21 AM               

Rocket and spacecraft design tends to be a somewhat reactionary thing. This means while testing takes place (usually) before an all up flight, sticking a man onboard becomes its own test and any major bugs encountered on the flight are addressed and fixed (hopefully) before the next one.

So, the risks faced by the Apollo 1 astronauts was much higher than it was for say Apollo 17 or ASTP that their spacecraft might kill them (although after nitrogen tetroxide fumes entered the Apollo on ASTP during descent, death of the crew was still a real possibility).

Soyuz is also the same way. Soyuz 1 had the parachute problem and it killed Komarov. But if Soyuz 2 had flown with its crew of three, chances of fatality while not being 100% necessarily were pretty high since apparently that craft had the same parachute flaw.

But by comparison, the death of the Soyuz 11 cosmonauts resulted in a better craft with the pressure suits and rapid re-pressurization capability for all crew that flew on Soyuz after. So death by asphyxiation in that particular manner (due to not wearing pressure suits) became an impossibility.

Granted so many other things exist that can still kill a cosmonaut or a NASA/ESA/JAXA astronaut on a mission. It is a form of Russian roulette in the manned spaceflight business. But instead of a six shot revolver with one bullet loaded, it is a revolver with millions of chambers and maybe hundreds of possible bullets loaded.

Each time a craft flies, the drum spins. But after it comes back, some of those bullets are taken out. But others can take their place over time as success leading to complacency can lead to its own magic bullet getting loaded (like ET foam from a bipod impacting an RCC panel on shuttle Columbia).

posted 09-02-2012 06:21 AM               

And while spaceflight will always be complex sometimes simple stats are useful. Looking at Apollo/Saturn and including Apollo 1, we get a 1 in 16 chance of dying (three deaths in 48 crew slots) but per the OP all the deaths happened in the first 5% of launches — the first launch if you will — leading to zero deaths in 45 crew slots for the rest of this program.

Leaving the Apollo fire out of the statistics, isn't it interesting that of three major programs (Apollo, Soyuz and Shuttle) spanning two nations and different designs all achieved about a 1 in 50 chance of a fatality during the flight for the flyers?

posted 09-02-2012 10:44 AM               

These two methods would give the exact same odds under two conditions: first, that every incident that kills any crew member kills ALL crew members (which has been the case every time so far, although there are undoubtedly some possible scenarios that could have resulted in the loss of some crew members with others surviving); and second, that the number of crew members is the same on every mission.

The second of those is obviously not true and results in the slight discrepancy between the two methods, simply because both flights that were lost had a higher number of crew (7) than the average. If both of the lost missions had been among the first four flights (with only 2 crew) then the numbers would have been skewed even further — then you would have 4 fatalities out of 847, which gives a much smaller percentage than 14, even though the same number of missions were lost.

Another thing that has to be considered is the sheer number of missions the shuttle flew compared to M-G-A. Only 10 Saturn Vs ever flew manned, for example, and because none of those missions lost a crew it can be said to have a 100 percent safety rate.

The corollary to that, though, is that the shuttle also had no losses in its first 10 missions — it took until 25 of them for anything to happen. (Although both the Saturn V and the shuttle certainly had "near misses" within their first 10.) How many missions could the Saturn V/Apollo combination have flown before suffering a crew loss? How many before suffering TWO crew losses? Pretty much impossible to say, really, but the fact that they came so close on Apollo 13 (which really had nothing to do with the booster, but still), along with additional potential losses on Apollo 12 and ASTP, would suggest that sooner or later it would have happened. (And yes, ASTP was a 1B, but you see the point.)

Even Mercury (with Grissom in the water, and discounting Glenn's heat shield indications and Carpenter's overshoot) and Gemini (Armstrong and Scott) each had a "near miss" in terms of a crew loss, even though they only flew 6 and 10 missions respectively.

Maybe a tangent to all this would be to suggest that (with the exception of the Apollo 1 fire, which I'm still not sure how to categorize) while M-G-A all had near misses, each time the mission/booster/craft/crew managed to survive in spite of the incident, while the shuttle was lost with all hands in both of its major incidents. Of course, that doesn't take into account all of the near misses that the shuttle experienced that did NOT result in the loss of a crew, either.