Re: >>> just imagine the (sea landing only) Orion will have a Soyuz-TMA11-like 500 km. landing site slippage >>>

John Schilling wrote:
On Tue, 22 Apr 2008 04:16:15 GMT, "Alan Erskine"
<alan.erskine@xxxxxxxxxxx> wrote:

"Jorge R. Frank" <jrfrank@xxxxxxxxxxx> wrote in message
news:H6adnZNXbKx_zpDVnZ2dnUVZ_ozinZ2d@xxxxxxxxxxxxxxx
John Schilling wrote:
Well, *these days*, we are launching astronauts to the ISS on a
somewhat more modern and reliable spacecraft that flies about twice
as often, carries about twice as many people, and usually lands
within a hundred meters of its touchdown point.
The Soyuz, in all its missions (how many 'manned' missions is it now?), has
only had two fatal incidents, whereas the shuttle, in just over 100
missions, has also had two - so much for reliability.

Soyuz has had 108 manned missions, vs. 120 for the Shuttle. Both have had
two fatal incidents, which gives the Shuttle a statistically insignificant
edge in safety. Soyuz has also had two nonfatal incidents resulting in
loss of mission and vehicle, which gives the Shuttle a real edge when it
comes to reliability.

Actually 98 vs. 122... the Soyuz currently at ISS is #99. Arguably one less, depending on whether you count Soyuz 32/34 as one mission or two. I avoid the problem by tallying manned ascents and entries separately.

That nit aside, you are correct to say that the difference in the two vehicles' fatal accident rates are statistically significant.

For that matter, the difference in fatality rates is likewise statistically insignificant, despite the shuttle having fourteen fatalities to Soyuz' four. That's three-and-a-half times the fatalities, but it happens that the shuttle has carried about three-and-a-half times as many people.
.

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