Newsgroups: sci.space.shuttle
Path: utzoo!henry
From: henry@zoo.toronto.edu (Henry Spencer)
Subject: Re: launch ratesDOWN 18
Message-ID: <1990Oct3.174312.27561@zoo.toronto.edu>
Organization: U of Toronto Zoology
References: <10195.26fde341@pbs.org> <1990Sep25.033816.16652@zoo.toronto.edu> <10209.26ff5e6c@pbs.org> <1990Sep26.174811.8026@zoo.toronto.edu> <10230.27023455@pbs.org> <1990Sep28.163456.25849@zoo.toronto.edu> <3264@phred.UUCP>
Date: Wed, 3 Oct 90 17:43:12 GMT

In article <3264@phred.UUCP> petej@phred.UUCP (Pete Jarvis) writes:
>>How long do you think it will be before the next orbiter loss?  Higher
>>flight rates will make that happen sooner.
>>
>You seem to assume there will be another Shuttle loss. Higher flight rates
>increase the *probability* of some kind of accident. Doesn't mean there is
>going to be one.

The observed shuttle reliability is one failure in 30-some flights (I forget
the exact current count).  Unless the actual reliability is *orders of
magnitude* higher than that -- which nobody believes, although a factor of
2 or 3 is plausible -- then it is quite likely that we will lose another
orbiter sometime in the next decade, with over 100 flights scheduled.
See the OTA report "Round Trip To Orbit" for numbers and graphs.  Of
particular note is that if you assume that the observed reliability
is the actual reliability (note that we have only something like 50%
confidence that the actual reliability isn't *worse* than observed), the
probability that another orbiter will be written off before space station
assembly finishes is something like 70%.

We can't say for sure that there is going to be another shuttle loss...
but that's the way to bet.
-- 
Imagine life with OS/360 the standard  | Henry Spencer at U of Toronto Zoology
operating system.  Now think about X.  |  henry@zoo.toronto.edu   utzoo!henry