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From: fcrary@headcrash.Berkeley.EDU (Frank Crary)
Newsgroups: sci.space.shuttle
Subject: Re: After Endeavour, what then?
Message-ID: <1991May9.034143.16916@agate.berkeley.edu>
Date: 9 May 91 03:41:43 GMT
References: <346.281f448d@mwk.uucp> <1991May7.212707.5380@aio.jsc.nasa.gov> <1991May8.092605.1@vf.jsc.nasa.gov>
Sender: root@agate.berkeley.edu (Charlie Root)
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In article <1991May8.092605.1@vf.jsc.nasa.gov> kent@vf.jsc.nasa.gov writes:
>10 / 4 Orbiters = 2.5 flights a year per vehicle.  The vehicles are rated at
>100 flights.  Plans are in work to assure parts and maintainablity thru the
>year 2020.  Beyond that, I do not know.    
>
>Assuming the year 2020 as the last shuttle flight:  29 years X 10 flights a
>year = 290 flights divided by 4 orbiters = 72.5 flight per vehicle plus about 
>10 flight each on Columbia , Discovery and Atlantis = 82.5 flights total.  
>
>Now if all the Orbiters are still around after 82 flights each is another 
>question entirely.

The 100 flight lifetime of an orbiter assumed an impossible reliability of
99.97%. The shuttle has demonstrated a 97.5% reliability (39 / 40 ).
At this rate, there is only a 0.065% (e.g. 1543:1 against) chance of the
shuttle fleet flying 290 missions without loosing an orbiter. In fact,
at 97.5% reliability, 3 more flights in 1991 and 12/year in 1992 and later,
there is only a 8.2% chance that all four orbiters will survive to see the
year 2000. Also, there is a 35% chance that one of the 17 space station
construction flights will result in an accident.

I find it hard to see the shuttle still in use after 2010 (at the latest).

					Frank Crary
					UC Berkeley