Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!sdd.hp.com!wuarchive!uunet!stanford.edu!eos!aio!vf.jsc.nasa.gov!kent
From: kent@vf.jsc.nasa.gov
Newsgroups: sci.space.shuttle
Subject: Re: After Endeavour, what then?
Message-ID: <1991May8.092605.1@vf.jsc.nasa.gov>
Date: 8 May 91 15:26:05 GMT
References: <346.281f448d@mwk.uucp> <1991May7.212707.5380@aio.jsc.nasa.gov>
Sender: news@aio.jsc.nasa.gov (USENET News System)
Organization: NASA Johnson Space Flight Center
Lines: 38

> 
> If I remember correctly, the shuttle was originally designed for a
> hundred cycles (flights).  That number was based on a flight schedule
> of 1 flight a week, or a turn-around time of 4 weeks on a single
> orbiter so I'm not sure what the current projections are.
> 
> Although we all love the shuttle, I doubt that it would last 100 years
> at an average rate of a little over one flight a year (the current
> average...counting the test program and Return to Flight).  It's
> pretty clear that shuttle was a pathfinder and a true,
> one-stage-to-orbut vehicle will be needed to service Space Station
> Freedom and it's siblings.
> 

Since the return to flight in 1988, each orbiter has flown about 3 times a
year.  It would be more realistic to count the flights per year based on a
flight rate of 8-12 total flights a year.  So....

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.

Flying 40 year old vehicles in not unreasonable, The B52 fleet is nearing
30-40 years old.  Also think of the average age of a DC3. The thought
of flying 40 year old space technolgy is a scary one.

-- 

Mike Kent -  	Lockheed Engineering and Sciences Company at NASA JSC
		2400 NASA Rd One, Houston, TX 77058 (713) 483-3791
		KENT@vf.jsc.nasa.gov