Re: Multiple Engines???

Derek Lyons <[EMAIL PROTECTED]> wrote:
>[EMAIL PROTECTED] (George William Herbert) wrote:
>>and you need to enforce on the design team (and ideally on
>>the operations team) that airframes are not going to be
>>shoehorned into either role. 
>
>That's going to be difficult-to-impossible to enforce.  Any self
>respecting scheduler/planner is going to grab a vehicle already in
>configuration x in order to fly a mission with requirements x.  His
>boss, and his bosses boss are gonna give him attaboys for saving the
>manhours.  And they'll be right in doing so,  over years and decades
>of operation, those little savings add up.
>
>>Establishing that in the operations and maintenance schedule
>>model would be great.
>
>Why?  You waste manhours, and enforce slow degredation of the vehicles
>by doing so.  Other than academic satisfaction, there is utterly no
>need for routine conversion between configurations.  Conversions
>should be driven by need, not ivory tower dictates.

Consider vehicle major maintenance checks.

Major reliability drivers that we can predict ahead of time
are going to be main engines and TPS.  We can also predict
that a lower stage engine failure or a lower stage TPS problem
are less critical than that of the orbiter, coming back
from 2x the velocity and 4x the energy...

Consider for example a vehicle maintenance rotation where
vehicles spend a year doing orbital work, then get their
engines rotated for the short nozzle models and OMS pods
unbolted, and then are used for booster flights for 2 years,
and then undergo the equivalent of a D-check and are put
back into orbital flight for another year.

System upgrades and such get introduced along with the
checks and refurbishment, in the vehicles that need it
the most... the ones which will be flying orbital
missions for the next year or so.  But the
vehicles flying orbital missions don't have to undergo
D-checks every year.  As their systems and structures
age somewhat you just shift them into less demanding
booster work for a while, with the short nozzles,
and then push them back into orbiter service after
the next major rebuild and upgrade cycle.


-george william herbert
[EMAIL PROTECTED]