On Tue, 18 Feb 2003, Randall Clague wrote:
> I think a total four man-hours per flight is not so much out of reach
> as out to lunch. Where did this figure come from?
That was umpteen zillion messages ago, you expect us to remember that far
back? :-)
It was arbitrary, and clearly something that would be feasible only as a
long-term goal. Still interesting to think about; extreme cases can show
you which way you should head, even if it'll be a long time before you
actually get there.
> When I take my car
> to Jiffy Lube for an oil change, it takes about a man hour to service
> my car and do the paperwork. Just refueling it takes over 1/10th of a
> man hour - and this is a vehicle with a 3% mass fraction.
Yep... but there's no reason why a bigger mass fraction would take much
longer. I don't know exactly how long it took to tank up a V-2, but it
wasn't lengthy.
> We talk a lot about wanting to emulate airline operations. OK, how
> many man hours does it take to turn around a 737? Two flight crew and
> two cabin crew * 15 minutes to clear the passengers is one man hour...
> ...We're up to 5 1/2 man
> hours, and we haven't even done any maintenance yet.
Careful here -- note that over half of that budget is passenger handling.
That's payload operations, done by the payload owner, not by the vehicle
operator. (The two roles may get muddled in the case of tourist flights,
but it's worth separating them for purposes of discussion.) The vehicle
operator just swaps out the payload pallet; what happens to it after that
is not his man-hours.
> ...even if
> we're dealing with fast turnaround cargo flights, prepping a (low
> margin) SSTO or mating a (high margin) TSTO are both going to take
> some minimum amount of time and effort, and I think that minimum will
> be well over four man hours.
I suspect that four man-hours is not impossible... eventually.
> And so what? The biggest driver of operations cost for a commercially
> developed RLV is debt service on the R&D budget...
Other things will start becoming significant eventually, when the
production runs start getting long enough to amortize R&D effectively.
Henry Spencer
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