[AR] Re: fatigue life (was Re: Re: SpaceX F9 Launch/Update...)
- From: David Weinshenker <daze39@xxxxxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Sat, 9 Jan 2016 10:55:58 -0800
On 01/09/2016 10:45 AM, David Gregory wrote:
I see the logic now. And I agree that you've made no errors. However
I don't see it as a useful way of looking at the value of re-usability.
Instead I think the inverse of the problem is more useful.
As an example - if I need to buy a car to commute to work 200 times a
year (200 missions) and the car costs $10000, and is worthless at the
end of the year (and gas is neglected etc. etc.), then i spend $10000
per year on my commuter vehicle.
If instead i throw the car away every other workday, i need to buy 100
cars, and there for my costs are 10,000% higher than my "reusable" car.
I dont see that as achieving 50% benefit over the 1 time use car, i
see it as 100 times more expensive.
In terms of the usual economic arguments related to "depreciation",
the underlying logic seems to be related to notions of expected resale
value - i.e., with respect to an automobile, the question would be
whether or when to sell it and buy a new one, vs. keep running and
maintaining the original one - and this has a lot to do with the
relative time scales of the declines of resale and use values.
Is a healthy, slightly used item worth (in resale value) almost as
much as a brand-new one - or does it lose a big chunk of "value"
at the moment of first sale? (The first may be true of some industrial
equipment; the second is said to be true of automobiles.)
Unless and until there's a resale market, I'm not sure calculations
of "depreciation" of market value are going to be as relevant; it's
really going to be more of a question of physical service life and
the relative cost of ongoing maintenance vs. new construction.
(Until we see what the relative rates of "shakedown" and "wear-out"
trends are going to look like for a given system type, it's sort of
hard to second-guess this in advance!)
-dave w
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