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One of the answers to this question is generating some discussion about the cost and lifetime of a satellite. The question is, will a satellite become cheaper when you can design it for a shorter lifetime?

At the moment, commercial geostationary satellites are designed for an on-orbit lifetime of 15 years, limited by propellant supply. Satellite operators would like to increase that by using more efficient engines.
If you were to build a satellite for half that lifetime, would it get much cheaper?

My guess: it wouldn't get much cheaper; the only savings you have is in fuel (and hence, size of the fuel tank and launch mass). Electronics still have to be rated for space, halving the projected lifetime isn't going to change the fundamentals of producing and qualifying the parts.

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There is some correlation between cost and lifetime. Higher cost systems tend to have redundant electronics, while lower cost tend not to have such backups. The fuel is actually a fairly significant part of the mass of a satellite, less fuel means less structure, smaller tanks, smaller engines, etc.

The correlation is somewhat weak, but it can be seen, if one looks carefully enough.

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    $\begingroup$ OTOH, if you look at cost of 1 satellite to last 20 years, vs 4 satellites of 5 years each, this ceases to look so well. $\endgroup$
    – SF.
    Jun 28, 2016 at 11:14
  • $\begingroup$ This is true, the 4 satellites are more expensive than the 1 more reliable satellite. $\endgroup$
    – PearsonArtPhoto ♦
    Jun 28, 2016 at 12:47
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    $\begingroup$ @SF. depends on the revenue opportunities of the 4 satellites. If they each cost 1/4 of the 1 satellite (including launch), but provide better capabilities in the future then you are making more profit on a smaller outlay and smaller total cost (thanks to time value of money). $\endgroup$
    – NPSF3000
    Jun 30, 2016 at 1:32
  • $\begingroup$ @NPSF3000: The bulk of cost of satellite (besides launch) is in mechanics: CMGs, bearings, thrusters with their valves and ignitors, gimbals, actuators, etc. You may save a lot on electronics, but if you use a plain ball bearing instead of one specially designed for space, it will cold-weld within the first minute in vacuum. And the difference in cost of a bearing made to last 5 years in space vs one to last 20 years is zilch. So building a satellite of the same functionality but merely shorter lifetime for 1/4 the cost is simply not viable. $\endgroup$
    – SF.
    Jun 30, 2016 at 8:44
  • $\begingroup$ @BPSF3000: Here you go. The revenue point is moot, since they won't cost 1/4 of the original. If the satellite becomes obsolete before EOL they can still build and send a newer one. $\endgroup$
    – SF.
    Jun 30, 2016 at 12:45
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For shorter life time you save fuel and you might save on EEE components (COTS). You might also propose not redundant functions (e.g. cubesats). Lead time might be shorter as well as launch cost (reduced mass).

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  • $\begingroup$ I can't figure out what "propose not redundant functions" is supposed to mean. $\endgroup$
    – Nathan Tuggy
    Sep 13, 2017 at 15:23
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If you look at the cost of designing and building ONE NEW satellite there is little difference, as typically around half the cost of a single new satellite is design and development costs, even if you can adapt already existing eqiuipment. The saving from smaller tanks is negligible, it may cost even more when you have to design and build from scratch. However if you look at a commercial satellite, the longer it operates, the longer it earns mony, and the cost of building the satellite is spread over more years, as well as the launch cost. Because the design and development cost are such a significant part of a single satellite it pays of big time when you can build a series of satellites, the initial (non-reccurrent) cost are spread over more satellites. Therefore it is clear that designing to maximize the lifetime is cheaper w.r.t cost per useful year. It is however ony part of the cost picture a commercial satellite operator has to consider, it costs money to operate the satellite, but thats a different story, however it may pay off to spent more on the design of the satellite in order to save operating cost later.

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