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Comment by samstave | Hacker News Reader

What would the condition of the satellite be if it re-entered the atmosphere? Total burn up? Or is there some remnants of a $3.5 billion dollar object that are worth recovery - at least to ensure none of it got picked up by another state?

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The SpaceX's FCC application[1] for their broadband satellite constellation came up in a recent discussion here. Page 65 has tables describing the parts of the satellites that are expected to survive all the way to the surface. These are very different kind of satellites compared to Zuma, but the tables (and the text they accompany) might give some idea of what kind of components might survive (until impact, anyway).

[1] https://licensing.fcc.gov/myibfs/download.do?attachment_key=...

They wouldn't want anyone to be able to recover anything from a re-entered satellite, and would presumably design it so that nothing would survive reentry. At some point, at the end of its service life, they would likely have wanted to de-orbit it anyway.

I presume building a second would cost far less.

Don't companies build at least two versions anyway? There are three almost exact replicas of the Curiosity mars rover if I recall correctly. Building two copies instead of just one adds very little cost (relative to the overall cost of the whole project).

I toured JPL years ago and it sounded like the duplicate rovers were for testing maneuvers and software updates after launch. More for testing/debugging than a failsafe.

One JPL-related source [1] indicates that the second copy can generally be obtained for 15% of the price of the first one. The primary source is "Interview with Gentry Lee, Jet Propulsion Laboratory, June 1, 1984." I doubt things have changed very much since.

[1] https://history.nasa.gov/computers/Ch6-3.html

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